| blob | ed54ee93bb615b138227800ab8063ecbd8031438 |
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. */
94 tree);
120 /* The following constants represent a bit based encoding of GCC's
121 comparison operators. This encoding simplifies transformations
122 on relational comparison operators, such as AND and OR. */
123 #define COMPCODE_FALSE 0
124 #define COMPCODE_LT 1
125 #define COMPCODE_EQ 2
126 #define COMPCODE_LE 3
127 #define COMPCODE_GT 4
128 #define COMPCODE_NE 5
129 #define COMPCODE_GE 6
130 #define COMPCODE_TRUE 7
132 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
133 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
134 and SUM1. Then this yields nonzero if overflow occurred during the
135 addition.
137 Overflow occurs if A and B have the same sign, but A and SUM differ in
138 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
139 sign. */
140 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
141 \f
142 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
143 We do that by representing the two-word integer in 4 words, with only
144 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
145 number. The value of the word is LOWPART + HIGHPART * BASE. */
147 #define LOWPART(x) \
148 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
149 #define HIGHPART(x) \
150 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
151 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
153 /* Unpack a two-word integer into 4 words.
154 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
155 WORDS points to the array of HOST_WIDE_INTs. */
157 static void
159 {
164 }
166 /* Pack an array of 4 words into a two-word integer.
167 WORDS points to the array of words.
168 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
170 static void
173 {
176 }
177 \f
178 /* Make the integer constant T valid for its type by setting to 0 or 1 all
179 the bits in the constant that don't belong in the type.
181 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
182 nonzero, a signed overflow has already occurred in calculating T, so
183 propagate it. */
185 int
187 {
189 HOST_WIDE_INT high;
193 {
194 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
195 Consider doing it via real_convert now. */
197 }
208 else
211 /* First clear all bits that are beyond the type's precision. */
214 ;
218 else
219 {
223 }
225 /* Unsigned types do not suffer sign extension or overflow unless they
226 are a sizetype. */
232 /* If the value's sign bit is set, extend the sign. */
240 {
241 /* Value is negative:
242 set to 1 all the bits that are outside this type's precision. */
246 else
247 {
251 }
252 }
254 /* Return nonzero if signed overflow occurred. */
255 return
258 }
259 \f
260 /* Add two doubleword integers with doubleword result.
261 Each argument is given as two `HOST_WIDE_INT' pieces.
262 One argument is L1 and H1; the other, L2 and H2.
263 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
265 int
269 {
271 HOST_WIDE_INT h;
279 }
281 /* Negate a doubleword integer with doubleword result.
282 Return nonzero if the operation overflows, assuming it's signed.
283 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
284 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
286 int
289 {
291 {
295 }
296 else
297 {
301 }
302 }
303 \f
304 /* Multiply two doubleword integers with doubleword result.
305 Return nonzero if the operation overflows, assuming it's signed.
306 Each argument is given as two `HOST_WIDE_INT' pieces.
307 One argument is L1 and H1; the other, L2 and H2.
308 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
310 int
314 {
329 {
332 {
334 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
336 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
340 }
342 }
346 /* Check for overflow by calculating the top half of the answer in full;
347 it should agree with the low half's sign bit. */
350 {
353 }
355 {
358 }
360 }
361 \f
362 /* Shift the doubleword integer in L1, H1 left by COUNT places
363 keeping only PREC bits of result.
364 Shift right if COUNT is negative.
365 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
366 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
368 void
372 {
376 {
379 }
385 {
386 /* Shifting by the host word size is undefined according to the
387 ANSI standard, so we must handle this as a special case. */
390 }
392 {
395 }
396 else
397 {
401 }
403 /* Sign extend all bits that are beyond the precision. */
411 ;
413 {
416 }
417 else
418 {
422 }
423 }
425 /* Shift the doubleword integer in L1, H1 right by COUNT places
426 keeping only PREC bits of result. COUNT must be positive.
427 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
428 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
430 void
435 {
438 signmask = (arith
446 {
447 /* Shifting by the host word size is undefined according to the
448 ANSI standard, so we must handle this as a special case. */
451 }
453 {
456 }
457 else
458 {
462 }
464 /* Zero / sign extend all bits that are beyond the precision. */
467 {
470 }
472 ;
474 {
477 }
478 else
479 {
483 }
484 }
485 \f
486 /* Rotate the doubleword integer in L1, H1 left by COUNT places
487 keeping only PREC bits of result.
488 Rotate right if COUNT is negative.
489 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
491 void
495 {
507 }
509 /* Rotate the doubleword integer in L1, H1 left by COUNT places
510 keeping only PREC bits of result. COUNT must be positive.
511 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
513 void
517 {
529 }
530 \f
531 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
532 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
533 CODE is a tree code for a kind of division, one of
534 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
535 or EXACT_DIV_EXPR
536 It controls how the quotient is rounded to an integer.
537 Return nonzero if the operation overflows.
538 UNS nonzero says do unsigned division. */
540 int
543 HOST_WIDE_INT hnum_orig,
545 HOST_WIDE_INT hden_orig,
549 {
565 /* Calculate quotient sign and convert operands to unsigned. */
567 {
569 {
571 /* (minimum integer) / (-1) is the only overflow case. */
575 }
577 {
580 }
581 }
586 /* This unsigned division rounds toward zero. */
589 }
593 /* hden != 0 already checked. */
598 }
608 /* Special code for when the divisor < BASE. */
610 {
611 /* hnum != 0 already checked. */
613 {
617 }
618 }
619 else
620 {
621 /* Full double precision division,
622 with thanks to Don Knuth's "Seminumerical Algorithms". */
626 /* Find the highest nonzero divisor digit. */
629 {
632 }
634 /* Insure that the first digit of the divisor is at least BASE/2.
635 This is required by the quotient digit estimation algorithm. */
642 {
646 }
651 {
656 }
657 }
661 /* Main loop */
663 {
664 /* Guess the next quotient digit, quo_est, by dividing the first
665 two remaining dividend digits by the high order quotient digit.
666 quo_est is never low and is at most 2 high. */
673 else
676 /* Refine quo_est so it's usually correct, and at most one high. */
681 quo_est--;
683 /* Try QUO_EST as the quotient digit, by multiplying the
684 divisor by QUO_EST and subtracting from the remaining dividend.
685 Keep in mind that QUO_EST is the I - 1st digit. */
689 {
695 }
697 /* If quo_est was high by one, then num[i] went negative and
698 we need to correct things. */
700 {
701 quo_est--;
704 {
708 }
711 }
713 /* Store the quotient digit. */
715 }
716 }
720 finish_up:
721 /* If result is negative, make it so. */
725 /* Compute trial remainder: rem = num - (quo * den) */
731 {
740 {
741 /* quo = quo - 1; */
744 }
745 else
752 {
755 }
756 else
762 {
768 /* Get absolute values. */
774 /* If (2 * abs (lrem) >= abs (lden)) */
783 {
785 /* quo = quo - 1; */
788 else
789 /* quo = quo + 1; */
792 }
793 else
795 }
800 }
802 /* Compute true remainder: rem = num - (quo * den) */
807 }
808 \f
809 /* Return true if built-in mathematical function specified by CODE
810 preserves the sign of it argument, i.e. -f(x) == f(-x). */
812 static bool
814 {
816 {
833 }
835 }
837 /* Determine whether an expression T can be cheaply negated using
838 the function negate_expr. */
840 static bool
842 {
845 tree type;
854 {
859 /* Check that -CST will not overflow type. */
862 {
867 }
868 else
885 /* -(A + B) -> (-B) - A. */
890 /* -(A + B) -> (-A) - B. */
894 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
903 /* Fall through. */
912 /* Negate -((double)float) as (double)(-float). */
914 {
918 }
922 /* Negate -f(x) as f(-x). */
928 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
930 {
936 }
941 }
943 }
945 /* Given T, an expression, return the negation of T. Allow for T to be
946 null, in which case return null. */
948 static tree
950 {
951 tree type;
952 tree tem;
961 {
972 /* Two's complement FP formats, such as c4x, may overflow. */
978 {
987 }
995 {
996 /* -(A + B) -> (-B) - A. */
1004 /* -(A + B) -> (-A) - B. */
1010 }
1014 /* - (A - B) -> B - A */
1027 /* Fall through. */
1031 {
1044 }
1048 /* Convert -((double)float) into (double)(-float). */
1050 {
1054 }
1058 /* Negate -f(x) as f(-x). */
1061 {
1068 }
1072 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1074 {
1079 {
1086 }
1087 }
1092 }
1096 }
1097 \f
1098 /* Split a tree IN into a constant, literal and variable parts that could be
1099 combined with CODE to make IN. "constant" means an expression with
1100 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1101 commutative arithmetic operation. Store the constant part into *CONP,
1102 the literal in *LITP and return the variable part. If a part isn't
1103 present, set it to null. If the tree does not decompose in this way,
1104 return the entire tree as the variable part and the other parts as null.
1106 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1107 case, we negate an operand that was subtracted. Except if it is a
1108 literal for which we use *MINUS_LITP instead.
1110 If NEGATE_P is true, we are negating all of IN, again except a literal
1111 for which we use *MINUS_LITP instead.
1113 If IN is itself a literal or constant, return it as appropriate.
1115 Note that we do not guarantee that any of the three values will be the
1116 same type as IN, but they will have the same signedness and mode. */
1118 static tree
1121 {
1128 /* Strip any conversions that don't change the machine mode or signedness. */
1135 /* We can associate addition and subtraction together (even
1136 though the C standard doesn't say so) for integers because
1137 the value is not affected. For reals, the value might be
1138 affected, so we can't. */
1141 {
1147 /* First see if either of the operands is a literal, then a constant. */
1158 /* If we haven't dealt with either operand, this is not a case we can
1159 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1164 else
1167 /* Now do any needed negations. */
1174 }
1177 else
1181 {
1188 }
1191 }
1193 /* Re-associate trees split by the above function. T1 and T2 are either
1194 expressions to associate or null. Return the new expression, if any. If
1195 we build an operation, do it in TYPE and with CODE. */
1197 static tree
1199 {
1205 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1206 try to fold this since we will have infinite recursion. But do
1207 deal with any NEGATE_EXPRs. */
1210 {
1212 {
1219 }
1222 }
1226 }
1227 \f
1228 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1229 to produce a new constant.
1231 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1233 tree
1235 {
1239 HOST_WIDE_INT hi;
1241 HOST_WIDE_INT garbageh;
1242 tree t;
1245 int is_sizetype
1256 {
1272 /* It's unclear from the C standard whether shifts can overflow.
1273 The following code ignores overflow; perhaps a C standard
1274 interpretation ruling is needed. */
1304 /* This is a shortcut for a common special case. */
1309 {
1315 }
1317 /* ... fall through ... */
1321 {
1324 }
1327 {
1330 }
1337 /* This is a shortcut for a common special case. */
1342 {
1347 }
1349 /* ... fall through ... */
1365 else
1371 else
1377 }
1379 /* If this is for a sizetype, can be represented as one (signed)
1380 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1381 constants. */
1387 else
1388 {
1391 }
1394 = ((notrunc
1401 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1402 So check if force_fit_type truncated the value. */
1413 }
1415 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1416 constant. We assume ARG1 and ARG2 have the same data type, or at least
1417 are the same kind of constant and the same machine mode.
1419 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1421 static tree
1423 {
1431 {
1433 REAL_VALUE_TYPE d1;
1434 REAL_VALUE_TYPE d2;
1435 REAL_VALUE_TYPE value;
1444 /* Don't perform operation if we honor signaling NaNs and
1445 either operand is a NaN. */
1450 /* Don't perform operation if it would raise a division
1451 by zero exception. */
1457 /* If either operand is a NaN, just return it. Otherwise, set up
1458 for floating-point trap; we return an overflow. */
1476 }
1478 {
1484 tree t;
1487 {
1507 notrunc),
1513 notrunc));
1517 {
1518 tree magsquared
1522 notrunc);
1525 const_binop
1530 notrunc),
1532 notrunc),
1533 notrunc),
1535 const_binop
1540 notrunc),
1542 notrunc),
1543 notrunc),
1545 }
1550 }
1552 }
1554 }
1556 /* These are the hash table functions for the hash table of INTEGER_CST
1557 nodes of a sizetype. */
1559 /* Return the hash code code X, an INTEGER_CST. */
1561 static hashval_t
1563 {
1569 }
1571 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1572 is the same as that given by *Y, which is the same. */
1574 static int
1576 {
1584 }
1585 \f
1586 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1587 bits are given by NUMBER and of the sizetype represented by KIND. */
1589 tree
1591 {
1593 }
1595 /* Likewise, but the desired type is specified explicitly. */
1599 htab_t size_htab;
1601 tree
1603 {
1607 {
1610 }
1612 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1613 hash table, we return the value from the hash table. Otherwise, we
1614 place that in the hash table and make a new node for the next time. */
1623 {
1629 }
1630 else
1632 }
1634 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1635 is a tree code. The type of the result is taken from the operands.
1636 Both must be the same type integer type and it must be a size type.
1637 If the operands are constant, so is the result. */
1639 tree
1641 {
1648 /* Handle the special case of two integer constants faster. */
1650 {
1651 /* And some specific cases even faster than that. */
1660 /* Handle general case of two integer constants. */
1662 }
1668 }
1670 /* Given two values, either both of sizetype or both of bitsizetype,
1671 compute the difference between the two values. Return the value
1672 in signed type corresponding to the type of the operands. */
1674 tree
1676 {
1678 tree ctype;
1684 /* If the type is already signed, just do the simple thing. */
1691 /* If either operand is not a constant, do the conversions to the signed
1692 type and subtract. The hardware will do the right thing with any
1693 overflow in the subtraction. */
1698 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1699 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1700 overflow) and negate (which can't either). Special-case a result
1701 of zero while we're here. */
1706 else
1710 }
1711 \f
1713 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1714 type TYPE. If no simplification can be done return NULL_TREE. */
1716 static tree
1718 {
1720 tree t;
1726 {
1728 {
1729 /* If we would build a constant wider than GCC supports,
1730 leave the conversion unfolded. */
1734 /* If we are trying to make a sizetype for a small integer, use
1735 size_int to pick up cached types to reduce duplicate nodes. */
1741 /* Given an integer constant, make new constant with new type,
1742 appropriately sign-extended or truncated. */
1746 /* Indicate an overflow if (1) ARG1 already overflowed,
1747 or (2) force_fit_type indicates an overflow.
1748 Tell force_fit_type that an overflow has already occurred
1749 if ARG1 is a too-large unsigned value and T is signed.
1750 But don't indicate an overflow if converting a pointer. */
1761 }
1763 {
1764 /* The following code implements the floating point to integer
1765 conversion rules required by the Java Language Specification,
1766 that IEEE NaNs are mapped to zero and values that overflow
1767 the target precision saturate, i.e. values greater than
1768 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1769 are mapped to INT_MIN. These semantics are allowed by the
1770 C and C++ standards that simply state that the behavior of
1771 FP-to-integer conversion is unspecified upon overflow. */
1775 REAL_VALUE_TYPE r;
1779 {
1798 }
1800 /* If R is NaN, return zero and show we have an overflow. */
1802 {
1806 }
1808 /* See if R is less than the lower bound or greater than the
1809 upper bound. */
1812 {
1816 {
1820 }
1821 }
1824 {
1827 {
1830 {
1834 }
1835 }
1836 }
1848 }
1849 }
1851 {
1855 {
1857 {
1858 /* We make a copy of ARG1 so that we don't modify an
1859 existing constant tree. */
1863 }
1874 }
1875 }
1877 }
1879 /* Convert expression ARG to type TYPE. Used by the middle-end for
1880 simple conversions in preference to calling the front-end's convert. */
1882 tree
1884 {
1886 tree tem;
1900 {
1902 {
1906 }
1910 {
1913 }
1918 }
1920 {
1922 {
1926 }
1928 {
1932 }
1940 {
1943 }
1944 }
1946 {
1954 {
1958 {
1962 }
1970 }
1971 }
1973 {
1982 }
1986 }
1987 \f
1988 /* Return an expr equal to X but certainly not valid as an lvalue. */
1990 tree
1992 {
1993 /* These things are certainly not lvalues. */
2002 }
2004 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2005 Zero means allow extended lvalues. */
2009 /* When pedantic, return an expr equal to X but certainly not valid as a
2010 pedantic lvalue. Otherwise, return X. */
2012 tree
2014 {
2017 else
2019 }
2020 \f
2021 /* Given a tree comparison code, return the code that is the logical inverse
2022 of the given code. It is not safe to do this for floating-point
2023 comparisons, except for NE_EXPR and EQ_EXPR. */
2025 static enum tree_code
2027 {
2029 {
2044 }
2045 }
2047 /* Similar, but return the comparison that results if the operands are
2048 swapped. This is safe for floating-point. */
2050 static enum tree_code
2052 {
2054 {
2068 }
2069 }
2072 /* Convert a comparison tree code from an enum tree_code representation
2073 into a compcode bit-based encoding. This function is the inverse of
2074 compcode_to_comparison. */
2076 static int
2078 {
2080 {
2095 }
2096 }
2098 /* Convert a compcode bit-based encoding of a comparison operator back
2099 to GCC's enum tree_code representation. This function is the
2100 inverse of comparison_to_compcode. */
2102 static enum tree_code
2104 {
2106 {
2121 }
2122 }
2124 /* Return nonzero if CODE is a tree code that represents a truth value. */
2126 static int
2128 {
2133 }
2134 \f
2135 /* Return nonzero if two operands (typically of the same tree node)
2136 are necessarily equal. If either argument has side-effects this
2137 function returns zero. FLAGS modifies behaviour as follows:
2139 If OEP_ONLY_CONST is set, only return nonzero for constants.
2140 This function tests whether the operands are indistinguishable;
2141 it does not test whether they are equal using C's == operation.
2142 The distinction is important for IEEE floating point, because
2143 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2144 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2146 If OEP_ONLY_CONST is unset, a VAR_DECL is considered equal to itself
2147 even though it may hold multiple values during a function.
2148 This is because a GCC tree node guarantees that nothing else is
2149 executed between the evaluation of its "operands" (which may often
2150 be evaluated in arbitrary order). Hence if the operands themselves
2151 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2152 same value in each operand/subexpression. Hence a zero value for
2153 ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
2154 If comparing arbitrary expression trees, such as from different
2155 statements, ONLY_CONST must usually be nonzero.
2157 If OEP_PURE_SAME is set, then pure functions with identical arguments
2158 are considered the same. It is used when the caller has other ways
2159 to ensure that global memory is unchanged in between. */
2161 int
2163 {
2164 /* If either is ERROR_MARK, they aren't equal. */
2168 /* If both types don't have the same signedness, then we can't consider
2169 them equal. We must check this before the STRIP_NOPS calls
2170 because they may change the signedness of the arguments. */
2178 /* This is needed for conversions and for COMPONENT_REF.
2179 Might as well play it safe and always test this. */
2185 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2186 We don't care about side effects in that case because the SAVE_EXPR
2187 takes care of that for us. In all other cases, two expressions are
2188 equal if they have no side effects. If we have two identical
2189 expressions with side effects that should be treated the same due
2190 to the only side effects being identical SAVE_EXPR's, that will
2191 be detected in the recursive calls below. */
2197 /* Next handle constant cases, those for which we can return 1 even
2198 if ONLY_CONST is set. */
2201 {
2214 {
2224 {
2226 flags))
2230 }
2233 }
2237 flags)
2239 flags));
2252 }
2258 {
2260 /* Two conversions are equal only if signedness and modes match. */
2276 /* For commutative ops, allow the other order. */
2284 /* If either of the pointer (or reference) expressions we are
2285 dereferencing contain a side effect, these cannot be equal. */
2291 {
2313 }
2317 {
2327 /* If the CALL_EXPRs call different functions, then they
2328 clearly can not be equal. */
2333 {
2337 else
2341 }
2343 /* Now see if all the arguments are the same. operand_equal_p
2344 does not handle TREE_LIST, so we walk the operands here
2345 feeding them to operand_equal_p. */
2349 {
2351 flags))
2356 }
2358 /* If we get here and both argument lists are exhausted
2359 then the CALL_EXPRs are equal. */
2364 }
2367 /* Consider __builtin_sqrt equal to sqrt. */
2375 }
2376 }
2377 \f
2378 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2379 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2381 When in doubt, return 0. */
2383 static int
2385 {
2397 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2398 and see if the inner values are the same. This removes any
2399 signedness comparison, which doesn't matter here. */
2406 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2407 actual comparison operand, ARG0.
2409 First throw away any conversions to wider types
2410 already present in the operands. */
2419 {
2422 /* Make sure shorter operand is extended the right way
2423 to match the longer operand. */
2429 }
2432 }
2433 \f
2434 /* See if ARG is an expression that is either a comparison or is performing
2435 arithmetic on comparisons. The comparisons must only be comparing
2436 two different values, which will be stored in *CVAL1 and *CVAL2; if
2437 they are nonzero it means that some operands have already been found.
2438 No variables may be used anywhere else in the expression except in the
2439 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2440 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2442 If this is true, return 1. Otherwise, return zero. */
2444 static int
2446 {
2450 /* We can handle some of the 'e' cases here. */
2460 {
2461 /* If we've already found a CVAL1 or CVAL2, this expression is
2462 two complex to handle. */
2468 }
2471 {
2494 /* First see if we can handle the first operand, then the second. For
2495 the second operand, we know *CVAL1 can't be zero. It must be that
2496 one side of the comparison is each of the values; test for the
2497 case where this isn't true by failing if the two operands
2498 are the same. */
2507 ;
2511 ;
2512 else
2516 ;
2520 ;
2521 else
2528 }
2529 }
2530 \f
2531 /* ARG is a tree that is known to contain just arithmetic operations and
2532 comparisons. Evaluate the operations in the tree substituting NEW0 for
2533 any occurrence of OLD0 as an operand of a comparison and likewise for
2534 NEW1 and OLD1. */
2536 static tree
2538 {
2543 /* We can handle some of the 'e' cases here. */
2551 {
2566 {
2583 }
2584 /* Fall through - ??? */
2587 {
2591 /* We need to check both for exact equality and tree equality. The
2592 former will be true if the operand has a side-effect. In that
2593 case, we know the operand occurred exactly once. */
2606 }
2610 }
2611 }
2612 \f
2613 /* Return a tree for the case when the result of an expression is RESULT
2614 converted to TYPE and OMITTED was previously an operand of the expression
2615 but is now not needed (e.g., we folded OMITTED * 0).
2617 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2618 the conversion of RESULT to TYPE. */
2620 tree
2622 {
2629 }
2631 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2633 static tree
2635 {
2642 }
2643 \f
2644 /* Return a simplified tree node for the truth-negation of ARG. This
2645 never alters ARG itself. We assume that ARG is an operation that
2646 returns a truth value (0 or 1). */
2648 tree
2650 {
2657 /* If this is a comparison, we can simply invert it, except for
2658 floating-point non-equality comparisons, in which case we just
2659 enclose a TRUTH_NOT_EXPR around what we have. */
2662 {
2664 && !flag_unsafe_math_optimizations
2676 else
2679 }
2682 {
2697 /* Here we can invert either operand. We invert the first operand
2698 unless the second operand is a TRUTH_NOT_EXPR in which case our
2699 result is the XOR of the first operand with the inside of the
2700 negation of the second operand. */
2705 else
2759 }
2763 }
2765 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2766 operands are another bit-wise operation with a common input. If so,
2767 distribute the bit operations to save an operation and possibly two if
2768 constants are involved. For example, convert
2769 (A | B) & (A | C) into A | (B & C)
2770 Further simplification will occur if B and C are constants.
2772 If this optimization cannot be done, 0 will be returned. */
2774 static tree
2776 {
2777 tree common;
2787 {
2791 }
2793 {
2797 }
2799 {
2803 }
2805 {
2809 }
2810 else
2815 }
2816 \f
2817 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2818 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2820 static tree
2823 {
2830 }
2832 /* Optimize a bit-field compare.
2834 There are two cases: First is a compare against a constant and the
2835 second is a comparison of two items where the fields are at the same
2836 bit position relative to the start of a chunk (byte, halfword, word)
2837 large enough to contain it. In these cases we can avoid the shift
2838 implicit in bitfield extractions.
2840 For constants, we emit a compare of the shifted constant with the
2841 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2842 compared. For two fields at the same position, we do the ANDs with the
2843 similar mask and compare the result of the ANDs.
2845 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2846 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2847 are the left and right operands of the comparison, respectively.
2849 If the optimization described above can be done, we return the resulting
2850 tree. Otherwise we return zero. */
2852 static tree
2855 {
2864 tree mask;
2865 tree offset;
2867 /* Get all the information about the extractions being done. If the bit size
2868 if the same as the size of the underlying object, we aren't doing an
2869 extraction at all and so can do nothing. We also don't want to
2870 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2871 then will no longer be able to replace it. */
2879 {
2880 /* If this is not a constant, we can only do something if bit positions,
2881 sizes, and signedness are the same. */
2889 }
2891 /* See if we can find a mode to refer to this field. We should be able to,
2892 but fail if we can't. */
2901 /* Set signed and unsigned types of the precision of this mode for the
2902 shifts below. */
2906 /* Compute the bit position and size for the new reference and our offset
2907 within it. If the new reference is the same size as the original, we
2908 won't optimize anything, so return zero. */
2918 /* Make the mask to be used against the extracted field. */
2928 /* If not comparing with constant, just rework the comparison
2929 and return. */
2934 mask),
2938 mask));
2940 /* Otherwise, we are handling the constant case. See if the constant is too
2941 big for the field. Warn and return a tree of for 0 (false) if so. We do
2942 this not only for its own sake, but to avoid having to test for this
2943 error case below. If we didn't, we might generate wrong code.
2945 For unsigned fields, the constant shifted right by the field length should
2946 be all zero. For signed fields, the high-order bits should agree with
2947 the sign bit. */
2950 {
2954 {
2960 }
2961 }
2962 else
2963 {
2967 {
2973 }
2974 }
2976 /* Single-bit compares should always be against zero. */
2978 {
2981 }
2983 /* Make a new bitfield reference, shift the constant over the
2984 appropriate number of bits and mask it with the computed mask
2985 (in case this was a signed field). If we changed it, make a new one. */
2988 {
2991 }
3001 rhs);
3002 }
3003 \f
3004 /* Subroutine for fold_truthop: decode a field reference.
3006 If EXP is a comparison reference, we return the innermost reference.
3008 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3009 set to the starting bit number.
3011 If the innermost field can be completely contained in a mode-sized
3012 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3014 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3015 otherwise it is not changed.
3017 *PUNSIGNEDP is set to the signedness of the field.
3019 *PMASK is set to the mask used. This is either contained in a
3020 BIT_AND_EXPR or derived from the width of the field.
3022 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3024 Return 0 if this is not a component reference or is one that we can't
3025 do anything with. */
3027 static tree
3032 {
3036 tree unsigned_type;
3039 /* All the optimizations using this function assume integer fields.
3040 There are problems with FP fields since the type_for_size call
3041 below can fail for, e.g., XFmode. */
3045 /* We are interested in the bare arrangement of bits, so strip everything
3046 that doesn't affect the machine mode. However, record the type of the
3047 outermost expression if it may matter below. */
3055 {
3061 }
3070 /* If the number of bits in the reference is the same as the bitsize of
3071 the outer type, then the outer type gives the signedness. Otherwise
3072 (in case of a small bitfield) the signedness is unchanged. */
3076 /* Compute the mask to access the bitfield. */
3086 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3094 }
3096 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3097 bit positions. */
3099 static int
3101 {
3104 tree tmask;
3109 return
3116 }
3118 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3119 represents the sign bit of EXP's type. If EXP represents a sign
3120 or zero extension, also test VAL against the unextended type.
3121 The return value is the (sub)expression whose sign bit is VAL,
3122 or NULL_TREE otherwise. */
3124 static tree
3126 {
3130 tree t;
3132 /* Tree EXP must have an integral type. */
3137 /* Tree VAL must be an integer constant. */
3144 {
3151 }
3152 else
3153 {
3160 }
3162 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3163 treat VAL as if it were unsigned. */
3168 /* Handle extension from a narrower type. */
3174 }
3176 /* Subroutine for fold_truthop: determine if an operand is simple enough
3177 to be evaluated unconditionally. */
3179 static int
3181 {
3182 /* Strip any conversions that don't change the machine mode. */
3194 /* Don't regard global variables as simple. They may be
3195 allocated in ways unknown to the compiler (shared memory,
3196 #pragma weak, etc). */
3199 /* Loading a static variable is unduly expensive, but global
3200 registers aren't expensive. */
3202 }
3203 \f
3204 /* The following functions are subroutines to fold_range_test and allow it to
3205 try to change a logical combination of comparisons into a range test.
3207 For example, both
3208 X == 2 || X == 3 || X == 4 || X == 5
3209 and
3210 X >= 2 && X <= 5
3211 are converted to
3212 (unsigned) (X - 2) <= 3
3214 We describe each set of comparisons as being either inside or outside
3215 a range, using a variable named like IN_P, and then describe the
3216 range with a lower and upper bound. If one of the bounds is omitted,
3217 it represents either the highest or lowest value of the type.
3219 In the comments below, we represent a range by two numbers in brackets
3220 preceded by a "+" to designate being inside that range, or a "-" to
3221 designate being outside that range, so the condition can be inverted by
3222 flipping the prefix. An omitted bound is represented by a "-". For
3223 example, "- [-, 10]" means being outside the range starting at the lowest
3224 possible value and ending at 10, in other words, being greater than 10.
3225 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3226 always false.
3228 We set up things so that the missing bounds are handled in a consistent
3229 manner so neither a missing bound nor "true" and "false" need to be
3230 handled using a special case. */
3232 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3233 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3234 and UPPER1_P are nonzero if the respective argument is an upper bound
3235 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3236 must be specified for a comparison. ARG1 will be converted to ARG0's
3237 type if both are specified. */
3239 static tree
3242 {
3243 tree tem;
3247 /* If neither arg represents infinity, do the normal operation.
3248 Else, if not a comparison, return infinity. Else handle the special
3249 comparison rules. Note that most of the cases below won't occur, but
3250 are handled for consistency. */
3253 {
3258 }
3263 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3264 for neither. In real maths, we cannot assume open ended ranges are
3265 the same. But, this is computer arithmetic, where numbers are finite.
3266 We can therefore make the transformation of any unbounded range with
3267 the value Z, Z being greater than any representable number. This permits
3268 us to treat unbounded ranges as equal. */
3272 {
3293 }
3296 }
3297 \f
3298 /* Given EXP, a logical expression, set the range it is testing into
3299 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3300 actually being tested. *PLOW and *PHIGH will be made of the same type
3301 as the returned expression. If EXP is not a comparison, we will most
3302 likely not be returning a useful value and range. */
3304 static tree
3306 {
3313 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3314 and see if we can refine the range. Some of the cases below may not
3315 happen, but it doesn't seem worth worrying about this. We "continue"
3316 the outer loop when we've changed something; otherwise we "break"
3317 the switch, which will "break" the while. */
3323 {
3327 {
3339 }
3341 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3342 lose a cast by accident. */
3347 {
3354 /* We can only do something if the range is testing for zero
3355 and if the second operand is an integer constant. Note that
3356 saying something is "in" the range we make is done by
3357 complementing IN_P since it will set in the initial case of
3358 being not equal to zero; "out" is leaving it alone. */
3365 {
3386 }
3390 /* If this is an unsigned comparison, we also know that EXP is
3391 greater than or equal to zero. We base the range tests we make
3392 on that fact, so we record it here so we can parse existing
3393 range tests. */
3395 {
3398 NULL_TREE))
3403 /* If the high bound is missing, but we have a nonzero low
3404 bound, reverse the range so it goes from zero to the low bound
3405 minus 1. */
3407 {
3412 }
3413 }
3417 /* (-x) IN [a,b] -> x in [-b, -a] */
3429 /* ~ X -> -X - 1 */
3438 /* If EXP is signed, any overflow in the computation is undefined,
3439 so we don't worry about it so long as our computations on
3440 the bounds don't overflow. For unsigned, overflow is defined
3441 and this is exactly the right thing. */
3450 /* Check for an unsigned range which has wrapped around the maximum
3451 value thus making n_high < n_low, and normalize it. */
3453 {
3459 /* If the range is of the form +/- [ x+1, x ], we won't
3460 be able to normalize it. But then, it represents the
3461 whole range or the empty set, so make it
3462 +/- [ -, - ]. */
3466 else
3468 }
3469 else
3492 /* If we're converting from an unsigned to a signed type,
3493 we will be doing the comparison as unsigned. The tests above
3494 have already verified that LOW and HIGH are both positive.
3496 So we have to make sure that the original unsigned value will
3497 be interpreted as positive. */
3499 {
3502 tree high_positive;
3504 /* A range without an upper bound is, naturally, unbounded.
3505 Since convert would have cropped a very large value, use
3506 the max value for the destination type. */
3507 high_positive
3514 high_positive),
3516 integer_one_node)));
3518 /* If the low bound is specified, "and" the range with the
3519 range for which the original unsigned value will be
3520 positive. */
3522 {
3526 high_positive))
3530 }
3531 else
3532 {
3533 /* Otherwise, "or" the range with the range of the input
3534 that will be interpreted as negative. */
3538 high_positive))
3542 }
3543 }
3551 }
3554 }
3556 /* If EXP is a constant, we can evaluate whether this is true or false. */
3558 {
3565 }
3569 }
3570 \f
3571 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3572 type, TYPE, return an expression to test if EXP is in (or out of, depending
3573 on IN_P) the range. */
3575 static tree
3577 {
3579 tree value;
3598 {
3600 {
3604 }
3606 }
3608 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3610 {
3612 HOST_WIDE_INT hi;
3617 {
3620 }
3621 else
3622 {
3625 }
3628 {
3630 {
3633 }
3636 }
3637 }
3644 value);
3647 }
3648 \f
3649 /* Given two ranges, see if we can merge them into one. Return 1 if we
3650 can, 0 if we can't. Set the output range into the specified parameters. */
3652 static int
3655 {
3659 tree tem;
3669 /* Make range 0 be the range that starts first, or ends last if they
3670 start at the same value. Swap them if it isn't. */
3673 || (lowequal
3676 {
3680 }
3682 /* Now flag two cases, whether the ranges are disjoint or whether the
3683 second range is totally subsumed in the first. Note that the tests
3684 below are simplified by the ones above. */
3690 /* We now have four cases, depending on whether we are including or
3691 excluding the two ranges. */
3693 {
3694 /* If they don't overlap, the result is false. If the second range
3695 is a subset it is the result. Otherwise, the range is from the start
3696 of the second to the end of the first. */
3701 else
3703 }
3706 {
3707 /* If they don't overlap, the result is the first range. If they are
3708 equal, the result is false. If the second range is a subset of the
3709 first, and the ranges begin at the same place, we go from just after
3710 the end of the first range to the end of the second. If the second
3711 range is not a subset of the first, or if it is a subset and both
3712 ranges end at the same place, the range starts at the start of the
3713 first range and ends just before the second range.
3714 Otherwise, we can't describe this as a single range. */
3720 {
3724 }
3726 {
3730 }
3731 else
3733 }
3736 {
3737 /* If they don't overlap, the result is the second range. If the second
3738 is a subset of the first, the result is false. Otherwise,
3739 the range starts just after the first range and ends at the
3740 end of the second. */
3745 else
3746 {
3750 }
3751 }
3753 else
3754 {
3755 /* The case where we are excluding both ranges. Here the complex case
3756 is if they don't overlap. In that case, the only time we have a
3757 range is if they are adjacent. If the second is a subset of the
3758 first, the result is the first. Otherwise, the range to exclude
3759 starts at the beginning of the first range and ends at the end of the
3760 second. */
3762 {
3769 else
3771 }
3774 else
3776 }
3780 }
3781 \f
3782 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3783 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3784 #endif
3786 /* EXP is some logical combination of boolean tests. See if we can
3787 merge it into some range test. Return the new tree if so. */
3789 static tree
3791 {
3798 tree tem;
3800 /* If this is an OR operation, invert both sides; we will invert
3801 again at the end. */
3805 /* If both expressions are the same, if we can merge the ranges, and we
3806 can build the range test, return it or it inverted. If one of the
3807 ranges is always true or always false, consider it to be the same
3808 expression as the other. */
3818 /* On machines where the branch cost is expensive, if this is a
3819 short-circuited branch and the underlying object on both sides
3820 is the same, make a non-short-circuit operation. */
3826 {
3827 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3828 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3829 which cases we can't do this. */
3838 {
3850 }
3851 }
3854 }
3855 \f
3856 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3857 bit value. Arrange things so the extra bits will be set to zero if and
3858 only if C is signed-extended to its full width. If MASK is nonzero,
3859 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3861 static tree
3863 {
3866 tree temp;
3871 /* We work by getting just the sign bit into the low-order bit, then
3872 into the high-order bit, then sign-extend. We then XOR that value
3873 with C. */
3877 /* We must use a signed type in order to get an arithmetic right shift.
3878 However, we must also avoid introducing accidental overflows, so that
3879 a subsequent call to integer_zerop will work. Hence we must
3880 do the type conversion here. At this point, the constant is either
3881 zero or one, and the conversion to a signed type can never overflow.
3882 We could get an overflow if this conversion is done anywhere else. */
3891 /* If necessary, convert the type back to match the type of C. */
3896 }
3897 \f
3898 /* Find ways of folding logical expressions of LHS and RHS:
3899 Try to merge two comparisons to the same innermost item.
3900 Look for range tests like "ch >= '0' && ch <= '9'".
3901 Look for combinations of simple terms on machines with expensive branches
3902 and evaluate the RHS unconditionally.
3904 For example, if we have p->a == 2 && p->b == 4 and we can make an
3905 object large enough to span both A and B, we can do this with a comparison
3906 against the object ANDed with the a mask.
3908 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3909 operations to do this with one comparison.
3911 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3912 function and the one above.
3914 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3915 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3917 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3918 two operands.
3920 We return the simplified tree or 0 if no optimization is possible. */
3922 static tree
3924 {
3925 /* If this is the "or" of two comparisons, we can do something if
3926 the comparisons are NE_EXPR. If this is the "and", we can do something
3927 if the comparisons are EQ_EXPR. I.e.,
3928 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3930 WANTED_CODE is this operation code. For single bit fields, we can
3931 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3932 comparison for one-bit fields. */
3952 /* Start by getting the comparison codes. Fail if anything is volatile.
3953 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3954 it were surrounded with a NE_EXPR. */
3979 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3983 {
3988 {
3996 }
3999 {
4008 }
4009 else
4019 }
4021 /* If the RHS can be evaluated unconditionally and its operands are
4022 simple, it wins to evaluate the RHS unconditionally on machines
4023 with expensive branches. In this case, this isn't a comparison
4024 that can be merged. Avoid doing this if the RHS is a floating-point
4025 comparison since those can trap. */
4031 {
4032 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4040 integer_zero_node);
4042 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4050 integer_zero_node);
4053 }
4055 /* See if the comparisons can be merged. Then get all the parameters for
4056 each side. */
4080 /* It must be true that the inner operation on the lhs of each
4081 comparison must be the same if we are to be able to do anything.
4082 Then see if we have constants. If not, the same must be true for
4083 the rhs's. */
4094 else
4097 /* If either comparison code is not correct for our logical operation,
4098 fail. However, we can convert a one-bit comparison against zero into
4099 the opposite comparison against that bit being set in the field. */
4103 {
4105 {
4106 /* Make the left operand unsigned, since we are only interested
4107 in the value of one bit. Otherwise we are doing the wrong
4108 thing below. */
4111 }
4112 else
4114 }
4116 /* This is analogous to the code for l_const above. */
4118 {
4120 {
4123 }
4124 else
4126 }
4128 /* After this point all optimizations will generate bit-field
4129 references, which we might not want. */
4133 /* See if we can find a mode that contains both fields being compared on
4134 the left. If we can't, fail. Otherwise, update all constants and masks
4135 to be relative to a field of that size. */
4140 volatilep);
4150 {
4153 }
4161 {
4169 {
4173 wanted_code == NE_EXPR
4175 }
4176 }
4178 {
4186 {
4190 wanted_code == NE_EXPR
4192 }
4193 }
4195 /* If the right sides are not constant, do the same for it. Also,
4196 disallow this optimization if a size or signedness mismatch occurs
4197 between the left and right sides. */
4199 {
4202 /* Make sure the two fields on the right
4203 correspond to the left without being swapped. */
4211 volatilep);
4221 {
4224 }
4231 /* Make a mask that corresponds to both fields being compared.
4232 Do this for both items being compared. If the operands are the
4233 same size and the bits being compared are in the same position
4234 then we can do this by masking both and comparing the masked
4235 results. */
4239 {
4251 }
4253 /* There is still another way we can do something: If both pairs of
4254 fields being compared are adjacent, we may be able to make a wider
4255 field containing them both.
4257 Note that we still must mask the lhs/rhs expressions. Furthermore,
4258 the mask must be shifted to account for the shift done by
4259 make_bit_field_ref. */
4264 {
4265 tree type;
4277 /* Convert to the smaller type before masking out unwanted bits. */
4280 {
4282 {
4286 }
4288 {
4292 }
4293 }
4302 }
4305 }
4307 /* Handle the case of comparisons with constants. If there is something in
4308 common between the masks, those bits of the constants must be the same.
4309 If not, the condition is always false. Test for this to avoid generating
4310 incorrect code below. */
4315 {
4317 {
4320 }
4321 else
4322 {
4325 }
4326 }
4328 /* Construct the expression we will return. First get the component
4329 reference we will make. Unless the mask is all ones the width of
4330 that field, perform the mask operation. Then compare with the
4331 merged constant. */
4341 }
4342 \f
4343 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4344 constant. */
4346 static tree
4348 {
4353 tree minmax_const;
4355 tree inner;
4365 /* If something does not permit us to optimize, return the original tree. */
4373 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4374 and GT_EXPR, doing the rest with recursive calls using logical
4375 simplifications. */
4377 {
4379 return
4383 return
4385 optimize_minmax_comparison
4387 optimize_minmax_comparison
4392 /* MAX (X, 0) == 0 -> X <= 0 */
4396 /* MAX (X, 0) == 5 -> X == 5 */
4400 /* MAX (X, 0) == -1 -> false */
4404 /* MIN (X, 0) == 0 -> X >= 0 */
4408 /* MIN (X, 0) == 5 -> false */
4411 else
4412 /* MIN (X, 0) == -1 -> X == -1 */
4417 /* MAX (X, 0) > 0 -> X > 0
4418 MAX (X, 0) > 5 -> X > 5 */
4422 /* MAX (X, 0) > -1 -> true */
4426 /* MIN (X, 0) > 0 -> false
4427 MIN (X, 0) > 5 -> false */
4430 else
4431 /* MIN (X, 0) > -1 -> X > -1 */
4436 }
4437 }
4438 \f
4439 /* T is an integer expression that is being multiplied, divided, or taken a
4440 modulus (CODE says which and what kind of divide or modulus) by a
4441 constant C. See if we can eliminate that operation by folding it with
4442 other operations already in T. WIDE_TYPE, if non-null, is a type that
4443 should be used for the computation if wider than our type.
4445 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4446 (X * 2) + (Y * 4). We must, however, be assured that either the original
4447 expression would not overflow or that overflow is undefined for the type
4448 in the language in question.
4450 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4451 the machine has a multiply-accumulate insn or that this is part of an
4452 addressing calculation.
4454 If we return a non-null expression, it is an equivalent form of the
4455 original computation, but need not be in the original type. */
4457 static tree
4459 {
4460 /* To avoid exponential search depth, refuse to allow recursion past
4461 three levels. Beyond that (1) it's highly unlikely that we'll find
4462 something interesting and (2) we've probably processed it before
4463 when we built the inner expression. */
4466 tree ret;
4471 depth++;
4473 depth--;
4476 }
4478 static tree
4480 {
4490 /* Don't deal with constants of zero here; they confuse the code below. */
4500 /* Note that we need not handle conditional operations here since fold
4501 already handles those cases. So just do arithmetic here. */
4503 {
4505 /* For a constant, we can always simplify if we are a multiply
4506 or (for divide and modulus) if it is a multiple of our constant. */
4514 /* If op0 is an expression ... */
4519 /* ... and is unsigned, and its type is smaller than ctype,
4520 then we cannot pass through as widening. */
4526 /* ... or its type is larger than ctype,
4527 then we cannot pass through this truncation. */
4530 /* ... or signedness changes for division or modulus,
4531 then we cannot pass through this conversion. */
4537 /* Pass the constant down and see if we can make a simplification. If
4538 we can, replace this expression with the inner simplification for
4539 possible later conversion to our or some other type. */
4544 code == MULT_EXPR
4555 /* If widening the type changes the signedness, then we can't perform
4556 this optimization as that changes the result. */
4560 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4563 {
4569 }
4573 /* If the second operand is constant, this is a multiplication
4574 or floor division, by a power of two, so we can treat it that
4575 way unless the multiplier or divisor overflows. */
4577 /* const_binop may not detect overflow correctly,
4578 so check for it explicitly here. */
4583 size_one_node,
4593 /* See if we can eliminate the operation on both sides. If we can, we
4594 can return a new PLUS or MINUS. If we can't, the only remaining
4595 cases where we can do anything are if the second operand is a
4596 constant. */
4601 /* If not multiplication, we can only do this if both operands
4602 are divisible by c. */
4608 /* If this was a subtraction, negate OP1 and set it to be an addition.
4609 This simplifies the logic below. */
4616 /* If either OP1 or C are negative, this optimization is not safe for
4617 some of the division and remainder types while for others we need
4618 to change the code. */
4620 {
4628 }
4630 /* If it's a multiply or a division/modulus operation of a multiple
4631 of our constant, do the operation and verify it doesn't overflow. */
4634 {
4637 /* We allow the constant to overflow with wrapping semantics. */
4641 }
4642 else
4645 /* If we have an unsigned type is not a sizetype, we cannot widen
4646 the operation since it will change the result if the original
4647 computation overflowed. */
4653 /* If we were able to eliminate our operation from the first side,
4654 apply our operation to the second side and reform the PLUS. */
4658 /* The last case is if we are a multiply. In that case, we can
4659 apply the distributive law to commute the multiply and addition
4660 if the multiplication of the constants doesn't overflow. */
4666 op1));
4671 /* We have a special case here if we are doing something like
4672 (C * 8) % 4 since we know that's zero. */
4679 /* ... fall through ... */
4683 /* If we can extract our operation from the LHS, do so and return a
4684 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4685 do something only if the second operand is a constant. */
4697 /* If these are the same operation types, we can associate them
4698 assuming no overflow. */
4705 /* If these operations "cancel" each other, we have the main
4706 optimizations of this pass, which occur when either constant is a
4707 multiple of the other, in which case we replace this with either an
4708 operation or CODE or TCODE.
4710 If we have an unsigned type that is not a sizetype, we cannot do
4711 this since it will change the result if the original computation
4712 overflowed. */
4715 && ! flag_wrapv
4720 {
4731 }
4736 }
4739 }
4740 \f
4741 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4742 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4743 that we may sometimes modify the tree. */
4745 static tree
4747 {
4750 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4755 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4756 don't bother handling any other types. */
4758 {
4762 }
4767 {
4770 }
4773 }
4774 \f
4775 /* Return a node which has the indicated constant VALUE (either 0 or
4776 1), and is of the indicated TYPE. */
4778 static tree
4780 {
4786 else
4787 {
4792 }
4793 }
4795 /* Utility function for the following routine, to see how complex a nesting of
4796 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4797 we don't care (to avoid spending too much time on complex expressions.). */
4799 static int
4801 {
4812 }
4814 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4815 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4816 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4817 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4818 COND is the first argument to CODE; otherwise (as in the example
4819 given here), it is the second argument. TYPE is the type of the
4820 original expression. Return NULL_TREE if no simplification is
4821 possible. */
4823 static tree
4826 {
4830 /* In the end, we'll produce a COND_EXPR. Both arms of the
4831 conditional expression will be binary operations. The left-hand
4832 side of the expression to be executed if the condition is true
4833 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4834 of the expression to be executed if the condition is true will be
4835 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4836 but apply to the expression to be executed if the conditional is
4837 false. */
4842 /* These are the codes to use for the left-hand side and right-hand
4843 side of the COND_EXPR. Normally, they are the same as CODE. */
4846 /* And these are the types of the expressions. */
4865 {
4869 }
4870 else
4871 {
4875 }
4878 {
4882 /* If this operand throws an expression, then it does not make
4883 sense to try to perform a logical or arithmetic operation
4884 involving it. Instead of building `a + throw 3' for example,
4885 we simply build `a, throw 3'. */
4887 {
4889 {
4892 }
4893 else
4895 }
4897 {
4899 {
4902 }
4903 else
4905 }
4906 }
4907 else
4908 {
4913 }
4915 /* If ARG is complex we want to make sure we only evaluate it once. Though
4916 this is only required if it is volatile, it might be more efficient even
4917 if it is not. However, if we succeed in folding one part to a constant,
4918 we do not need to make this SAVE_EXPR. Since we do this optimization
4919 primarily to see if we do end up with constant and this SAVE_EXPR
4920 interferes with later optimizations, suppressing it when we can is
4921 important.
4923 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4924 do so. Don't try to see if the result is a constant if an arm is a
4925 COND_EXPR since we get exponential behavior in that case. */
4934 {
4943 {
4947 }
4948 }
4957 /* If ARG involves a SAVE_EXPR, we need to ensure it is evaluated
4958 ahead of the COND_EXPR we made. Otherwise we would have it only
4959 evaluated in one branch, with the other branch using the result
4960 but missing the evaluation code. Beware that the save_expr call
4961 above might not return a SAVE_EXPR, so testing the TREE_CODE
4962 of ARG is not enough to decide here. Â */
4967 else
4969 }
4971 \f
4972 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4974 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4975 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4976 ADDEND is the same as X.
4978 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4979 and finite. The problematic cases are when X is zero, and its mode
4980 has signed zeros. In the case of rounding towards -infinity,
4981 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4982 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4984 static bool
4986 {
4990 /* Don't allow the fold with -fsignaling-nans. */
4994 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4998 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
5003 /* The mode has signed zeros, and we have to honor their sign.
5004 In this situation, there is only one case we can return true for.
5005 X - 0 is the same as X unless rounding towards -infinity is
5006 supported. */
5008 }
5010 /* Subroutine of fold() that checks comparisons of built-in math
5011 functions against real constants.
5013 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
5014 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
5015 is the type of the result and ARG0 and ARG1 are the operands of the
5016 comparison. ARG1 must be a TREE_REAL_CST.
5018 The function returns the constant folded tree if a simplification
5019 can be made, and NULL_TREE otherwise. */
5021 static tree
5024 {
5025 REAL_VALUE_TYPE c;
5028 {
5034 {
5035 /* sqrt(x) < y is always false, if y is negative. */
5039 arg);
5041 /* sqrt(x) > y is always true, if y is negative and we
5042 don't care about NaNs, i.e. negative values of x. */
5046 arg);
5048 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5051 }
5053 {
5054 REAL_VALUE_TYPE c2;
5060 {
5061 /* sqrt(x) > y is x == +Inf, when y is very large. */
5066 /* sqrt(x) > y is always false, when y is very large
5067 and we don't care about infinities. */
5070 arg);
5071 }
5073 /* sqrt(x) > c is the same as x > c*c. */
5076 }
5078 {
5079 REAL_VALUE_TYPE c2;
5085 {
5086 /* sqrt(x) < y is always true, when y is a very large
5087 value and we don't care about NaNs or Infinities. */
5091 arg);
5093 /* sqrt(x) < y is x != +Inf when y is very large and we
5094 don't care about NaNs. */
5099 /* sqrt(x) < y is x >= 0 when y is very large and we
5100 don't care about Infinities. */
5105 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5114 dconst0))),
5117 c2)))));
5118 }
5120 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5125 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5128 {
5133 dconst0))),
5136 c2)))));
5137 }
5138 }
5139 }
5142 }
5144 /* Subroutine of fold() that optimizes comparisons against Infinities,
5145 either +Inf or -Inf.
5147 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5148 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5149 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5151 The function returns the constant folded tree if a simplification
5152 can be made, and NULL_TREE otherwise. */
5154 static tree
5156 {
5158 REAL_VALUE_TYPE max;
5159 tree temp;
5164 /* For negative infinity swap the sense of the comparison. */
5170 {
5172 /* x > +Inf is always false, if with ignore sNANs. */
5177 arg0);
5180 /* x <= +Inf is always true, if we don't case about NaNs. */
5184 arg0);
5186 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5189 {
5192 }
5197 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5203 /* x < +Inf is always equal to x <= DBL_MAX. */
5209 /* x != +Inf is always equal to !(x > DBL_MAX). */
5220 }
5223 }
5225 /* Subroutine of fold() that optimizes comparisons of a division by
5226 a non-zero integer constant against an integer constant, i.e.
5227 X/C1 op C2.
5229 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5230 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5231 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5233 The function returns the constant folded tree if a simplification
5234 can be made, and NULL_TREE otherwise. */
5236 static tree
5238 {
5243 HOST_WIDE_INT hpart;
5246 /* We have to do this the hard way to detect unsigned overflow.
5247 prod = int_const_binop (MULT_EXPR, arg01, arg1, 0); */
5260 {
5264 /* Likewise hi = int_const_binop (PLUS_EXPR, prod, tmp, 0). */
5277 }
5279 {
5282 {
5300 }
5301 }
5302 else
5303 {
5306 {
5324 }
5325 }
5328 {
5369 }
5372 }
5375 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5376 equality/inequality test, then return a simplified form of
5377 the test using shifts and logical operations. Otherwise return
5378 NULL. TYPE is the desired result type. */
5380 tree
5382 tree result_type)
5383 {
5384 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5385 operand 0. */
5387 {
5392 /* Extract the arguments of the EQ/NE. */
5396 /* This requires us to invert the code. */
5398 }
5400 /* If this is testing a single bit, we can optimize the test. */
5404 {
5411 tree arg00;
5413 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5414 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5417 {
5422 }
5424 /* At this point, we know that arg0 is not testing the sign bit. */
5428 /* Otherwise we have (A & C) != 0 where C is a single bit,
5429 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5430 Similarly for (A & C) == 0. */
5432 /* If INNER is a right shift of a constant and it plus BITNUM does
5433 not overflow, adjust BITNUM and INNER. */
5440 {
5443 }
5445 /* If we are going to be able to omit the AND below, we must do our
5446 operations as unsigned. If we must use the AND, we have a choice.
5447 Normally unsigned is faster, but for some machines signed is. */
5448 #ifdef LOAD_EXTEND_OP
5450 #else
5452 #endif
5467 /* Put the AND last so it can combine with more things. */
5471 /* Make sure to return the proper type. */
5475 }
5477 }
5479 /* Check whether we are allowed to reorder operands arg0 and arg1,
5480 such that the evaluation of arg1 occurs before arg0. */
5482 static bool
5484 {
5491 }
5493 /* Test whether it is preferable two swap two operands, ARG0 and
5494 ARG1, for example because ARG0 is an integer constant and ARG1
5495 isn't. If REORDER is true, only recommend swapping if we can
5496 evaluate the operands in reverse order. */
5498 static bool
5500 {
5546 }
5548 /* Perform constant folding and related simplification of EXPR.
5549 The related simplifications include x*1 => x, x*0 => 0, etc.,
5550 and application of the associative law.
5551 NOP_EXPR conversions may be removed freely (as long as we
5552 are careful not to change the type of the overall expression).
5553 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5554 but we can constant-fold them if they have constant operands. */
5556 #ifdef ENABLE_FOLD_CHECKING
5557 # define fold(x) fold_1 (x)
5559 static
5560 #endif
5561 tree
5563 {
5567 tree tem;
5572 /* WINS will be nonzero when the switch is done
5573 if all operands are constant. */
5576 /* Don't try to process an RTL_EXPR since its operands aren't trees.
5577 Likewise for a SAVE_EXPR that's already been evaluated. */
5581 /* Return right away if a constant. */
5586 {
5587 tree subop;
5589 /* Special case for conversion ops that can have fixed point args. */
5592 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
5598 else
5603 /* Note that TREE_CONSTANT isn't enough:
5604 static var addresses are constant but we can't
5605 do arithmetic on them. */
5607 }
5609 {
5613 {
5615 tree subop;
5620 /* Strip any conversions that don't change the mode. This is
5621 safe for every expression, except for a comparison expression
5622 because its signedness is derived from its operands. So, in
5623 the latter case, only strip conversions that don't change the
5624 signedness.
5626 Note that this is done as an internal manipulation within the
5627 constant folder, in order to find the simplest representation
5628 of the arguments so that their form can be studied. In any
5629 cases, the appropriate type conversions should be put back in
5630 the tree that will get out of the constant folder. */
5633 else
5638 else
5643 /* Note that TREE_CONSTANT isn't enough:
5644 static var addresses are constant but we can't
5645 do arithmetic on them. */
5652 }
5653 }
5655 /* If this is a commutative operation, and ARG0 is a constant, move it
5656 to ARG1 to reduce the number of tests below. */
5662 /* Now WINS is set as described above,
5663 ARG0 is the first operand of EXPR,
5664 and ARG1 is the second operand (if it has more than one operand).
5666 First check for cases where an arithmetic operation is applied to a
5667 compound, conditional, or comparison operation. Push the arithmetic
5668 operation inside the compound or conditional to see if any folding
5669 can then be done. Convert comparison to conditional for this purpose.
5670 The also optimizes non-constant cases that used to be done in
5671 expand_expr.
5673 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5674 one of the operands is a comparison and the other is a comparison, a
5675 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5676 code below would make the expression more complex. Change it to a
5677 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5678 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5690 {
5701 }
5704 {
5709 {
5719 /* If this was a conversion, and all we did was to move into
5720 inside the COND_EXPR, bring it back out. But leave it if
5721 it is a conversion from integer to integer and the
5722 result precision is no wider than a word since such a
5723 conversion is cheap and may be optimized away by combine,
5724 while it couldn't if it were outside the COND_EXPR. Then return
5725 so we don't get into an infinite recursion loop taking the
5726 conversion out and then back in. */
5738 && (INTEGRAL_TYPE_P
5749 }
5751 {
5753 {
5757 }
5762 }
5763 }
5774 {
5786 {
5791 }
5795 {
5800 }
5801 }
5804 {
5818 /* Handle cases of two conversions in a row. */
5821 {
5840 /* In addition to the cases of two conversions in a row
5841 handled below, if we are converting something to its own
5842 type via an object of identical or wider precision, neither
5843 conversion is needed. */
5850 /* Likewise, if the intermediate and final types are either both
5851 float or both integer, we don't need the middle conversion if
5852 it is wider than the final type and doesn't change the signedness
5853 (for integers). Avoid this if the final type is a pointer
5854 since then we sometimes need the inner conversion. Likewise if
5855 the outer has a precision not equal to the size of its mode. */
5866 /* If we have a sign-extension of a zero-extended value, we can
5867 replace that by a single zero-extension. */
5874 /* Two conversions in a row are not needed unless:
5875 - some conversion is floating-point (overstrict for now), or
5876 - the intermediate type is narrower than both initial and
5877 final, or
5878 - the intermediate type and innermost type differ in signedness,
5879 and the outermost type is wider than the intermediate, or
5880 - the initial type is a pointer type and the precisions of the
5881 intermediate and final types differ, or
5882 - the final type is a pointer type and the precisions of the
5883 initial and intermediate types differ. */
5898 }
5902 /* Detect assigning a bitfield. */
5905 {
5906 /* Don't leave an assignment inside a conversion
5907 unless assigning a bitfield. */
5911 /* First do the assignment, then return converted constant. */
5916 }
5918 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5919 constants (if x has signed type, the sign bit cannot be set
5920 in c). This folds extension into the BIT_AND_EXPR. */
5925 {
5935 <= HOST_BITS_PER_WIDE_INT
5937 {
5944 #ifdef LOAD_EXTEND_OP
5948 {
5952 }
5953 #endif
5954 }
5959 }
5961 /* Convert (T1)((T2)X op Y) into (T1)X op Y, for pointer types T1 and
5962 T2 being pointers to types of the same size. */
5967 {
5979 }
5993 {
5997 }
6002 {
6007 }
6021 /* Convert fabs((double)float) into (double)fabsf(float). */
6024 {
6029 targ0)));
6030 }
6057 {
6065 }
6071 /* A + (-B) -> A - B */
6074 /* (-A) + B -> B - A */
6079 {
6083 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
6084 with a constant, and the two constants have no bits in common,
6085 we should treat this as a BIT_IOR_EXPR since this may produce more
6086 simplifications. */
6094 {
6097 }
6099 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
6100 (plus (plus (mult) (mult)) (foo)) so that we can
6101 take advantage of the factoring cases below. */
6106 {
6111 else
6132 }
6135 {
6139 /* (A * C) + (B * C) -> (A+B) * C.
6140 We are most concerned about the case where C is a constant,
6141 but other combinations show up during loop reduction. Since
6142 it is not difficult, try all four possibilities. */
6159 /* No identical multiplicands; see if we can find a common
6160 power-of-two factor in non-power-of-two multiplies. This
6161 can help in multi-dimensional array access. */
6166 {
6171 /* Move min of absolute values to int11. */
6174 {
6178 }
6181 {
6186 }
6187 }
6192 same));
6193 }
6194 }
6195 else
6196 {
6197 /* See if ARG1 is zero and X + ARG1 reduces to X. */
6201 /* Likewise if the operands are reversed. */
6205 /* Convert x+x into x*2.0. */
6211 /* Convert x*c+x into x*(c+1). */
6217 {
6218 REAL_VALUE_TYPE c;
6224 }
6226 /* Convert x+x*c into x*(c+1). */
6232 {
6233 REAL_VALUE_TYPE c;
6239 }
6241 /* Convert x*c1+x*c2 into x*(c1+c2). */
6251 {
6260 }
6261 /* Convert a + (b*c + d*e) into (a + b*c) + d*e */
6265 {
6270 {
6271 tree tree0;
6274 }
6275 }
6276 /* Convert (b*c + d*e) + a into b*c + (d*e +a) */
6280 {
6285 {
6286 tree tree0;
6289 }
6290 }
6291 }
6293 bit_rotate:
6294 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
6295 is a rotate of A by C1 bits. */
6296 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
6297 is a rotate of A by B bits. */
6298 {
6307 {
6326 {
6334 TYPE_PRECISION
6339 ? LROTATE_EXPR
6342 }
6344 {
6352 TYPE_PRECISION
6357 ? LROTATE_EXPR
6360 }
6361 }
6362 }
6364 associate:
6365 /* In most languages, can't associate operations on floats through
6366 parentheses. Rather than remember where the parentheses were, we
6367 don't associate floats at all, unless the user has specified
6368 -funsafe-math-optimizations. */
6372 {
6376 /* Split both trees into variables, constants, and literals. Then
6377 associate each group together, the constants with literals,
6378 then the result with variables. This increases the chances of
6379 literals being recombined later and of generating relocatable
6380 expressions for the sum of a constant and literal. */
6385 /* Only do something if we found more than two objects. Otherwise,
6386 nothing has changed and we risk infinite recursion. */
6391 {
6392 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6401 /* Preserve the MINUS_EXPR if the negative part of the literal is
6402 greater than the positive part. Otherwise, the multiplicative
6403 folding code (i.e extract_muldiv) may be fooled in case
6404 unsigned constants are subtracted, like in the following
6405 example: ((X*2 + 4) - 8U)/2. */
6407 {
6411 {
6415 }
6416 else
6417 {
6421 }
6422 }
6424 {
6429 else
6430 {
6436 }
6437 }
6442 }
6443 }
6445 binary:
6449 {
6450 /* The return value should always have
6451 the same type as the original expression. */
6456 }
6460 /* A - (-B) -> A + B */
6463 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6473 {
6479 /* Fold A - (A & B) into ~B & A. */
6482 {
6487 arg0));
6492 arg0));
6493 }
6495 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6496 any power of 2 minus 1. */
6501 {
6507 {
6511 }
6512 }
6513 }
6515 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6519 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6520 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6521 (-ARG1 + ARG0) reduces to -ARG1. */
6525 /* Fold &x - &x. This can happen from &x.foo - &x.
6526 This is unsafe for certain floats even in non-IEEE formats.
6527 In IEEE, it is unsafe because it does wrong for NaNs.
6528 Also note that operand_equal_p is always false if an operand
6529 is volatile. */
6535 /* A - B -> A + (-B) if B is easily negatable. */
6544 {
6545 /* (A * C) - (B * C) -> (A-B) * C. */
6553 /* (A * C1) - (A * C2) -> A * (C1-C2). */
6561 }
6566 /* (-A) * (-B) -> A * B */
6577 {
6583 /* (a * (1 << b)) is (a << b) */
6599 }
6600 else
6601 {
6602 /* Maybe fold x * 0 to 0. The expressions aren't the same
6603 when x is NaN, since x * 0 is also NaN. Nor are they the
6604 same in modes with signed zeros, since multiplying a
6605 negative value by 0 gives -0, not +0. */
6610 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
6615 /* Transform x * -1.0 into -x. */
6620 /* Convert (C1/X)*C2 into (C1*C2)/X. */
6625 {
6631 }
6634 {
6638 /* Optimizations of root(...)*root(...). */
6640 {
6645 /* Optimize sqrt(x)*sqrt(x) as x. */
6651 /* Optimize root(x)*root(y) as root(x*y). */
6656 }
6658 /* Optimize expN(x)*expN(y) as expN(x+y). */
6660 {
6667 }
6669 /* Optimizations of pow(...)*pow(...). */
6673 {
6681 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
6683 {
6688 arg01));
6690 }
6692 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
6694 {
6699 arg));
6701 }
6702 }
6704 /* Optimize tan(x)*cos(x) as sin(x). */
6713 {
6719 }
6721 /* Optimize x*pow(x,c) as pow(x,c+1). */
6725 {
6732 {
6734 REAL_VALUE_TYPE c;
6743 }
6744 }
6746 /* Optimize pow(x,c)*x as pow(x,c+1). */
6750 {
6757 {
6759 REAL_VALUE_TYPE c;
6768 }
6769 }
6771 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
6774 {
6778 {
6783 }
6784 }
6785 }
6786 }
6790 bit_ior:
6801 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6803 This results in more efficient code for machines without a NAND
6804 instruction. Combine will canonicalize to the first form
6805 which will allow use of NAND instructions provided by the
6806 backend if they exist. */
6809 {
6814 }
6816 /* See if this can be simplified into a rotate first. If that
6817 is unsuccessful continue in the association code. */
6828 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6829 with a constant, and the two constants have no bits in common,
6830 we should treat this as a BIT_IOR_EXPR since this may produce more
6831 simplifications. */
6839 {
6842 }
6844 /* See if this can be simplified into a rotate first. If that
6845 is unsuccessful continue in the association code. */
6858 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6861 {
6862 unsigned int prec
6869 }
6871 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6873 This results in more efficient code for machines without a NOR
6874 instruction. Combine will canonicalize to the first form
6875 which will allow use of NOR instructions provided by the
6876 backend if they exist. */
6879 {
6884 }
6889 /* Don't touch a floating-point divide by zero unless the mode
6890 of the constant can represent infinity. */
6896 /* (-A) / (-B) -> A / B */
6906 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6911 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
6916 /* If ARG1 is a constant, we can convert this to a multiply by the
6917 reciprocal. This does not have the same rounding properties,
6918 so only do this if -funsafe-math-optimizations. We can actually
6919 always safely do it if ARG1 is a power of two, but it's hard to
6920 tell if it is or not in a portable manner. */
6922 {
6927 /* Find the reciprocal if optimizing and the result is exact. */
6929 {
6930 REAL_VALUE_TYPE r;
6933 {
6936 }
6937 }
6938 }
6939 /* Convert A/B/C to A/(B*C). */
6946 /* Convert A/(B/C) to (A/B)*C. */
6954 /* Convert C1/(X*C2) into (C1/C2)/X. */
6959 {
6965 }
6968 {
6970 /* Optimize x/expN(y) into x*expN(-y). */
6972 {
6979 }
6981 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6985 {
6994 }
6995 }
6998 {
7002 /* Optimize sin(x)/cos(x) as tan(x). */
7008 {
7014 }
7016 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
7022 {
7026 {
7031 tmp));
7032 }
7033 }
7035 /* Optimize pow(x,c)/x as pow(x,c-1). */
7039 {
7045 {
7047 REAL_VALUE_TYPE c;
7056 }
7057 }
7058 }
7070 /* X / -1 is -X. */
7077 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
7078 operation, EXACT_DIV_EXPR.
7080 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
7081 At one time others generated faster code, it's not clear if they do
7082 after the last round to changes to the DIV code in expmed.c. */
7102 /* X % -1 is zero. */
7123 /* Optimize -1 >> x for arithmetic right shifts. */
7126 /* ... fall through ... */
7129 shift:
7135 /* Since negative shift count is not well-defined,
7136 don't try to compute it in the compiler. */
7139 /* Rewrite an LROTATE_EXPR by a constant into an
7140 RROTATE_EXPR by a new constant. */
7142 {
7147 }
7149 /* If we have a rotate of a bit operation with the rotate count and
7150 the second operand of the bit operation both constant,
7151 permute the two operations. */
7163 /* Two consecutive rotates adding up to the width of the mode can
7164 be ignored. */
7195 /* Note that the operand of this must be an int
7196 and its values must be 0 or 1.
7197 ("true" is a fixed value perhaps depending on the language,
7198 but we don't handle values other than 1 correctly yet.) */
7200 /* Avoid infinite recursion. */
7202 {
7207 }
7211 /* Note that the operands of this must be ints
7212 and their values must be 0 or 1.
7213 ("true" is a fixed value perhaps depending on the language.) */
7214 /* If first arg is constant zero, return it. */
7218 /* If either arg is constant true, drop it. */
7222 /* Preserve sequence points. */
7225 /* If second arg is constant zero, result is zero, but first arg
7226 must be evaluated. */
7229 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
7230 case will be handled here. */
7234 truth_andor:
7235 /* We only do these simplifications if we are optimizing. */
7239 /* Check for things like (A || B) && (A || C). We can convert this
7240 to A || (B && C). Note that either operator can be any of the four
7241 truth and/or operations and the transformation will still be
7242 valid. Also note that we only care about order for the
7243 ANDIF and ORIF operators. If B contains side effects, this
7244 might change the truth-value of A. */
7251 {
7271 /* This case if tricky because we must either have commutative
7272 operators or else A10 must not have side-effects. */
7278 a01));
7279 }
7281 /* See if we can build a range comparison. */
7285 /* Check for the possibility of merging component references. If our
7286 lhs is another similar operation, try to merge its rhs with our
7287 rhs. Then try to merge our lhs and rhs. */
7299 /* Note that the operands of this must be ints
7300 and their values must be 0 or true.
7301 ("true" is a fixed value perhaps depending on the language.) */
7302 /* If first arg is constant true, return it. */
7306 /* If either arg is constant zero, drop it. */
7310 /* Preserve sequence points. */
7313 /* If second arg is constant true, result is true, but we must
7314 evaluate first arg. */
7317 /* Likewise for first arg, but note this only occurs here for
7318 TRUTH_OR_EXPR. */
7324 /* If either arg is constant zero, drop it. */
7329 /* If either arg is constant true, this is a logical inversion. */
7334 /* Identical arguments cancel to zero. */
7345 /* If one arg is a real or integer constant, put it last. */
7349 /* If this is an equality comparison of the address of a non-weak
7350 object against zero, then we know the result. */
7356 {
7359 else
7361 }
7363 /* If this is an equality comparison of the address of two non-weak,
7364 unaliased symbols neither of which are extern (since we do not
7365 have access to attributes for externs), then we know the result. */
7379 {
7383 else
7386 }
7389 {
7397 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7402 /* (-a) CMP (-b) -> b CMP a */
7409 {
7410 REAL_VALUE_TYPE cst;
7413 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7415 return
7421 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7422 /* a CMP (-0) -> a CMP 0 */
7427 /* x != NaN is always true, other ops are always false. */
7430 {
7433 }
7435 /* Fold comparisons against infinity. */
7437 {
7441 }
7442 }
7444 /* If this is a comparison of a real constant with a PLUS_EXPR
7445 or a MINUS_EXPR of a real constant, we can convert it into a
7446 comparison with a revised real constant as long as no overflow
7447 occurs when unsafe_math_optimizations are enabled. */
7459 /* Likewise, we can simplify a comparison of a real constant with
7460 a MINUS_EXPR whose first operand is also a real constant, i.e.
7461 (c1 - x) < c2 becomes x > c1-c2. */
7472 /* Fold comparisons against built-in math functions. */
7474 && flag_unsafe_math_optimizations
7476 {
7480 {
7484 }
7485 }
7486 }
7488 /* Convert foo++ == CONST into ++foo == CONST + INCR. */
7492 /* This optimization is invalid for ordered comparisons
7493 if CONST+INCR overflows or if foo+incr might overflow.
7494 This optimization is invalid for floating point due to rounding.
7495 For pointer types we assume overflow doesn't happen. */
7499 {
7503 {
7509 }
7510 else
7511 {
7517 }
7520 /* If VAROP is a reference to a bitfield, we must mask
7521 the constant by the width of the field. */
7524 {
7529 /* First check whether the comparison would come out
7530 always the same. If we don't do that we would
7531 change the meaning with the masking. */
7534 arg1));
7545 }
7548 }
7550 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
7551 This transformation affects the cases which are handled in later
7552 optimizations involving comparisons with non-negative constants. */
7556 {
7558 {
7569 }
7570 }
7572 /* Comparisons with the highest or lowest possible integer of
7573 the specified size will have known values.
7575 This is quite similar to fold_relational_hi_lo; however, my
7576 attempts to share the code have been nothing but trouble.
7577 I give up for now. */
7578 {
7586 {
7593 {
7596 }
7597 else
7598 {
7601 }
7606 {
7610 integer_zero_node),
7611 arg0);
7618 integer_one_node),
7619 arg0);
7623 /* The GE_EXPR and LT_EXPR cases above are not normally
7624 reached because of previous transformations. */
7628 }
7632 {
7641 }
7645 {
7649 integer_zero_node),
7650 arg0);
7657 integer_one_node),
7658 arg0);
7664 }
7668 {
7677 }
7683 /* signed_type does not work on pointer types. */
7685 {
7686 /* The following case also applies to X < signed_max+1
7687 and X >= signed_max+1 because previous transformations. */
7689 {
7693 return fold
7697 }
7698 }
7699 }
7700 }
7702 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
7703 a MINUS_EXPR of a constant, we can convert it into a comparison with
7704 a revised constant as long as no overflow occurs. */
7716 /* Similarly for a NEGATE_EXPR. */
7725 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7726 for !=. Don't do this for ordered comparisons due to overflow. */
7732 /* If we are widening one operand of an integer comparison,
7733 see if the other operand is similarly being widened. Perhaps we
7734 can do the comparison in the narrower type. */
7748 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7749 constant, we can simplify it. */
7756 /* If we are comparing an ABS_EXPR with a constant, we can
7757 convert all the cases into explicit comparisons, but they may
7758 well not be faster than doing the ABS and one comparison.
7759 But ABS (X) <= C is a range comparison, which becomes a subtraction
7760 and a comparison, and is probably faster. */
7772 /* If this is an EQ or NE comparison with zero and ARG0 is
7773 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7774 two operations, but the latter can be done in one less insn
7775 on machines that have only two-operand insns or on which a
7776 constant cannot be the first operand. */
7779 {
7782 return
7790 integer_one_node)),
7791 arg1));
7794 return
7802 integer_one_node)),
7803 arg1));
7804 }
7806 /* If this is an NE or EQ comparison of zero against the result of a
7807 signed MOD operation whose second operand is a power of 2, make
7808 the MOD operation unsigned since it is simpler and equivalent. */
7817 {
7826 }
7828 /* If this is an NE comparison of zero with an AND of one, remove the
7829 comparison since the AND will give the correct value. */
7835 /* If we have (A & C) == C where C is a power of 2, convert this into
7836 (A & C) != 0. Similarly for NE_EXPR. */
7844 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7845 2, then fold the expression into shifts and logical operations. */
7850 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
7851 Similarly for NE_EXPR. */
7856 {
7857 tree dandnotc
7865 }
7867 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
7868 Similarly for NE_EXPR. */
7873 {
7874 tree candnotd
7881 }
7883 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7884 and similarly for >= into !=. */
7900 return
7908 /* Simplify comparison of something with itself. (For IEEE
7909 floating-point, we can only do some of these simplifications.) */
7911 {
7913 {
7928 /* For NE, we can only do this simplification if integer
7929 or we don't honor IEEE floating point NaNs. */
7933 /* ... fall through ... */
7939 }
7940 }
7942 /* If we are comparing an expression that just has comparisons
7943 of two integer values, arithmetic expressions of those comparisons,
7944 and constants, we can simplify it. There are only three cases
7945 to check: the two values can either be equal, the first can be
7946 greater, or the second can be greater. Fold the expression for
7947 those three values. Since each value must be 0 or 1, we have
7948 eight possibilities, each of which corresponds to the constant 0
7949 or 1 or one of the six possible comparisons.
7951 This handles common cases like (a > b) == 0 but also handles
7952 expressions like ((x > y) - (y > x)) > 0, which supposedly
7953 occur in macroized code. */
7956 {
7961 /* Don't handle degenerate cases here; they should already
7962 have been handled anyway. */
7971 {
7975 /* We can't just pass T to eval_subst in case cval1 or cval2
7976 was the same as ARG1. */
7978 tree high_result
7981 arg1));
7982 tree equal_result
7985 arg1));
7986 tree low_result
7989 arg1));
7991 /* All three of these results should be 0 or 1. Confirm they
7992 are. Then use those values to select the proper code
7993 to use. */
8001 {
8002 /* Make a 3-bit mask with the high-order bit being the
8003 value for `>', the next for '=', and the low for '<'. */
8007 {
8009 /* Always false. */
8030 /* Always true. */
8032 }
8037 else
8039 }
8040 }
8041 }
8043 /* If this is a comparison of a field, we may be able to simplify it. */
8048 /* Handle the constant case even without -O
8049 to make sure the warnings are given. */
8051 {
8055 }
8057 /* If this is a comparison of complex values and either or both sides
8058 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
8059 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
8060 This may prevent needless evaluations. */
8067 {
8080 type,
8083 }
8085 /* Optimize comparisons of strlen vs zero to a compare of the
8086 first character of the string vs zero. To wit,
8087 strlen(ptr) == 0 => *ptr == 0
8088 strlen(ptr) != 0 => *ptr != 0
8089 Other cases should reduce to one of these two (or a constant)
8090 due to the return value of strlen being unsigned. */
8094 {
8096 tree arglist;
8108 integer_zero_node));
8109 }
8111 /* We can fold X/C1 op C2 where C1 and C2 are integer constants
8112 into a single range test. */
8119 {
8123 }
8125 /* Both ARG0 and ARG1 are known to be constants at this point. */
8130 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
8131 so all simple results must be passed through pedantic_non_lvalue. */
8133 {
8135 /* Only optimize constant conditions when the selected branch
8136 has the same type as the COND_EXPR. This avoids optimizing
8137 away "c ? x : throw", where the throw has a void type. */
8142 }
8146 /* If we have A op B ? A : C, we may be able to convert this to a
8147 simpler expression, depending on the operation and the values
8148 of B and C. Signed zeros prevent all of these transformations,
8149 for reasons given above each one. */
8155 {
8161 /* If we have A op 0 ? A : -A, consider applying the following
8162 transformations:
8164 A == 0? A : -A same as -A
8165 A != 0? A : -A same as A
8166 A >= 0? A : -A same as abs (A)
8167 A > 0? A : -A same as abs (A)
8168 A <= 0? A : -A same as -abs (A)
8169 A < 0? A : -A same as -abs (A)
8171 None of these transformations work for modes with signed
8172 zeros. If A is +/-0, the first two transformations will
8173 change the sign of the result (from +0 to -0, or vice
8174 versa). The last four will fix the sign of the result,
8175 even though the original expressions could be positive or
8176 negative, depending on the sign of A.
8178 Note that all these transformations are correct if A is
8179 NaN, since the two alternatives (A and -A) are also NaNs. */
8186 {
8210 }
8212 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
8213 A == 0 ? A : 0 is always 0 unless A is -0. Note that
8214 both transformations are correct when A is NaN: A != 0
8215 is then true, and A == 0 is false. */
8218 {
8223 }
8225 /* Try some transformations of A op B ? A : B.
8227 A == B? A : B same as B
8228 A != B? A : B same as A
8229 A >= B? A : B same as max (A, B)
8230 A > B? A : B same as max (B, A)
8231 A <= B? A : B same as min (A, B)
8232 A < B? A : B same as min (B, A)
8234 As above, these transformations don't work in the presence
8235 of signed zeros. For example, if A and B are zeros of
8236 opposite sign, the first two transformations will change
8237 the sign of the result. In the last four, the original
8238 expressions give different results for (A=+0, B=-0) and
8239 (A=-0, B=+0), but the transformed expressions do not.
8241 The first two transformations are correct if either A or B
8242 is a NaN. In the first transformation, the condition will
8243 be false, and B will indeed be chosen. In the case of the
8244 second transformation, the condition A != B will be true,
8245 and A will be chosen.
8247 The conversions to max() and min() are not correct if B is
8248 a number and A is not. The conditions in the original
8249 expressions will be false, so all four give B. The min()
8250 and max() versions would give a NaN instead. */
8253 {
8258 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
8260 {
8264 }
8267 {
8274 /* In C++ a ?: expression can be an lvalue, so put the
8275 operand which will be used if they are equal first
8276 so that we can convert this back to the
8277 corresponding COND_EXPR. */
8298 }
8299 }
8301 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
8302 we might still be able to simplify this. For example,
8303 if C1 is one less or one more than C2, this might have started
8304 out as a MIN or MAX and been transformed by this function.
8305 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
8311 {
8313 /* We can replace A with C1 in this case. */
8319 /* If C1 is C2 + 1, this is min(A, C2). */
8321 OEP_ONLY_CONST)
8325 OEP_ONLY_CONST))
8326 return pedantic_non_lvalue
8331 /* If C1 is C2 - 1, this is min(A, C2). */
8333 OEP_ONLY_CONST)
8337 OEP_ONLY_CONST))
8338 return pedantic_non_lvalue
8343 /* If C1 is C2 - 1, this is max(A, C2). */
8345 OEP_ONLY_CONST)
8349 OEP_ONLY_CONST))
8350 return pedantic_non_lvalue
8355 /* If C1 is C2 + 1, this is max(A, C2). */
8357 OEP_ONLY_CONST)
8361 OEP_ONLY_CONST))
8362 return pedantic_non_lvalue
8369 }
8370 }
8372 /* If the second operand is simpler than the third, swap them
8373 since that produces better jump optimization results. */
8376 {
8377 /* See if this can be inverted. If it can't, possibly because
8378 it was a floating-point inequality comparison, don't do
8379 anything. */
8385 }
8387 /* Convert A ? 1 : 0 to simply A. */
8390 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8391 call to fold will try to move the conversion inside
8392 a COND, which will recurse. In that case, the COND_EXPR
8393 is probably the best choice, so leave it alone. */
8397 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8398 over COND_EXPR in cases such as floating point comparisons. */
8405 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
8406 operation is simply A & 2. */
8418 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8425 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8429 {
8430 /* Only perform transformation if ARG0 is easily inverted. */
8435 }
8440 /* When pedantic, a compound expression can be neither an lvalue
8441 nor an integer constant expression. */
8444 /* Don't let (0, 0) be null pointer constant. */
8486 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8487 appropriate. */
8492 {
8496 tree arg01;
8507 {
8521 arg01));
8522 }
8525 }
8528 /* Check for a built-in function. */
8533 {
8537 }
8543 }
8545 #ifdef ENABLE_FOLD_CHECKING
8546 #undef fold
8552 /* When --enable-checking=fold, compute a digest of expr before
8553 and after actual fold call to see if fold did not accidentally
8554 change original expr. */
8556 tree
8558 {
8559 tree ret;
8562 htab_t ht;
8581 }
8583 void
8585 {
8588 htab_t ht;
8598 }
8600 static void
8602 {
8604 }
8606 static void
8608 {
8626 {
8627 /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified. */
8631 }
8633 {
8634 /* Allow DECL_ASSEMBLER_NAME to be modified. */
8638 }
8641 {
8642 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
8647 }
8654 {
8657 {
8671 }
8675 {
8686 }
8690 {
8696 }
8697 /* Fall through. */
8733 }
8734 }
8736 #endif
8738 /* Perform constant folding and related simplification of initializer
8739 expression EXPR. This behaves identically to "fold" but ignores
8740 potential run-time traps and exceptions that fold must preserve. */
8742 tree
8744 {
8748 tree result;
8761 }
8763 /* Determine if first argument is a multiple of second argument. Return 0 if
8764 it is not, or we cannot easily determined it to be.
8766 An example of the sort of thing we care about (at this point; this routine
8767 could surely be made more general, and expanded to do what the *_DIV_EXPR's
8768 fold cases do now) is discovering that
8770 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8772 is a multiple of
8774 SAVE_EXPR (J * 8)
8776 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
8778 This code also handles discovering that
8780 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8782 is a multiple of 8 so we don't have to worry about dealing with a
8783 possible remainder.
8785 Note that we *look* inside a SAVE_EXPR only to determine how it was
8786 calculated; it is not safe for fold to do much of anything else with the
8787 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
8788 at run time. For example, the latter example above *cannot* be implemented
8789 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
8790 evaluation time of the original SAVE_EXPR is not necessarily the same at
8791 the time the new expression is evaluated. The only optimization of this
8792 sort that would be valid is changing
8794 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
8796 divided by 8 to
8798 SAVE_EXPR (I) * SAVE_EXPR (J)
8800 (where the same SAVE_EXPR (J) is used in the original and the
8801 transformed version). */
8803 static int
8805 {
8813 {
8825 {
8829 /* const_binop may not detect overflow correctly,
8830 so check for it explicitly here. */
8836 size_one_node,
8840 }
8844 /* Can't handle conversions from non-integral or wider integral type. */
8850 /* .. fall through ... */
8866 }
8867 }
8869 /* Return true if `t' is known to be non-negative. */
8871 int
8873 {
8875 {
8890 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8891 both unsigned and at least 2 bits shorter than the result. */
8895 {
8900 {
8904 }
8905 }
8910 {
8911 /* x * x for floating point x is always non-negative. */
8916 }
8918 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8919 both unsigned and their total bits is shorter than the result. */
8923 {
8930 }
8959 {
8964 {
8968 {
8972 }
8973 }
8975 {
8981 }
8982 }
9010 {
9017 {
9018 #define CASE_BUILTIN_F(BUILT_IN_FN) \
9019 case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
9020 #define CASE_BUILTIN_I(BUILT_IN_FN) \
9021 case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:
9040 /* Always true. */
9066 /* True if the 1st argument is nonnegative. */
9070 /* True if the 1st OR 2nd arguments are nonnegative. */
9075 /* True if the 1st AND 2nd arguments are nonnegative. */
9080 /* True if the 2nd argument is nonnegative. */
9085 #undef CASE_BUILTIN_F
9086 #undef CASE_BUILTIN_I
9087 }
9088 }
9090 /* ... fall through ... */
9094 /* Truth values evaluate to 0 or 1, which is nonnegative. */
9096 }
9098 /* We don't know sign of `t', so be conservative and return false. */
9100 }
9102 /* Return true when T is an address and is known to be nonzero.
9103 For floating point we further ensure that T is not denormal.
9104 Similar logic is present in nonzero_address in rtlanal.h */
9106 static bool
9108 {
9111 /* Doing something useful for floating point would need more work. */
9116 {
9126 {
9127 /* With the presence of negative values it is hard
9128 to say something. */
9132 /* One of operands must be positive and the other non-negative. */
9135 }
9140 {
9143 }
9147 {
9153 }
9157 /* Weak declarations may link to NULL. */
9160 /* Constants and all other cases are never weak. */
9173 {
9174 /* When both operands are nonzero, then MAX must be too. */
9178 /* MAX where operand 0 is positive is positive. */
9180 }
9181 /* MAX where operand 1 is positive is positive. */
9202 }
9204 }
9206 /* Return true if `r' is known to be non-negative.
9207 Only handles constants at the moment. */
9209 int
9211 {
9213 {
9223 {
9225 rtx elt;
9230 {
9234 }
9237 }
9241 /* These are always nonnegative. */
9246 }
9247 }
9250 /* See if we are applying CODE, a relational to the highest or lowest
9251 possible integer of TYPE. If so, then the result is a compile
9252 time constant. */
9254 static tree
9257 {
9268 {
9275 {
9278 }
9279 else
9280 {
9283 }
9288 {
9292 op0);
9299 op0);
9304 /* The GE_EXPR and LT_EXPR cases above are not normally
9305 reached because of previous transformations. */
9309 }
9313 {
9324 }
9328 {
9332 op0);
9340 op0);
9347 }
9351 {
9362 }
9367 /* signed_type does not work on pointer types. */
9369 {
9370 /* The following case also applies to X < signed_max+1
9371 and X >= signed_max+1 because previous transformations. */
9373 {
9379 type,
9383 retval
9389 /* If we are in gimple form, then returning EXP would create
9390 non-gimple expressions. Clearing it is safe and insures
9391 we do not allow a non-gimple expression to escape. */
9396 }
9397 }
9398 }
9401 }
9404 /* Given the components of a binary expression CODE, TYPE, OP0 and OP1,
9405 attempt to fold the expression to a constant without modifying TYPE,
9406 OP0 or OP1.
9408 If the expression could be simplified to a constant, then return
9409 the constant. If the expression would not be simplified to a
9410 constant, then return NULL_TREE.
9412 Note this is primarily designed to be called after gimplification
9413 of the tree structures and when at least one operand is a constant.
9414 As a result of those simplifying assumptions this routine is far
9415 simpler than the generic fold routine. */
9417 tree
9420 {
9422 tree subop0;
9423 tree subop1;
9424 tree tem;
9426 /* If this is a commutative operation, and ARG0 is a constant, move it
9427 to ARG1 to reduce the number of tests below. */
9430 {
9434 }
9436 /* If either operand is a complex type, extract its real component. */
9439 else
9444 else
9447 /* Note if either argument is not a real or integer constant.
9448 With a few exceptions, simplification is limited to cases
9449 where both arguments are constants. */
9457 {
9459 /* (plus (address) (const_int)) is a constant. */
9467 {
9470 }
9473 binary:
9477 /* Both arguments are constants. Simplify. */
9480 {
9481 /* The return value should always have the same type as
9482 the original expression. */
9487 }
9491 /* Fold &x - &x. This can happen from &x.foo - &x.
9492 This is unsafe for certain floats even in non-IEEE formats.
9493 In IEEE, it is unsafe because it does wrong for NaNs.
9494 Also note that operand_equal_p is always false if an
9495 operand is volatile. */
9503 /* Special case multiplication or bitwise AND where one argument
9504 is zero. */
9507 else
9516 /* Special case when we know the result will be all ones. */
9532 /* Division by zero is undefined. */
9559 /* Optimize -1 >> x for arithmetic right shifts. */
9562 /* ... fall through ... */
9568 /* Since negative shift count is not well-defined, don't
9569 try to compute it in the compiler. */
9577 /* -1 rotated either direction by any amount is still -1. */
9581 /* 0 rotated either direction by any amount is still zero. */
9598 /* If one arg is a real or integer constant, put it last. */
9603 {
9604 tree temp;
9610 }
9612 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
9613 This transformation affects the cases which are handled in later
9614 optimizations involving comparisons with non-negative constants. */
9618 {
9620 {
9633 }
9634 }
9646 /* This could probably be handled. */
9650 /* If second arg is constant zero, result is zero, but first arg
9651 must be evaluated. */
9654 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
9655 case will be handled here. */
9659 {
9664 }
9668 /* If second arg is constant true, result is true, but we must
9669 evaluate first arg. */
9672 /* Likewise for first arg, but note this only occurs here for
9673 TRUTH_OR_EXPR. */
9677 {
9682 }
9687 {
9692 }
9697 }
9698 }
9700 /* Given the components of a unary expression CODE, TYPE and OP0,
9701 attempt to fold the expression to a constant without modifying
9702 TYPE or OP0.
9704 If the expression could be simplified to a constant, then return
9705 the constant. If the expression would not be simplified to a
9706 constant, then return NULL_TREE.
9708 Note this is primarily designed to be called after gimplification
9709 of the tree structures and when op0 is a constant. As a result
9710 of those simplifying assumptions this routine is far simpler than
9711 the generic fold routine. */
9713 tree
9715 tree op0)
9716 {
9717 tree t;
9719 /* Make sure we have a suitable constant argument. */
9721 {
9722 tree subop;
9726 else
9731 }
9734 {
9746 else
9752 else
9757 {
9764 }
9765 else
9771 else
9777 else
9789 }
9790 }
9792 /* If EXP represents referencing an element in a constant string
9793 (either via pointer arithmetic or array indexing), return the
9794 tree representing the value accessed, otherwise return NULL. */
9796 tree
9798 {
9800 {
9802 tree index;
9803 tree string;
9806 {
9808 }
9809 else
9810 {
9815 /* Optimize the special-case of a zero lower bound.
9817 We convert the low_bound to sizetype to avoid some problems
9818 with constant folding. (E.g. suppose the lower bound is 1,
9819 and its mode is QI. Without the conversion,l (ARRAY
9820 +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
9821 +INDEX), which becomes (ARRAY+255+INDEX). Opps!) */
9826 }
9837 }
9839 }
9841 /* Return the tree for neg (ARG0) when ARG0 is known to be either
9842 an integer constant or real constant.
9844 TYPE is the type of the result. */
9846 static tree
9848 {
9852 {
9854 HOST_WIDE_INT high;
9865 }
9868 #ifdef ENABLE_CHECKING
9869 else
9871 #endif
9874 }
9876 /* Return the tree for abs (ARG0) when ARG0 is known to be either
9877 an integer constant or real constant.
9879 TYPE is the type of the result. */
9881 static tree
9883 {
9887 {
9888 /* If the value is unsigned, then the absolute value is
9889 the same as the ordinary value. */
9892 /* Similarly, if the value is non-negative. */
9895 /* If the value is negative, then the absolute value is
9896 its negation. */
9897 else
9898 {
9900 HOST_WIDE_INT high;
9912 }
9913 }
9915 {
9918 else
9920 }
9921 #ifdef ENABLE_CHECKING
9922 else
9924 #endif
9927 }
9929 /* Given CODE, a relational operator, the target type, TYPE and two
9930 constant operands OP0 and OP1, return the result of the
9931 relational operation. If the result is not a compile time
9932 constant, then return NULL_TREE. */
9934 static tree
9936 {
9937 tree tem;
9940 /* From here on, the only cases we handle are when the result is
9941 known to be a constant.
9943 To compute GT, swap the arguments and do LT.
9944 To compute GE, do LT and invert the result.
9945 To compute LE, swap the arguments, do LT and invert the result.
9946 To compute NE, do EQ and invert the result.
9948 Therefore, the code below must handle only EQ and LT. */
9951 {
9954 }
9956 /* Note that it is safe to invert for real values here because we
9957 will check below in the one case that it matters. */
9962 {
9965 }
9967 /* Compute a result for LT or EQ if args permit;
9968 Otherwise return T. */
9970 {
9973 else
9978 }
9984 /* Two real constants can be compared explicitly. */
9986 {
9987 /* If either operand is a NaN, the result is false with two
9988 exceptions: First, an NE_EXPR is true on NaNs, but that case
9989 is already handled correctly since we will be inverting the
9990 result for NE_EXPR. Second, if we had inverted a LE_EXPR
9991 or a GE_EXPR into a LT_EXPR, we must return true so that it
9992 will be inverted into false. */
10002 else
10006 }
10018 }