| blob | e976117d133a1f4a14030e0d4767c8a1f7a25416 |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 02111-1307, USA. */
22 /*@@ This file should be rewritten to use an arbitrary precision
23 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
24 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
25 @@ The routines that translate from the ap rep should
26 @@ warn if precision et. al. is lost.
27 @@ This would also make life easier when this technology is used
28 @@ for cross-compilers. */
30 /* The entry points in this file are fold, size_int_wide, size_binop
31 and force_fit_type.
33 fold takes a tree as argument and returns a simplified tree.
35 size_binop takes a tree code for an arithmetic operation
36 and two operands that are trees, and produces a tree for the
37 result, assuming the type comes from `sizetype'.
39 size_int takes an integer value, and creates a tree constant
40 with type from `sizetype'.
42 force_fit_type takes a constant and prior overflow indicator, and
43 forces the value to fit the type. It returns an overflow indicator. */
61 /* The following constants represent a bit based encoding of GCC's
62 comparison operators. This encoding simplifies transformations
63 on relational comparison operators, such as AND and OR. */
81 };
117 tree);
142 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
143 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
144 and SUM1. Then this yields nonzero if overflow occurred during the
145 addition.
147 Overflow occurs if A and B have the same sign, but A and SUM differ in
148 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
149 sign. */
150 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
151 \f
152 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
153 We do that by representing the two-word integer in 4 words, with only
154 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
155 number. The value of the word is LOWPART + HIGHPART * BASE. */
157 #define LOWPART(x) \
158 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
159 #define HIGHPART(x) \
160 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
161 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
163 /* Unpack a two-word integer into 4 words.
164 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
165 WORDS points to the array of HOST_WIDE_INTs. */
167 static void
169 {
174 }
176 /* Pack an array of 4 words into a two-word integer.
177 WORDS points to the array of words.
178 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
180 static void
183 {
186 }
187 \f
188 /* Make the integer constant T valid for its type by setting to 0 or 1 all
189 the bits in the constant that don't belong in the type.
191 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
192 nonzero, a signed overflow has already occurred in calculating T, so
193 propagate it. */
195 int
197 {
199 HOST_WIDE_INT high;
203 {
204 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
205 Consider doing it via real_convert now. */
207 }
218 else
221 /* First clear all bits that are beyond the type's precision. */
224 ;
228 else
229 {
233 }
235 /* Unsigned types do not suffer sign extension or overflow unless they
236 are a sizetype. */
242 /* If the value's sign bit is set, extend the sign. */
250 {
251 /* Value is negative:
252 set to 1 all the bits that are outside this type's precision. */
256 else
257 {
261 }
262 }
264 /* Return nonzero if signed overflow occurred. */
265 return
268 }
269 \f
270 /* Add two doubleword integers with doubleword result.
271 Each argument is given as two `HOST_WIDE_INT' pieces.
272 One argument is L1 and H1; the other, L2 and H2.
273 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
275 int
279 {
281 HOST_WIDE_INT h;
289 }
291 /* Negate a doubleword integer with doubleword result.
292 Return nonzero if the operation overflows, assuming it's signed.
293 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
294 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
296 int
299 {
301 {
305 }
306 else
307 {
311 }
312 }
313 \f
314 /* Multiply two doubleword integers with doubleword result.
315 Return nonzero if the operation overflows, assuming it's signed.
316 Each argument is given as two `HOST_WIDE_INT' pieces.
317 One argument is L1 and H1; the other, L2 and H2.
318 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
320 int
324 {
339 {
342 {
344 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
346 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
350 }
352 }
356 /* Check for overflow by calculating the top half of the answer in full;
357 it should agree with the low half's sign bit. */
360 {
363 }
365 {
368 }
370 }
371 \f
372 /* Shift the doubleword integer in L1, H1 left by COUNT places
373 keeping only PREC bits of result.
374 Shift right if COUNT is negative.
375 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
376 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
378 void
382 {
386 {
389 }
395 {
396 /* Shifting by the host word size is undefined according to the
397 ANSI standard, so we must handle this as a special case. */
400 }
402 {
405 }
406 else
407 {
411 }
413 /* Sign extend all bits that are beyond the precision. */
421 ;
423 {
426 }
427 else
428 {
432 }
433 }
435 /* Shift the doubleword integer in L1, H1 right by COUNT places
436 keeping only PREC bits of result. COUNT must be positive.
437 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
438 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
440 void
445 {
448 signmask = (arith
456 {
457 /* Shifting by the host word size is undefined according to the
458 ANSI standard, so we must handle this as a special case. */
461 }
463 {
466 }
467 else
468 {
472 }
474 /* Zero / sign extend all bits that are beyond the precision. */
477 {
480 }
482 ;
484 {
487 }
488 else
489 {
493 }
494 }
495 \f
496 /* Rotate the doubleword integer in L1, H1 left by COUNT places
497 keeping only PREC bits of result.
498 Rotate right if COUNT is negative.
499 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
501 void
505 {
517 }
519 /* Rotate the doubleword integer in L1, H1 left by COUNT places
520 keeping only PREC bits of result. COUNT must be positive.
521 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
523 void
527 {
539 }
540 \f
541 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
542 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
543 CODE is a tree code for a kind of division, one of
544 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
545 or EXACT_DIV_EXPR
546 It controls how the quotient is rounded to an integer.
547 Return nonzero if the operation overflows.
548 UNS nonzero says do unsigned division. */
550 int
553 HOST_WIDE_INT hnum_orig,
555 HOST_WIDE_INT hden_orig,
559 {
575 /* Calculate quotient sign and convert operands to unsigned. */
577 {
579 {
581 /* (minimum integer) / (-1) is the only overflow case. */
585 }
587 {
590 }
591 }
596 /* This unsigned division rounds toward zero. */
599 }
603 /* hden != 0 already checked. */
608 }
618 /* Special code for when the divisor < BASE. */
620 {
621 /* hnum != 0 already checked. */
623 {
627 }
628 }
629 else
630 {
631 /* Full double precision division,
632 with thanks to Don Knuth's "Seminumerical Algorithms". */
636 /* Find the highest nonzero divisor digit. */
639 {
642 }
644 /* Insure that the first digit of the divisor is at least BASE/2.
645 This is required by the quotient digit estimation algorithm. */
652 {
656 }
661 {
666 }
667 }
671 /* Main loop */
673 {
674 /* Guess the next quotient digit, quo_est, by dividing the first
675 two remaining dividend digits by the high order quotient digit.
676 quo_est is never low and is at most 2 high. */
683 else
686 /* Refine quo_est so it's usually correct, and at most one high. */
691 quo_est--;
693 /* Try QUO_EST as the quotient digit, by multiplying the
694 divisor by QUO_EST and subtracting from the remaining dividend.
695 Keep in mind that QUO_EST is the I - 1st digit. */
699 {
705 }
707 /* If quo_est was high by one, then num[i] went negative and
708 we need to correct things. */
710 {
711 quo_est--;
714 {
718 }
721 }
723 /* Store the quotient digit. */
725 }
726 }
730 finish_up:
731 /* If result is negative, make it so. */
735 /* Compute trial remainder: rem = num - (quo * den) */
741 {
750 {
751 /* quo = quo - 1; */
754 }
755 else
762 {
765 }
766 else
772 {
778 /* Get absolute values. */
784 /* If (2 * abs (lrem) >= abs (lden)) */
793 {
795 /* quo = quo - 1; */
798 else
799 /* quo = quo + 1; */
802 }
803 else
805 }
810 }
812 /* Compute true remainder: rem = num - (quo * den) */
817 }
818 \f
819 /* Return true if built-in mathematical function specified by CODE
820 preserves the sign of it argument, i.e. -f(x) == f(-x). */
822 static bool
824 {
826 {
843 }
845 }
847 /* Determine whether an expression T can be cheaply negated using
848 the function negate_expr. */
850 static bool
852 {
855 tree type;
864 {
869 /* Check that -CST will not overflow type. */
872 {
877 }
878 else
895 /* -(A + B) -> (-B) - A. */
900 /* -(A + B) -> (-A) - B. */
904 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
913 /* Fall through. */
922 /* Negate -((double)float) as (double)(-float). */
924 {
928 }
932 /* Negate -f(x) as f(-x). */
938 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
940 {
946 }
951 }
953 }
955 /* Given T, an expression, return the negation of T. Allow for T to be
956 null, in which case return null. */
958 static tree
960 {
961 tree type;
962 tree tem;
971 {
982 /* Two's complement FP formats, such as c4x, may overflow. */
988 {
997 }
1005 {
1006 /* -(A + B) -> (-B) - A. */
1010 {
1015 }
1017 /* -(A + B) -> (-A) - B. */
1019 {
1024 }
1025 }
1029 /* - (A - B) -> B - A */
1042 /* Fall through. */
1046 {
1059 }
1063 /* Convert -((double)float) into (double)(-float). */
1065 {
1069 }
1073 /* Negate -f(x) as f(-x). */
1076 {
1083 }
1087 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1089 {
1094 {
1101 }
1102 }
1107 }
1111 }
1112 \f
1113 /* Split a tree IN into a constant, literal and variable parts that could be
1114 combined with CODE to make IN. "constant" means an expression with
1115 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1116 commutative arithmetic operation. Store the constant part into *CONP,
1117 the literal in *LITP and return the variable part. If a part isn't
1118 present, set it to null. If the tree does not decompose in this way,
1119 return the entire tree as the variable part and the other parts as null.
1121 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1122 case, we negate an operand that was subtracted. Except if it is a
1123 literal for which we use *MINUS_LITP instead.
1125 If NEGATE_P is true, we are negating all of IN, again except a literal
1126 for which we use *MINUS_LITP instead.
1128 If IN is itself a literal or constant, return it as appropriate.
1130 Note that we do not guarantee that any of the three values will be the
1131 same type as IN, but they will have the same signedness and mode. */
1133 static tree
1136 {
1143 /* Strip any conversions that don't change the machine mode or signedness. */
1150 /* We can associate addition and subtraction together (even
1151 though the C standard doesn't say so) for integers because
1152 the value is not affected. For reals, the value might be
1153 affected, so we can't. */
1156 {
1162 /* First see if either of the operands is a literal, then a constant. */
1173 /* If we haven't dealt with either operand, this is not a case we can
1174 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1179 else
1182 /* Now do any needed negations. */
1189 }
1192 else
1196 {
1203 }
1206 }
1208 /* Re-associate trees split by the above function. T1 and T2 are either
1209 expressions to associate or null. Return the new expression, if any. If
1210 we build an operation, do it in TYPE and with CODE. */
1212 static tree
1214 {
1220 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1221 try to fold this since we will have infinite recursion. But do
1222 deal with any NEGATE_EXPRs. */
1225 {
1227 {
1234 }
1237 }
1241 }
1242 \f
1243 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1244 to produce a new constant.
1246 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1248 tree
1250 {
1254 HOST_WIDE_INT hi;
1256 HOST_WIDE_INT garbageh;
1257 tree t;
1260 int is_sizetype
1271 {
1287 /* It's unclear from the C standard whether shifts can overflow.
1288 The following code ignores overflow; perhaps a C standard
1289 interpretation ruling is needed. */
1319 /* This is a shortcut for a common special case. */
1324 {
1330 }
1332 /* ... fall through ... */
1336 {
1339 }
1342 {
1345 }
1352 /* This is a shortcut for a common special case. */
1357 {
1362 }
1364 /* ... fall through ... */
1380 else
1386 else
1392 }
1394 /* If this is for a sizetype, can be represented as one (signed)
1395 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1396 constants. */
1402 else
1403 {
1406 }
1409 = ((notrunc
1416 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1417 So check if force_fit_type truncated the value. */
1428 }
1430 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1431 constant. We assume ARG1 and ARG2 have the same data type, or at least
1432 are the same kind of constant and the same machine mode.
1434 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1436 static tree
1438 {
1446 {
1448 REAL_VALUE_TYPE d1;
1449 REAL_VALUE_TYPE d2;
1450 REAL_VALUE_TYPE value;
1459 /* Don't perform operation if we honor signaling NaNs and
1460 either operand is a NaN. */
1465 /* Don't perform operation if it would raise a division
1466 by zero exception. */
1472 /* If either operand is a NaN, just return it. Otherwise, set up
1473 for floating-point trap; we return an overflow. */
1491 }
1493 {
1499 tree t;
1502 {
1522 notrunc),
1528 notrunc));
1532 {
1533 tree magsquared
1537 notrunc);
1540 const_binop
1545 notrunc),
1547 notrunc),
1548 notrunc),
1550 const_binop
1555 notrunc),
1557 notrunc),
1558 notrunc),
1560 }
1565 }
1567 }
1569 }
1571 /* These are the hash table functions for the hash table of INTEGER_CST
1572 nodes of a sizetype. */
1574 /* Return the hash code code X, an INTEGER_CST. */
1576 static hashval_t
1578 {
1584 }
1586 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1587 is the same as that given by *Y, which is the same. */
1589 static int
1591 {
1599 }
1600 \f
1601 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1602 bits are given by NUMBER and of the sizetype represented by KIND. */
1604 tree
1606 {
1608 }
1610 /* Likewise, but the desired type is specified explicitly. */
1614 htab_t size_htab;
1616 tree
1618 {
1622 {
1625 }
1627 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1628 hash table, we return the value from the hash table. Otherwise, we
1629 place that in the hash table and make a new node for the next time. */
1638 {
1644 }
1645 else
1647 }
1649 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1650 is a tree code. The type of the result is taken from the operands.
1651 Both must be the same type integer type and it must be a size type.
1652 If the operands are constant, so is the result. */
1654 tree
1656 {
1663 /* Handle the special case of two integer constants faster. */
1665 {
1666 /* And some specific cases even faster than that. */
1675 /* Handle general case of two integer constants. */
1677 }
1683 }
1685 /* Given two values, either both of sizetype or both of bitsizetype,
1686 compute the difference between the two values. Return the value
1687 in signed type corresponding to the type of the operands. */
1689 tree
1691 {
1693 tree ctype;
1699 /* If the type is already signed, just do the simple thing. */
1706 /* If either operand is not a constant, do the conversions to the signed
1707 type and subtract. The hardware will do the right thing with any
1708 overflow in the subtraction. */
1713 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1714 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1715 overflow) and negate (which can't either). Special-case a result
1716 of zero while we're here. */
1721 else
1725 }
1726 \f
1728 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1729 type TYPE. If no simplification can be done return NULL_TREE. */
1731 static tree
1733 {
1735 tree t;
1741 {
1743 {
1744 /* If we would build a constant wider than GCC supports,
1745 leave the conversion unfolded. */
1749 /* If we are trying to make a sizetype for a small integer, use
1750 size_int to pick up cached types to reduce duplicate nodes. */
1756 /* Given an integer constant, make new constant with new type,
1757 appropriately sign-extended or truncated. */
1761 /* Indicate an overflow if (1) ARG1 already overflowed,
1762 or (2) force_fit_type indicates an overflow.
1763 Tell force_fit_type that an overflow has already occurred
1764 if ARG1 is a too-large unsigned value and T is signed.
1765 But don't indicate an overflow if converting a pointer. */
1776 }
1778 {
1779 /* The following code implements the floating point to integer
1780 conversion rules required by the Java Language Specification,
1781 that IEEE NaNs are mapped to zero and values that overflow
1782 the target precision saturate, i.e. values greater than
1783 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1784 are mapped to INT_MIN. These semantics are allowed by the
1785 C and C++ standards that simply state that the behavior of
1786 FP-to-integer conversion is unspecified upon overflow. */
1790 REAL_VALUE_TYPE r;
1794 {
1813 }
1815 /* If R is NaN, return zero and show we have an overflow. */
1817 {
1821 }
1823 /* See if R is less than the lower bound or greater than the
1824 upper bound. */
1827 {
1831 {
1835 }
1836 }
1839 {
1842 {
1845 {
1849 }
1850 }
1851 }
1863 }
1864 }
1866 {
1870 {
1872 {
1873 /* We make a copy of ARG1 so that we don't modify an
1874 existing constant tree. */
1878 }
1889 }
1890 }
1892 }
1894 /* Convert expression ARG to type TYPE. Used by the middle-end for
1895 simple conversions in preference to calling the front-end's convert. */
1897 tree
1899 {
1901 tree tem;
1918 {
1920 {
1924 }
1929 {
1932 }
1936 }
1938 {
1940 {
1944 }
1946 {
1950 }
1958 {
1961 }
1962 }
1964 {
1972 {
1976 {
1980 }
1988 }
1989 }
1991 {
1998 }
2002 }
2003 \f
2004 /* Return an expr equal to X but certainly not valid as an lvalue. */
2006 tree
2008 {
2009 /* We only need to wrap lvalue tree codes. */
2011 {
2044 /* Assume the worst for front-end tree codes. */
2048 }
2050 }
2052 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2053 Zero means allow extended lvalues. */
2057 /* When pedantic, return an expr equal to X but certainly not valid as a
2058 pedantic lvalue. Otherwise, return X. */
2060 tree
2062 {
2065 else
2067 }
2068 \f
2069 /* Given a tree comparison code, return the code that is the logical inverse
2070 of the given code. It is not safe to do this for floating-point
2071 comparisons, except for NE_EXPR and EQ_EXPR, so we receive a machine mode
2072 as well: if reversing the comparison is unsafe, return ERROR_MARK. */
2074 static enum tree_code
2076 {
2081 {
2112 }
2113 }
2115 /* Similar, but return the comparison that results if the operands are
2116 swapped. This is safe for floating-point. */
2118 enum tree_code
2120 {
2122 {
2136 }
2137 }
2140 /* Convert a comparison tree code from an enum tree_code representation
2141 into a compcode bit-based encoding. This function is the inverse of
2142 compcode_to_comparison. */
2144 static enum comparison_code
2146 {
2148 {
2179 }
2180 }
2182 /* Convert a compcode bit-based encoding of a comparison operator back
2183 to GCC's enum tree_code representation. This function is the
2184 inverse of comparison_to_compcode. */
2186 static enum tree_code
2188 {
2190 {
2221 }
2222 }
2224 /* Return a tree for the comparison which is the combination of
2225 doing the AND or OR (depending on CODE) of the two operations LCODE
2226 and RCODE on the identical operands LL_ARG and LR_ARG. Take into account
2227 the possibility of trapping if the mode has NaNs, and return NULL_TREE
2228 if this makes the transformation invalid. */
2230 tree
2234 {
2241 {
2252 }
2255 {
2256 /* Eliminate unordered comparisons, as well as LTGT and ORD
2257 which are not used unless the mode has NaNs. */
2263 }
2265 {
2266 /* Check that the original operation and the optimized ones will trap
2267 under the same condition. */
2278 /* In a short-circuited boolean expression the LHS might be
2279 such that the RHS, if evaluated, will never trap. For
2280 example, in ORD (x, y) && (x < y), we evaluate the RHS only
2281 if neither x nor y is NaN. (This is a mixed blessing: for
2282 example, the expression above will never trap, hence
2283 optimizing it to x < y would be invalid). */
2288 /* If the comparison was short-circuited, and only the RHS
2289 trapped, we may now generate a spurious trap. */
2294 /* If we changed the conditions that cause a trap, we lose. */
2297 }
2303 else
2306 }
2308 /* Return nonzero if CODE is a tree code that represents a truth value. */
2310 static int
2312 {
2317 }
2318 \f
2319 /* Return nonzero if two operands (typically of the same tree node)
2320 are necessarily equal. If either argument has side-effects this
2321 function returns zero. FLAGS modifies behavior as follows:
2323 If OEP_ONLY_CONST is set, only return nonzero for constants.
2324 This function tests whether the operands are indistinguishable;
2325 it does not test whether they are equal using C's == operation.
2326 The distinction is important for IEEE floating point, because
2327 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2328 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2330 If OEP_ONLY_CONST is unset, a VAR_DECL is considered equal to itself
2331 even though it may hold multiple values during a function.
2332 This is because a GCC tree node guarantees that nothing else is
2333 executed between the evaluation of its "operands" (which may often
2334 be evaluated in arbitrary order). Hence if the operands themselves
2335 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2336 same value in each operand/subexpression. Hence leaving OEP_ONLY_CONST
2337 unset means assuming isochronic (or instantaneous) tree equivalence.
2338 Unless comparing arbitrary expression trees, such as from different
2339 statements, this flag can usually be left unset.
2341 If OEP_PURE_SAME is set, then pure functions with identical arguments
2342 are considered the same. It is used when the caller has other ways
2343 to ensure that global memory is unchanged in between. */
2345 int
2347 {
2348 /* If one is specified and the other isn't, they aren't equal and if
2349 neither is specified, they are.
2351 ??? This is temporary and is meant only to handle the cases of the
2352 optional operands for COMPONENT_REF and ARRAY_REF. */
2357 /* If either is ERROR_MARK, they aren't equal. */
2361 /* If both types don't have the same signedness, then we can't consider
2362 them equal. We must check this before the STRIP_NOPS calls
2363 because they may change the signedness of the arguments. */
2371 /* This is needed for conversions and for COMPONENT_REF.
2372 Might as well play it safe and always test this. */
2378 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2379 We don't care about side effects in that case because the SAVE_EXPR
2380 takes care of that for us. In all other cases, two expressions are
2381 equal if they have no side effects. If we have two identical
2382 expressions with side effects that should be treated the same due
2383 to the only side effects being identical SAVE_EXPR's, that will
2384 be detected in the recursive calls below. */
2390 /* Next handle constant cases, those for which we can return 1 even
2391 if ONLY_CONST is set. */
2394 {
2407 {
2417 {
2419 flags))
2423 }
2426 }
2430 flags)
2432 flags));
2445 }
2451 {
2453 /* Two conversions are equal only if signedness and modes match. */
2470 /* For commutative ops, allow the other order. */
2478 /* If either of the pointer (or reference) expressions we are
2479 dereferencing contain a side effect, these cannot be equal. */
2485 {
2522 }
2526 {
2552 /* If the CALL_EXPRs call different functions, then they
2553 clearly can not be equal. */
2558 {
2562 else
2566 }
2568 /* Now see if all the arguments are the same. operand_equal_p
2569 does not handle TREE_LIST, so we walk the operands here
2570 feeding them to operand_equal_p. */
2574 {
2576 flags))
2581 }
2583 /* If we get here and both argument lists are exhausted
2584 then the CALL_EXPRs are equal. */
2589 }
2592 /* Consider __builtin_sqrt equal to sqrt. */
2600 }
2601 }
2602 \f
2603 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2604 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2606 When in doubt, return 0. */
2608 static int
2610 {
2622 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2623 and see if the inner values are the same. This removes any
2624 signedness comparison, which doesn't matter here. */
2631 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2632 actual comparison operand, ARG0.
2634 First throw away any conversions to wider types
2635 already present in the operands. */
2644 {
2647 /* Make sure shorter operand is extended the right way
2648 to match the longer operand. */
2654 }
2657 }
2658 \f
2659 /* See if ARG is an expression that is either a comparison or is performing
2660 arithmetic on comparisons. The comparisons must only be comparing
2661 two different values, which will be stored in *CVAL1 and *CVAL2; if
2662 they are nonzero it means that some operands have already been found.
2663 No variables may be used anywhere else in the expression except in the
2664 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2665 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2667 If this is true, return 1. Otherwise, return zero. */
2669 static int
2671 {
2675 /* We can handle some of the 'e' cases here. */
2685 {
2686 /* If we've already found a CVAL1 or CVAL2, this expression is
2687 two complex to handle. */
2693 }
2696 {
2719 /* First see if we can handle the first operand, then the second. For
2720 the second operand, we know *CVAL1 can't be zero. It must be that
2721 one side of the comparison is each of the values; test for the
2722 case where this isn't true by failing if the two operands
2723 are the same. */
2732 ;
2736 ;
2737 else
2741 ;
2745 ;
2746 else
2753 }
2754 }
2755 \f
2756 /* ARG is a tree that is known to contain just arithmetic operations and
2757 comparisons. Evaluate the operations in the tree substituting NEW0 for
2758 any occurrence of OLD0 as an operand of a comparison and likewise for
2759 NEW1 and OLD1. */
2761 static tree
2763 {
2768 /* We can handle some of the 'e' cases here. */
2776 {
2791 {
2808 }
2809 /* Fall through - ??? */
2812 {
2816 /* We need to check both for exact equality and tree equality. The
2817 former will be true if the operand has a side-effect. In that
2818 case, we know the operand occurred exactly once. */
2831 }
2835 }
2836 }
2837 \f
2838 /* Return a tree for the case when the result of an expression is RESULT
2839 converted to TYPE and OMITTED was previously an operand of the expression
2840 but is now not needed (e.g., we folded OMITTED * 0).
2842 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2843 the conversion of RESULT to TYPE. */
2845 tree
2847 {
2854 }
2856 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2858 static tree
2860 {
2867 }
2869 /* Return a tree for the case when the result of an expression is RESULT
2870 converted to TYPE and OMITTED1 and OMITTED2 were previously operands
2871 of the expression but are now not needed.
2873 If OMITTED1 or OMITTED2 has side effects, they must be evaluated.
2874 If both OMITTED1 and OMITTED2 have side effects, OMITTED1 is
2875 evaluated before OMITTED2. Otherwise, if neither has side effects,
2876 just do the conversion of RESULT to TYPE. */
2878 tree
2880 {
2889 }
2891 \f
2892 /* Return a simplified tree node for the truth-negation of ARG. This
2893 never alters ARG itself. We assume that ARG is an operation that
2894 returns a truth value (0 or 1).
2896 FIXME: one would think we would fold the result, but it causes
2897 problems with the dominator optimizer. */
2898 tree
2900 {
2907 /* If this is a comparison, we can simply invert it, except for
2908 floating-point non-equality comparisons, in which case we just
2909 enclose a TRUTH_NOT_EXPR around what we have. */
2912 {
2915 && flag_trapping_math
2919 else
2920 {
2925 else
2928 }
2929 }
2932 {
2947 /* Here we can invert either operand. We invert the first operand
2948 unless the second operand is a TRUTH_NOT_EXPR in which case our
2949 result is the XOR of the first operand with the inside of the
2950 negation of the second operand. */
2955 else
3009 }
3013 }
3015 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
3016 operands are another bit-wise operation with a common input. If so,
3017 distribute the bit operations to save an operation and possibly two if
3018 constants are involved. For example, convert
3019 (A | B) & (A | C) into A | (B & C)
3020 Further simplification will occur if B and C are constants.
3022 If this optimization cannot be done, 0 will be returned. */
3024 static tree
3026 {
3027 tree common;
3037 {
3041 }
3043 {
3047 }
3049 {
3053 }
3055 {
3059 }
3060 else
3065 }
3066 \f
3067 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
3068 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
3070 static tree
3073 {
3080 }
3082 /* Optimize a bit-field compare.
3084 There are two cases: First is a compare against a constant and the
3085 second is a comparison of two items where the fields are at the same
3086 bit position relative to the start of a chunk (byte, halfword, word)
3087 large enough to contain it. In these cases we can avoid the shift
3088 implicit in bitfield extractions.
3090 For constants, we emit a compare of the shifted constant with the
3091 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
3092 compared. For two fields at the same position, we do the ANDs with the
3093 similar mask and compare the result of the ANDs.
3095 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
3096 COMPARE_TYPE is the type of the comparison, and LHS and RHS
3097 are the left and right operands of the comparison, respectively.
3099 If the optimization described above can be done, we return the resulting
3100 tree. Otherwise we return zero. */
3102 static tree
3105 {
3114 tree mask;
3115 tree offset;
3117 /* Get all the information about the extractions being done. If the bit size
3118 if the same as the size of the underlying object, we aren't doing an
3119 extraction at all and so can do nothing. We also don't want to
3120 do anything if the inner expression is a PLACEHOLDER_EXPR since we
3121 then will no longer be able to replace it. */
3129 {
3130 /* If this is not a constant, we can only do something if bit positions,
3131 sizes, and signedness are the same. */
3139 }
3141 /* See if we can find a mode to refer to this field. We should be able to,
3142 but fail if we can't. */
3151 /* Set signed and unsigned types of the precision of this mode for the
3152 shifts below. */
3156 /* Compute the bit position and size for the new reference and our offset
3157 within it. If the new reference is the same size as the original, we
3158 won't optimize anything, so return zero. */
3168 /* Make the mask to be used against the extracted field. */
3178 /* If not comparing with constant, just rework the comparison
3179 and return. */
3184 mask),
3188 mask));
3190 /* Otherwise, we are handling the constant case. See if the constant is too
3191 big for the field. Warn and return a tree of for 0 (false) if so. We do
3192 this not only for its own sake, but to avoid having to test for this
3193 error case below. If we didn't, we might generate wrong code.
3195 For unsigned fields, the constant shifted right by the field length should
3196 be all zero. For signed fields, the high-order bits should agree with
3197 the sign bit. */
3200 {
3204 {
3208 }
3209 }
3210 else
3211 {
3215 {
3219 }
3220 }
3222 /* Single-bit compares should always be against zero. */
3224 {
3227 }
3229 /* Make a new bitfield reference, shift the constant over the
3230 appropriate number of bits and mask it with the computed mask
3231 (in case this was a signed field). If we changed it, make a new one. */
3234 {
3237 }
3247 rhs);
3248 }
3249 \f
3250 /* Subroutine for fold_truthop: decode a field reference.
3252 If EXP is a comparison reference, we return the innermost reference.
3254 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3255 set to the starting bit number.
3257 If the innermost field can be completely contained in a mode-sized
3258 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3260 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3261 otherwise it is not changed.
3263 *PUNSIGNEDP is set to the signedness of the field.
3265 *PMASK is set to the mask used. This is either contained in a
3266 BIT_AND_EXPR or derived from the width of the field.
3268 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3270 Return 0 if this is not a component reference or is one that we can't
3271 do anything with. */
3273 static tree
3278 {
3282 tree unsigned_type;
3285 /* All the optimizations using this function assume integer fields.
3286 There are problems with FP fields since the type_for_size call
3287 below can fail for, e.g., XFmode. */
3291 /* We are interested in the bare arrangement of bits, so strip everything
3292 that doesn't affect the machine mode. However, record the type of the
3293 outermost expression if it may matter below. */
3301 {
3307 }
3316 /* If the number of bits in the reference is the same as the bitsize of
3317 the outer type, then the outer type gives the signedness. Otherwise
3318 (in case of a small bitfield) the signedness is unchanged. */
3322 /* Compute the mask to access the bitfield. */
3332 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3340 }
3342 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3343 bit positions. */
3345 static int
3347 {
3350 tree tmask;
3355 return
3362 }
3364 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3365 represents the sign bit of EXP's type. If EXP represents a sign
3366 or zero extension, also test VAL against the unextended type.
3367 The return value is the (sub)expression whose sign bit is VAL,
3368 or NULL_TREE otherwise. */
3370 static tree
3372 {
3376 tree t;
3378 /* Tree EXP must have an integral type. */
3383 /* Tree VAL must be an integer constant. */
3390 {
3397 }
3398 else
3399 {
3406 }
3408 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3409 treat VAL as if it were unsigned. */
3414 /* Handle extension from a narrower type. */
3420 }
3422 /* Subroutine for fold_truthop: determine if an operand is simple enough
3423 to be evaluated unconditionally. */
3425 static int
3427 {
3428 /* Strip any conversions that don't change the machine mode. */
3440 /* Don't regard global variables as simple. They may be
3441 allocated in ways unknown to the compiler (shared memory,
3442 #pragma weak, etc). */
3445 /* Loading a static variable is unduly expensive, but global
3446 registers aren't expensive. */
3448 }
3449 \f
3450 /* The following functions are subroutines to fold_range_test and allow it to
3451 try to change a logical combination of comparisons into a range test.
3453 For example, both
3454 X == 2 || X == 3 || X == 4 || X == 5
3455 and
3456 X >= 2 && X <= 5
3457 are converted to
3458 (unsigned) (X - 2) <= 3
3460 We describe each set of comparisons as being either inside or outside
3461 a range, using a variable named like IN_P, and then describe the
3462 range with a lower and upper bound. If one of the bounds is omitted,
3463 it represents either the highest or lowest value of the type.
3465 In the comments below, we represent a range by two numbers in brackets
3466 preceded by a "+" to designate being inside that range, or a "-" to
3467 designate being outside that range, so the condition can be inverted by
3468 flipping the prefix. An omitted bound is represented by a "-". For
3469 example, "- [-, 10]" means being outside the range starting at the lowest
3470 possible value and ending at 10, in other words, being greater than 10.
3471 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3472 always false.
3474 We set up things so that the missing bounds are handled in a consistent
3475 manner so neither a missing bound nor "true" and "false" need to be
3476 handled using a special case. */
3478 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3479 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3480 and UPPER1_P are nonzero if the respective argument is an upper bound
3481 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3482 must be specified for a comparison. ARG1 will be converted to ARG0's
3483 type if both are specified. */
3485 static tree
3488 {
3489 tree tem;
3493 /* If neither arg represents infinity, do the normal operation.
3494 Else, if not a comparison, return infinity. Else handle the special
3495 comparison rules. Note that most of the cases below won't occur, but
3496 are handled for consistency. */
3499 {
3504 }
3509 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3510 for neither. In real maths, we cannot assume open ended ranges are
3511 the same. But, this is computer arithmetic, where numbers are finite.
3512 We can therefore make the transformation of any unbounded range with
3513 the value Z, Z being greater than any representable number. This permits
3514 us to treat unbounded ranges as equal. */
3518 {
3539 }
3542 }
3543 \f
3544 /* Given EXP, a logical expression, set the range it is testing into
3545 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3546 actually being tested. *PLOW and *PHIGH will be made of the same type
3547 as the returned expression. If EXP is not a comparison, we will most
3548 likely not be returning a useful value and range. */
3550 static tree
3552 {
3559 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3560 and see if we can refine the range. Some of the cases below may not
3561 happen, but it doesn't seem worth worrying about this. We "continue"
3562 the outer loop when we've changed something; otherwise we "break"
3563 the switch, which will "break" the while. */
3569 {
3574 {
3586 }
3589 {
3596 /* We can only do something if the range is testing for zero
3597 and if the second operand is an integer constant. Note that
3598 saying something is "in" the range we make is done by
3599 complementing IN_P since it will set in the initial case of
3600 being not equal to zero; "out" is leaving it alone. */
3607 {
3628 }
3630 /* If this is an unsigned comparison, we also know that EXP is
3631 greater than or equal to zero. We base the range tests we make
3632 on that fact, so we record it here so we can parse existing
3633 range tests. We test arg0_type since often the return type
3634 of, e.g. EQ_EXPR, is boolean. */
3636 {
3639 NULL_TREE))
3644 /* If the high bound is missing, but we have a nonzero low
3645 bound, reverse the range so it goes from zero to the low bound
3646 minus 1. */
3648 {
3653 }
3654 }
3660 /* (-x) IN [a,b] -> x in [-b, -a] */
3672 /* ~ X -> -X - 1 */
3681 /* If EXP is signed, any overflow in the computation is undefined,
3682 so we don't worry about it so long as our computations on
3683 the bounds don't overflow. For unsigned, overflow is defined
3684 and this is exactly the right thing. */
3693 /* Check for an unsigned range which has wrapped around the maximum
3694 value thus making n_high < n_low, and normalize it. */
3696 {
3702 /* If the range is of the form +/- [ x+1, x ], we won't
3703 be able to normalize it. But then, it represents the
3704 whole range or the empty set, so make it
3705 +/- [ -, - ]. */
3709 else
3711 }
3712 else
3736 /* If we're converting arg0 from an unsigned type, to exp,
3737 a signed type, we will be doing the comparison as unsigned.
3738 The tests above have already verified that LOW and HIGH
3739 are both positive.
3741 So we have to ensure that we will handle large unsigned
3742 values the same way that the current signed bounds treat
3743 negative values. */
3746 {
3747 tree high_positive;
3751 /* A range without an upper bound is, naturally, unbounded.
3752 Since convert would have cropped a very large value, use
3753 the max value for the destination type. */
3754 high_positive
3761 high_positive),
3763 integer_one_node)));
3765 /* If the low bound is specified, "and" the range with the
3766 range for which the original unsigned value will be
3767 positive. */
3769 {
3773 high_positive))
3777 }
3778 else
3779 {
3780 /* Otherwise, "or" the range with the range of the input
3781 that will be interpreted as negative. */
3785 high_positive))
3789 }
3790 }
3798 }
3801 }
3803 /* If EXP is a constant, we can evaluate whether this is true or false. */
3805 {
3812 }
3816 }
3817 \f
3818 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3819 type, TYPE, return an expression to test if EXP is in (or out of, depending
3820 on IN_P) the range. Return 0 if the test couldn't be created. */
3822 static tree
3824 {
3826 tree value;
3829 {
3835 }
3850 {
3852 {
3856 }
3858 }
3860 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3862 {
3864 HOST_WIDE_INT hi;
3869 {
3872 }
3873 else
3874 {
3877 }
3880 {
3882 {
3885 }
3888 }
3889 }
3893 {
3896 /* Check if (unsigned) INT_MAX + 1 == (unsigned) INT_MIN
3897 for the type in question, as we rely on this here. */
3899 {
3910 {
3916 }
3920 }
3921 }
3927 value);
3930 }
3931 \f
3932 /* Given two ranges, see if we can merge them into one. Return 1 if we
3933 can, 0 if we can't. Set the output range into the specified parameters. */
3935 static int
3938 {
3942 tree tem;
3952 /* Make range 0 be the range that starts first, or ends last if they
3953 start at the same value. Swap them if it isn't. */
3956 || (lowequal
3959 {
3963 }
3965 /* Now flag two cases, whether the ranges are disjoint or whether the
3966 second range is totally subsumed in the first. Note that the tests
3967 below are simplified by the ones above. */
3973 /* We now have four cases, depending on whether we are including or
3974 excluding the two ranges. */
3976 {
3977 /* If they don't overlap, the result is false. If the second range
3978 is a subset it is the result. Otherwise, the range is from the start
3979 of the second to the end of the first. */
3984 else
3986 }
3989 {
3990 /* If they don't overlap, the result is the first range. If they are
3991 equal, the result is false. If the second range is a subset of the
3992 first, and the ranges begin at the same place, we go from just after
3993 the end of the first range to the end of the second. If the second
3994 range is not a subset of the first, or if it is a subset and both
3995 ranges end at the same place, the range starts at the start of the
3996 first range and ends just before the second range.
3997 Otherwise, we can't describe this as a single range. */
4003 {
4007 }
4009 {
4013 }
4014 else
4016 }
4019 {
4020 /* If they don't overlap, the result is the second range. If the second
4021 is a subset of the first, the result is false. Otherwise,
4022 the range starts just after the first range and ends at the
4023 end of the second. */
4028 else
4029 {
4033 }
4034 }
4036 else
4037 {
4038 /* The case where we are excluding both ranges. Here the complex case
4039 is if they don't overlap. In that case, the only time we have a
4040 range is if they are adjacent. If the second is a subset of the
4041 first, the result is the first. Otherwise, the range to exclude
4042 starts at the beginning of the first range and ends at the end of the
4043 second. */
4045 {
4052 else
4053 {
4054 /* Canonicalize - [min, x] into - [-, x]. */
4057 {
4062 /* FALLTHROUGH */
4076 }
4078 /* Canonicalize - [x, max] into - [x, -]. */
4081 {
4086 /* FALLTHROUGH */
4102 }
4104 /* The ranges might be also adjacent between the maximum and
4105 minimum values of the given type. For
4106 - [{min,-}, x] and - [y, {max,-}] ranges where x + 1 < y
4107 return + [x + 1, y - 1]. */
4109 {
4118 }
4119 else
4121 }
4122 }
4125 else
4127 }
4131 }
4132 \f
4134 /* Subroutine of fold, looking inside expressions of the form
4135 A op B ? A : C, where ARG0, ARG1 and ARG2 are the three operands
4136 of the COND_EXPR. This function is being used also to optimize
4137 A op B ? C : A, by reversing the comparison first.
4139 Return a folded expression whose code is not a COND_EXPR
4140 anymore, or NULL_TREE if no folding opportunity is found. */
4142 static tree
4144 {
4149 tree tem;
4154 /* If we have A op 0 ? A : -A, consider applying the following
4155 transformations:
4157 A == 0? A : -A same as -A
4158 A != 0? A : -A same as A
4159 A >= 0? A : -A same as abs (A)
4160 A > 0? A : -A same as abs (A)
4161 A <= 0? A : -A same as -abs (A)
4162 A < 0? A : -A same as -abs (A)
4164 None of these transformations work for modes with signed
4165 zeros. If A is +/-0, the first two transformations will
4166 change the sign of the result (from +0 to -0, or vice
4167 versa). The last four will fix the sign of the result,
4168 even though the original expressions could be positive or
4169 negative, depending on the sign of A.
4171 Note that all these transformations are correct if A is
4172 NaN, since the two alternatives (A and -A) are also NaNs. */
4179 {
4201 }
4203 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
4204 A == 0 ? A : 0 is always 0 unless A is -0. Note that
4205 both transformations are correct when A is NaN: A != 0
4206 is then true, and A == 0 is false. */
4209 {
4214 }
4216 /* Try some transformations of A op B ? A : B.
4218 A == B? A : B same as B
4219 A != B? A : B same as A
4220 A >= B? A : B same as max (A, B)
4221 A > B? A : B same as max (B, A)
4222 A <= B? A : B same as min (A, B)
4223 A < B? A : B same as min (B, A)
4225 As above, these transformations don't work in the presence
4226 of signed zeros. For example, if A and B are zeros of
4227 opposite sign, the first two transformations will change
4228 the sign of the result. In the last four, the original
4229 expressions give different results for (A=+0, B=-0) and
4230 (A=-0, B=+0), but the transformed expressions do not.
4232 The first two transformations are correct if either A or B
4233 is a NaN. In the first transformation, the condition will
4234 be false, and B will indeed be chosen. In the case of the
4235 second transformation, the condition A != B will be true,
4236 and A will be chosen.
4238 The conversions to max() and min() are not correct if B is
4239 a number and A is not. The conditions in the original
4240 expressions will be false, so all four give B. The min()
4241 and max() versions would give a NaN instead. */
4243 {
4248 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
4250 {
4254 }
4257 {
4264 /* In C++ a ?: expression can be an lvalue, so put the
4265 operand which will be used if they are equal first
4266 so that we can convert this back to the
4267 corresponding COND_EXPR. */
4288 }
4289 }
4291 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
4292 we might still be able to simplify this. For example,
4293 if C1 is one less or one more than C2, this might have started
4294 out as a MIN or MAX and been transformed by this function.
4295 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
4301 {
4303 /* We can replace A with C1 in this case. */
4308 /* If C1 is C2 + 1, this is min(A, C2). */
4310 OEP_ONLY_CONST)
4314 OEP_ONLY_CONST))
4320 /* If C1 is C2 - 1, this is min(A, C2). */
4322 OEP_ONLY_CONST)
4326 OEP_ONLY_CONST))
4332 /* If C1 is C2 - 1, this is max(A, C2). */
4334 OEP_ONLY_CONST)
4338 OEP_ONLY_CONST))
4344 /* If C1 is C2 + 1, this is max(A, C2). */
4346 OEP_ONLY_CONST)
4350 OEP_ONLY_CONST))
4358 }
4361 }
4364 \f
4365 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
4366 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
4367 #endif
4369 /* EXP is some logical combination of boolean tests. See if we can
4370 merge it into some range test. Return the new tree if so. */
4372 static tree
4374 {
4381 tree tem;
4383 /* If this is an OR operation, invert both sides; we will invert
4384 again at the end. */
4388 /* If both expressions are the same, if we can merge the ranges, and we
4389 can build the range test, return it or it inverted. If one of the
4390 ranges is always true or always false, consider it to be the same
4391 expression as the other. */
4401 /* On machines where the branch cost is expensive, if this is a
4402 short-circuited branch and the underlying object on both sides
4403 is the same, make a non-short-circuit operation. */
4409 {
4410 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
4411 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
4412 which cases we can't do this. */
4421 {
4433 }
4434 }
4437 }
4438 \f
4439 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
4440 bit value. Arrange things so the extra bits will be set to zero if and
4441 only if C is signed-extended to its full width. If MASK is nonzero,
4442 it is an INTEGER_CST that should be AND'ed with the extra bits. */
4444 static tree
4446 {
4449 tree temp;
4454 /* We work by getting just the sign bit into the low-order bit, then
4455 into the high-order bit, then sign-extend. We then XOR that value
4456 with C. */
4460 /* We must use a signed type in order to get an arithmetic right shift.
4461 However, we must also avoid introducing accidental overflows, so that
4462 a subsequent call to integer_zerop will work. Hence we must
4463 do the type conversion here. At this point, the constant is either
4464 zero or one, and the conversion to a signed type can never overflow.
4465 We could get an overflow if this conversion is done anywhere else. */
4474 /* If necessary, convert the type back to match the type of C. */
4479 }
4480 \f
4481 /* Find ways of folding logical expressions of LHS and RHS:
4482 Try to merge two comparisons to the same innermost item.
4483 Look for range tests like "ch >= '0' && ch <= '9'".
4484 Look for combinations of simple terms on machines with expensive branches
4485 and evaluate the RHS unconditionally.
4487 For example, if we have p->a == 2 && p->b == 4 and we can make an
4488 object large enough to span both A and B, we can do this with a comparison
4489 against the object ANDed with the a mask.
4491 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
4492 operations to do this with one comparison.
4494 We check for both normal comparisons and the BIT_AND_EXPRs made this by
4495 function and the one above.
4497 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
4498 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
4500 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
4501 two operands.
4503 We return the simplified tree or 0 if no optimization is possible. */
4505 static tree
4507 {
4508 /* If this is the "or" of two comparisons, we can do something if
4509 the comparisons are NE_EXPR. If this is the "and", we can do something
4510 if the comparisons are EQ_EXPR. I.e.,
4511 (a->b == 2 && a->c == 4) can become (a->new == NEW).
4513 WANTED_CODE is this operation code. For single bit fields, we can
4514 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
4515 comparison for one-bit fields. */
4535 /* Start by getting the comparison codes. Fail if anything is volatile.
4536 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
4537 it were surrounded with a NE_EXPR. */
4546 {
4549 }
4552 {
4555 }
4565 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
4568 {
4569 tree result;
4572 {
4577 }
4580 {
4586 }
4587 }
4592 /* If the RHS can be evaluated unconditionally and its operands are
4593 simple, it wins to evaluate the RHS unconditionally on machines
4594 with expensive branches. In this case, this isn't a comparison
4595 that can be merged. Avoid doing this if the RHS is a floating-point
4596 comparison since those can trap. */
4602 {
4603 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4613 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4624 }
4626 /* See if the comparisons can be merged. Then get all the parameters for
4627 each side. */
4651 /* It must be true that the inner operation on the lhs of each
4652 comparison must be the same if we are to be able to do anything.
4653 Then see if we have constants. If not, the same must be true for
4654 the rhs's. */
4665 else
4668 /* If either comparison code is not correct for our logical operation,
4669 fail. However, we can convert a one-bit comparison against zero into
4670 the opposite comparison against that bit being set in the field. */
4674 {
4676 {
4677 /* Make the left operand unsigned, since we are only interested
4678 in the value of one bit. Otherwise we are doing the wrong
4679 thing below. */
4682 }
4683 else
4685 }
4687 /* This is analogous to the code for l_const above. */
4689 {
4691 {
4694 }
4695 else
4697 }
4699 /* After this point all optimizations will generate bit-field
4700 references, which we might not want. */
4704 /* See if we can find a mode that contains both fields being compared on
4705 the left. If we can't, fail. Otherwise, update all constants and masks
4706 to be relative to a field of that size. */
4711 volatilep);
4721 {
4724 }
4732 {
4740 {
4744 }
4745 }
4747 {
4755 {
4759 }
4760 }
4762 /* If the right sides are not constant, do the same for it. Also,
4763 disallow this optimization if a size or signedness mismatch occurs
4764 between the left and right sides. */
4766 {
4769 /* Make sure the two fields on the right
4770 correspond to the left without being swapped. */
4778 volatilep);
4788 {
4791 }
4798 /* Make a mask that corresponds to both fields being compared.
4799 Do this for both items being compared. If the operands are the
4800 same size and the bits being compared are in the same position
4801 then we can do this by masking both and comparing the masked
4802 results. */
4806 {
4818 }
4820 /* There is still another way we can do something: If both pairs of
4821 fields being compared are adjacent, we may be able to make a wider
4822 field containing them both.
4824 Note that we still must mask the lhs/rhs expressions. Furthermore,
4825 the mask must be shifted to account for the shift done by
4826 make_bit_field_ref. */
4831 {
4832 tree type;
4844 /* Convert to the smaller type before masking out unwanted bits. */
4847 {
4849 {
4853 }
4855 {
4859 }
4860 }
4869 }
4872 }
4874 /* Handle the case of comparisons with constants. If there is something in
4875 common between the masks, those bits of the constants must be the same.
4876 If not, the condition is always false. Test for this to avoid generating
4877 incorrect code below. */
4882 {
4884 {
4887 }
4888 else
4889 {
4892 }
4893 }
4895 /* Construct the expression we will return. First get the component
4896 reference we will make. Unless the mask is all ones the width of
4897 that field, perform the mask operation. Then compare with the
4898 merged constant. */
4908 }
4909 \f
4910 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4911 constant. */
4913 static tree
4915 {
4920 tree minmax_const;
4922 tree inner;
4932 /* If something does not permit us to optimize, return the original tree. */
4940 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4941 and GT_EXPR, doing the rest with recursive calls using logical
4942 simplifications. */
4944 {
4946 return
4950 return
4952 optimize_minmax_comparison
4954 optimize_minmax_comparison
4959 /* MAX (X, 0) == 0 -> X <= 0 */
4963 /* MAX (X, 0) == 5 -> X == 5 */
4967 /* MAX (X, 0) == -1 -> false */
4971 /* MIN (X, 0) == 0 -> X >= 0 */
4975 /* MIN (X, 0) == 5 -> false */
4978 else
4979 /* MIN (X, 0) == -1 -> X == -1 */
4984 /* MAX (X, 0) > 0 -> X > 0
4985 MAX (X, 0) > 5 -> X > 5 */
4989 /* MAX (X, 0) > -1 -> true */
4993 /* MIN (X, 0) > 0 -> false
4994 MIN (X, 0) > 5 -> false */
4997 else
4998 /* MIN (X, 0) > -1 -> X > -1 */
5003 }
5004 }
5005 \f
5006 /* T is an integer expression that is being multiplied, divided, or taken a
5007 modulus (CODE says which and what kind of divide or modulus) by a
5008 constant C. See if we can eliminate that operation by folding it with
5009 other operations already in T. WIDE_TYPE, if non-null, is a type that
5010 should be used for the computation if wider than our type.
5012 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
5013 (X * 2) + (Y * 4). We must, however, be assured that either the original
5014 expression would not overflow or that overflow is undefined for the type
5015 in the language in question.
5017 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
5018 the machine has a multiply-accumulate insn or that this is part of an
5019 addressing calculation.
5021 If we return a non-null expression, it is an equivalent form of the
5022 original computation, but need not be in the original type. */
5024 static tree
5026 {
5027 /* To avoid exponential search depth, refuse to allow recursion past
5028 three levels. Beyond that (1) it's highly unlikely that we'll find
5029 something interesting and (2) we've probably processed it before
5030 when we built the inner expression. */
5033 tree ret;
5038 depth++;
5040 depth--;
5043 }
5045 static tree
5047 {
5057 /* Don't deal with constants of zero here; they confuse the code below. */
5067 /* Note that we need not handle conditional operations here since fold
5068 already handles those cases. So just do arithmetic here. */
5070 {
5072 /* For a constant, we can always simplify if we are a multiply
5073 or (for divide and modulus) if it is a multiple of our constant. */
5081 /* If op0 is an expression ... */
5086 /* ... and is unsigned, and its type is smaller than ctype,
5087 then we cannot pass through as widening. */
5093 /* ... or its type is larger than ctype,
5094 then we cannot pass through this truncation. */
5097 /* ... or signedness changes for division or modulus,
5098 then we cannot pass through this conversion. */
5104 /* Pass the constant down and see if we can make a simplification. If
5105 we can, replace this expression with the inner simplification for
5106 possible later conversion to our or some other type. */
5111 code == MULT_EXPR
5122 /* If widening the type changes the signedness, then we can't perform
5123 this optimization as that changes the result. */
5127 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
5130 {
5136 }
5140 /* If the second operand is constant, this is a multiplication
5141 or floor division, by a power of two, so we can treat it that
5142 way unless the multiplier or divisor overflows. */
5144 /* const_binop may not detect overflow correctly,
5145 so check for it explicitly here. */
5150 size_one_node,
5160 /* See if we can eliminate the operation on both sides. If we can, we
5161 can return a new PLUS or MINUS. If we can't, the only remaining
5162 cases where we can do anything are if the second operand is a
5163 constant. */
5168 /* If not multiplication, we can only do this if both operands
5169 are divisible by c. */
5175 /* If this was a subtraction, negate OP1 and set it to be an addition.
5176 This simplifies the logic below. */
5183 /* If either OP1 or C are negative, this optimization is not safe for
5184 some of the division and remainder types while for others we need
5185 to change the code. */
5187 {
5195 }
5197 /* If it's a multiply or a division/modulus operation of a multiple
5198 of our constant, do the operation and verify it doesn't overflow. */
5201 {
5204 /* We allow the constant to overflow with wrapping semantics. */
5208 }
5209 else
5212 /* If we have an unsigned type is not a sizetype, we cannot widen
5213 the operation since it will change the result if the original
5214 computation overflowed. */
5220 /* If we were able to eliminate our operation from the first side,
5221 apply our operation to the second side and reform the PLUS. */
5225 /* The last case is if we are a multiply. In that case, we can
5226 apply the distributive law to commute the multiply and addition
5227 if the multiplication of the constants doesn't overflow. */
5233 op1));
5238 /* We have a special case here if we are doing something like
5239 (C * 8) % 4 since we know that's zero. */
5246 /* ... fall through ... */
5250 /* If we can extract our operation from the LHS, do so and return a
5251 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
5252 do something only if the second operand is a constant. */
5264 /* If these are the same operation types, we can associate them
5265 assuming no overflow. */
5272 /* If these operations "cancel" each other, we have the main
5273 optimizations of this pass, which occur when either constant is a
5274 multiple of the other, in which case we replace this with either an
5275 operation or CODE or TCODE.
5277 If we have an unsigned type that is not a sizetype, we cannot do
5278 this since it will change the result if the original computation
5279 overflowed. */
5282 && ! flag_wrapv
5287 {
5298 }
5303 }
5306 }
5307 \f
5308 /* Return a node which has the indicated constant VALUE (either 0 or
5309 1), and is of the indicated TYPE. */
5311 static tree
5313 {
5321 else
5322 {
5327 }
5328 }
5330 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
5331 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
5332 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
5333 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
5334 COND is the first argument to CODE; otherwise (as in the example
5335 given here), it is the second argument. TYPE is the type of the
5336 original expression. Return NULL_TREE if no simplification is
5337 possible. */
5339 static tree
5342 {
5347 /* This transformation is only worthwhile if we don't have to wrap
5348 arg in a SAVE_EXPR, and the operation can be simplified on atleast
5349 one of the branches once its pushed inside the COND_EXPR. */
5354 {
5358 /* If this operand throws an expression, then it does not make
5359 sense to try to perform a logical or arithmetic operation
5360 involving it. */
5365 }
5366 else
5367 {
5372 }
5383 }
5385 \f
5386 /* Subroutine of fold() that checks for the addition of +/- 0.0.
5388 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
5389 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
5390 ADDEND is the same as X.
5392 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
5393 and finite. The problematic cases are when X is zero, and its mode
5394 has signed zeros. In the case of rounding towards -infinity,
5395 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
5396 modes, X + 0 is not the same as X because -0 + 0 is 0. */
5398 static bool
5400 {
5404 /* Don't allow the fold with -fsignaling-nans. */
5408 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
5412 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
5417 /* The mode has signed zeros, and we have to honor their sign.
5418 In this situation, there is only one case we can return true for.
5419 X - 0 is the same as X unless rounding towards -infinity is
5420 supported. */
5422 }
5424 /* Subroutine of fold() that checks comparisons of built-in math
5425 functions against real constants.
5427 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
5428 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
5429 is the type of the result and ARG0 and ARG1 are the operands of the
5430 comparison. ARG1 must be a TREE_REAL_CST.
5432 The function returns the constant folded tree if a simplification
5433 can be made, and NULL_TREE otherwise. */
5435 static tree
5438 {
5439 REAL_VALUE_TYPE c;
5442 {
5448 {
5449 /* sqrt(x) < y is always false, if y is negative. */
5453 /* sqrt(x) > y is always true, if y is negative and we
5454 don't care about NaNs, i.e. negative values of x. */
5458 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5461 }
5463 {
5464 REAL_VALUE_TYPE c2;
5470 {
5471 /* sqrt(x) > y is x == +Inf, when y is very large. */
5476 /* sqrt(x) > y is always false, when y is very large
5477 and we don't care about infinities. */
5479 }
5481 /* sqrt(x) > c is the same as x > c*c. */
5484 }
5486 {
5487 REAL_VALUE_TYPE c2;
5493 {
5494 /* sqrt(x) < y is always true, when y is a very large
5495 value and we don't care about NaNs or Infinities. */
5499 /* sqrt(x) < y is x != +Inf when y is very large and we
5500 don't care about NaNs. */
5505 /* sqrt(x) < y is x >= 0 when y is very large and we
5506 don't care about Infinities. */
5511 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5520 dconst0))),
5523 c2)))));
5524 }
5526 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5531 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5534 {
5539 dconst0))),
5542 c2)))));
5543 }
5544 }
5545 }
5548 }
5550 /* Subroutine of fold() that optimizes comparisons against Infinities,
5551 either +Inf or -Inf.
5553 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5554 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5555 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5557 The function returns the constant folded tree if a simplification
5558 can be made, and NULL_TREE otherwise. */
5560 static tree
5562 {
5564 REAL_VALUE_TYPE max;
5565 tree temp;
5570 /* For negative infinity swap the sense of the comparison. */
5576 {
5578 /* x > +Inf is always false, if with ignore sNANs. */
5584 /* x <= +Inf is always true, if we don't case about NaNs. */
5588 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5591 {
5594 }
5599 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5605 /* x < +Inf is always equal to x <= DBL_MAX. */
5611 /* x != +Inf is always equal to !(x > DBL_MAX). */
5617 /* The transformation below creates non-gimple code and thus is
5618 not appropriate if we are in gimple form. */
5628 }
5631 }
5633 /* Subroutine of fold() that optimizes comparisons of a division by
5634 a nonzero integer constant against an integer constant, i.e.
5635 X/C1 op C2.
5637 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5638 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5639 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5641 The function returns the constant folded tree if a simplification
5642 can be made, and NULL_TREE otherwise. */
5644 static tree
5646 {
5651 HOST_WIDE_INT hpart;
5654 /* We have to do this the hard way to detect unsigned overflow.
5655 prod = int_const_binop (MULT_EXPR, arg01, arg1, 0); */
5668 {
5672 /* Likewise hi = int_const_binop (PLUS_EXPR, prod, tmp, 0). */
5685 }
5687 {
5690 {
5708 }
5709 }
5710 else
5711 {
5714 {
5732 }
5733 }
5736 {
5777 }
5780 }
5783 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5784 equality/inequality test, then return a simplified form of
5785 the test using shifts and logical operations. Otherwise return
5786 NULL. TYPE is the desired result type. */
5788 tree
5790 tree result_type)
5791 {
5792 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5793 operand 0. */
5795 {
5800 /* Extract the arguments of the EQ/NE. */
5804 /* This requires us to invert the code. */
5806 }
5808 /* If this is testing a single bit, we can optimize the test. */
5812 {
5819 tree arg00;
5821 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5822 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5825 /* This is only a win if casting to a signed type is cheap,
5826 i.e. when arg00's type is not a partial mode. */
5829 {
5834 }
5836 /* Otherwise we have (A & C) != 0 where C is a single bit,
5837 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5838 Similarly for (A & C) == 0. */
5840 /* If INNER is a right shift of a constant and it plus BITNUM does
5841 not overflow, adjust BITNUM and INNER. */
5848 {
5851 }
5853 /* If we are going to be able to omit the AND below, we must do our
5854 operations as unsigned. If we must use the AND, we have a choice.
5855 Normally unsigned is faster, but for some machines signed is. */
5856 #ifdef LOAD_EXTEND_OP
5858 #else
5860 #endif
5875 /* Put the AND last so it can combine with more things. */
5879 /* Make sure to return the proper type. */
5883 }
5885 }
5887 /* Check whether we are allowed to reorder operands arg0 and arg1,
5888 such that the evaluation of arg1 occurs before arg0. */
5890 static bool
5892 {
5899 }
5901 /* Test whether it is preferable two swap two operands, ARG0 and
5902 ARG1, for example because ARG0 is an integer constant and ARG1
5903 isn't. If REORDER is true, only recommend swapping if we can
5904 evaluate the operands in reverse order. */
5906 bool
5908 {
5953 /* It is preferable to swap two SSA_NAME to ensure a canonical form
5954 for commutative and comparison operators. Ensuring a canonical
5955 form allows the optimizers to find additional redundancies without
5956 having to explicitly check for both orderings. */
5963 }
5965 /* Perform constant folding and related simplification of EXPR.
5966 The related simplifications include x*1 => x, x*0 => 0, etc.,
5967 and application of the associative law.
5968 NOP_EXPR conversions may be removed freely (as long as we
5969 are careful not to change the type of the overall expression).
5970 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5971 but we can constant-fold them if they have constant operands. */
5973 #ifdef ENABLE_FOLD_CHECKING
5974 # define fold(x) fold_1 (x)
5976 static
5977 #endif
5978 tree
5980 {
5984 tree tem;
5989 /* WINS will be nonzero when the switch is done
5990 if all operands are constant. */
5993 /* Return right away if a constant. */
5998 {
5999 tree subop;
6001 /* Special case for conversion ops that can have fixed point args. */
6004 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
6010 else
6015 /* Note that TREE_CONSTANT isn't enough:
6016 static var addresses are constant but we can't
6017 do arithmetic on them. */
6019 }
6021 {
6025 {
6027 tree subop;
6032 /* Strip any conversions that don't change the mode. This is
6033 safe for every expression, except for a comparison expression
6034 because its signedness is derived from its operands. So, in
6035 the latter case, only strip conversions that don't change the
6036 signedness.
6038 Note that this is done as an internal manipulation within the
6039 constant folder, in order to find the simplest representation
6040 of the arguments so that their form can be studied. In any
6041 cases, the appropriate type conversions should be put back in
6042 the tree that will get out of the constant folder. */
6045 else
6050 else
6055 /* Note that TREE_CONSTANT isn't enough:
6056 static var addresses are constant but we can't
6057 do arithmetic on them. */
6064 }
6065 }
6067 /* If this is a commutative operation, and ARG0 is a constant, move it
6068 to ARG1 to reduce the number of tests below. */
6074 /* Now WINS is set as described above,
6075 ARG0 is the first operand of EXPR,
6076 and ARG1 is the second operand (if it has more than one operand).
6078 First check for cases where an arithmetic operation is applied to a
6079 compound, conditional, or comparison operation. Push the arithmetic
6080 operation inside the compound or conditional to see if any folding
6081 can then be done. Convert comparison to conditional for this purpose.
6082 The also optimizes non-constant cases that used to be done in
6083 expand_expr.
6085 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
6086 one of the operands is a comparison and the other is a comparison, a
6087 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
6088 code below would make the expression more complex. Change it to a
6089 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
6090 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
6102 {
6113 }
6116 {
6121 {
6131 /* If this was a conversion, and all we did was to move into
6132 inside the COND_EXPR, bring it back out. But leave it if
6133 it is a conversion from integer to integer and the
6134 result precision is no wider than a word since such a
6135 conversion is cheap and may be optimized away by combine,
6136 while it couldn't if it were outside the COND_EXPR. Then return
6137 so we don't get into an infinite recursion loop taking the
6138 conversion out and then back in. */
6150 && (INTEGRAL_TYPE_P
6161 }
6163 {
6165 {
6169 }
6173 integer_one_node)),
6175 integer_zero_node))));
6176 }
6177 }
6188 {
6192 arg1)));
6201 {
6206 }
6210 {
6215 }
6216 }
6219 {
6233 /* Handle cases of two conversions in a row. */
6236 {
6255 /* In addition to the cases of two conversions in a row
6256 handled below, if we are converting something to its own
6257 type via an object of identical or wider precision, neither
6258 conversion is needed. */
6265 /* Likewise, if the intermediate and final types are either both
6266 float or both integer, we don't need the middle conversion if
6267 it is wider than the final type and doesn't change the signedness
6268 (for integers). Avoid this if the final type is a pointer
6269 since then we sometimes need the inner conversion. Likewise if
6270 the outer has a precision not equal to the size of its mode. */
6281 /* If we have a sign-extension of a zero-extended value, we can
6282 replace that by a single zero-extension. */
6289 /* Two conversions in a row are not needed unless:
6290 - some conversion is floating-point (overstrict for now), or
6291 - the intermediate type is narrower than both initial and
6292 final, or
6293 - the intermediate type and innermost type differ in signedness,
6294 and the outermost type is wider than the intermediate, or
6295 - the initial type is a pointer type and the precisions of the
6296 intermediate and final types differ, or
6297 - the final type is a pointer type and the precisions of the
6298 initial and intermediate types differ. */
6313 }
6317 /* Detect assigning a bitfield. */
6320 {
6321 /* Don't leave an assignment inside a conversion
6322 unless assigning a bitfield. */
6326 /* First do the assignment, then return converted constant. */
6331 }
6333 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
6334 constants (if x has signed type, the sign bit cannot be set
6335 in c). This folds extension into the BIT_AND_EXPR. */
6340 {
6350 <= HOST_BITS_PER_WIDE_INT
6352 {
6359 #ifdef LOAD_EXTEND_OP
6363 {
6367 }
6368 #endif
6369 }
6374 }
6376 /* Convert (T1)((T2)X op Y) into (T1)X op Y, for pointer types T1 and
6377 T2 being pointers to types of the same size. */
6382 {
6394 }
6408 {
6412 }
6417 {
6422 }
6435 /* Convert fabs((double)float) into (double)fabsf(float). */
6438 {
6443 targ0)));
6444 }
6477 /* A + (-B) -> A - B */
6480 /* (-A) + B -> B - A */
6485 {
6489 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
6490 with a constant, and the two constants have no bits in common,
6491 we should treat this as a BIT_IOR_EXPR since this may produce more
6492 simplifications. */
6500 {
6503 }
6505 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
6506 (plus (plus (mult) (mult)) (foo)) so that we can
6507 take advantage of the factoring cases below. */
6512 {
6517 else
6538 }
6541 {
6545 /* (A * C) + (B * C) -> (A+B) * C.
6546 We are most concerned about the case where C is a constant,
6547 but other combinations show up during loop reduction. Since
6548 it is not difficult, try all four possibilities. */
6565 /* No identical multiplicands; see if we can find a common
6566 power-of-two factor in non-power-of-two multiplies. This
6567 can help in multi-dimensional array access. */
6572 {
6577 /* Move min of absolute values to int11. */
6580 {
6584 }
6587 {
6592 }
6593 }
6599 same));
6600 }
6601 }
6602 else
6603 {
6604 /* See if ARG1 is zero and X + ARG1 reduces to X. */
6608 /* Likewise if the operands are reversed. */
6612 /* Convert X + -C into X - C. */
6615 {
6621 }
6623 /* Convert x+x into x*2.0. */
6629 /* Convert x*c+x into x*(c+1). */
6635 {
6636 REAL_VALUE_TYPE c;
6642 }
6644 /* Convert x+x*c into x*(c+1). */
6650 {
6651 REAL_VALUE_TYPE c;
6657 }
6659 /* Convert x*c1+x*c2 into x*(c1+c2). */
6669 {
6678 }
6679 /* Convert a + (b*c + d*e) into (a + b*c) + d*e */
6683 {
6688 {
6689 tree tree0;
6692 }
6693 }
6694 /* Convert (b*c + d*e) + a into b*c + (d*e +a) */
6698 {
6703 {
6704 tree tree0;
6707 }
6708 }
6709 }
6711 bit_rotate:
6712 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
6713 is a rotate of A by C1 bits. */
6714 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
6715 is a rotate of A by B bits. */
6716 {
6725 {
6744 {
6752 TYPE_PRECISION
6757 ? LROTATE_EXPR
6760 }
6762 {
6770 TYPE_PRECISION
6775 ? LROTATE_EXPR
6778 }
6779 }
6780 }
6782 associate:
6783 /* In most languages, can't associate operations on floats through
6784 parentheses. Rather than remember where the parentheses were, we
6785 don't associate floats at all, unless the user has specified
6786 -funsafe-math-optimizations. */
6790 {
6794 /* Split both trees into variables, constants, and literals. Then
6795 associate each group together, the constants with literals,
6796 then the result with variables. This increases the chances of
6797 literals being recombined later and of generating relocatable
6798 expressions for the sum of a constant and literal. */
6803 /* Only do something if we found more than two objects. Otherwise,
6804 nothing has changed and we risk infinite recursion. */
6809 {
6810 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6819 /* Preserve the MINUS_EXPR if the negative part of the literal is
6820 greater than the positive part. Otherwise, the multiplicative
6821 folding code (i.e extract_muldiv) may be fooled in case
6822 unsigned constants are subtracted, like in the following
6823 example: ((X*2 + 4) - 8U)/2. */
6825 {
6829 {
6833 }
6834 else
6835 {
6839 }
6840 }
6842 {
6847 else
6848 {
6854 }
6855 }
6860 }
6861 }
6863 binary:
6867 {
6868 /* The return value should always have
6869 the same type as the original expression. */
6874 }
6878 /* A - (-B) -> A + B */
6881 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6891 {
6897 /* Fold A - (A & B) into ~B & A. */
6900 {
6905 arg0));
6910 arg0));
6911 }
6913 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6914 any power of 2 minus 1. */
6919 {
6925 {
6929 }
6930 }
6931 }
6933 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6937 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6938 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6939 (-ARG1 + ARG0) reduces to -ARG1. */
6943 /* Fold &x - &x. This can happen from &x.foo - &x.
6944 This is unsafe for certain floats even in non-IEEE formats.
6945 In IEEE, it is unsafe because it does wrong for NaNs.
6946 Also note that operand_equal_p is always false if an operand
6947 is volatile. */
6953 /* A - B -> A + (-B) if B is easily negatable. */
6956 /* Avoid this transformation if B is a positive REAL_CST. */
6965 {
6966 /* (A * C) - (B * C) -> (A-B) * C. */
6974 /* (A * C1) - (A * C2) -> A * (C1-C2). */
6982 }
6987 /* (-A) * (-B) -> A * B */
6998 {
7004 /* (a * (1 << b)) is (a << b) */
7020 }
7021 else
7022 {
7023 /* Maybe fold x * 0 to 0. The expressions aren't the same
7024 when x is NaN, since x * 0 is also NaN. Nor are they the
7025 same in modes with signed zeros, since multiplying a
7026 negative value by 0 gives -0, not +0. */
7031 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
7036 /* Transform x * -1.0 into -x. */
7041 /* Convert (C1/X)*C2 into (C1*C2)/X. */
7046 {
7052 }
7055 {
7059 /* Optimizations of root(...)*root(...). */
7061 {
7066 /* Optimize sqrt(x)*sqrt(x) as x. */
7072 /* Optimize root(x)*root(y) as root(x*y). */
7077 }
7079 /* Optimize expN(x)*expN(y) as expN(x+y). */
7081 {
7088 }
7090 /* Optimizations of pow(...)*pow(...). */
7094 {
7102 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
7104 {
7109 arg01));
7111 }
7113 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
7115 {
7120 arg));
7122 }
7123 }
7125 /* Optimize tan(x)*cos(x) as sin(x). */
7134 {
7140 }
7142 /* Optimize x*pow(x,c) as pow(x,c+1). */
7146 {
7153 {
7155 REAL_VALUE_TYPE c;
7164 }
7165 }
7167 /* Optimize pow(x,c)*x as pow(x,c+1). */
7171 {
7178 {
7180 REAL_VALUE_TYPE c;
7189 }
7190 }
7192 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
7195 {
7199 {
7204 }
7205 }
7206 }
7207 }
7211 bit_ior:
7219 /* ~X | X is -1. */
7222 {
7227 }
7229 /* X | ~X is -1. */
7232 {
7237 }
7243 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
7245 This results in more efficient code for machines without a NAND
7246 instruction. Combine will canonicalize to the first form
7247 which will allow use of NAND instructions provided by the
7248 backend if they exist. */
7251 {
7256 }
7258 /* See if this can be simplified into a rotate first. If that
7259 is unsuccessful continue in the association code. */
7270 /* ~X ^ X is -1. */
7273 {
7278 }
7280 /* X ^ ~X is -1. */
7283 {
7288 }
7290 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
7291 with a constant, and the two constants have no bits in common,
7292 we should treat this as a BIT_IOR_EXPR since this may produce more
7293 simplifications. */
7301 {
7304 }
7306 /* See if this can be simplified into a rotate first. If that
7307 is unsuccessful continue in the association code. */
7318 /* ~X & X is always zero. */
7323 /* X & ~X is always zero. */
7331 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
7334 {
7335 unsigned int prec
7342 }
7344 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
7346 This results in more efficient code for machines without a NOR
7347 instruction. Combine will canonicalize to the first form
7348 which will allow use of NOR instructions provided by the
7349 backend if they exist. */
7352 {
7357 }
7362 /* Don't touch a floating-point divide by zero unless the mode
7363 of the constant can represent infinity. */
7369 /* (-A) / (-B) -> A / B */
7379 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
7384 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
7389 /* If ARG1 is a constant, we can convert this to a multiply by the
7390 reciprocal. This does not have the same rounding properties,
7391 so only do this if -funsafe-math-optimizations. We can actually
7392 always safely do it if ARG1 is a power of two, but it's hard to
7393 tell if it is or not in a portable manner. */
7395 {
7400 /* Find the reciprocal if optimizing and the result is exact. */
7402 {
7403 REAL_VALUE_TYPE r;
7406 {
7409 }
7410 }
7411 }
7412 /* Convert A/B/C to A/(B*C). */
7419 /* Convert A/(B/C) to (A/B)*C. */
7427 /* Convert C1/(X*C2) into (C1/C2)/X. */
7432 {
7438 }
7441 {
7443 /* Optimize x/expN(y) into x*expN(-y). */
7445 {
7452 }
7454 /* Optimize x/pow(y,z) into x*pow(y,-z). */
7458 {
7467 }
7468 }
7471 {
7475 /* Optimize sin(x)/cos(x) as tan(x). */
7481 {
7487 }
7489 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
7495 {
7499 {
7504 }
7505 }
7507 /* Optimize pow(x,c)/x as pow(x,c-1). */
7511 {
7517 {
7519 REAL_VALUE_TYPE c;
7528 }
7529 }
7530 }
7542 /* X / -1 is -X. */
7549 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
7550 operation, EXACT_DIV_EXPR.
7552 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
7553 At one time others generated faster code, it's not clear if they do
7554 after the last round to changes to the DIV code in expmed.c. */
7575 /* X % -1 is zero. */
7582 /* Optimize unsigned TRUNC_MOD_EXPR by a power of two into a
7583 BIT_AND_EXPR, i.e. "X % C" into "X & C2". */
7587 {
7589 tree mask;
7594 {
7598 }
7599 else
7600 {
7603 }
7609 }
7611 /* X % -C is the same as X % C (for all rounding moduli). */
7615 && !flag_trapv
7616 /* Avoid this transformation if C is INT_MIN, i.e. C == -C. */
7621 /* X % -Y is the same as X % Y (for all rounding moduli). */
7642 /* Optimize -1 >> x for arithmetic right shifts. */
7645 /* ... fall through ... */
7648 shift:
7654 /* Since negative shift count is not well-defined,
7655 don't try to compute it in the compiler. */
7658 /* Rewrite an LROTATE_EXPR by a constant into an
7659 RROTATE_EXPR by a new constant. */
7661 {
7666 }
7668 /* If we have a rotate of a bit operation with the rotate count and
7669 the second operand of the bit operation both constant,
7670 permute the two operations. */
7682 /* Two consecutive rotates adding up to the width of the mode can
7683 be ignored. */
7714 /* The argument to invert_truthvalue must have Boolean type. */
7718 /* Note that the operand of this must be an int
7719 and its values must be 0 or 1.
7720 ("true" is a fixed value perhaps depending on the language,
7721 but we don't handle values other than 1 correctly yet.) */
7723 /* Avoid infinite recursion. */
7725 {
7730 }
7734 /* Note that the operands of this must be ints
7735 and their values must be 0 or 1.
7736 ("true" is a fixed value perhaps depending on the language.) */
7737 /* If first arg is constant zero, return it. */
7741 /* If either arg is constant true, drop it. */
7745 /* Preserve sequence points. */
7748 /* If second arg is constant zero, result is zero, but first arg
7749 must be evaluated. */
7752 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
7753 case will be handled here. */
7757 /* !X && X is always false. */
7761 /* X && !X is always false. */
7766 truth_andor:
7767 /* We only do these simplifications if we are optimizing. */
7771 /* Check for things like (A || B) && (A || C). We can convert this
7772 to A || (B && C). Note that either operator can be any of the four
7773 truth and/or operations and the transformation will still be
7774 valid. Also note that we only care about order for the
7775 ANDIF and ORIF operators. If B contains side effects, this
7776 might change the truth-value of A. */
7783 {
7803 /* This case if tricky because we must either have commutative
7804 operators or else A10 must not have side-effects. */
7810 a01));
7811 }
7813 /* See if we can build a range comparison. */
7817 /* Check for the possibility of merging component references. If our
7818 lhs is another similar operation, try to merge its rhs with our
7819 rhs. Then try to merge our lhs and rhs. */
7831 /* Note that the operands of this must be ints
7832 and their values must be 0 or true.
7833 ("true" is a fixed value perhaps depending on the language.) */
7834 /* If first arg is constant true, return it. */
7838 /* If either arg is constant zero, drop it. */
7842 /* Preserve sequence points. */
7845 /* If second arg is constant true, result is true, but we must
7846 evaluate first arg. */
7849 /* Likewise for first arg, but note this only occurs here for
7850 TRUTH_OR_EXPR. */
7854 /* !X || X is always true. */
7858 /* X || !X is always true. */
7866 /* If the second arg is constant zero, drop it. */
7869 /* If the second arg is constant true, this is a logical inversion. */
7872 /* Identical arguments cancel to zero. */
7876 /* !X ^ X is always true. */
7881 /* X ^ !X is always true. */
7894 /* If one arg is a real or integer constant, put it last. */
7898 /* If this is an equality comparison of the address of a non-weak
7899 object against zero, then we know the result. */
7907 /* If this is an equality comparison of the address of two non-weak,
7908 unaliased symbols neither of which are extern (since we do not
7909 have access to attributes for externs), then we know the result. */
7925 type);
7928 {
7936 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7941 /* (-a) CMP (-b) -> b CMP a */
7948 {
7949 REAL_VALUE_TYPE cst;
7952 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7954 return
7960 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7961 /* a CMP (-0) -> a CMP 0 */
7966 /* x != NaN is always true, other ops are always false. */
7969 {
7972 }
7974 /* Fold comparisons against infinity. */
7976 {
7980 }
7981 }
7983 /* If this is a comparison of a real constant with a PLUS_EXPR
7984 or a MINUS_EXPR of a real constant, we can convert it into a
7985 comparison with a revised real constant as long as no overflow
7986 occurs when unsafe_math_optimizations are enabled. */
7998 /* Likewise, we can simplify a comparison of a real constant with
7999 a MINUS_EXPR whose first operand is also a real constant, i.e.
8000 (c1 - x) < c2 becomes x > c1-c2. */
8011 /* Fold comparisons against built-in math functions. */
8013 && flag_unsafe_math_optimizations
8015 {
8019 {
8023 }
8024 }
8025 }
8027 /* Convert foo++ == CONST into ++foo == CONST + INCR. */
8031 /* This optimization is invalid for ordered comparisons
8032 if CONST+INCR overflows or if foo+incr might overflow.
8033 This optimization is invalid for floating point due to rounding.
8034 For pointer types we assume overflow doesn't happen. */
8038 {
8042 {
8048 }
8049 else
8050 {
8056 }
8059 /* If VAROP is a reference to a bitfield, we must mask
8060 the constant by the width of the field. */
8065 {
8070 /* First check whether the comparison would come out
8071 always the same. If we don't do that we would
8072 change the meaning with the masking. */
8086 }
8089 }
8091 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
8092 This transformation affects the cases which are handled in later
8093 optimizations involving comparisons with non-negative constants. */
8097 {
8099 {
8110 }
8111 }
8113 /* Comparisons with the highest or lowest possible integer of
8114 the specified size will have known values.
8116 This is quite similar to fold_relational_hi_lo; however, my
8117 attempts to share the code have been nothing but trouble.
8118 I give up for now. */
8119 {
8127 {
8134 {
8137 }
8138 else
8139 {
8142 }
8147 {
8160 /* The GE_EXPR and LT_EXPR cases above are not normally
8161 reached because of previous transformations. */
8165 }
8169 {
8178 }
8182 {
8197 }
8201 {
8210 }
8216 /* signed_type does not work on pointer types. */
8218 {
8219 /* The following case also applies to X < signed_max+1
8220 and X >= signed_max+1 because previous transformations. */
8222 {
8226 return fold
8230 }
8231 }
8232 }
8233 }
8235 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
8236 a MINUS_EXPR of a constant, we can convert it into a comparison with
8237 a revised constant as long as no overflow occurs. */
8249 /* Similarly for a NEGATE_EXPR. */
8258 /* If we have X - Y == 0, we can convert that to X == Y and similarly
8259 for !=. Don't do this for ordered comparisons due to overflow. */
8265 /* If we are widening one operand of an integer comparison,
8266 see if the other operand is similarly being widened. Perhaps we
8267 can do the comparison in the narrower type. */
8281 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
8282 constant, we can simplify it. */
8289 /* If we are comparing an ABS_EXPR with a constant, we can
8290 convert all the cases into explicit comparisons, but they may
8291 well not be faster than doing the ABS and one comparison.
8292 But ABS (X) <= C is a range comparison, which becomes a subtraction
8293 and a comparison, and is probably faster. */
8306 /* If this is an EQ or NE comparison with zero and ARG0 is
8307 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
8308 two operations, but the latter can be done in one less insn
8309 on machines that have only two-operand insns or on which a
8310 constant cannot be the first operand. */
8313 {
8318 return
8324 integer_one_node)),
8325 arg1));
8328 return
8334 integer_one_node)),
8335 arg1));
8336 }
8338 /* If this is an NE or EQ comparison of zero against the result of a
8339 signed MOD operation whose second operand is a power of 2, make
8340 the MOD operation unsigned since it is simpler and equivalent. */
8349 {
8359 }
8361 /* If this is an NE comparison of zero with an AND of one, remove the
8362 comparison since the AND will give the correct value. */
8368 /* If we have (A & C) == C where C is a power of 2, convert this into
8369 (A & C) != 0. Similarly for NE_EXPR. */
8377 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
8378 2, then fold the expression into shifts and logical operations. */
8383 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
8384 Similarly for NE_EXPR. */
8389 {
8390 tree dandnotc
8398 }
8400 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
8401 Similarly for NE_EXPR. */
8406 {
8407 tree candnotd
8414 }
8416 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
8417 and similarly for >= into !=. */
8433 return
8441 /* Simplify comparison of something with itself. (For IEEE
8442 floating-point, we can only do some of these simplifications.) */
8444 {
8446 {
8461 /* For NE, we can only do this simplification if integer
8462 or we don't honor IEEE floating point NaNs. */
8466 /* ... fall through ... */
8472 }
8473 }
8475 /* If we are comparing an expression that just has comparisons
8476 of two integer values, arithmetic expressions of those comparisons,
8477 and constants, we can simplify it. There are only three cases
8478 to check: the two values can either be equal, the first can be
8479 greater, or the second can be greater. Fold the expression for
8480 those three values. Since each value must be 0 or 1, we have
8481 eight possibilities, each of which corresponds to the constant 0
8482 or 1 or one of the six possible comparisons.
8484 This handles common cases like (a > b) == 0 but also handles
8485 expressions like ((x > y) - (y > x)) > 0, which supposedly
8486 occur in macroized code. */
8489 {
8494 /* Don't handle degenerate cases here; they should already
8495 have been handled anyway. */
8504 {
8508 /* We can't just pass T to eval_subst in case cval1 or cval2
8509 was the same as ARG1. */
8511 tree high_result
8515 arg1));
8516 tree equal_result
8520 arg1));
8521 tree low_result
8525 arg1));
8527 /* All three of these results should be 0 or 1. Confirm they
8528 are. Then use those values to select the proper code
8529 to use. */
8537 {
8538 /* Make a 3-bit mask with the high-order bit being the
8539 value for `>', the next for '=', and the low for '<'. */
8543 {
8545 /* Always false. */
8566 /* Always true. */
8568 }
8573 else
8575 }
8576 }
8577 }
8579 /* If this is a comparison of a field, we may be able to simplify it. */
8584 /* Handle the constant case even without -O
8585 to make sure the warnings are given. */
8587 {
8591 }
8593 /* If this is a comparison of complex values and either or both sides
8594 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
8595 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
8596 This may prevent needless evaluations. */
8603 {
8616 type,
8619 }
8621 /* Optimize comparisons of strlen vs zero to a compare of the
8622 first character of the string vs zero. To wit,
8623 strlen(ptr) == 0 => *ptr == 0
8624 strlen(ptr) != 0 => *ptr != 0
8625 Other cases should reduce to one of these two (or a constant)
8626 due to the return value of strlen being unsigned. */
8630 {
8632 tree arglist;
8644 integer_zero_node));
8645 }
8647 /* We can fold X/C1 op C2 where C1 and C2 are integer constants
8648 into a single range test. */
8655 {
8659 }
8679 {
8683 }
8685 /* If the first operand is NaN, the result is constant. */
8689 {
8691 ? integer_zero_node
8694 }
8696 /* If the second operand is NaN, the result is constant. */
8700 {
8702 ? integer_zero_node
8705 }
8707 /* Simplify unordered comparison of something with itself. */
8713 && !flag_trapping_math
8717 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
8718 {
8729 }
8734 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
8735 so all simple results must be passed through pedantic_non_lvalue. */
8737 {
8739 /* Only optimize constant conditions when the selected branch
8740 has the same type as the COND_EXPR. This avoids optimizing
8741 away "c ? x : throw", where the throw has a void type. */
8746 }
8750 /* If we have A op B ? A : C, we may be able to convert this to a
8751 simpler expression, depending on the operation and the values
8752 of B and C. Signed zeros prevent all of these transformations,
8753 for reasons given above each one.
8755 Also try swapping the arguments and inverting the conditional. */
8760 {
8766 }
8773 {
8776 {
8782 }
8783 }
8785 /* If the second operand is simpler than the third, swap them
8786 since that produces better jump optimization results. */
8789 {
8790 /* See if this can be inverted. If it can't, possibly because
8791 it was a floating-point inequality comparison, don't do
8792 anything. */
8798 }
8800 /* Convert A ? 1 : 0 to simply A. */
8803 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8804 call to fold will try to move the conversion inside
8805 a COND, which will recurse. In that case, the COND_EXPR
8806 is probably the best choice, so leave it alone. */
8810 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8811 over COND_EXPR in cases such as floating point comparisons. */
8818 /* A < 0 ? <sign bit of A> : 0 is simply (A & <sign bit of A>). */
8826 /* (A >> N) & 1 ? (1 << N) : 0 is simply A & (1 << N). A & 1 was
8827 already handled above. */
8832 {
8840 }
8842 /* A & N ? N : 0 is simply A & N if N is a power of two. This
8843 is probably obsolete because the first operand should be a
8844 truth value (that's why we have the two cases above), but let's
8845 leave it in until we can confirm this for all front-ends. */
8856 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8862 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8866 {
8867 /* Only perform transformation if ARG0 is easily inverted. */
8871 }
8873 /* Convert A ? 0 : B into !A && B if A and B are truth values. */
8877 {
8878 /* Only perform transformation if ARG0 is easily inverted. */
8883 }
8885 /* Convert A ? 1 : B into A || B if A and B are truth values. */
8895 /* When pedantic, a compound expression can be neither an lvalue
8896 nor an integer constant expression. */
8899 /* Don't let (0, 0) be null pointer constant. */
8941 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8942 appropriate. */
8947 {
8951 tree arg01;
8962 {
8976 arg01));
8977 }
8980 }
8983 /* Check for a built-in function. */
8988 {
8992 }
8998 }
9000 #ifdef ENABLE_FOLD_CHECKING
9001 #undef fold
9007 /* When --enable-checking=fold, compute a digest of expr before
9008 and after actual fold call to see if fold did not accidentally
9009 change original expr. */
9011 tree
9013 {
9014 tree ret;
9017 htab_t ht;
9036 }
9038 void
9040 {
9043 htab_t ht;
9053 }
9055 static void
9057 {
9059 }
9061 static void
9063 {
9081 {
9082 /* Allow DECL_ASSEMBLER_NAME to be modified. */
9086 }
9089 {
9090 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
9095 }
9101 {
9104 {
9118 }
9122 {
9133 }
9167 {
9170 }
9177 }
9178 }
9180 #endif
9182 /* Perform constant folding and related simplification of initializer
9183 expression EXPR. This behaves identically to "fold" but ignores
9184 potential run-time traps and exceptions that fold must preserve. */
9186 tree
9188 {
9192 tree result;
9205 }
9207 /* Determine if first argument is a multiple of second argument. Return 0 if
9208 it is not, or we cannot easily determined it to be.
9210 An example of the sort of thing we care about (at this point; this routine
9211 could surely be made more general, and expanded to do what the *_DIV_EXPR's
9212 fold cases do now) is discovering that
9214 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
9216 is a multiple of
9218 SAVE_EXPR (J * 8)
9220 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
9222 This code also handles discovering that
9224 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
9226 is a multiple of 8 so we don't have to worry about dealing with a
9227 possible remainder.
9229 Note that we *look* inside a SAVE_EXPR only to determine how it was
9230 calculated; it is not safe for fold to do much of anything else with the
9231 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
9232 at run time. For example, the latter example above *cannot* be implemented
9233 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
9234 evaluation time of the original SAVE_EXPR is not necessarily the same at
9235 the time the new expression is evaluated. The only optimization of this
9236 sort that would be valid is changing
9238 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
9240 divided by 8 to
9242 SAVE_EXPR (I) * SAVE_EXPR (J)
9244 (where the same SAVE_EXPR (J) is used in the original and the
9245 transformed version). */
9247 static int
9249 {
9257 {
9269 {
9273 /* const_binop may not detect overflow correctly,
9274 so check for it explicitly here. */
9280 size_one_node,
9284 }
9288 /* Can't handle conversions from non-integral or wider integral type. */
9294 /* .. fall through ... */
9310 }
9311 }
9313 /* Return true if `t' is known to be non-negative. */
9315 int
9317 {
9319 {
9334 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
9335 both unsigned and at least 2 bits shorter than the result. */
9339 {
9344 {
9348 }
9349 }
9354 {
9355 /* x * x for floating point x is always non-negative. */
9360 }
9362 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
9363 both unsigned and their total bits is shorter than the result. */
9367 {
9374 }
9403 {
9408 {
9412 {
9416 }
9417 }
9419 {
9425 }
9426 }
9452 {
9456 /* If the initializer is non-void, then it's a normal expression
9457 that will be assigned to the slot. */
9461 /* Otherwise, the initializer sets the slot in some way. One common
9462 way is an assignment statement at the end of the initializer. */
9464 {
9472 else
9474 }
9480 }
9483 {
9490 {
9491 #define CASE_BUILTIN_F(BUILT_IN_FN) \
9492 case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
9493 #define CASE_BUILTIN_I(BUILT_IN_FN) \
9494 case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:
9512 /* Always true. */
9516 /* sqrt(-0.0) is -0.0. */
9544 /* True if the 1st argument is nonnegative. */
9548 /* True if the 1st OR 2nd arguments are nonnegative. */
9553 /* True if the 1st AND 2nd arguments are nonnegative. */
9558 /* True if the 2nd argument is nonnegative. */
9563 #undef CASE_BUILTIN_F
9564 #undef CASE_BUILTIN_I
9565 }
9566 }
9568 /* ... fall through ... */
9572 /* Truth values evaluate to 0 or 1, which is nonnegative. */
9574 }
9576 /* We don't know sign of `t', so be conservative and return false. */
9578 }
9580 /* Return true when T is an address and is known to be nonzero.
9581 For floating point we further ensure that T is not denormal.
9582 Similar logic is present in nonzero_address in rtlanal.h */
9584 static bool
9586 {
9589 /* Doing something useful for floating point would need more work. */
9594 {
9604 {
9605 /* With the presence of negative values it is hard
9606 to say something. */
9610 /* One of operands must be positive and the other non-negative. */
9613 }
9618 {
9621 }
9625 {
9631 }
9635 /* Weak declarations may link to NULL. */
9638 /* Constants and all other cases are never weak. */
9651 {
9652 /* When both operands are nonzero, then MAX must be too. */
9656 /* MAX where operand 0 is positive is positive. */
9658 }
9659 /* MAX where operand 1 is positive is positive. */
9680 }
9682 }
9684 /* Return true if `r' is known to be non-negative.
9685 Only handles constants at the moment. */
9687 int
9689 {
9691 {
9701 {
9703 rtx elt;
9708 {
9712 }
9715 }
9719 /* These are always nonnegative. */
9724 }
9725 }
9728 /* See if we are applying CODE, a relational to the highest or lowest
9729 possible integer of TYPE. If so, then the result is a compile
9730 time constant. */
9732 static tree
9735 {
9746 {
9753 {
9756 }
9757 else
9758 {
9761 }
9766 {
9780 /* The GE_EXPR and LT_EXPR cases above are not normally
9781 reached because of previous transformations. */
9785 }
9789 {
9800 }
9804 {
9821 }
9825 {
9836 }
9841 /* signed_type does not work on pointer types. */
9843 {
9844 /* The following case also applies to X < signed_max+1
9845 and X >= signed_max+1 because previous transformations. */
9847 {
9853 type,
9857 retval
9863 /* If we are in gimple form, then returning EXP would create
9864 non-gimple expressions. Clearing it is safe and insures
9865 we do not allow a non-gimple expression to escape. */
9870 }
9871 }
9872 }
9875 }
9878 /* Given the components of a binary expression CODE, TYPE, OP0 and OP1,
9879 attempt to fold the expression to a constant without modifying TYPE,
9880 OP0 or OP1.
9882 If the expression could be simplified to a constant, then return
9883 the constant. If the expression would not be simplified to a
9884 constant, then return NULL_TREE.
9886 Note this is primarily designed to be called after gimplification
9887 of the tree structures and when at least one operand is a constant.
9888 As a result of those simplifying assumptions this routine is far
9889 simpler than the generic fold routine. */
9891 tree
9894 {
9896 tree subop0;
9897 tree subop1;
9898 tree tem;
9900 /* If this is a commutative operation, and ARG0 is a constant, move it
9901 to ARG1 to reduce the number of tests below. */
9904 {
9908 }
9910 /* If either operand is a complex type, extract its real component. */
9913 else
9918 else
9921 /* Note if either argument is not a real or integer constant.
9922 With a few exceptions, simplification is limited to cases
9923 where both arguments are constants. */
9931 {
9933 /* (plus (address) (const_int)) is a constant. */
9941 {
9945 }
9948 binary:
9952 /* Both arguments are constants. Simplify. */
9955 {
9956 /* The return value should always have the same type as
9957 the original expression. */
9962 }
9966 /* Fold &x - &x. This can happen from &x.foo - &x.
9967 This is unsafe for certain floats even in non-IEEE formats.
9968 In IEEE, it is unsafe because it does wrong for NaNs.
9969 Also note that operand_equal_p is always false if an
9970 operand is volatile. */
9978 /* Special case multiplication or bitwise AND where one argument
9979 is zero. */
9982 else
9991 /* Special case when we know the result will be all ones. */
10007 /* Division by zero is undefined. */
10034 /* Optimize -1 >> x for arithmetic right shifts. */
10037 /* ... fall through ... */
10043 /* Since negative shift count is not well-defined, don't
10044 try to compute it in the compiler. */
10052 /* -1 rotated either direction by any amount is still -1. */
10056 /* 0 rotated either direction by any amount is still zero. */
10073 /* If one arg is a real or integer constant, put it last. */
10078 {
10079 tree temp;
10085 }
10087 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
10088 This transformation affects the cases which are handled in later
10089 optimizations involving comparisons with non-negative constants. */
10093 {
10095 {
10108 }
10109 }
10115 /* Fall through. */
10131 /* This could probably be handled. */
10135 /* If second arg is constant zero, result is zero, but first arg
10136 must be evaluated. */
10139 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
10140 case will be handled here. */
10148 /* If second arg is constant true, result is true, but we must
10149 evaluate first arg. */
10152 /* Likewise for first arg, but note this only occurs here for
10153 TRUTH_OR_EXPR. */
10162 {
10165 }
10170 }
10171 }
10173 /* Given the components of a unary expression CODE, TYPE and OP0,
10174 attempt to fold the expression to a constant without modifying
10175 TYPE or OP0.
10177 If the expression could be simplified to a constant, then return
10178 the constant. If the expression would not be simplified to a
10179 constant, then return NULL_TREE.
10181 Note this is primarily designed to be called after gimplification
10182 of the tree structures and when op0 is a constant. As a result
10183 of those simplifying assumptions this routine is far simpler than
10184 the generic fold routine. */
10186 tree
10188 tree op0)
10189 {
10190 /* Make sure we have a suitable constant argument. */
10192 {
10193 tree subop;
10197 else
10202 }
10205 {
10217 else
10223 else
10229 else
10235 else
10241 else
10253 }
10254 }
10256 /* If EXP represents referencing an element in a constant string
10257 (either via pointer arithmetic or array indexing), return the
10258 tree representing the value accessed, otherwise return NULL. */
10260 tree
10262 {
10264 {
10266 tree index;
10267 tree string;
10271 else
10272 {
10276 /* Optimize the special-case of a zero lower bound.
10278 We convert the low_bound to sizetype to avoid some problems
10279 with constant folding. (E.g. suppose the lower bound is 1,
10280 and its mode is QI. Without the conversion,l (ARRAY
10281 +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
10282 +INDEX), which becomes (ARRAY+255+INDEX). Opps!) */
10287 }
10300 }
10302 }
10304 /* Return the tree for neg (ARG0) when ARG0 is known to be either
10305 an integer constant or real constant.
10307 TYPE is the type of the result. */
10309 static tree
10311 {
10315 {
10317 HOST_WIDE_INT high;
10328 }
10331 #ifdef ENABLE_CHECKING
10332 else
10334 #endif
10337 }
10339 /* Return the tree for abs (ARG0) when ARG0 is known to be either
10340 an integer constant or real constant.
10342 TYPE is the type of the result. */
10344 tree
10346 {
10350 {
10351 /* If the value is unsigned, then the absolute value is
10352 the same as the ordinary value. */
10355 /* Similarly, if the value is non-negative. */
10358 /* If the value is negative, then the absolute value is
10359 its negation. */
10360 else
10361 {
10363 HOST_WIDE_INT high;
10375 }
10376 }
10378 {
10381 else
10383 }
10384 #ifdef ENABLE_CHECKING
10385 else
10387 #endif
10390 }
10392 /* Return the tree for not (ARG0) when ARG0 is known to be an integer
10393 constant. TYPE is the type of the result. */
10395 static tree
10397 {
10401 {
10408 }
10409 #ifdef ENABLE_CHECKING
10410 else
10412 #endif
10415 }
10417 /* Given CODE, a relational operator, the target type, TYPE and two
10418 constant operands OP0 and OP1, return the result of the
10419 relational operation. If the result is not a compile time
10420 constant, then return NULL_TREE. */
10422 static tree
10424 {
10427 /* From here on, the only cases we handle are when the result is
10428 known to be a constant. */
10431 {
10435 /* Handle the cases where either operand is a NaN. */
10437 {
10439 {
10467 }
10470 }
10473 }
10475 /* From here on we only handle LT, LE, GT, GE, EQ and NE.
10477 To compute GT, swap the arguments and do LT.
10478 To compute GE, do LT and invert the result.
10479 To compute LE, swap the arguments, do LT and invert the result.
10480 To compute NE, do EQ and invert the result.
10482 Therefore, the code below must handle only EQ and LT. */
10485 {
10490 }
10492 /* Note that it is safe to invert for real values here because we
10493 have already handled the one case that it matters. */
10497 {
10500 }
10502 /* Compute a result for LT or EQ if args permit;
10503 Otherwise return T. */
10505 {
10510 else
10512 }
10513 else
10519 }
10521 /* Build an expression for the address of T. Folds away INDIRECT_REF to
10522 avoid confusing the gimplify process. */
10524 tree
10526 {
10528 {
10532 }
10533 else
10534 {
10545 }
10548 }
10550 tree
10552 {
10554 }
10556 /* Builds an expression for an indirection through T, simplifying some
10557 cases. */
10559 tree
10561 {
10564 tree subtype;
10568 {
10571 /* *&p => p */
10574 /* *(foo *)&fooarray => fooarray[0] */
10578 }
10580 /* *(foo *)fooarrptr => (*fooarrptr)[0] */
10584 {
10587 }
10590 }
10592 /* Strip non-trapping, non-side-effecting tree nodes from an expression
10593 whose result is ignored. The type of the returned tree need not be
10594 the same as the original expression. */
10596 tree
10598 {
10604 {
10615 else
10621 {
10637 }
10642 }
10643 }