| blob | 02f4128af49f4c11b32843137c4834280c80167b |
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 };
118 tree);
143 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
144 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
145 and SUM1. Then this yields nonzero if overflow occurred during the
146 addition.
148 Overflow occurs if A and B have the same sign, but A and SUM differ in
149 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
150 sign. */
151 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
152 \f
153 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
154 We do that by representing the two-word integer in 4 words, with only
155 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
156 number. The value of the word is LOWPART + HIGHPART * BASE. */
158 #define LOWPART(x) \
159 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
160 #define HIGHPART(x) \
161 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
162 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
164 /* Unpack a two-word integer into 4 words.
165 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
166 WORDS points to the array of HOST_WIDE_INTs. */
168 static void
170 {
175 }
177 /* Pack an array of 4 words into a two-word integer.
178 WORDS points to the array of words.
179 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
181 static void
184 {
187 }
188 \f
189 /* Make the integer constant T valid for its type by setting to 0 or 1 all
190 the bits in the constant that don't belong in the type.
192 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
193 nonzero, a signed overflow has already occurred in calculating T, so
194 propagate it. */
196 int
198 {
200 HOST_WIDE_INT high;
204 {
205 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
206 Consider doing it via real_convert now. */
208 }
219 else
222 /* First clear all bits that are beyond the type's precision. */
225 ;
229 else
230 {
234 }
236 /* Unsigned types do not suffer sign extension or overflow unless they
237 are a sizetype. */
243 /* If the value's sign bit is set, extend the sign. */
251 {
252 /* Value is negative:
253 set to 1 all the bits that are outside this type's precision. */
257 else
258 {
262 }
263 }
265 /* Return nonzero if signed overflow occurred. */
266 return
269 }
270 \f
271 /* Add two doubleword integers with doubleword result.
272 Each argument is given as two `HOST_WIDE_INT' pieces.
273 One argument is L1 and H1; the other, L2 and H2.
274 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
276 int
280 {
282 HOST_WIDE_INT h;
290 }
292 /* Negate a doubleword integer with doubleword result.
293 Return nonzero if the operation overflows, assuming it's signed.
294 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
295 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
297 int
300 {
302 {
306 }
307 else
308 {
312 }
313 }
314 \f
315 /* Multiply two doubleword integers with doubleword result.
316 Return nonzero if the operation overflows, assuming it's signed.
317 Each argument is given as two `HOST_WIDE_INT' pieces.
318 One argument is L1 and H1; the other, L2 and H2.
319 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
321 int
325 {
340 {
343 {
345 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
347 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
351 }
353 }
357 /* Check for overflow by calculating the top half of the answer in full;
358 it should agree with the low half's sign bit. */
361 {
364 }
366 {
369 }
371 }
372 \f
373 /* Shift the doubleword integer in L1, H1 left by COUNT places
374 keeping only PREC bits of result.
375 Shift right if COUNT is negative.
376 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
377 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
379 void
383 {
387 {
390 }
396 {
397 /* Shifting by the host word size is undefined according to the
398 ANSI standard, so we must handle this as a special case. */
401 }
403 {
406 }
407 else
408 {
412 }
414 /* Sign extend all bits that are beyond the precision. */
422 ;
424 {
427 }
428 else
429 {
433 }
434 }
436 /* Shift the doubleword integer in L1, H1 right by COUNT places
437 keeping only PREC bits of result. COUNT must be positive.
438 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
439 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
441 void
446 {
449 signmask = (arith
457 {
458 /* Shifting by the host word size is undefined according to the
459 ANSI standard, so we must handle this as a special case. */
462 }
464 {
467 }
468 else
469 {
473 }
475 /* Zero / sign extend all bits that are beyond the precision. */
478 {
481 }
483 ;
485 {
488 }
489 else
490 {
494 }
495 }
496 \f
497 /* Rotate the doubleword integer in L1, H1 left by COUNT places
498 keeping only PREC bits of result.
499 Rotate right if COUNT is negative.
500 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
502 void
506 {
518 }
520 /* Rotate the doubleword integer in L1, H1 left by COUNT places
521 keeping only PREC bits of result. COUNT must be positive.
522 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
524 void
528 {
540 }
541 \f
542 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
543 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
544 CODE is a tree code for a kind of division, one of
545 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
546 or EXACT_DIV_EXPR
547 It controls how the quotient is rounded to an integer.
548 Return nonzero if the operation overflows.
549 UNS nonzero says do unsigned division. */
551 int
554 HOST_WIDE_INT hnum_orig,
556 HOST_WIDE_INT hden_orig,
560 {
576 /* Calculate quotient sign and convert operands to unsigned. */
578 {
580 {
582 /* (minimum integer) / (-1) is the only overflow case. */
586 }
588 {
591 }
592 }
597 /* This unsigned division rounds toward zero. */
600 }
604 /* hden != 0 already checked. */
609 }
619 /* Special code for when the divisor < BASE. */
621 {
622 /* hnum != 0 already checked. */
624 {
628 }
629 }
630 else
631 {
632 /* Full double precision division,
633 with thanks to Don Knuth's "Seminumerical Algorithms". */
637 /* Find the highest nonzero divisor digit. */
640 {
643 }
645 /* Insure that the first digit of the divisor is at least BASE/2.
646 This is required by the quotient digit estimation algorithm. */
653 {
657 }
662 {
667 }
668 }
672 /* Main loop */
674 {
675 /* Guess the next quotient digit, quo_est, by dividing the first
676 two remaining dividend digits by the high order quotient digit.
677 quo_est is never low and is at most 2 high. */
684 else
687 /* Refine quo_est so it's usually correct, and at most one high. */
692 quo_est--;
694 /* Try QUO_EST as the quotient digit, by multiplying the
695 divisor by QUO_EST and subtracting from the remaining dividend.
696 Keep in mind that QUO_EST is the I - 1st digit. */
700 {
706 }
708 /* If quo_est was high by one, then num[i] went negative and
709 we need to correct things. */
711 {
712 quo_est--;
715 {
719 }
722 }
724 /* Store the quotient digit. */
726 }
727 }
731 finish_up:
732 /* If result is negative, make it so. */
736 /* Compute trial remainder: rem = num - (quo * den) */
742 {
751 {
752 /* quo = quo - 1; */
755 }
756 else
763 {
766 }
767 else
773 {
779 /* Get absolute values. */
785 /* If (2 * abs (lrem) >= abs (lden)) */
794 {
796 /* quo = quo - 1; */
799 else
800 /* quo = quo + 1; */
803 }
804 else
806 }
811 }
813 /* Compute true remainder: rem = num - (quo * den) */
818 }
819 \f
820 /* Return true if built-in mathematical function specified by CODE
821 preserves the sign of it argument, i.e. -f(x) == f(-x). */
823 static bool
825 {
827 {
844 }
846 }
848 /* Determine whether an expression T can be cheaply negated using
849 the function negate_expr. */
851 static bool
853 {
856 tree type;
865 {
870 /* Check that -CST will not overflow type. */
873 {
878 }
879 else
896 /* -(A + B) -> (-B) - A. */
901 /* -(A + B) -> (-A) - B. */
905 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
914 /* Fall through. */
923 /* Negate -((double)float) as (double)(-float). */
925 {
929 }
933 /* Negate -f(x) as f(-x). */
939 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
941 {
947 }
952 }
954 }
956 /* Given T, an expression, return the negation of T. Allow for T to be
957 null, in which case return null. */
959 static tree
961 {
962 tree type;
963 tree tem;
972 {
983 /* Two's complement FP formats, such as c4x, may overflow. */
989 {
998 }
1006 {
1007 /* -(A + B) -> (-B) - A. */
1011 {
1016 }
1018 /* -(A + B) -> (-A) - B. */
1020 {
1025 }
1026 }
1030 /* - (A - B) -> B - A */
1043 /* Fall through. */
1047 {
1060 }
1064 /* Convert -((double)float) into (double)(-float). */
1066 {
1070 }
1074 /* Negate -f(x) as f(-x). */
1077 {
1084 }
1088 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1090 {
1095 {
1102 }
1103 }
1108 }
1112 }
1113 \f
1114 /* Split a tree IN into a constant, literal and variable parts that could be
1115 combined with CODE to make IN. "constant" means an expression with
1116 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1117 commutative arithmetic operation. Store the constant part into *CONP,
1118 the literal in *LITP and return the variable part. If a part isn't
1119 present, set it to null. If the tree does not decompose in this way,
1120 return the entire tree as the variable part and the other parts as null.
1122 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1123 case, we negate an operand that was subtracted. Except if it is a
1124 literal for which we use *MINUS_LITP instead.
1126 If NEGATE_P is true, we are negating all of IN, again except a literal
1127 for which we use *MINUS_LITP instead.
1129 If IN is itself a literal or constant, return it as appropriate.
1131 Note that we do not guarantee that any of the three values will be the
1132 same type as IN, but they will have the same signedness and mode. */
1134 static tree
1137 {
1144 /* Strip any conversions that don't change the machine mode or signedness. */
1151 /* We can associate addition and subtraction together (even
1152 though the C standard doesn't say so) for integers because
1153 the value is not affected. For reals, the value might be
1154 affected, so we can't. */
1157 {
1163 /* First see if either of the operands is a literal, then a constant. */
1174 /* If we haven't dealt with either operand, this is not a case we can
1175 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1180 else
1183 /* Now do any needed negations. */
1190 }
1193 else
1197 {
1204 }
1207 }
1209 /* Re-associate trees split by the above function. T1 and T2 are either
1210 expressions to associate or null. Return the new expression, if any. If
1211 we build an operation, do it in TYPE and with CODE. */
1213 static tree
1215 {
1221 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1222 try to fold this since we will have infinite recursion. But do
1223 deal with any NEGATE_EXPRs. */
1226 {
1228 {
1235 }
1238 }
1242 }
1243 \f
1244 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1245 to produce a new constant.
1247 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1249 tree
1251 {
1255 HOST_WIDE_INT hi;
1257 HOST_WIDE_INT garbageh;
1258 tree t;
1261 int is_sizetype
1272 {
1288 /* It's unclear from the C standard whether shifts can overflow.
1289 The following code ignores overflow; perhaps a C standard
1290 interpretation ruling is needed. */
1320 /* This is a shortcut for a common special case. */
1325 {
1331 }
1333 /* ... fall through ... */
1337 {
1340 }
1343 {
1346 }
1353 /* This is a shortcut for a common special case. */
1358 {
1363 }
1365 /* ... fall through ... */
1381 else
1387 else
1393 }
1395 /* If this is for a sizetype, can be represented as one (signed)
1396 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1397 constants. */
1403 else
1404 {
1407 }
1410 = ((notrunc
1417 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1418 So check if force_fit_type truncated the value. */
1429 }
1431 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1432 constant. We assume ARG1 and ARG2 have the same data type, or at least
1433 are the same kind of constant and the same machine mode.
1435 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1437 static tree
1439 {
1447 {
1449 REAL_VALUE_TYPE d1;
1450 REAL_VALUE_TYPE d2;
1451 REAL_VALUE_TYPE value;
1460 /* Don't perform operation if we honor signaling NaNs and
1461 either operand is a NaN. */
1466 /* Don't perform operation if it would raise a division
1467 by zero exception. */
1473 /* If either operand is a NaN, just return it. Otherwise, set up
1474 for floating-point trap; we return an overflow. */
1492 }
1494 {
1500 tree t;
1503 {
1523 notrunc),
1529 notrunc));
1533 {
1534 tree magsquared
1538 notrunc);
1541 const_binop
1546 notrunc),
1548 notrunc),
1549 notrunc),
1551 const_binop
1556 notrunc),
1558 notrunc),
1559 notrunc),
1561 }
1566 }
1568 }
1570 }
1572 /* These are the hash table functions for the hash table of INTEGER_CST
1573 nodes of a sizetype. */
1575 /* Return the hash code code X, an INTEGER_CST. */
1577 static hashval_t
1579 {
1585 }
1587 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1588 is the same as that given by *Y, which is the same. */
1590 static int
1592 {
1600 }
1601 \f
1602 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1603 bits are given by NUMBER and of the sizetype represented by KIND. */
1605 tree
1607 {
1609 }
1611 /* Likewise, but the desired type is specified explicitly. */
1615 htab_t size_htab;
1617 tree
1619 {
1623 {
1626 }
1628 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1629 hash table, we return the value from the hash table. Otherwise, we
1630 place that in the hash table and make a new node for the next time. */
1639 {
1645 }
1646 else
1648 }
1650 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1651 is a tree code. The type of the result is taken from the operands.
1652 Both must be the same type integer type and it must be a size type.
1653 If the operands are constant, so is the result. */
1655 tree
1657 {
1664 /* Handle the special case of two integer constants faster. */
1666 {
1667 /* And some specific cases even faster than that. */
1676 /* Handle general case of two integer constants. */
1678 }
1684 }
1686 /* Given two values, either both of sizetype or both of bitsizetype,
1687 compute the difference between the two values. Return the value
1688 in signed type corresponding to the type of the operands. */
1690 tree
1692 {
1694 tree ctype;
1700 /* If the type is already signed, just do the simple thing. */
1707 /* If either operand is not a constant, do the conversions to the signed
1708 type and subtract. The hardware will do the right thing with any
1709 overflow in the subtraction. */
1714 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1715 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1716 overflow) and negate (which can't either). Special-case a result
1717 of zero while we're here. */
1722 else
1726 }
1727 \f
1729 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1730 type TYPE. If no simplification can be done return NULL_TREE. */
1732 static tree
1734 {
1736 tree t;
1742 {
1744 {
1745 /* If we would build a constant wider than GCC supports,
1746 leave the conversion unfolded. */
1750 /* If we are trying to make a sizetype for a small integer, use
1751 size_int to pick up cached types to reduce duplicate nodes. */
1757 /* Given an integer constant, make new constant with new type,
1758 appropriately sign-extended or truncated. */
1762 /* Indicate an overflow if (1) ARG1 already overflowed,
1763 or (2) force_fit_type indicates an overflow.
1764 Tell force_fit_type that an overflow has already occurred
1765 if ARG1 is a too-large unsigned value and T is signed.
1766 But don't indicate an overflow if converting a pointer. */
1777 }
1779 {
1780 /* The following code implements the floating point to integer
1781 conversion rules required by the Java Language Specification,
1782 that IEEE NaNs are mapped to zero and values that overflow
1783 the target precision saturate, i.e. values greater than
1784 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1785 are mapped to INT_MIN. These semantics are allowed by the
1786 C and C++ standards that simply state that the behavior of
1787 FP-to-integer conversion is unspecified upon overflow. */
1791 REAL_VALUE_TYPE r;
1795 {
1814 }
1816 /* If R is NaN, return zero and show we have an overflow. */
1818 {
1822 }
1824 /* See if R is less than the lower bound or greater than the
1825 upper bound. */
1828 {
1832 {
1836 }
1837 }
1840 {
1843 {
1846 {
1850 }
1851 }
1852 }
1864 }
1865 }
1867 {
1871 {
1873 {
1874 /* We make a copy of ARG1 so that we don't modify an
1875 existing constant tree. */
1879 }
1890 }
1891 }
1893 }
1895 /* Convert expression ARG to type TYPE. Used by the middle-end for
1896 simple conversions in preference to calling the front-end's convert. */
1898 tree
1900 {
1902 tree tem;
1917 {
1919 {
1923 }
1928 {
1931 }
1936 }
1938 {
1940 {
1944 }
1946 {
1950 }
1958 {
1961 }
1962 }
1964 {
1972 {
1976 {
1980 }
1988 }
1989 }
1991 {
2000 }
2004 }
2005 \f
2006 /* Return an expr equal to X but certainly not valid as an lvalue. */
2008 tree
2010 {
2011 /* We only need to wrap lvalue tree codes. */
2013 {
2048 /* Assume the worst for front-end tree codes. */
2052 }
2054 }
2056 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2057 Zero means allow extended lvalues. */
2061 /* When pedantic, return an expr equal to X but certainly not valid as a
2062 pedantic lvalue. Otherwise, return X. */
2064 tree
2066 {
2069 else
2071 }
2072 \f
2073 /* Given a tree comparison code, return the code that is the logical inverse
2074 of the given code. It is not safe to do this for floating-point
2075 comparisons, except for NE_EXPR and EQ_EXPR, so we receive a machine mode
2076 as well: if reversing the comparison is unsafe, return ERROR_MARK. */
2078 static enum tree_code
2080 {
2085 {
2116 }
2117 }
2119 /* Similar, but return the comparison that results if the operands are
2120 swapped. This is safe for floating-point. */
2122 static enum tree_code
2124 {
2126 {
2140 }
2141 }
2144 /* Convert a comparison tree code from an enum tree_code representation
2145 into a compcode bit-based encoding. This function is the inverse of
2146 compcode_to_comparison. */
2148 static enum comparison_code
2150 {
2152 {
2183 }
2184 }
2186 /* Convert a compcode bit-based encoding of a comparison operator back
2187 to GCC's enum tree_code representation. This function is the
2188 inverse of comparison_to_compcode. */
2190 static enum tree_code
2192 {
2194 {
2225 }
2226 }
2228 /* Return a tree for the comparison which is the combination of
2229 doing the AND or OR (depending on CODE) of the two operations LCODE
2230 and RCODE on the identical operands LL_ARG and LR_ARG. Take into account
2231 the possibility of trapping if the mode has NaNs, and return NULL_TREE
2232 if this makes the transformation invalid. */
2234 tree
2238 {
2245 {
2256 }
2259 {
2260 /* Eliminate unordered comparisons, as well as LTGT and ORD
2261 which are not used unless the mode has NaNs. */
2267 }
2269 {
2270 /* Check that the original operation and the optimized ones will trap
2271 under the same condition. */
2282 /* In a short-circuited boolean expression the LHS might be
2283 such that the RHS, if evaluated, will never trap. For
2284 example, in ORD (x, y) && (x < y), we evaluate the RHS only
2285 if neither x nor y is NaN. (This is a mixed blessing: for
2286 example, the expression above will never trap, hence
2287 optimizing it to x < y would be invalid). */
2292 /* If the comparison was short-circuited, and only the RHS
2293 trapped, we may now generate a spurious trap. */
2298 /* If we changed the conditions that cause a trap, we lose. */
2301 }
2307 else
2310 }
2312 /* Return nonzero if CODE is a tree code that represents a truth value. */
2314 static int
2316 {
2321 }
2322 \f
2323 /* Return nonzero if two operands (typically of the same tree node)
2324 are necessarily equal. If either argument has side-effects this
2325 function returns zero. FLAGS modifies behavior as follows:
2327 If OEP_ONLY_CONST is set, only return nonzero for constants.
2328 This function tests whether the operands are indistinguishable;
2329 it does not test whether they are equal using C's == operation.
2330 The distinction is important for IEEE floating point, because
2331 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2332 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2334 If OEP_ONLY_CONST is unset, a VAR_DECL is considered equal to itself
2335 even though it may hold multiple values during a function.
2336 This is because a GCC tree node guarantees that nothing else is
2337 executed between the evaluation of its "operands" (which may often
2338 be evaluated in arbitrary order). Hence if the operands themselves
2339 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2340 same value in each operand/subexpression. Hence a zero value for
2341 ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
2342 If comparing arbitrary expression trees, such as from different
2343 statements, ONLY_CONST must usually be nonzero.
2345 If OEP_PURE_SAME is set, then pure functions with identical arguments
2346 are considered the same. It is used when the caller has other ways
2347 to ensure that global memory is unchanged in between. */
2349 int
2351 {
2352 /* If either is ERROR_MARK, they aren't equal. */
2356 /* If both types don't have the same signedness, then we can't consider
2357 them equal. We must check this before the STRIP_NOPS calls
2358 because they may change the signedness of the arguments. */
2366 /* This is needed for conversions and for COMPONENT_REF.
2367 Might as well play it safe and always test this. */
2373 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2374 We don't care about side effects in that case because the SAVE_EXPR
2375 takes care of that for us. In all other cases, two expressions are
2376 equal if they have no side effects. If we have two identical
2377 expressions with side effects that should be treated the same due
2378 to the only side effects being identical SAVE_EXPR's, that will
2379 be detected in the recursive calls below. */
2385 /* Next handle constant cases, those for which we can return 1 even
2386 if ONLY_CONST is set. */
2389 {
2402 {
2412 {
2414 flags))
2418 }
2421 }
2425 flags)
2427 flags));
2440 }
2446 {
2448 /* Two conversions are equal only if signedness and modes match. */
2464 /* For commutative ops, allow the other order. */
2472 /* If either of the pointer (or reference) expressions we are
2473 dereferencing contain a side effect, these cannot be equal. */
2479 {
2501 }
2505 {
2515 /* If the CALL_EXPRs call different functions, then they
2516 clearly can not be equal. */
2521 {
2525 else
2529 }
2531 /* Now see if all the arguments are the same. operand_equal_p
2532 does not handle TREE_LIST, so we walk the operands here
2533 feeding them to operand_equal_p. */
2537 {
2539 flags))
2544 }
2546 /* If we get here and both argument lists are exhausted
2547 then the CALL_EXPRs are equal. */
2552 }
2555 /* Consider __builtin_sqrt equal to sqrt. */
2563 }
2564 }
2565 \f
2566 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2567 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2569 When in doubt, return 0. */
2571 static int
2573 {
2585 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2586 and see if the inner values are the same. This removes any
2587 signedness comparison, which doesn't matter here. */
2594 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2595 actual comparison operand, ARG0.
2597 First throw away any conversions to wider types
2598 already present in the operands. */
2607 {
2610 /* Make sure shorter operand is extended the right way
2611 to match the longer operand. */
2617 }
2620 }
2621 \f
2622 /* See if ARG is an expression that is either a comparison or is performing
2623 arithmetic on comparisons. The comparisons must only be comparing
2624 two different values, which will be stored in *CVAL1 and *CVAL2; if
2625 they are nonzero it means that some operands have already been found.
2626 No variables may be used anywhere else in the expression except in the
2627 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2628 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2630 If this is true, return 1. Otherwise, return zero. */
2632 static int
2634 {
2638 /* We can handle some of the 'e' cases here. */
2648 {
2649 /* If we've already found a CVAL1 or CVAL2, this expression is
2650 two complex to handle. */
2656 }
2659 {
2682 /* First see if we can handle the first operand, then the second. For
2683 the second operand, we know *CVAL1 can't be zero. It must be that
2684 one side of the comparison is each of the values; test for the
2685 case where this isn't true by failing if the two operands
2686 are the same. */
2695 ;
2699 ;
2700 else
2704 ;
2708 ;
2709 else
2716 }
2717 }
2718 \f
2719 /* ARG is a tree that is known to contain just arithmetic operations and
2720 comparisons. Evaluate the operations in the tree substituting NEW0 for
2721 any occurrence of OLD0 as an operand of a comparison and likewise for
2722 NEW1 and OLD1. */
2724 static tree
2726 {
2731 /* We can handle some of the 'e' cases here. */
2739 {
2754 {
2771 }
2772 /* Fall through - ??? */
2775 {
2779 /* We need to check both for exact equality and tree equality. The
2780 former will be true if the operand has a side-effect. In that
2781 case, we know the operand occurred exactly once. */
2794 }
2798 }
2799 }
2800 \f
2801 /* Return a tree for the case when the result of an expression is RESULT
2802 converted to TYPE and OMITTED was previously an operand of the expression
2803 but is now not needed (e.g., we folded OMITTED * 0).
2805 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2806 the conversion of RESULT to TYPE. */
2808 tree
2810 {
2817 }
2819 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2821 static tree
2823 {
2830 }
2832 /* Return a tree for the case when the result of an expression is RESULT
2833 converted to TYPE and OMITTED1 and OMITTED2 were previously operands
2834 of the expression but are now not needed.
2836 If OMITTED1 or OMITTED2 has side effects, they must be evaluated.
2837 If both OMITTED1 and OMITTED2 have side effects, OMITTED1 is
2838 evaluated before OMITTED2. Otherwise, if neither has side effects,
2839 just do the conversion of RESULT to TYPE. */
2841 tree
2843 {
2852 }
2854 \f
2855 /* Return a simplified tree node for the truth-negation of ARG. This
2856 never alters ARG itself. We assume that ARG is an operation that
2857 returns a truth value (0 or 1).
2859 FIXME: one would think we would fold the result, but it causes
2860 problems with the dominator optimizer. */
2861 tree
2863 {
2870 /* If this is a comparison, we can simply invert it, except for
2871 floating-point non-equality comparisons, in which case we just
2872 enclose a TRUTH_NOT_EXPR around what we have. */
2875 {
2878 && flag_trapping_math
2882 else
2883 {
2888 else
2891 }
2892 }
2895 {
2910 /* Here we can invert either operand. We invert the first operand
2911 unless the second operand is a TRUTH_NOT_EXPR in which case our
2912 result is the XOR of the first operand with the inside of the
2913 negation of the second operand. */
2918 else
2972 }
2976 }
2978 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2979 operands are another bit-wise operation with a common input. If so,
2980 distribute the bit operations to save an operation and possibly two if
2981 constants are involved. For example, convert
2982 (A | B) & (A | C) into A | (B & C)
2983 Further simplification will occur if B and C are constants.
2985 If this optimization cannot be done, 0 will be returned. */
2987 static tree
2989 {
2990 tree common;
3000 {
3004 }
3006 {
3010 }
3012 {
3016 }
3018 {
3022 }
3023 else
3028 }
3029 \f
3030 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
3031 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
3033 static tree
3036 {
3043 }
3045 /* Optimize a bit-field compare.
3047 There are two cases: First is a compare against a constant and the
3048 second is a comparison of two items where the fields are at the same
3049 bit position relative to the start of a chunk (byte, halfword, word)
3050 large enough to contain it. In these cases we can avoid the shift
3051 implicit in bitfield extractions.
3053 For constants, we emit a compare of the shifted constant with the
3054 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
3055 compared. For two fields at the same position, we do the ANDs with the
3056 similar mask and compare the result of the ANDs.
3058 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
3059 COMPARE_TYPE is the type of the comparison, and LHS and RHS
3060 are the left and right operands of the comparison, respectively.
3062 If the optimization described above can be done, we return the resulting
3063 tree. Otherwise we return zero. */
3065 static tree
3068 {
3077 tree mask;
3078 tree offset;
3080 /* Get all the information about the extractions being done. If the bit size
3081 if the same as the size of the underlying object, we aren't doing an
3082 extraction at all and so can do nothing. We also don't want to
3083 do anything if the inner expression is a PLACEHOLDER_EXPR since we
3084 then will no longer be able to replace it. */
3092 {
3093 /* If this is not a constant, we can only do something if bit positions,
3094 sizes, and signedness are the same. */
3102 }
3104 /* See if we can find a mode to refer to this field. We should be able to,
3105 but fail if we can't. */
3114 /* Set signed and unsigned types of the precision of this mode for the
3115 shifts below. */
3119 /* Compute the bit position and size for the new reference and our offset
3120 within it. If the new reference is the same size as the original, we
3121 won't optimize anything, so return zero. */
3131 /* Make the mask to be used against the extracted field. */
3141 /* If not comparing with constant, just rework the comparison
3142 and return. */
3147 mask),
3151 mask));
3153 /* Otherwise, we are handling the constant case. See if the constant is too
3154 big for the field. Warn and return a tree of for 0 (false) if so. We do
3155 this not only for its own sake, but to avoid having to test for this
3156 error case below. If we didn't, we might generate wrong code.
3158 For unsigned fields, the constant shifted right by the field length should
3159 be all zero. For signed fields, the high-order bits should agree with
3160 the sign bit. */
3163 {
3167 {
3171 }
3172 }
3173 else
3174 {
3178 {
3182 }
3183 }
3185 /* Single-bit compares should always be against zero. */
3187 {
3190 }
3192 /* Make a new bitfield reference, shift the constant over the
3193 appropriate number of bits and mask it with the computed mask
3194 (in case this was a signed field). If we changed it, make a new one. */
3197 {
3200 }
3210 rhs);
3211 }
3212 \f
3213 /* Subroutine for fold_truthop: decode a field reference.
3215 If EXP is a comparison reference, we return the innermost reference.
3217 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3218 set to the starting bit number.
3220 If the innermost field can be completely contained in a mode-sized
3221 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3223 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3224 otherwise it is not changed.
3226 *PUNSIGNEDP is set to the signedness of the field.
3228 *PMASK is set to the mask used. This is either contained in a
3229 BIT_AND_EXPR or derived from the width of the field.
3231 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3233 Return 0 if this is not a component reference or is one that we can't
3234 do anything with. */
3236 static tree
3241 {
3245 tree unsigned_type;
3248 /* All the optimizations using this function assume integer fields.
3249 There are problems with FP fields since the type_for_size call
3250 below can fail for, e.g., XFmode. */
3254 /* We are interested in the bare arrangement of bits, so strip everything
3255 that doesn't affect the machine mode. However, record the type of the
3256 outermost expression if it may matter below. */
3264 {
3270 }
3279 /* If the number of bits in the reference is the same as the bitsize of
3280 the outer type, then the outer type gives the signedness. Otherwise
3281 (in case of a small bitfield) the signedness is unchanged. */
3285 /* Compute the mask to access the bitfield. */
3295 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3303 }
3305 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3306 bit positions. */
3308 static int
3310 {
3313 tree tmask;
3318 return
3325 }
3327 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3328 represents the sign bit of EXP's type. If EXP represents a sign
3329 or zero extension, also test VAL against the unextended type.
3330 The return value is the (sub)expression whose sign bit is VAL,
3331 or NULL_TREE otherwise. */
3333 static tree
3335 {
3339 tree t;
3341 /* Tree EXP must have an integral type. */
3346 /* Tree VAL must be an integer constant. */
3353 {
3360 }
3361 else
3362 {
3369 }
3371 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3372 treat VAL as if it were unsigned. */
3377 /* Handle extension from a narrower type. */
3383 }
3385 /* Subroutine for fold_truthop: determine if an operand is simple enough
3386 to be evaluated unconditionally. */
3388 static int
3390 {
3391 /* Strip any conversions that don't change the machine mode. */
3403 /* Don't regard global variables as simple. They may be
3404 allocated in ways unknown to the compiler (shared memory,
3405 #pragma weak, etc). */
3408 /* Loading a static variable is unduly expensive, but global
3409 registers aren't expensive. */
3411 }
3412 \f
3413 /* The following functions are subroutines to fold_range_test and allow it to
3414 try to change a logical combination of comparisons into a range test.
3416 For example, both
3417 X == 2 || X == 3 || X == 4 || X == 5
3418 and
3419 X >= 2 && X <= 5
3420 are converted to
3421 (unsigned) (X - 2) <= 3
3423 We describe each set of comparisons as being either inside or outside
3424 a range, using a variable named like IN_P, and then describe the
3425 range with a lower and upper bound. If one of the bounds is omitted,
3426 it represents either the highest or lowest value of the type.
3428 In the comments below, we represent a range by two numbers in brackets
3429 preceded by a "+" to designate being inside that range, or a "-" to
3430 designate being outside that range, so the condition can be inverted by
3431 flipping the prefix. An omitted bound is represented by a "-". For
3432 example, "- [-, 10]" means being outside the range starting at the lowest
3433 possible value and ending at 10, in other words, being greater than 10.
3434 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3435 always false.
3437 We set up things so that the missing bounds are handled in a consistent
3438 manner so neither a missing bound nor "true" and "false" need to be
3439 handled using a special case. */
3441 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3442 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3443 and UPPER1_P are nonzero if the respective argument is an upper bound
3444 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3445 must be specified for a comparison. ARG1 will be converted to ARG0's
3446 type if both are specified. */
3448 static tree
3451 {
3452 tree tem;
3456 /* If neither arg represents infinity, do the normal operation.
3457 Else, if not a comparison, return infinity. Else handle the special
3458 comparison rules. Note that most of the cases below won't occur, but
3459 are handled for consistency. */
3462 {
3467 }
3472 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3473 for neither. In real maths, we cannot assume open ended ranges are
3474 the same. But, this is computer arithmetic, where numbers are finite.
3475 We can therefore make the transformation of any unbounded range with
3476 the value Z, Z being greater than any representable number. This permits
3477 us to treat unbounded ranges as equal. */
3481 {
3502 }
3505 }
3506 \f
3507 /* Given EXP, a logical expression, set the range it is testing into
3508 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3509 actually being tested. *PLOW and *PHIGH will be made of the same type
3510 as the returned expression. If EXP is not a comparison, we will most
3511 likely not be returning a useful value and range. */
3513 static tree
3515 {
3522 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3523 and see if we can refine the range. Some of the cases below may not
3524 happen, but it doesn't seem worth worrying about this. We "continue"
3525 the outer loop when we've changed something; otherwise we "break"
3526 the switch, which will "break" the while. */
3532 {
3536 {
3548 }
3550 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3551 lose a cast by accident. */
3556 {
3563 /* We can only do something if the range is testing for zero
3564 and if the second operand is an integer constant. Note that
3565 saying something is "in" the range we make is done by
3566 complementing IN_P since it will set in the initial case of
3567 being not equal to zero; "out" is leaving it alone. */
3574 {
3595 }
3599 /* If this is an unsigned comparison, we also know that EXP is
3600 greater than or equal to zero. We base the range tests we make
3601 on that fact, so we record it here so we can parse existing
3602 range tests. */
3604 {
3607 NULL_TREE))
3612 /* If the high bound is missing, but we have a nonzero low
3613 bound, reverse the range so it goes from zero to the low bound
3614 minus 1. */
3616 {
3621 }
3622 }
3626 /* (-x) IN [a,b] -> x in [-b, -a] */
3638 /* ~ X -> -X - 1 */
3647 /* If EXP is signed, any overflow in the computation is undefined,
3648 so we don't worry about it so long as our computations on
3649 the bounds don't overflow. For unsigned, overflow is defined
3650 and this is exactly the right thing. */
3659 /* Check for an unsigned range which has wrapped around the maximum
3660 value thus making n_high < n_low, and normalize it. */
3662 {
3668 /* If the range is of the form +/- [ x+1, x ], we won't
3669 be able to normalize it. But then, it represents the
3670 whole range or the empty set, so make it
3671 +/- [ -, - ]. */
3675 else
3677 }
3678 else
3701 /* If we're converting from an unsigned to a signed type,
3702 we will be doing the comparison as unsigned. The tests above
3703 have already verified that LOW and HIGH are both positive.
3705 So we have to make sure that the original unsigned value will
3706 be interpreted as positive. */
3708 {
3711 tree high_positive;
3713 /* A range without an upper bound is, naturally, unbounded.
3714 Since convert would have cropped a very large value, use
3715 the max value for the destination type. */
3716 high_positive
3723 high_positive),
3725 integer_one_node)));
3727 /* If the low bound is specified, "and" the range with the
3728 range for which the original unsigned value will be
3729 positive. */
3731 {
3735 high_positive))
3739 }
3740 else
3741 {
3742 /* Otherwise, "or" the range with the range of the input
3743 that will be interpreted as negative. */
3747 high_positive))
3751 }
3752 }
3760 }
3763 }
3765 /* If EXP is a constant, we can evaluate whether this is true or false. */
3767 {
3774 }
3778 }
3779 \f
3780 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3781 type, TYPE, return an expression to test if EXP is in (or out of, depending
3782 on IN_P) the range. */
3784 static tree
3786 {
3788 tree value;
3807 {
3809 {
3813 }
3815 }
3817 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3819 {
3821 HOST_WIDE_INT hi;
3826 {
3829 }
3830 else
3831 {
3834 }
3837 {
3839 {
3842 }
3845 }
3846 }
3853 value);
3856 }
3857 \f
3858 /* Given two ranges, see if we can merge them into one. Return 1 if we
3859 can, 0 if we can't. Set the output range into the specified parameters. */
3861 static int
3864 {
3868 tree tem;
3878 /* Make range 0 be the range that starts first, or ends last if they
3879 start at the same value. Swap them if it isn't. */
3882 || (lowequal
3885 {
3889 }
3891 /* Now flag two cases, whether the ranges are disjoint or whether the
3892 second range is totally subsumed in the first. Note that the tests
3893 below are simplified by the ones above. */
3899 /* We now have four cases, depending on whether we are including or
3900 excluding the two ranges. */
3902 {
3903 /* If they don't overlap, the result is false. If the second range
3904 is a subset it is the result. Otherwise, the range is from the start
3905 of the second to the end of the first. */
3910 else
3912 }
3915 {
3916 /* If they don't overlap, the result is the first range. If they are
3917 equal, the result is false. If the second range is a subset of the
3918 first, and the ranges begin at the same place, we go from just after
3919 the end of the first range to the end of the second. If the second
3920 range is not a subset of the first, or if it is a subset and both
3921 ranges end at the same place, the range starts at the start of the
3922 first range and ends just before the second range.
3923 Otherwise, we can't describe this as a single range. */
3929 {
3933 }
3935 {
3939 }
3940 else
3942 }
3945 {
3946 /* If they don't overlap, the result is the second range. If the second
3947 is a subset of the first, the result is false. Otherwise,
3948 the range starts just after the first range and ends at the
3949 end of the second. */
3954 else
3955 {
3959 }
3960 }
3962 else
3963 {
3964 /* The case where we are excluding both ranges. Here the complex case
3965 is if they don't overlap. In that case, the only time we have a
3966 range is if they are adjacent. If the second is a subset of the
3967 first, the result is the first. Otherwise, the range to exclude
3968 starts at the beginning of the first range and ends at the end of the
3969 second. */
3971 {
3978 else
3980 }
3983 else
3985 }
3989 }
3990 \f
3991 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3992 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3993 #endif
3995 /* EXP is some logical combination of boolean tests. See if we can
3996 merge it into some range test. Return the new tree if so. */
3998 static tree
4000 {
4007 tree tem;
4009 /* If this is an OR operation, invert both sides; we will invert
4010 again at the end. */
4014 /* If both expressions are the same, if we can merge the ranges, and we
4015 can build the range test, return it or it inverted. If one of the
4016 ranges is always true or always false, consider it to be the same
4017 expression as the other. */
4027 /* On machines where the branch cost is expensive, if this is a
4028 short-circuited branch and the underlying object on both sides
4029 is the same, make a non-short-circuit operation. */
4035 {
4036 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
4037 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
4038 which cases we can't do this. */
4047 {
4059 }
4060 }
4063 }
4064 \f
4065 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
4066 bit value. Arrange things so the extra bits will be set to zero if and
4067 only if C is signed-extended to its full width. If MASK is nonzero,
4068 it is an INTEGER_CST that should be AND'ed with the extra bits. */
4070 static tree
4072 {
4075 tree temp;
4080 /* We work by getting just the sign bit into the low-order bit, then
4081 into the high-order bit, then sign-extend. We then XOR that value
4082 with C. */
4086 /* We must use a signed type in order to get an arithmetic right shift.
4087 However, we must also avoid introducing accidental overflows, so that
4088 a subsequent call to integer_zerop will work. Hence we must
4089 do the type conversion here. At this point, the constant is either
4090 zero or one, and the conversion to a signed type can never overflow.
4091 We could get an overflow if this conversion is done anywhere else. */
4100 /* If necessary, convert the type back to match the type of C. */
4105 }
4106 \f
4107 /* Find ways of folding logical expressions of LHS and RHS:
4108 Try to merge two comparisons to the same innermost item.
4109 Look for range tests like "ch >= '0' && ch <= '9'".
4110 Look for combinations of simple terms on machines with expensive branches
4111 and evaluate the RHS unconditionally.
4113 For example, if we have p->a == 2 && p->b == 4 and we can make an
4114 object large enough to span both A and B, we can do this with a comparison
4115 against the object ANDed with the a mask.
4117 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
4118 operations to do this with one comparison.
4120 We check for both normal comparisons and the BIT_AND_EXPRs made this by
4121 function and the one above.
4123 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
4124 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
4126 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
4127 two operands.
4129 We return the simplified tree or 0 if no optimization is possible. */
4131 static tree
4133 {
4134 /* If this is the "or" of two comparisons, we can do something if
4135 the comparisons are NE_EXPR. If this is the "and", we can do something
4136 if the comparisons are EQ_EXPR. I.e.,
4137 (a->b == 2 && a->c == 4) can become (a->new == NEW).
4139 WANTED_CODE is this operation code. For single bit fields, we can
4140 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
4141 comparison for one-bit fields. */
4161 /* Start by getting the comparison codes. Fail if anything is volatile.
4162 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
4163 it were surrounded with a NE_EXPR. */
4172 {
4175 }
4178 {
4181 }
4191 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
4194 {
4195 tree result;
4198 {
4203 }
4206 {
4212 }
4213 }
4218 /* If the RHS can be evaluated unconditionally and its operands are
4219 simple, it wins to evaluate the RHS unconditionally on machines
4220 with expensive branches. In this case, this isn't a comparison
4221 that can be merged. Avoid doing this if the RHS is a floating-point
4222 comparison since those can trap. */
4228 {
4229 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4239 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4250 }
4252 /* See if the comparisons can be merged. Then get all the parameters for
4253 each side. */
4277 /* It must be true that the inner operation on the lhs of each
4278 comparison must be the same if we are to be able to do anything.
4279 Then see if we have constants. If not, the same must be true for
4280 the rhs's. */
4291 else
4294 /* If either comparison code is not correct for our logical operation,
4295 fail. However, we can convert a one-bit comparison against zero into
4296 the opposite comparison against that bit being set in the field. */
4300 {
4302 {
4303 /* Make the left operand unsigned, since we are only interested
4304 in the value of one bit. Otherwise we are doing the wrong
4305 thing below. */
4308 }
4309 else
4311 }
4313 /* This is analogous to the code for l_const above. */
4315 {
4317 {
4320 }
4321 else
4323 }
4325 /* After this point all optimizations will generate bit-field
4326 references, which we might not want. */
4330 /* See if we can find a mode that contains both fields being compared on
4331 the left. If we can't, fail. Otherwise, update all constants and masks
4332 to be relative to a field of that size. */
4337 volatilep);
4347 {
4350 }
4358 {
4366 {
4370 }
4371 }
4373 {
4381 {
4385 }
4386 }
4388 /* If the right sides are not constant, do the same for it. Also,
4389 disallow this optimization if a size or signedness mismatch occurs
4390 between the left and right sides. */
4392 {
4395 /* Make sure the two fields on the right
4396 correspond to the left without being swapped. */
4404 volatilep);
4414 {
4417 }
4424 /* Make a mask that corresponds to both fields being compared.
4425 Do this for both items being compared. If the operands are the
4426 same size and the bits being compared are in the same position
4427 then we can do this by masking both and comparing the masked
4428 results. */
4432 {
4444 }
4446 /* There is still another way we can do something: If both pairs of
4447 fields being compared are adjacent, we may be able to make a wider
4448 field containing them both.
4450 Note that we still must mask the lhs/rhs expressions. Furthermore,
4451 the mask must be shifted to account for the shift done by
4452 make_bit_field_ref. */
4457 {
4458 tree type;
4470 /* Convert to the smaller type before masking out unwanted bits. */
4473 {
4475 {
4479 }
4481 {
4485 }
4486 }
4495 }
4498 }
4500 /* Handle the case of comparisons with constants. If there is something in
4501 common between the masks, those bits of the constants must be the same.
4502 If not, the condition is always false. Test for this to avoid generating
4503 incorrect code below. */
4508 {
4510 {
4513 }
4514 else
4515 {
4518 }
4519 }
4521 /* Construct the expression we will return. First get the component
4522 reference we will make. Unless the mask is all ones the width of
4523 that field, perform the mask operation. Then compare with the
4524 merged constant. */
4534 }
4535 \f
4536 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4537 constant. */
4539 static tree
4541 {
4546 tree minmax_const;
4548 tree inner;
4558 /* If something does not permit us to optimize, return the original tree. */
4566 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4567 and GT_EXPR, doing the rest with recursive calls using logical
4568 simplifications. */
4570 {
4572 return
4576 return
4578 optimize_minmax_comparison
4580 optimize_minmax_comparison
4585 /* MAX (X, 0) == 0 -> X <= 0 */
4589 /* MAX (X, 0) == 5 -> X == 5 */
4593 /* MAX (X, 0) == -1 -> false */
4597 /* MIN (X, 0) == 0 -> X >= 0 */
4601 /* MIN (X, 0) == 5 -> false */
4604 else
4605 /* MIN (X, 0) == -1 -> X == -1 */
4610 /* MAX (X, 0) > 0 -> X > 0
4611 MAX (X, 0) > 5 -> X > 5 */
4615 /* MAX (X, 0) > -1 -> true */
4619 /* MIN (X, 0) > 0 -> false
4620 MIN (X, 0) > 5 -> false */
4623 else
4624 /* MIN (X, 0) > -1 -> X > -1 */
4629 }
4630 }
4631 \f
4632 /* T is an integer expression that is being multiplied, divided, or taken a
4633 modulus (CODE says which and what kind of divide or modulus) by a
4634 constant C. See if we can eliminate that operation by folding it with
4635 other operations already in T. WIDE_TYPE, if non-null, is a type that
4636 should be used for the computation if wider than our type.
4638 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4639 (X * 2) + (Y * 4). We must, however, be assured that either the original
4640 expression would not overflow or that overflow is undefined for the type
4641 in the language in question.
4643 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4644 the machine has a multiply-accumulate insn or that this is part of an
4645 addressing calculation.
4647 If we return a non-null expression, it is an equivalent form of the
4648 original computation, but need not be in the original type. */
4650 static tree
4652 {
4653 /* To avoid exponential search depth, refuse to allow recursion past
4654 three levels. Beyond that (1) it's highly unlikely that we'll find
4655 something interesting and (2) we've probably processed it before
4656 when we built the inner expression. */
4659 tree ret;
4664 depth++;
4666 depth--;
4669 }
4671 static tree
4673 {
4683 /* Don't deal with constants of zero here; they confuse the code below. */
4693 /* Note that we need not handle conditional operations here since fold
4694 already handles those cases. So just do arithmetic here. */
4696 {
4698 /* For a constant, we can always simplify if we are a multiply
4699 or (for divide and modulus) if it is a multiple of our constant. */
4707 /* If op0 is an expression ... */
4712 /* ... and is unsigned, and its type is smaller than ctype,
4713 then we cannot pass through as widening. */
4719 /* ... or its type is larger than ctype,
4720 then we cannot pass through this truncation. */
4723 /* ... or signedness changes for division or modulus,
4724 then we cannot pass through this conversion. */
4730 /* Pass the constant down and see if we can make a simplification. If
4731 we can, replace this expression with the inner simplification for
4732 possible later conversion to our or some other type. */
4737 code == MULT_EXPR
4748 /* If widening the type changes the signedness, then we can't perform
4749 this optimization as that changes the result. */
4753 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4756 {
4762 }
4766 /* If the second operand is constant, this is a multiplication
4767 or floor division, by a power of two, so we can treat it that
4768 way unless the multiplier or divisor overflows. */
4770 /* const_binop may not detect overflow correctly,
4771 so check for it explicitly here. */
4776 size_one_node,
4786 /* See if we can eliminate the operation on both sides. If we can, we
4787 can return a new PLUS or MINUS. If we can't, the only remaining
4788 cases where we can do anything are if the second operand is a
4789 constant. */
4794 /* If not multiplication, we can only do this if both operands
4795 are divisible by c. */
4801 /* If this was a subtraction, negate OP1 and set it to be an addition.
4802 This simplifies the logic below. */
4809 /* If either OP1 or C are negative, this optimization is not safe for
4810 some of the division and remainder types while for others we need
4811 to change the code. */
4813 {
4821 }
4823 /* If it's a multiply or a division/modulus operation of a multiple
4824 of our constant, do the operation and verify it doesn't overflow. */
4827 {
4830 /* We allow the constant to overflow with wrapping semantics. */
4834 }
4835 else
4838 /* If we have an unsigned type is not a sizetype, we cannot widen
4839 the operation since it will change the result if the original
4840 computation overflowed. */
4846 /* If we were able to eliminate our operation from the first side,
4847 apply our operation to the second side and reform the PLUS. */
4851 /* The last case is if we are a multiply. In that case, we can
4852 apply the distributive law to commute the multiply and addition
4853 if the multiplication of the constants doesn't overflow. */
4859 op1));
4864 /* We have a special case here if we are doing something like
4865 (C * 8) % 4 since we know that's zero. */
4872 /* ... fall through ... */
4876 /* If we can extract our operation from the LHS, do so and return a
4877 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4878 do something only if the second operand is a constant. */
4890 /* If these are the same operation types, we can associate them
4891 assuming no overflow. */
4898 /* If these operations "cancel" each other, we have the main
4899 optimizations of this pass, which occur when either constant is a
4900 multiple of the other, in which case we replace this with either an
4901 operation or CODE or TCODE.
4903 If we have an unsigned type that is not a sizetype, we cannot do
4904 this since it will change the result if the original computation
4905 overflowed. */
4908 && ! flag_wrapv
4913 {
4924 }
4929 }
4932 }
4933 \f
4934 /* Return a node which has the indicated constant VALUE (either 0 or
4935 1), and is of the indicated TYPE. */
4937 static tree
4939 {
4945 else
4946 {
4951 }
4952 }
4954 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4955 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4956 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4957 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4958 COND is the first argument to CODE; otherwise (as in the example
4959 given here), it is the second argument. TYPE is the type of the
4960 original expression. Return NULL_TREE if no simplification is
4961 possible. */
4963 static tree
4966 {
4971 /* This transformation is only worthwhile if we don't have to wrap
4972 arg in a SAVE_EXPR, and the operation can be simplified on atleast
4973 one of the branches once its pushed inside the COND_EXPR. */
4978 {
4982 /* If this operand throws an expression, then it does not make
4983 sense to try to perform a logical or arithmetic operation
4984 involving it. */
4989 }
4990 else
4991 {
4996 }
5007 }
5009 \f
5010 /* Subroutine of fold() that checks for the addition of +/- 0.0.
5012 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
5013 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
5014 ADDEND is the same as X.
5016 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
5017 and finite. The problematic cases are when X is zero, and its mode
5018 has signed zeros. In the case of rounding towards -infinity,
5019 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
5020 modes, X + 0 is not the same as X because -0 + 0 is 0. */
5022 static bool
5024 {
5028 /* Don't allow the fold with -fsignaling-nans. */
5032 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
5036 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
5041 /* The mode has signed zeros, and we have to honor their sign.
5042 In this situation, there is only one case we can return true for.
5043 X - 0 is the same as X unless rounding towards -infinity is
5044 supported. */
5046 }
5048 /* Subroutine of fold() that checks comparisons of built-in math
5049 functions against real constants.
5051 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
5052 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
5053 is the type of the result and ARG0 and ARG1 are the operands of the
5054 comparison. ARG1 must be a TREE_REAL_CST.
5056 The function returns the constant folded tree if a simplification
5057 can be made, and NULL_TREE otherwise. */
5059 static tree
5062 {
5063 REAL_VALUE_TYPE c;
5066 {
5072 {
5073 /* sqrt(x) < y is always false, if y is negative. */
5077 /* sqrt(x) > y is always true, if y is negative and we
5078 don't care about NaNs, i.e. negative values of x. */
5082 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5085 }
5087 {
5088 REAL_VALUE_TYPE c2;
5094 {
5095 /* sqrt(x) > y is x == +Inf, when y is very large. */
5100 /* sqrt(x) > y is always false, when y is very large
5101 and we don't care about infinities. */
5103 }
5105 /* sqrt(x) > c is the same as x > c*c. */
5108 }
5110 {
5111 REAL_VALUE_TYPE c2;
5117 {
5118 /* sqrt(x) < y is always true, when y is a very large
5119 value and we don't care about NaNs or Infinities. */
5123 /* sqrt(x) < y is x != +Inf when y is very large and we
5124 don't care about NaNs. */
5129 /* sqrt(x) < y is x >= 0 when y is very large and we
5130 don't care about Infinities. */
5135 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5144 dconst0))),
5147 c2)))));
5148 }
5150 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5155 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5158 {
5163 dconst0))),
5166 c2)))));
5167 }
5168 }
5169 }
5172 }
5174 /* Subroutine of fold() that optimizes comparisons against Infinities,
5175 either +Inf or -Inf.
5177 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5178 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5179 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5181 The function returns the constant folded tree if a simplification
5182 can be made, and NULL_TREE otherwise. */
5184 static tree
5186 {
5188 REAL_VALUE_TYPE max;
5189 tree temp;
5194 /* For negative infinity swap the sense of the comparison. */
5200 {
5202 /* x > +Inf is always false, if with ignore sNANs. */
5208 /* x <= +Inf is always true, if we don't case about NaNs. */
5212 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5215 {
5218 }
5223 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5229 /* x < +Inf is always equal to x <= DBL_MAX. */
5235 /* x != +Inf is always equal to !(x > DBL_MAX). */
5241 /* The transformation below creates non-gimple code and thus is
5242 not appropriate if we are in gimple form. */
5252 }
5255 }
5257 /* Subroutine of fold() that optimizes comparisons of a division by
5258 a nonzero integer constant against an integer constant, i.e.
5259 X/C1 op C2.
5261 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5262 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5263 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5265 The function returns the constant folded tree if a simplification
5266 can be made, and NULL_TREE otherwise. */
5268 static tree
5270 {
5275 HOST_WIDE_INT hpart;
5278 /* We have to do this the hard way to detect unsigned overflow.
5279 prod = int_const_binop (MULT_EXPR, arg01, arg1, 0); */
5292 {
5296 /* Likewise hi = int_const_binop (PLUS_EXPR, prod, tmp, 0). */
5309 }
5311 {
5314 {
5332 }
5333 }
5334 else
5335 {
5338 {
5356 }
5357 }
5360 {
5401 }
5404 }
5407 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5408 equality/inequality test, then return a simplified form of
5409 the test using shifts and logical operations. Otherwise return
5410 NULL. TYPE is the desired result type. */
5412 tree
5414 tree result_type)
5415 {
5416 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5417 operand 0. */
5419 {
5424 /* Extract the arguments of the EQ/NE. */
5428 /* This requires us to invert the code. */
5430 }
5432 /* If this is testing a single bit, we can optimize the test. */
5436 {
5443 tree arg00;
5445 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5446 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5449 /* This is only a win if casting to a signed type is cheap,
5450 i.e. when arg00's type is not a partial mode. */
5453 {
5458 }
5460 /* Otherwise we have (A & C) != 0 where C is a single bit,
5461 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5462 Similarly for (A & C) == 0. */
5464 /* If INNER is a right shift of a constant and it plus BITNUM does
5465 not overflow, adjust BITNUM and INNER. */
5472 {
5475 }
5477 /* If we are going to be able to omit the AND below, we must do our
5478 operations as unsigned. If we must use the AND, we have a choice.
5479 Normally unsigned is faster, but for some machines signed is. */
5480 #ifdef LOAD_EXTEND_OP
5482 #else
5484 #endif
5499 /* Put the AND last so it can combine with more things. */
5503 /* Make sure to return the proper type. */
5507 }
5509 }
5511 /* Check whether we are allowed to reorder operands arg0 and arg1,
5512 such that the evaluation of arg1 occurs before arg0. */
5514 static bool
5516 {
5523 }
5525 /* Test whether it is preferable two swap two operands, ARG0 and
5526 ARG1, for example because ARG0 is an integer constant and ARG1
5527 isn't. If REORDER is true, only recommend swapping if we can
5528 evaluate the operands in reverse order. */
5530 static bool
5532 {
5578 }
5580 /* Perform constant folding and related simplification of EXPR.
5581 The related simplifications include x*1 => x, x*0 => 0, etc.,
5582 and application of the associative law.
5583 NOP_EXPR conversions may be removed freely (as long as we
5584 are careful not to change the type of the overall expression).
5585 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5586 but we can constant-fold them if they have constant operands. */
5588 #ifdef ENABLE_FOLD_CHECKING
5589 # define fold(x) fold_1 (x)
5591 static
5592 #endif
5593 tree
5595 {
5599 tree tem;
5604 /* WINS will be nonzero when the switch is done
5605 if all operands are constant. */
5608 /* Don't try to process an RTL_EXPR since its operands aren't trees.
5609 Likewise for a SAVE_EXPR that's already been evaluated. */
5613 /* Return right away if a constant. */
5618 {
5619 tree subop;
5621 /* Special case for conversion ops that can have fixed point args. */
5624 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
5630 else
5635 /* Note that TREE_CONSTANT isn't enough:
5636 static var addresses are constant but we can't
5637 do arithmetic on them. */
5639 }
5641 {
5645 {
5647 tree subop;
5652 /* Strip any conversions that don't change the mode. This is
5653 safe for every expression, except for a comparison expression
5654 because its signedness is derived from its operands. So, in
5655 the latter case, only strip conversions that don't change the
5656 signedness.
5658 Note that this is done as an internal manipulation within the
5659 constant folder, in order to find the simplest representation
5660 of the arguments so that their form can be studied. In any
5661 cases, the appropriate type conversions should be put back in
5662 the tree that will get out of the constant folder. */
5665 else
5670 else
5675 /* Note that TREE_CONSTANT isn't enough:
5676 static var addresses are constant but we can't
5677 do arithmetic on them. */
5684 }
5685 }
5687 /* If this is a commutative operation, and ARG0 is a constant, move it
5688 to ARG1 to reduce the number of tests below. */
5694 /* Now WINS is set as described above,
5695 ARG0 is the first operand of EXPR,
5696 and ARG1 is the second operand (if it has more than one operand).
5698 First check for cases where an arithmetic operation is applied to a
5699 compound, conditional, or comparison operation. Push the arithmetic
5700 operation inside the compound or conditional to see if any folding
5701 can then be done. Convert comparison to conditional for this purpose.
5702 The also optimizes non-constant cases that used to be done in
5703 expand_expr.
5705 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5706 one of the operands is a comparison and the other is a comparison, a
5707 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5708 code below would make the expression more complex. Change it to a
5709 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5710 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5722 {
5733 }
5736 {
5741 {
5751 /* If this was a conversion, and all we did was to move into
5752 inside the COND_EXPR, bring it back out. But leave it if
5753 it is a conversion from integer to integer and the
5754 result precision is no wider than a word since such a
5755 conversion is cheap and may be optimized away by combine,
5756 while it couldn't if it were outside the COND_EXPR. Then return
5757 so we don't get into an infinite recursion loop taking the
5758 conversion out and then back in. */
5770 && (INTEGRAL_TYPE_P
5781 }
5783 {
5785 {
5789 }
5793 integer_one_node)),
5795 integer_zero_node))));
5796 }
5797 }
5808 {
5812 arg1)));
5821 {
5826 }
5830 {
5835 }
5836 }
5839 {
5853 /* Handle cases of two conversions in a row. */
5856 {
5875 /* In addition to the cases of two conversions in a row
5876 handled below, if we are converting something to its own
5877 type via an object of identical or wider precision, neither
5878 conversion is needed. */
5885 /* Likewise, if the intermediate and final types are either both
5886 float or both integer, we don't need the middle conversion if
5887 it is wider than the final type and doesn't change the signedness
5888 (for integers). Avoid this if the final type is a pointer
5889 since then we sometimes need the inner conversion. Likewise if
5890 the outer has a precision not equal to the size of its mode. */
5901 /* If we have a sign-extension of a zero-extended value, we can
5902 replace that by a single zero-extension. */
5909 /* Two conversions in a row are not needed unless:
5910 - some conversion is floating-point (overstrict for now), or
5911 - the intermediate type is narrower than both initial and
5912 final, or
5913 - the intermediate type and innermost type differ in signedness,
5914 and the outermost type is wider than the intermediate, or
5915 - the initial type is a pointer type and the precisions of the
5916 intermediate and final types differ, or
5917 - the final type is a pointer type and the precisions of the
5918 initial and intermediate types differ. */
5933 }
5937 /* Detect assigning a bitfield. */
5940 {
5941 /* Don't leave an assignment inside a conversion
5942 unless assigning a bitfield. */
5946 /* First do the assignment, then return converted constant. */
5951 }
5953 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5954 constants (if x has signed type, the sign bit cannot be set
5955 in c). This folds extension into the BIT_AND_EXPR. */
5960 {
5970 <= HOST_BITS_PER_WIDE_INT
5972 {
5979 #ifdef LOAD_EXTEND_OP
5983 {
5987 }
5988 #endif
5989 }
5994 }
5996 /* Convert (T1)((T2)X op Y) into (T1)X op Y, for pointer types T1 and
5997 T2 being pointers to types of the same size. */
6002 {
6014 }
6028 {
6032 }
6037 {
6042 }
6055 /* Convert fabs((double)float) into (double)fabsf(float). */
6058 {
6063 targ0)));
6064 }
6097 /* A + (-B) -> A - B */
6100 /* (-A) + B -> B - A */
6105 {
6109 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
6110 with a constant, and the two constants have no bits in common,
6111 we should treat this as a BIT_IOR_EXPR since this may produce more
6112 simplifications. */
6120 {
6123 }
6125 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
6126 (plus (plus (mult) (mult)) (foo)) so that we can
6127 take advantage of the factoring cases below. */
6132 {
6137 else
6158 }
6161 {
6165 /* (A * C) + (B * C) -> (A+B) * C.
6166 We are most concerned about the case where C is a constant,
6167 but other combinations show up during loop reduction. Since
6168 it is not difficult, try all four possibilities. */
6185 /* No identical multiplicands; see if we can find a common
6186 power-of-two factor in non-power-of-two multiplies. This
6187 can help in multi-dimensional array access. */
6192 {
6197 /* Move min of absolute values to int11. */
6200 {
6204 }
6207 {
6212 }
6213 }
6219 same));
6220 }
6221 }
6222 else
6223 {
6224 /* See if ARG1 is zero and X + ARG1 reduces to X. */
6228 /* Likewise if the operands are reversed. */
6232 /* Convert x+x into x*2.0. */
6238 /* Convert x*c+x into x*(c+1). */
6244 {
6245 REAL_VALUE_TYPE c;
6251 }
6253 /* Convert x+x*c into x*(c+1). */
6259 {
6260 REAL_VALUE_TYPE c;
6266 }
6268 /* Convert x*c1+x*c2 into x*(c1+c2). */
6278 {
6287 }
6288 /* Convert a + (b*c + d*e) into (a + b*c) + d*e */
6292 {
6297 {
6298 tree tree0;
6301 }
6302 }
6303 /* Convert (b*c + d*e) + a into b*c + (d*e +a) */
6307 {
6312 {
6313 tree tree0;
6316 }
6317 }
6318 }
6320 bit_rotate:
6321 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
6322 is a rotate of A by C1 bits. */
6323 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
6324 is a rotate of A by B bits. */
6325 {
6334 {
6353 {
6361 TYPE_PRECISION
6366 ? LROTATE_EXPR
6369 }
6371 {
6379 TYPE_PRECISION
6384 ? LROTATE_EXPR
6387 }
6388 }
6389 }
6391 associate:
6392 /* In most languages, can't associate operations on floats through
6393 parentheses. Rather than remember where the parentheses were, we
6394 don't associate floats at all, unless the user has specified
6395 -funsafe-math-optimizations. */
6399 {
6403 /* Split both trees into variables, constants, and literals. Then
6404 associate each group together, the constants with literals,
6405 then the result with variables. This increases the chances of
6406 literals being recombined later and of generating relocatable
6407 expressions for the sum of a constant and literal. */
6412 /* Only do something if we found more than two objects. Otherwise,
6413 nothing has changed and we risk infinite recursion. */
6418 {
6419 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6428 /* Preserve the MINUS_EXPR if the negative part of the literal is
6429 greater than the positive part. Otherwise, the multiplicative
6430 folding code (i.e extract_muldiv) may be fooled in case
6431 unsigned constants are subtracted, like in the following
6432 example: ((X*2 + 4) - 8U)/2. */
6434 {
6438 {
6442 }
6443 else
6444 {
6448 }
6449 }
6451 {
6456 else
6457 {
6463 }
6464 }
6469 }
6470 }
6472 binary:
6476 {
6477 /* The return value should always have
6478 the same type as the original expression. */
6483 }
6487 /* A - (-B) -> A + B */
6490 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6500 {
6506 /* Fold A - (A & B) into ~B & A. */
6509 {
6514 arg0));
6519 arg0));
6520 }
6522 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6523 any power of 2 minus 1. */
6528 {
6534 {
6538 }
6539 }
6540 }
6542 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6546 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6547 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6548 (-ARG1 + ARG0) reduces to -ARG1. */
6552 /* Fold &x - &x. This can happen from &x.foo - &x.
6553 This is unsafe for certain floats even in non-IEEE formats.
6554 In IEEE, it is unsafe because it does wrong for NaNs.
6555 Also note that operand_equal_p is always false if an operand
6556 is volatile. */
6562 /* A - B -> A + (-B) if B is easily negatable. */
6571 {
6572 /* (A * C) - (B * C) -> (A-B) * C. */
6580 /* (A * C1) - (A * C2) -> A * (C1-C2). */
6588 }
6593 /* (-A) * (-B) -> A * B */
6604 {
6610 /* (a * (1 << b)) is (a << b) */
6626 }
6627 else
6628 {
6629 /* Maybe fold x * 0 to 0. The expressions aren't the same
6630 when x is NaN, since x * 0 is also NaN. Nor are they the
6631 same in modes with signed zeros, since multiplying a
6632 negative value by 0 gives -0, not +0. */
6637 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
6642 /* Transform x * -1.0 into -x. */
6647 /* Convert (C1/X)*C2 into (C1*C2)/X. */
6652 {
6658 }
6661 {
6665 /* Optimizations of root(...)*root(...). */
6667 {
6672 /* Optimize sqrt(x)*sqrt(x) as x. */
6678 /* Optimize root(x)*root(y) as root(x*y). */
6683 }
6685 /* Optimize expN(x)*expN(y) as expN(x+y). */
6687 {
6694 }
6696 /* Optimizations of pow(...)*pow(...). */
6700 {
6708 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
6710 {
6715 arg01));
6717 }
6719 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
6721 {
6726 arg));
6728 }
6729 }
6731 /* Optimize tan(x)*cos(x) as sin(x). */
6740 {
6746 }
6748 /* Optimize x*pow(x,c) as pow(x,c+1). */
6752 {
6759 {
6761 REAL_VALUE_TYPE c;
6770 }
6771 }
6773 /* Optimize pow(x,c)*x as pow(x,c+1). */
6777 {
6784 {
6786 REAL_VALUE_TYPE c;
6795 }
6796 }
6798 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
6801 {
6805 {
6810 }
6811 }
6812 }
6813 }
6817 bit_ior:
6828 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6830 This results in more efficient code for machines without a NAND
6831 instruction. Combine will canonicalize to the first form
6832 which will allow use of NAND instructions provided by the
6833 backend if they exist. */
6836 {
6841 }
6843 /* See if this can be simplified into a rotate first. If that
6844 is unsuccessful continue in the association code. */
6855 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6856 with a constant, and the two constants have no bits in common,
6857 we should treat this as a BIT_IOR_EXPR since this may produce more
6858 simplifications. */
6866 {
6869 }
6871 /* See if this can be simplified into a rotate first. If that
6872 is unsuccessful continue in the association code. */
6885 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6888 {
6889 unsigned int prec
6896 }
6898 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6900 This results in more efficient code for machines without a NOR
6901 instruction. Combine will canonicalize to the first form
6902 which will allow use of NOR instructions provided by the
6903 backend if they exist. */
6906 {
6911 }
6916 /* Don't touch a floating-point divide by zero unless the mode
6917 of the constant can represent infinity. */
6923 /* (-A) / (-B) -> A / B */
6933 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6938 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
6943 /* If ARG1 is a constant, we can convert this to a multiply by the
6944 reciprocal. This does not have the same rounding properties,
6945 so only do this if -funsafe-math-optimizations. We can actually
6946 always safely do it if ARG1 is a power of two, but it's hard to
6947 tell if it is or not in a portable manner. */
6949 {
6954 /* Find the reciprocal if optimizing and the result is exact. */
6956 {
6957 REAL_VALUE_TYPE r;
6960 {
6963 }
6964 }
6965 }
6966 /* Convert A/B/C to A/(B*C). */
6973 /* Convert A/(B/C) to (A/B)*C. */
6981 /* Convert C1/(X*C2) into (C1/C2)/X. */
6986 {
6992 }
6995 {
6997 /* Optimize x/expN(y) into x*expN(-y). */
6999 {
7006 }
7008 /* Optimize x/pow(y,z) into x*pow(y,-z). */
7012 {
7021 }
7022 }
7025 {
7029 /* Optimize sin(x)/cos(x) as tan(x). */
7035 {
7041 }
7043 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
7049 {
7053 {
7058 }
7059 }
7061 /* Optimize pow(x,c)/x as pow(x,c-1). */
7065 {
7071 {
7073 REAL_VALUE_TYPE c;
7082 }
7083 }
7084 }
7096 /* X / -1 is -X. */
7103 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
7104 operation, EXACT_DIV_EXPR.
7106 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
7107 At one time others generated faster code, it's not clear if they do
7108 after the last round to changes to the DIV code in expmed.c. */
7128 /* X % -1 is zero. */
7149 /* Optimize -1 >> x for arithmetic right shifts. */
7152 /* ... fall through ... */
7155 shift:
7161 /* Since negative shift count is not well-defined,
7162 don't try to compute it in the compiler. */
7165 /* Rewrite an LROTATE_EXPR by a constant into an
7166 RROTATE_EXPR by a new constant. */
7168 {
7173 }
7175 /* If we have a rotate of a bit operation with the rotate count and
7176 the second operand of the bit operation both constant,
7177 permute the two operations. */
7189 /* Two consecutive rotates adding up to the width of the mode can
7190 be ignored. */
7221 /* The argument to invert_truthvalue must have Boolean type. */
7225 /* Note that the operand of this must be an int
7226 and its values must be 0 or 1.
7227 ("true" is a fixed value perhaps depending on the language,
7228 but we don't handle values other than 1 correctly yet.) */
7230 /* Avoid infinite recursion. */
7232 {
7237 }
7241 /* Note that the operands of this must be ints
7242 and their values must be 0 or 1.
7243 ("true" is a fixed value perhaps depending on the language.) */
7244 /* If first arg is constant zero, return it. */
7248 /* If either arg is constant true, drop it. */
7252 /* Preserve sequence points. */
7255 /* If second arg is constant zero, result is zero, but first arg
7256 must be evaluated. */
7259 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
7260 case will be handled here. */
7264 truth_andor:
7265 /* We only do these simplifications if we are optimizing. */
7269 /* Check for things like (A || B) && (A || C). We can convert this
7270 to A || (B && C). Note that either operator can be any of the four
7271 truth and/or operations and the transformation will still be
7272 valid. Also note that we only care about order for the
7273 ANDIF and ORIF operators. If B contains side effects, this
7274 might change the truth-value of A. */
7281 {
7301 /* This case if tricky because we must either have commutative
7302 operators or else A10 must not have side-effects. */
7308 a01));
7309 }
7311 /* See if we can build a range comparison. */
7315 /* Check for the possibility of merging component references. If our
7316 lhs is another similar operation, try to merge its rhs with our
7317 rhs. Then try to merge our lhs and rhs. */
7329 /* Note that the operands of this must be ints
7330 and their values must be 0 or true.
7331 ("true" is a fixed value perhaps depending on the language.) */
7332 /* If first arg is constant true, return it. */
7336 /* If either arg is constant zero, drop it. */
7340 /* Preserve sequence points. */
7343 /* If second arg is constant true, result is true, but we must
7344 evaluate first arg. */
7347 /* Likewise for first arg, but note this only occurs here for
7348 TRUTH_OR_EXPR. */
7354 /* If either arg is constant zero, drop it. */
7359 /* If either arg is constant true, this is a logical inversion. */
7364 /* Identical arguments cancel to zero. */
7375 /* If one arg is a real or integer constant, put it last. */
7379 /* If this is an equality comparison of the address of a non-weak
7380 object against zero, then we know the result. */
7388 /* If this is an equality comparison of the address of two non-weak,
7389 unaliased symbols neither of which are extern (since we do not
7390 have access to attributes for externs), then we know the result. */
7406 type);
7409 {
7417 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7422 /* (-a) CMP (-b) -> b CMP a */
7429 {
7430 REAL_VALUE_TYPE cst;
7433 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7435 return
7441 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7442 /* a CMP (-0) -> a CMP 0 */
7447 /* x != NaN is always true, other ops are always false. */
7450 {
7453 }
7455 /* Fold comparisons against infinity. */
7457 {
7461 }
7462 }
7464 /* If this is a comparison of a real constant with a PLUS_EXPR
7465 or a MINUS_EXPR of a real constant, we can convert it into a
7466 comparison with a revised real constant as long as no overflow
7467 occurs when unsafe_math_optimizations are enabled. */
7479 /* Likewise, we can simplify a comparison of a real constant with
7480 a MINUS_EXPR whose first operand is also a real constant, i.e.
7481 (c1 - x) < c2 becomes x > c1-c2. */
7492 /* Fold comparisons against built-in math functions. */
7494 && flag_unsafe_math_optimizations
7496 {
7500 {
7504 }
7505 }
7506 }
7508 /* Convert foo++ == CONST into ++foo == CONST + INCR. */
7512 /* This optimization is invalid for ordered comparisons
7513 if CONST+INCR overflows or if foo+incr might overflow.
7514 This optimization is invalid for floating point due to rounding.
7515 For pointer types we assume overflow doesn't happen. */
7519 {
7523 {
7529 }
7530 else
7531 {
7537 }
7540 /* If VAROP is a reference to a bitfield, we must mask
7541 the constant by the width of the field. */
7544 {
7549 /* First check whether the comparison would come out
7550 always the same. If we don't do that we would
7551 change the meaning with the masking. */
7554 arg1));
7565 }
7568 }
7570 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
7571 This transformation affects the cases which are handled in later
7572 optimizations involving comparisons with non-negative constants. */
7576 {
7578 {
7589 }
7590 }
7592 /* Comparisons with the highest or lowest possible integer of
7593 the specified size will have known values.
7595 This is quite similar to fold_relational_hi_lo; however, my
7596 attempts to share the code have been nothing but trouble.
7597 I give up for now. */
7598 {
7606 {
7613 {
7616 }
7617 else
7618 {
7621 }
7626 {
7639 /* The GE_EXPR and LT_EXPR cases above are not normally
7640 reached because of previous transformations. */
7644 }
7648 {
7657 }
7661 {
7676 }
7680 {
7689 }
7695 /* signed_type does not work on pointer types. */
7697 {
7698 /* The following case also applies to X < signed_max+1
7699 and X >= signed_max+1 because previous transformations. */
7701 {
7705 return fold
7709 }
7710 }
7711 }
7712 }
7714 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
7715 a MINUS_EXPR of a constant, we can convert it into a comparison with
7716 a revised constant as long as no overflow occurs. */
7728 /* Similarly for a NEGATE_EXPR. */
7737 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7738 for !=. Don't do this for ordered comparisons due to overflow. */
7744 /* If we are widening one operand of an integer comparison,
7745 see if the other operand is similarly being widened. Perhaps we
7746 can do the comparison in the narrower type. */
7760 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7761 constant, we can simplify it. */
7768 /* If we are comparing an ABS_EXPR with a constant, we can
7769 convert all the cases into explicit comparisons, but they may
7770 well not be faster than doing the ABS and one comparison.
7771 But ABS (X) <= C is a range comparison, which becomes a subtraction
7772 and a comparison, and is probably faster. */
7785 /* If this is an EQ or NE comparison with zero and ARG0 is
7786 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7787 two operations, but the latter can be done in one less insn
7788 on machines that have only two-operand insns or on which a
7789 constant cannot be the first operand. */
7792 {
7797 return
7803 integer_one_node)),
7804 arg1));
7807 return
7813 integer_one_node)),
7814 arg1));
7815 }
7817 /* If this is an NE or EQ comparison of zero against the result of a
7818 signed MOD operation whose second operand is a power of 2, make
7819 the MOD operation unsigned since it is simpler and equivalent. */
7828 {
7837 }
7839 /* If this is an NE comparison of zero with an AND of one, remove the
7840 comparison since the AND will give the correct value. */
7846 /* If we have (A & C) == C where C is a power of 2, convert this into
7847 (A & C) != 0. Similarly for NE_EXPR. */
7855 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7856 2, then fold the expression into shifts and logical operations. */
7861 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
7862 Similarly for NE_EXPR. */
7867 {
7868 tree dandnotc
7876 }
7878 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
7879 Similarly for NE_EXPR. */
7884 {
7885 tree candnotd
7892 }
7894 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7895 and similarly for >= into !=. */
7911 return
7919 /* Simplify comparison of something with itself. (For IEEE
7920 floating-point, we can only do some of these simplifications.) */
7922 {
7924 {
7939 /* For NE, we can only do this simplification if integer
7940 or we don't honor IEEE floating point NaNs. */
7944 /* ... fall through ... */
7950 }
7951 }
7953 /* If we are comparing an expression that just has comparisons
7954 of two integer values, arithmetic expressions of those comparisons,
7955 and constants, we can simplify it. There are only three cases
7956 to check: the two values can either be equal, the first can be
7957 greater, or the second can be greater. Fold the expression for
7958 those three values. Since each value must be 0 or 1, we have
7959 eight possibilities, each of which corresponds to the constant 0
7960 or 1 or one of the six possible comparisons.
7962 This handles common cases like (a > b) == 0 but also handles
7963 expressions like ((x > y) - (y > x)) > 0, which supposedly
7964 occur in macroized code. */
7967 {
7972 /* Don't handle degenerate cases here; they should already
7973 have been handled anyway. */
7982 {
7986 /* We can't just pass T to eval_subst in case cval1 or cval2
7987 was the same as ARG1. */
7989 tree high_result
7993 arg1));
7994 tree equal_result
7998 arg1));
7999 tree low_result
8003 arg1));
8005 /* All three of these results should be 0 or 1. Confirm they
8006 are. Then use those values to select the proper code
8007 to use. */
8015 {
8016 /* Make a 3-bit mask with the high-order bit being the
8017 value for `>', the next for '=', and the low for '<'. */
8021 {
8023 /* Always false. */
8044 /* Always true. */
8046 }
8051 else
8053 }
8054 }
8055 }
8057 /* If this is a comparison of a field, we may be able to simplify it. */
8062 /* Handle the constant case even without -O
8063 to make sure the warnings are given. */
8065 {
8069 }
8071 /* If this is a comparison of complex values and either or both sides
8072 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
8073 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
8074 This may prevent needless evaluations. */
8081 {
8094 type,
8097 }
8099 /* Optimize comparisons of strlen vs zero to a compare of the
8100 first character of the string vs zero. To wit,
8101 strlen(ptr) == 0 => *ptr == 0
8102 strlen(ptr) != 0 => *ptr != 0
8103 Other cases should reduce to one of these two (or a constant)
8104 due to the return value of strlen being unsigned. */
8108 {
8110 tree arglist;
8122 integer_zero_node));
8123 }
8125 /* We can fold X/C1 op C2 where C1 and C2 are integer constants
8126 into a single range test. */
8133 {
8137 }
8139 /* Both ARG0 and ARG1 are known to be constants at this point. */
8144 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
8145 so all simple results must be passed through pedantic_non_lvalue. */
8147 {
8149 /* Only optimize constant conditions when the selected branch
8150 has the same type as the COND_EXPR. This avoids optimizing
8151 away "c ? x : throw", where the throw has a void type. */
8156 }
8160 /* If we have A op B ? A : C, we may be able to convert this to a
8161 simpler expression, depending on the operation and the values
8162 of B and C. Signed zeros prevent all of these transformations,
8163 for reasons given above each one. */
8169 {
8175 /* If we have A op 0 ? A : -A, consider applying the following
8176 transformations:
8178 A == 0? A : -A same as -A
8179 A != 0? A : -A same as A
8180 A >= 0? A : -A same as abs (A)
8181 A > 0? A : -A same as abs (A)
8182 A <= 0? A : -A same as -abs (A)
8183 A < 0? A : -A same as -abs (A)
8185 None of these transformations work for modes with signed
8186 zeros. If A is +/-0, the first two transformations will
8187 change the sign of the result (from +0 to -0, or vice
8188 versa). The last four will fix the sign of the result,
8189 even though the original expressions could be positive or
8190 negative, depending on the sign of A.
8192 Note that all these transformations are correct if A is
8193 NaN, since the two alternatives (A and -A) are also NaNs. */
8200 {
8224 }
8226 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
8227 A == 0 ? A : 0 is always 0 unless A is -0. Note that
8228 both transformations are correct when A is NaN: A != 0
8229 is then true, and A == 0 is false. */
8232 {
8237 }
8239 /* Try some transformations of A op B ? A : B.
8241 A == B? A : B same as B
8242 A != B? A : B same as A
8243 A >= B? A : B same as max (A, B)
8244 A > B? A : B same as max (B, A)
8245 A <= B? A : B same as min (A, B)
8246 A < B? A : B same as min (B, A)
8248 As above, these transformations don't work in the presence
8249 of signed zeros. For example, if A and B are zeros of
8250 opposite sign, the first two transformations will change
8251 the sign of the result. In the last four, the original
8252 expressions give different results for (A=+0, B=-0) and
8253 (A=-0, B=+0), but the transformed expressions do not.
8255 The first two transformations are correct if either A or B
8256 is a NaN. In the first transformation, the condition will
8257 be false, and B will indeed be chosen. In the case of the
8258 second transformation, the condition A != B will be true,
8259 and A will be chosen.
8261 The conversions to max() and min() are not correct if B is
8262 a number and A is not. The conditions in the original
8263 expressions will be false, so all four give B. The min()
8264 and max() versions would give a NaN instead. */
8267 {
8272 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
8274 {
8278 }
8281 {
8288 /* In C++ a ?: expression can be an lvalue, so put the
8289 operand which will be used if they are equal first
8290 so that we can convert this back to the
8291 corresponding COND_EXPR. */
8312 }
8313 }
8315 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
8316 we might still be able to simplify this. For example,
8317 if C1 is one less or one more than C2, this might have started
8318 out as a MIN or MAX and been transformed by this function.
8319 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
8325 {
8327 /* We can replace A with C1 in this case. */
8333 /* If C1 is C2 + 1, this is min(A, C2). */
8335 OEP_ONLY_CONST)
8339 OEP_ONLY_CONST))
8340 return pedantic_non_lvalue
8345 /* If C1 is C2 - 1, this is min(A, C2). */
8347 OEP_ONLY_CONST)
8351 OEP_ONLY_CONST))
8352 return pedantic_non_lvalue
8357 /* If C1 is C2 - 1, this is max(A, C2). */
8359 OEP_ONLY_CONST)
8363 OEP_ONLY_CONST))
8364 return pedantic_non_lvalue
8369 /* If C1 is C2 + 1, this is max(A, C2). */
8371 OEP_ONLY_CONST)
8375 OEP_ONLY_CONST))
8376 return pedantic_non_lvalue
8383 }
8384 }
8386 /* If the second operand is simpler than the third, swap them
8387 since that produces better jump optimization results. */
8390 {
8391 /* See if this can be inverted. If it can't, possibly because
8392 it was a floating-point inequality comparison, don't do
8393 anything. */
8399 }
8401 /* Convert A ? 1 : 0 to simply A. */
8404 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8405 call to fold will try to move the conversion inside
8406 a COND, which will recurse. In that case, the COND_EXPR
8407 is probably the best choice, so leave it alone. */
8411 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8412 over COND_EXPR in cases such as floating point comparisons. */
8419 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
8420 operation is simply A & 2. */
8432 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8439 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8443 {
8444 /* Only perform transformation if ARG0 is easily inverted. */
8449 }
8454 /* When pedantic, a compound expression can be neither an lvalue
8455 nor an integer constant expression. */
8458 /* Don't let (0, 0) be null pointer constant. */
8500 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8501 appropriate. */
8506 {
8510 tree arg01;
8521 {
8535 arg01));
8536 }
8539 }
8542 /* Check for a built-in function. */
8547 {
8551 }
8557 }
8559 #ifdef ENABLE_FOLD_CHECKING
8560 #undef fold
8566 /* When --enable-checking=fold, compute a digest of expr before
8567 and after actual fold call to see if fold did not accidentally
8568 change original expr. */
8570 tree
8572 {
8573 tree ret;
8576 htab_t ht;
8595 }
8597 void
8599 {
8602 htab_t ht;
8612 }
8614 static void
8616 {
8618 }
8620 static void
8622 {
8640 {
8641 /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified. */
8645 }
8647 {
8648 /* Allow DECL_ASSEMBLER_NAME to be modified. */
8652 }
8655 {
8656 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
8661 }
8668 {
8671 {
8685 }
8689 {
8700 }
8704 {
8710 }
8711 /* Fall through. */
8747 }
8748 }
8750 #endif
8752 /* Perform constant folding and related simplification of initializer
8753 expression EXPR. This behaves identically to "fold" but ignores
8754 potential run-time traps and exceptions that fold must preserve. */
8756 tree
8758 {
8762 tree result;
8775 }
8777 /* Determine if first argument is a multiple of second argument. Return 0 if
8778 it is not, or we cannot easily determined it to be.
8780 An example of the sort of thing we care about (at this point; this routine
8781 could surely be made more general, and expanded to do what the *_DIV_EXPR's
8782 fold cases do now) is discovering that
8784 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8786 is a multiple of
8788 SAVE_EXPR (J * 8)
8790 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
8792 This code also handles discovering that
8794 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8796 is a multiple of 8 so we don't have to worry about dealing with a
8797 possible remainder.
8799 Note that we *look* inside a SAVE_EXPR only to determine how it was
8800 calculated; it is not safe for fold to do much of anything else with the
8801 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
8802 at run time. For example, the latter example above *cannot* be implemented
8803 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
8804 evaluation time of the original SAVE_EXPR is not necessarily the same at
8805 the time the new expression is evaluated. The only optimization of this
8806 sort that would be valid is changing
8808 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
8810 divided by 8 to
8812 SAVE_EXPR (I) * SAVE_EXPR (J)
8814 (where the same SAVE_EXPR (J) is used in the original and the
8815 transformed version). */
8817 static int
8819 {
8827 {
8839 {
8843 /* const_binop may not detect overflow correctly,
8844 so check for it explicitly here. */
8850 size_one_node,
8854 }
8858 /* Can't handle conversions from non-integral or wider integral type. */
8864 /* .. fall through ... */
8880 }
8881 }
8883 /* Return true if `t' is known to be non-negative. */
8885 int
8887 {
8889 {
8904 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8905 both unsigned and at least 2 bits shorter than the result. */
8909 {
8914 {
8918 }
8919 }
8924 {
8925 /* x * x for floating point x is always non-negative. */
8930 }
8932 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8933 both unsigned and their total bits is shorter than the result. */
8937 {
8944 }
8973 {
8978 {
8982 {
8986 }
8987 }
8989 {
8995 }
8996 }
9024 {
9031 {
9032 #define CASE_BUILTIN_F(BUILT_IN_FN) \
9033 case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
9034 #define CASE_BUILTIN_I(BUILT_IN_FN) \
9035 case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:
9053 /* Always true. */
9057 /* sqrt(-0.0) is -0.0. */
9085 /* True if the 1st argument is nonnegative. */
9089 /* True if the 1st OR 2nd arguments are nonnegative. */
9094 /* True if the 1st AND 2nd arguments are nonnegative. */
9099 /* True if the 2nd argument is nonnegative. */
9104 #undef CASE_BUILTIN_F
9105 #undef CASE_BUILTIN_I
9106 }
9107 }
9109 /* ... fall through ... */
9113 /* Truth values evaluate to 0 or 1, which is nonnegative. */
9115 }
9117 /* We don't know sign of `t', so be conservative and return false. */
9119 }
9121 /* Return true when T is an address and is known to be nonzero.
9122 For floating point we further ensure that T is not denormal.
9123 Similar logic is present in nonzero_address in rtlanal.h */
9125 static bool
9127 {
9130 /* Doing something useful for floating point would need more work. */
9135 {
9145 {
9146 /* With the presence of negative values it is hard
9147 to say something. */
9151 /* One of operands must be positive and the other non-negative. */
9154 }
9159 {
9162 }
9166 {
9172 }
9176 /* Weak declarations may link to NULL. */
9179 /* Constants and all other cases are never weak. */
9192 {
9193 /* When both operands are nonzero, then MAX must be too. */
9197 /* MAX where operand 0 is positive is positive. */
9199 }
9200 /* MAX where operand 1 is positive is positive. */
9221 }
9223 }
9225 /* Return true if `r' is known to be non-negative.
9226 Only handles constants at the moment. */
9228 int
9230 {
9232 {
9242 {
9244 rtx elt;
9249 {
9253 }
9256 }
9260 /* These are always nonnegative. */
9265 }
9266 }
9269 /* See if we are applying CODE, a relational to the highest or lowest
9270 possible integer of TYPE. If so, then the result is a compile
9271 time constant. */
9273 static tree
9276 {
9287 {
9294 {
9297 }
9298 else
9299 {
9302 }
9307 {
9321 /* The GE_EXPR and LT_EXPR cases above are not normally
9322 reached because of previous transformations. */
9326 }
9330 {
9341 }
9345 {
9362 }
9366 {
9377 }
9382 /* signed_type does not work on pointer types. */
9384 {
9385 /* The following case also applies to X < signed_max+1
9386 and X >= signed_max+1 because previous transformations. */
9388 {
9394 type,
9398 retval
9404 /* If we are in gimple form, then returning EXP would create
9405 non-gimple expressions. Clearing it is safe and insures
9406 we do not allow a non-gimple expression to escape. */
9411 }
9412 }
9413 }
9416 }
9419 /* Given the components of a binary expression CODE, TYPE, OP0 and OP1,
9420 attempt to fold the expression to a constant without modifying TYPE,
9421 OP0 or OP1.
9423 If the expression could be simplified to a constant, then return
9424 the constant. If the expression would not be simplified to a
9425 constant, then return NULL_TREE.
9427 Note this is primarily designed to be called after gimplification
9428 of the tree structures and when at least one operand is a constant.
9429 As a result of those simplifying assumptions this routine is far
9430 simpler than the generic fold routine. */
9432 tree
9435 {
9437 tree subop0;
9438 tree subop1;
9439 tree tem;
9441 /* If this is a commutative operation, and ARG0 is a constant, move it
9442 to ARG1 to reduce the number of tests below. */
9445 {
9449 }
9451 /* If either operand is a complex type, extract its real component. */
9454 else
9459 else
9462 /* Note if either argument is not a real or integer constant.
9463 With a few exceptions, simplification is limited to cases
9464 where both arguments are constants. */
9472 {
9474 /* (plus (address) (const_int)) is a constant. */
9482 {
9486 }
9489 binary:
9493 /* Both arguments are constants. Simplify. */
9496 {
9497 /* The return value should always have the same type as
9498 the original expression. */
9503 }
9507 /* Fold &x - &x. This can happen from &x.foo - &x.
9508 This is unsafe for certain floats even in non-IEEE formats.
9509 In IEEE, it is unsafe because it does wrong for NaNs.
9510 Also note that operand_equal_p is always false if an
9511 operand is volatile. */
9519 /* Special case multiplication or bitwise AND where one argument
9520 is zero. */
9523 else
9532 /* Special case when we know the result will be all ones. */
9548 /* Division by zero is undefined. */
9575 /* Optimize -1 >> x for arithmetic right shifts. */
9578 /* ... fall through ... */
9584 /* Since negative shift count is not well-defined, don't
9585 try to compute it in the compiler. */
9593 /* -1 rotated either direction by any amount is still -1. */
9597 /* 0 rotated either direction by any amount is still zero. */
9614 /* If one arg is a real or integer constant, put it last. */
9619 {
9620 tree temp;
9626 }
9628 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
9629 This transformation affects the cases which are handled in later
9630 optimizations involving comparisons with non-negative constants. */
9634 {
9636 {
9649 }
9650 }
9662 /* This could probably be handled. */
9666 /* If second arg is constant zero, result is zero, but first arg
9667 must be evaluated. */
9670 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
9671 case will be handled here. */
9679 /* If second arg is constant true, result is true, but we must
9680 evaluate first arg. */
9683 /* Likewise for first arg, but note this only occurs here for
9684 TRUTH_OR_EXPR. */
9693 {
9696 }
9701 }
9702 }
9704 /* Given the components of a unary expression CODE, TYPE and OP0,
9705 attempt to fold the expression to a constant without modifying
9706 TYPE or OP0.
9708 If the expression could be simplified to a constant, then return
9709 the constant. If the expression would not be simplified to a
9710 constant, then return NULL_TREE.
9712 Note this is primarily designed to be called after gimplification
9713 of the tree structures and when op0 is a constant. As a result
9714 of those simplifying assumptions this routine is far simpler than
9715 the generic fold routine. */
9717 tree
9719 tree op0)
9720 {
9721 /* Make sure we have a suitable constant argument. */
9723 {
9724 tree subop;
9728 else
9733 }
9736 {
9748 else
9754 else
9760 else
9766 else
9772 else
9784 }
9785 }
9787 /* If EXP represents referencing an element in a constant string
9788 (either via pointer arithmetic or array indexing), return the
9789 tree representing the value accessed, otherwise return NULL. */
9791 tree
9793 {
9795 {
9797 tree index;
9798 tree string;
9801 {
9803 }
9804 else
9805 {
9810 /* Optimize the special-case of a zero lower bound.
9812 We convert the low_bound to sizetype to avoid some problems
9813 with constant folding. (E.g. suppose the lower bound is 1,
9814 and its mode is QI. Without the conversion,l (ARRAY
9815 +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
9816 +INDEX), which becomes (ARRAY+255+INDEX). Opps!) */
9821 }
9833 }
9835 }
9837 /* Return the tree for neg (ARG0) when ARG0 is known to be either
9838 an integer constant or real constant.
9840 TYPE is the type of the result. */
9842 static tree
9844 {
9848 {
9850 HOST_WIDE_INT high;
9861 }
9864 #ifdef ENABLE_CHECKING
9865 else
9867 #endif
9870 }
9872 /* Return the tree for abs (ARG0) when ARG0 is known to be either
9873 an integer constant or real constant.
9875 TYPE is the type of the result. */
9877 tree
9879 {
9883 {
9884 /* If the value is unsigned, then the absolute value is
9885 the same as the ordinary value. */
9888 /* Similarly, if the value is non-negative. */
9891 /* If the value is negative, then the absolute value is
9892 its negation. */
9893 else
9894 {
9896 HOST_WIDE_INT high;
9908 }
9909 }
9911 {
9914 else
9916 }
9917 #ifdef ENABLE_CHECKING
9918 else
9920 #endif
9923 }
9925 /* Return the tree for not (ARG0) when ARG0 is known to be an integer
9926 constant. TYPE is the type of the result. */
9928 static tree
9930 {
9934 {
9941 }
9942 #ifdef ENABLE_CHECKING
9943 else
9945 #endif
9948 }
9950 /* Given CODE, a relational operator, the target type, TYPE and two
9951 constant operands OP0 and OP1, return the result of the
9952 relational operation. If the result is not a compile time
9953 constant, then return NULL_TREE. */
9955 static tree
9957 {
9958 tree tem;
9961 /* From here on, the only cases we handle are when the result is
9962 known to be a constant.
9964 To compute GT, swap the arguments and do LT.
9965 To compute GE, do LT and invert the result.
9966 To compute LE, swap the arguments, do LT and invert the result.
9967 To compute NE, do EQ and invert the result.
9969 Therefore, the code below must handle only EQ and LT. */
9972 {
9975 }
9977 /* Note that it is safe to invert for real values here because we
9978 will check below in the one case that it matters. */
9983 {
9986 }
9988 /* Compute a result for LT or EQ if args permit;
9989 Otherwise return T. */
9991 {
9994 else
9999 }
10005 /* Two real constants can be compared explicitly. */
10007 {
10008 /* If either operand is a NaN, the result is false with two
10009 exceptions: First, an NE_EXPR is true on NaNs, but that case
10010 is already handled correctly since we will be inverting the
10011 result for NE_EXPR. Second, if we had inverted a LE_EXPR
10012 or a GE_EXPR into a LT_EXPR, we must return true so that it
10013 will be inverted into false. */
10023 else
10027 }
10039 }
10041 /* Build an expression for the address of T. Folds away INDIRECT_REF to
10042 avoid confusing the gimplify process. */
10044 tree
10046 {
10048 {
10052 }
10053 else
10054 {
10063 }
10066 }
10068 tree
10070 {
10072 }
10074 /* Builds an expression for an indirection through T, simplifying some
10075 cases. */
10077 tree
10079 {
10082 tree subtype;
10086 {
10089 /* *&p => p */
10092 /* *(foo *)&fooarray => fooarray[0] */
10096 }
10098 /* *(foo *)fooarrptr => (*fooarrptr)[0] */
10102 {
10105 }
10108 }