| blob | 1c2bdf4e1c2acb3f1aec104b7f37532a0c0d2717 |
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. */
95 tree);
119 /* The following constants represent a bit based encoding of GCC's
120 comparison operators. This encoding simplifies transformations
121 on relational comparison operators, such as AND and OR. */
122 #define COMPCODE_FALSE 0
123 #define COMPCODE_LT 1
124 #define COMPCODE_EQ 2
125 #define COMPCODE_LE 3
126 #define COMPCODE_GT 4
127 #define COMPCODE_NE 5
128 #define COMPCODE_GE 6
129 #define COMPCODE_TRUE 7
131 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
132 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
133 and SUM1. Then this yields nonzero if overflow occurred during the
134 addition.
136 Overflow occurs if A and B have the same sign, but A and SUM differ in
137 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
138 sign. */
139 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
140 \f
141 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
142 We do that by representing the two-word integer in 4 words, with only
143 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
144 number. The value of the word is LOWPART + HIGHPART * BASE. */
146 #define LOWPART(x) \
147 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
148 #define HIGHPART(x) \
149 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
150 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
152 /* Unpack a two-word integer into 4 words.
153 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
154 WORDS points to the array of HOST_WIDE_INTs. */
156 static void
158 {
163 }
165 /* Pack an array of 4 words into a two-word integer.
166 WORDS points to the array of words.
167 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
169 static void
172 {
175 }
176 \f
177 /* Make the integer constant T valid for its type by setting to 0 or 1 all
178 the bits in the constant that don't belong in the type.
180 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
181 nonzero, a signed overflow has already occurred in calculating T, so
182 propagate it. */
184 int
186 {
188 HOST_WIDE_INT high;
192 {
193 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
194 Consider doing it via real_convert now. */
196 }
207 else
210 /* First clear all bits that are beyond the type's precision. */
213 ;
217 else
218 {
222 }
224 /* Unsigned types do not suffer sign extension or overflow unless they
225 are a sizetype. */
231 /* If the value's sign bit is set, extend the sign. */
239 {
240 /* Value is negative:
241 set to 1 all the bits that are outside this type's precision. */
245 else
246 {
250 }
251 }
253 /* Return nonzero if signed overflow occurred. */
254 return
257 }
258 \f
259 /* Add two doubleword integers with doubleword result.
260 Each argument is given as two `HOST_WIDE_INT' pieces.
261 One argument is L1 and H1; the other, L2 and H2.
262 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
264 int
268 {
270 HOST_WIDE_INT h;
278 }
280 /* Negate a doubleword integer with doubleword result.
281 Return nonzero if the operation overflows, assuming it's signed.
282 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
283 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
285 int
288 {
290 {
294 }
295 else
296 {
300 }
301 }
302 \f
303 /* Multiply two doubleword integers with doubleword result.
304 Return nonzero if the operation overflows, assuming it's signed.
305 Each argument is given as two `HOST_WIDE_INT' pieces.
306 One argument is L1 and H1; the other, L2 and H2.
307 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
309 int
313 {
328 {
331 {
333 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
335 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
339 }
341 }
345 /* Check for overflow by calculating the top half of the answer in full;
346 it should agree with the low half's sign bit. */
349 {
352 }
354 {
357 }
359 }
360 \f
361 /* Shift the doubleword integer in L1, H1 left by COUNT places
362 keeping only PREC bits of result.
363 Shift right if COUNT is negative.
364 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
365 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
367 void
371 {
375 {
378 }
384 {
385 /* Shifting by the host word size is undefined according to the
386 ANSI standard, so we must handle this as a special case. */
389 }
391 {
394 }
395 else
396 {
400 }
402 /* Sign extend all bits that are beyond the precision. */
410 ;
412 {
415 }
416 else
417 {
421 }
422 }
424 /* Shift the doubleword integer in L1, H1 right by COUNT places
425 keeping only PREC bits of result. COUNT must be positive.
426 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
427 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
429 void
434 {
437 signmask = (arith
445 {
446 /* Shifting by the host word size is undefined according to the
447 ANSI standard, so we must handle this as a special case. */
450 }
452 {
455 }
456 else
457 {
461 }
463 /* Zero / sign extend all bits that are beyond the precision. */
466 {
469 }
471 ;
473 {
476 }
477 else
478 {
482 }
483 }
484 \f
485 /* Rotate the doubleword integer in L1, H1 left by COUNT places
486 keeping only PREC bits of result.
487 Rotate right if COUNT is negative.
488 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
490 void
494 {
506 }
508 /* Rotate the doubleword integer in L1, H1 left by COUNT places
509 keeping only PREC bits of result. COUNT must be positive.
510 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
512 void
516 {
528 }
529 \f
530 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
531 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
532 CODE is a tree code for a kind of division, one of
533 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
534 or EXACT_DIV_EXPR
535 It controls how the quotient is rounded to an integer.
536 Return nonzero if the operation overflows.
537 UNS nonzero says do unsigned division. */
539 int
542 HOST_WIDE_INT hnum_orig,
544 HOST_WIDE_INT hden_orig,
548 {
564 /* Calculate quotient sign and convert operands to unsigned. */
566 {
568 {
570 /* (minimum integer) / (-1) is the only overflow case. */
574 }
576 {
579 }
580 }
585 /* This unsigned division rounds toward zero. */
588 }
592 /* hden != 0 already checked. */
597 }
607 /* Special code for when the divisor < BASE. */
609 {
610 /* hnum != 0 already checked. */
612 {
616 }
617 }
618 else
619 {
620 /* Full double precision division,
621 with thanks to Don Knuth's "Seminumerical Algorithms". */
625 /* Find the highest nonzero divisor digit. */
628 {
631 }
633 /* Insure that the first digit of the divisor is at least BASE/2.
634 This is required by the quotient digit estimation algorithm. */
641 {
645 }
650 {
655 }
656 }
660 /* Main loop */
662 {
663 /* Guess the next quotient digit, quo_est, by dividing the first
664 two remaining dividend digits by the high order quotient digit.
665 quo_est is never low and is at most 2 high. */
672 else
675 /* Refine quo_est so it's usually correct, and at most one high. */
680 quo_est--;
682 /* Try QUO_EST as the quotient digit, by multiplying the
683 divisor by QUO_EST and subtracting from the remaining dividend.
684 Keep in mind that QUO_EST is the I - 1st digit. */
688 {
694 }
696 /* If quo_est was high by one, then num[i] went negative and
697 we need to correct things. */
699 {
700 quo_est--;
703 {
707 }
710 }
712 /* Store the quotient digit. */
714 }
715 }
719 finish_up:
720 /* If result is negative, make it so. */
724 /* Compute trial remainder: rem = num - (quo * den) */
730 {
739 {
740 /* quo = quo - 1; */
743 }
744 else
751 {
754 }
755 else
761 {
767 /* Get absolute values. */
773 /* If (2 * abs (lrem) >= abs (lden)) */
782 {
784 /* quo = quo - 1; */
787 else
788 /* quo = quo + 1; */
791 }
792 else
794 }
799 }
801 /* Compute true remainder: rem = num - (quo * den) */
806 }
807 \f
808 /* Return true if built-in mathematical function specified by CODE
809 preserves the sign of it argument, i.e. -f(x) == f(-x). */
811 static bool
813 {
815 {
832 }
834 }
836 /* Determine whether an expression T can be cheaply negated using
837 the function negate_expr. */
839 static bool
841 {
844 tree type;
853 {
858 /* Check that -CST will not overflow type. */
861 {
866 }
867 else
884 /* -(A + B) -> (-B) - A. */
889 /* -(A + B) -> (-A) - B. */
893 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
902 /* Fall through. */
911 /* Negate -((double)float) as (double)(-float). */
913 {
917 }
921 /* Negate -f(x) as f(-x). */
927 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
929 {
935 }
940 }
942 }
944 /* Given T, an expression, return the negation of T. Allow for T to be
945 null, in which case return null. */
947 static tree
949 {
950 tree type;
951 tree tem;
960 {
971 /* Two's complement FP formats, such as c4x, may overflow. */
977 {
986 }
994 {
995 /* -(A + B) -> (-B) - A. */
1003 /* -(A + B) -> (-A) - B. */
1009 }
1013 /* - (A - B) -> B - A */
1026 /* Fall through. */
1030 {
1043 }
1047 /* Convert -((double)float) into (double)(-float). */
1049 {
1053 }
1057 /* Negate -f(x) as f(-x). */
1060 {
1067 }
1071 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1073 {
1078 {
1085 }
1086 }
1091 }
1095 }
1096 \f
1097 /* Split a tree IN into a constant, literal and variable parts that could be
1098 combined with CODE to make IN. "constant" means an expression with
1099 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1100 commutative arithmetic operation. Store the constant part into *CONP,
1101 the literal in *LITP and return the variable part. If a part isn't
1102 present, set it to null. If the tree does not decompose in this way,
1103 return the entire tree as the variable part and the other parts as null.
1105 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1106 case, we negate an operand that was subtracted. Except if it is a
1107 literal for which we use *MINUS_LITP instead.
1109 If NEGATE_P is true, we are negating all of IN, again except a literal
1110 for which we use *MINUS_LITP instead.
1112 If IN is itself a literal or constant, return it as appropriate.
1114 Note that we do not guarantee that any of the three values will be the
1115 same type as IN, but they will have the same signedness and mode. */
1117 static tree
1120 {
1127 /* Strip any conversions that don't change the machine mode or signedness. */
1134 /* We can associate addition and subtraction together (even
1135 though the C standard doesn't say so) for integers because
1136 the value is not affected. For reals, the value might be
1137 affected, so we can't. */
1140 {
1146 /* First see if either of the operands is a literal, then a constant. */
1157 /* If we haven't dealt with either operand, this is not a case we can
1158 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1163 else
1166 /* Now do any needed negations. */
1173 }
1176 else
1180 {
1187 }
1190 }
1192 /* Re-associate trees split by the above function. T1 and T2 are either
1193 expressions to associate or null. Return the new expression, if any. If
1194 we build an operation, do it in TYPE and with CODE. */
1196 static tree
1198 {
1204 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1205 try to fold this since we will have infinite recursion. But do
1206 deal with any NEGATE_EXPRs. */
1209 {
1211 {
1218 }
1221 }
1225 }
1226 \f
1227 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1228 to produce a new constant.
1230 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1232 static tree
1234 {
1238 HOST_WIDE_INT hi;
1240 HOST_WIDE_INT garbageh;
1241 tree t;
1244 int is_sizetype
1255 {
1271 /* It's unclear from the C standard whether shifts can overflow.
1272 The following code ignores overflow; perhaps a C standard
1273 interpretation ruling is needed. */
1303 /* This is a shortcut for a common special case. */
1308 {
1314 }
1316 /* ... fall through ... */
1320 {
1323 }
1326 {
1329 }
1336 /* This is a shortcut for a common special case. */
1341 {
1346 }
1348 /* ... fall through ... */
1364 else
1370 else
1376 }
1378 /* If this is for a sizetype, can be represented as one (signed)
1379 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1380 constants. */
1386 else
1387 {
1390 }
1393 = ((notrunc
1400 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1401 So check if force_fit_type truncated the value. */
1412 }
1414 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1415 constant. We assume ARG1 and ARG2 have the same data type, or at least
1416 are the same kind of constant and the same machine mode.
1418 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1420 static tree
1422 {
1430 {
1432 REAL_VALUE_TYPE d1;
1433 REAL_VALUE_TYPE d2;
1434 REAL_VALUE_TYPE value;
1443 /* Don't perform operation if we honor signaling NaNs and
1444 either operand is a NaN. */
1449 /* Don't perform operation if it would raise a division
1450 by zero exception. */
1456 /* If either operand is a NaN, just return it. Otherwise, set up
1457 for floating-point trap; we return an overflow. */
1475 }
1477 {
1483 tree t;
1486 {
1506 notrunc),
1512 notrunc));
1516 {
1517 tree magsquared
1521 notrunc);
1524 const_binop
1529 notrunc),
1531 notrunc),
1532 notrunc),
1534 const_binop
1539 notrunc),
1541 notrunc),
1542 notrunc),
1544 }
1549 }
1551 }
1553 }
1555 /* These are the hash table functions for the hash table of INTEGER_CST
1556 nodes of a sizetype. */
1558 /* Return the hash code code X, an INTEGER_CST. */
1560 static hashval_t
1562 {
1568 }
1570 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1571 is the same as that given by *Y, which is the same. */
1573 static int
1575 {
1583 }
1584 \f
1585 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1586 bits are given by NUMBER and of the sizetype represented by KIND. */
1588 tree
1590 {
1592 }
1594 /* Likewise, but the desired type is specified explicitly. */
1598 htab_t size_htab;
1600 tree
1602 {
1606 {
1609 }
1611 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1612 hash table, we return the value from the hash table. Otherwise, we
1613 place that in the hash table and make a new node for the next time. */
1622 {
1628 }
1629 else
1631 }
1633 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1634 is a tree code. The type of the result is taken from the operands.
1635 Both must be the same type integer type and it must be a size type.
1636 If the operands are constant, so is the result. */
1638 tree
1640 {
1647 /* Handle the special case of two integer constants faster. */
1649 {
1650 /* And some specific cases even faster than that. */
1659 /* Handle general case of two integer constants. */
1661 }
1667 }
1669 /* Given two values, either both of sizetype or both of bitsizetype,
1670 compute the difference between the two values. Return the value
1671 in signed type corresponding to the type of the operands. */
1673 tree
1675 {
1677 tree ctype;
1683 /* If the type is already signed, just do the simple thing. */
1690 /* If either operand is not a constant, do the conversions to the signed
1691 type and subtract. The hardware will do the right thing with any
1692 overflow in the subtraction. */
1697 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1698 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1699 overflow) and negate (which can't either). Special-case a result
1700 of zero while we're here. */
1705 else
1709 }
1710 \f
1712 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1713 type TYPE. If no simplification can be done return NULL_TREE. */
1715 static tree
1717 {
1719 tree t;
1725 {
1727 {
1728 /* If we would build a constant wider than GCC supports,
1729 leave the conversion unfolded. */
1733 /* If we are trying to make a sizetype for a small integer, use
1734 size_int to pick up cached types to reduce duplicate nodes. */
1740 /* Given an integer constant, make new constant with new type,
1741 appropriately sign-extended or truncated. */
1745 /* Indicate an overflow if (1) ARG1 already overflowed,
1746 or (2) force_fit_type indicates an overflow.
1747 Tell force_fit_type that an overflow has already occurred
1748 if ARG1 is a too-large unsigned value and T is signed.
1749 But don't indicate an overflow if converting a pointer. */
1760 }
1762 {
1763 /* The following code implements the floating point to integer
1764 conversion rules required by the Java Language Specification,
1765 that IEEE NaNs are mapped to zero and values that overflow
1766 the target precision saturate, i.e. values greater than
1767 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1768 are mapped to INT_MIN. These semantics are allowed by the
1769 C and C++ standards that simply state that the behavior of
1770 FP-to-integer conversion is unspecified upon overflow. */
1774 REAL_VALUE_TYPE r;
1778 {
1797 }
1799 /* If R is NaN, return zero and show we have an overflow. */
1801 {
1805 }
1807 /* See if R is less than the lower bound or greater than the
1808 upper bound. */
1811 {
1815 {
1819 }
1820 }
1823 {
1826 {
1829 {
1833 }
1834 }
1835 }
1847 }
1848 }
1850 {
1854 {
1856 {
1857 /* We make a copy of ARG1 so that we don't modify an
1858 existing constant tree. */
1862 }
1873 }
1874 }
1876 }
1878 /* Convert expression ARG to type TYPE. Used by the middle-end for
1879 simple conversions in preference to calling the front-end's convert. */
1881 tree
1883 {
1885 tree tem;
1899 {
1901 {
1905 }
1909 {
1912 }
1917 }
1919 {
1921 {
1925 }
1927 {
1931 }
1939 {
1942 }
1943 }
1945 {
1953 {
1957 {
1961 }
1969 }
1970 }
1972 {
1981 }
1985 }
1986 \f
1987 /* Return an expr equal to X but certainly not valid as an lvalue. */
1989 tree
1991 {
1992 tree result;
1994 /* These things are certainly not lvalues. */
2005 }
2007 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2008 Zero means allow extended lvalues. */
2012 /* When pedantic, return an expr equal to X but certainly not valid as a
2013 pedantic lvalue. Otherwise, return X. */
2015 tree
2017 {
2020 else
2022 }
2023 \f
2024 /* Given a tree comparison code, return the code that is the logical inverse
2025 of the given code. It is not safe to do this for floating-point
2026 comparisons, except for NE_EXPR and EQ_EXPR. */
2028 static enum tree_code
2030 {
2032 {
2047 }
2048 }
2050 /* Similar, but return the comparison that results if the operands are
2051 swapped. This is safe for floating-point. */
2053 static enum tree_code
2055 {
2057 {
2071 }
2072 }
2075 /* Convert a comparison tree code from an enum tree_code representation
2076 into a compcode bit-based encoding. This function is the inverse of
2077 compcode_to_comparison. */
2079 static int
2081 {
2083 {
2098 }
2099 }
2101 /* Convert a compcode bit-based encoding of a comparison operator back
2102 to GCC's enum tree_code representation. This function is the
2103 inverse of comparison_to_compcode. */
2105 static enum tree_code
2107 {
2109 {
2124 }
2125 }
2127 /* Return nonzero if CODE is a tree code that represents a truth value. */
2129 static int
2131 {
2136 }
2137 \f
2138 /* Return nonzero if two operands (typically of the same tree node)
2139 are necessarily equal. If either argument has side-effects this
2140 function returns zero.
2142 If ONLY_CONST is nonzero, only return nonzero for constants.
2143 This function tests whether the operands are indistinguishable;
2144 it does not test whether they are equal using C's == operation.
2145 The distinction is important for IEEE floating point, because
2146 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2147 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2149 If ONLY_CONST is zero, a VAR_DECL is considered equal to itself
2150 even though it may hold multiple values during a function.
2151 This is because a GCC tree node guarantees that nothing else is
2152 executed between the evaluation of its "operands" (which may often
2153 be evaluated in arbitrary order). Hence if the operands themselves
2154 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2155 same value in each operand/subexpression. Hence a zero value for
2156 ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
2157 If comparing arbitrary expression trees, such as from different
2158 statements, ONLY_CONST must usually be nonzero. */
2160 int
2162 {
2163 tree fndecl;
2165 /* If either is ERROR_MARK, they aren't equal. */
2169 /* If both types don't have the same signedness, then we can't consider
2170 them equal. We must check this before the STRIP_NOPS calls
2171 because they may change the signedness of the arguments. */
2179 /* This is needed for conversions and for COMPONENT_REF.
2180 Might as well play it safe and always test this. */
2186 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2187 We don't care about side effects in that case because the SAVE_EXPR
2188 takes care of that for us. In all other cases, two expressions are
2189 equal if they have no side effects. If we have two identical
2190 expressions with side effects that should be treated the same due
2191 to the only side effects being identical SAVE_EXPR's, that will
2192 be detected in the recursive calls below. */
2198 /* Next handle constant cases, those for which we can return 1 even
2199 if ONLY_CONST is set. */
2202 {
2215 {
2225 {
2227 only_const))
2231 }
2234 }
2238 only_const)
2240 only_const));
2253 }
2259 {
2261 /* Two conversions are equal only if signedness and modes match. */
2277 /* For commutative ops, allow the other order. */
2285 /* If either of the pointer (or reference) expressions we are
2286 dereferencing contain a side effect, these cannot be equal. */
2292 {
2314 }
2318 {
2328 /* If the CALL_EXPRs call different functions, then they
2329 clearly can not be equal. */
2334 /* Only consider const functions equivalent. */
2340 /* Now see if all the arguments are the same. operand_equal_p
2341 does not handle TREE_LIST, so we walk the operands here
2342 feeding them to operand_equal_p. */
2346 {
2352 }
2354 /* If we get here and both argument lists are exhausted
2355 then the CALL_EXPRs are equal. */
2360 }
2363 /* Consider __builtin_sqrt equal to sqrt. */
2371 }
2372 }
2373 \f
2374 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2375 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2377 When in doubt, return 0. */
2379 static int
2381 {
2393 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2394 and see if the inner values are the same. This removes any
2395 signedness comparison, which doesn't matter here. */
2402 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2403 actual comparison operand, ARG0.
2405 First throw away any conversions to wider types
2406 already present in the operands. */
2415 {
2418 /* Make sure shorter operand is extended the right way
2419 to match the longer operand. */
2425 }
2428 }
2429 \f
2430 /* See if ARG is an expression that is either a comparison or is performing
2431 arithmetic on comparisons. The comparisons must only be comparing
2432 two different values, which will be stored in *CVAL1 and *CVAL2; if
2433 they are nonzero it means that some operands have already been found.
2434 No variables may be used anywhere else in the expression except in the
2435 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2436 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2438 If this is true, return 1. Otherwise, return zero. */
2440 static int
2442 {
2446 /* We can handle some of the 'e' cases here. */
2456 {
2457 /* If we've already found a CVAL1 or CVAL2, this expression is
2458 two complex to handle. */
2464 }
2467 {
2490 /* First see if we can handle the first operand, then the second. For
2491 the second operand, we know *CVAL1 can't be zero. It must be that
2492 one side of the comparison is each of the values; test for the
2493 case where this isn't true by failing if the two operands
2494 are the same. */
2503 ;
2507 ;
2508 else
2512 ;
2516 ;
2517 else
2524 }
2525 }
2526 \f
2527 /* ARG is a tree that is known to contain just arithmetic operations and
2528 comparisons. Evaluate the operations in the tree substituting NEW0 for
2529 any occurrence of OLD0 as an operand of a comparison and likewise for
2530 NEW1 and OLD1. */
2532 static tree
2534 {
2539 /* We can handle some of the 'e' cases here. */
2547 {
2562 {
2579 }
2580 /* Fall through - ??? */
2583 {
2587 /* We need to check both for exact equality and tree equality. The
2588 former will be true if the operand has a side-effect. In that
2589 case, we know the operand occurred exactly once. */
2602 }
2606 }
2607 }
2608 \f
2609 /* Return a tree for the case when the result of an expression is RESULT
2610 converted to TYPE and OMITTED was previously an operand of the expression
2611 but is now not needed (e.g., we folded OMITTED * 0).
2613 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2614 the conversion of RESULT to TYPE. */
2616 tree
2618 {
2625 }
2627 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2629 static tree
2631 {
2638 }
2639 \f
2640 /* Return a simplified tree node for the truth-negation of ARG. This
2641 never alters ARG itself. We assume that ARG is an operation that
2642 returns a truth value (0 or 1). */
2644 tree
2646 {
2653 /* If this is a comparison, we can simply invert it, except for
2654 floating-point non-equality comparisons, in which case we just
2655 enclose a TRUTH_NOT_EXPR around what we have. */
2658 {
2660 && !flag_unsafe_math_optimizations
2672 else
2675 }
2678 {
2693 /* Here we can invert either operand. We invert the first operand
2694 unless the second operand is a TRUTH_NOT_EXPR in which case our
2695 result is the XOR of the first operand with the inside of the
2696 negation of the second operand. */
2701 else
2752 }
2756 }
2758 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2759 operands are another bit-wise operation with a common input. If so,
2760 distribute the bit operations to save an operation and possibly two if
2761 constants are involved. For example, convert
2762 (A | B) & (A | C) into A | (B & C)
2763 Further simplification will occur if B and C are constants.
2765 If this optimization cannot be done, 0 will be returned. */
2767 static tree
2769 {
2770 tree common;
2780 {
2784 }
2786 {
2790 }
2792 {
2796 }
2798 {
2802 }
2803 else
2808 }
2809 \f
2810 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2811 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2813 static tree
2816 {
2823 }
2825 /* Optimize a bit-field compare.
2827 There are two cases: First is a compare against a constant and the
2828 second is a comparison of two items where the fields are at the same
2829 bit position relative to the start of a chunk (byte, halfword, word)
2830 large enough to contain it. In these cases we can avoid the shift
2831 implicit in bitfield extractions.
2833 For constants, we emit a compare of the shifted constant with the
2834 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2835 compared. For two fields at the same position, we do the ANDs with the
2836 similar mask and compare the result of the ANDs.
2838 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2839 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2840 are the left and right operands of the comparison, respectively.
2842 If the optimization described above can be done, we return the resulting
2843 tree. Otherwise we return zero. */
2845 static tree
2848 {
2857 tree mask;
2858 tree offset;
2860 /* Get all the information about the extractions being done. If the bit size
2861 if the same as the size of the underlying object, we aren't doing an
2862 extraction at all and so can do nothing. We also don't want to
2863 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2864 then will no longer be able to replace it. */
2872 {
2873 /* If this is not a constant, we can only do something if bit positions,
2874 sizes, and signedness are the same. */
2882 }
2884 /* See if we can find a mode to refer to this field. We should be able to,
2885 but fail if we can't. */
2894 /* Set signed and unsigned types of the precision of this mode for the
2895 shifts below. */
2899 /* Compute the bit position and size for the new reference and our offset
2900 within it. If the new reference is the same size as the original, we
2901 won't optimize anything, so return zero. */
2911 /* Make the mask to be used against the extracted field. */
2921 /* If not comparing with constant, just rework the comparison
2922 and return. */
2927 mask),
2931 mask));
2933 /* Otherwise, we are handling the constant case. See if the constant is too
2934 big for the field. Warn and return a tree of for 0 (false) if so. We do
2935 this not only for its own sake, but to avoid having to test for this
2936 error case below. If we didn't, we might generate wrong code.
2938 For unsigned fields, the constant shifted right by the field length should
2939 be all zero. For signed fields, the high-order bits should agree with
2940 the sign bit. */
2943 {
2947 {
2953 }
2954 }
2955 else
2956 {
2960 {
2966 }
2967 }
2969 /* Single-bit compares should always be against zero. */
2971 {
2974 }
2976 /* Make a new bitfield reference, shift the constant over the
2977 appropriate number of bits and mask it with the computed mask
2978 (in case this was a signed field). If we changed it, make a new one. */
2981 {
2984 }
2994 rhs);
2995 }
2996 \f
2997 /* Subroutine for fold_truthop: decode a field reference.
2999 If EXP is a comparison reference, we return the innermost reference.
3001 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3002 set to the starting bit number.
3004 If the innermost field can be completely contained in a mode-sized
3005 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3007 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3008 otherwise it is not changed.
3010 *PUNSIGNEDP is set to the signedness of the field.
3012 *PMASK is set to the mask used. This is either contained in a
3013 BIT_AND_EXPR or derived from the width of the field.
3015 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3017 Return 0 if this is not a component reference or is one that we can't
3018 do anything with. */
3020 static tree
3025 {
3029 tree unsigned_type;
3032 /* All the optimizations using this function assume integer fields.
3033 There are problems with FP fields since the type_for_size call
3034 below can fail for, e.g., XFmode. */
3038 /* We are interested in the bare arrangement of bits, so strip everything
3039 that doesn't affect the machine mode. However, record the type of the
3040 outermost expression if it may matter below. */
3048 {
3054 }
3063 /* If the number of bits in the reference is the same as the bitsize of
3064 the outer type, then the outer type gives the signedness. Otherwise
3065 (in case of a small bitfield) the signedness is unchanged. */
3069 /* Compute the mask to access the bitfield. */
3079 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3087 }
3089 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3090 bit positions. */
3092 static int
3094 {
3097 tree tmask;
3102 return
3109 }
3111 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3112 represents the sign bit of EXP's type. If EXP represents a sign
3113 or zero extension, also test VAL against the unextended type.
3114 The return value is the (sub)expression whose sign bit is VAL,
3115 or NULL_TREE otherwise. */
3117 static tree
3119 {
3123 tree t;
3125 /* Tree EXP must have an integral type. */
3130 /* Tree VAL must be an integer constant. */
3137 {
3144 }
3145 else
3146 {
3153 }
3155 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3156 treat VAL as if it were unsigned. */
3161 /* Handle extension from a narrower type. */
3167 }
3169 /* Subroutine for fold_truthop: determine if an operand is simple enough
3170 to be evaluated unconditionally. */
3172 static int
3174 {
3175 /* Strip any conversions that don't change the machine mode. */
3187 /* Don't regard global variables as simple. They may be
3188 allocated in ways unknown to the compiler (shared memory,
3189 #pragma weak, etc). */
3192 /* Loading a static variable is unduly expensive, but global
3193 registers aren't expensive. */
3195 }
3196 \f
3197 /* The following functions are subroutines to fold_range_test and allow it to
3198 try to change a logical combination of comparisons into a range test.
3200 For example, both
3201 X == 2 || X == 3 || X == 4 || X == 5
3202 and
3203 X >= 2 && X <= 5
3204 are converted to
3205 (unsigned) (X - 2) <= 3
3207 We describe each set of comparisons as being either inside or outside
3208 a range, using a variable named like IN_P, and then describe the
3209 range with a lower and upper bound. If one of the bounds is omitted,
3210 it represents either the highest or lowest value of the type.
3212 In the comments below, we represent a range by two numbers in brackets
3213 preceded by a "+" to designate being inside that range, or a "-" to
3214 designate being outside that range, so the condition can be inverted by
3215 flipping the prefix. An omitted bound is represented by a "-". For
3216 example, "- [-, 10]" means being outside the range starting at the lowest
3217 possible value and ending at 10, in other words, being greater than 10.
3218 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3219 always false.
3221 We set up things so that the missing bounds are handled in a consistent
3222 manner so neither a missing bound nor "true" and "false" need to be
3223 handled using a special case. */
3225 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3226 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3227 and UPPER1_P are nonzero if the respective argument is an upper bound
3228 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3229 must be specified for a comparison. ARG1 will be converted to ARG0's
3230 type if both are specified. */
3232 static tree
3235 {
3236 tree tem;
3240 /* If neither arg represents infinity, do the normal operation.
3241 Else, if not a comparison, return infinity. Else handle the special
3242 comparison rules. Note that most of the cases below won't occur, but
3243 are handled for consistency. */
3246 {
3251 }
3256 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3257 for neither. In real maths, we cannot assume open ended ranges are
3258 the same. But, this is computer arithmetic, where numbers are finite.
3259 We can therefore make the transformation of any unbounded range with
3260 the value Z, Z being greater than any representable number. This permits
3261 us to treat unbounded ranges as equal. */
3265 {
3286 }
3289 }
3290 \f
3291 /* Given EXP, a logical expression, set the range it is testing into
3292 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3293 actually being tested. *PLOW and *PHIGH will be made of the same type
3294 as the returned expression. If EXP is not a comparison, we will most
3295 likely not be returning a useful value and range. */
3297 static tree
3299 {
3306 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3307 and see if we can refine the range. Some of the cases below may not
3308 happen, but it doesn't seem worth worrying about this. We "continue"
3309 the outer loop when we've changed something; otherwise we "break"
3310 the switch, which will "break" the while. */
3316 {
3320 {
3332 }
3334 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3335 lose a cast by accident. */
3340 {
3347 /* We can only do something if the range is testing for zero
3348 and if the second operand is an integer constant. Note that
3349 saying something is "in" the range we make is done by
3350 complementing IN_P since it will set in the initial case of
3351 being not equal to zero; "out" is leaving it alone. */
3358 {
3379 }
3383 /* If this is an unsigned comparison, we also know that EXP is
3384 greater than or equal to zero. We base the range tests we make
3385 on that fact, so we record it here so we can parse existing
3386 range tests. */
3388 {
3391 NULL_TREE))
3396 /* If the high bound is missing, but we have a nonzero low
3397 bound, reverse the range so it goes from zero to the low bound
3398 minus 1. */
3400 {
3405 }
3406 }
3410 /* (-x) IN [a,b] -> x in [-b, -a] */
3422 /* ~ X -> -X - 1 */
3431 /* If EXP is signed, any overflow in the computation is undefined,
3432 so we don't worry about it so long as our computations on
3433 the bounds don't overflow. For unsigned, overflow is defined
3434 and this is exactly the right thing. */
3443 /* Check for an unsigned range which has wrapped around the maximum
3444 value thus making n_high < n_low, and normalize it. */
3446 {
3452 /* If the range is of the form +/- [ x+1, x ], we won't
3453 be able to normalize it. But then, it represents the
3454 whole range or the empty set, so make it
3455 +/- [ -, - ]. */
3459 else
3461 }
3462 else
3485 /* If we're converting from an unsigned to a signed type,
3486 we will be doing the comparison as unsigned. The tests above
3487 have already verified that LOW and HIGH are both positive.
3489 So we have to make sure that the original unsigned value will
3490 be interpreted as positive. */
3492 {
3495 tree high_positive;
3497 /* A range without an upper bound is, naturally, unbounded.
3498 Since convert would have cropped a very large value, use
3499 the max value for the destination type. */
3500 high_positive
3507 high_positive),
3509 integer_one_node)));
3511 /* If the low bound is specified, "and" the range with the
3512 range for which the original unsigned value will be
3513 positive. */
3515 {
3519 high_positive))
3523 }
3524 else
3525 {
3526 /* Otherwise, "or" the range with the range of the input
3527 that will be interpreted as negative. */
3531 high_positive))
3535 }
3536 }
3544 }
3547 }
3549 /* If EXP is a constant, we can evaluate whether this is true or false. */
3551 {
3558 }
3562 }
3563 \f
3564 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3565 type, TYPE, return an expression to test if EXP is in (or out of, depending
3566 on IN_P) the range. */
3568 static tree
3570 {
3572 tree value;
3591 {
3593 {
3597 }
3599 }
3601 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3603 {
3605 HOST_WIDE_INT hi;
3610 {
3613 }
3614 else
3615 {
3618 }
3621 {
3623 {
3626 }
3629 }
3630 }
3637 value);
3640 }
3641 \f
3642 /* Given two ranges, see if we can merge them into one. Return 1 if we
3643 can, 0 if we can't. Set the output range into the specified parameters. */
3645 static int
3648 {
3652 tree tem;
3662 /* Make range 0 be the range that starts first, or ends last if they
3663 start at the same value. Swap them if it isn't. */
3666 || (lowequal
3669 {
3673 }
3675 /* Now flag two cases, whether the ranges are disjoint or whether the
3676 second range is totally subsumed in the first. Note that the tests
3677 below are simplified by the ones above. */
3683 /* We now have four cases, depending on whether we are including or
3684 excluding the two ranges. */
3686 {
3687 /* If they don't overlap, the result is false. If the second range
3688 is a subset it is the result. Otherwise, the range is from the start
3689 of the second to the end of the first. */
3694 else
3696 }
3699 {
3700 /* If they don't overlap, the result is the first range. If they are
3701 equal, the result is false. If the second range is a subset of the
3702 first, and the ranges begin at the same place, we go from just after
3703 the end of the first range to the end of the second. If the second
3704 range is not a subset of the first, or if it is a subset and both
3705 ranges end at the same place, the range starts at the start of the
3706 first range and ends just before the second range.
3707 Otherwise, we can't describe this as a single range. */
3713 {
3717 }
3719 {
3723 }
3724 else
3726 }
3729 {
3730 /* If they don't overlap, the result is the second range. If the second
3731 is a subset of the first, the result is false. Otherwise,
3732 the range starts just after the first range and ends at the
3733 end of the second. */
3738 else
3739 {
3743 }
3744 }
3746 else
3747 {
3748 /* The case where we are excluding both ranges. Here the complex case
3749 is if they don't overlap. In that case, the only time we have a
3750 range is if they are adjacent. If the second is a subset of the
3751 first, the result is the first. Otherwise, the range to exclude
3752 starts at the beginning of the first range and ends at the end of the
3753 second. */
3755 {
3762 else
3764 }
3767 else
3769 }
3773 }
3774 \f
3775 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3776 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3777 #endif
3779 /* EXP is some logical combination of boolean tests. See if we can
3780 merge it into some range test. Return the new tree if so. */
3782 static tree
3784 {
3791 tree tem;
3793 /* If this is an OR operation, invert both sides; we will invert
3794 again at the end. */
3798 /* If both expressions are the same, if we can merge the ranges, and we
3799 can build the range test, return it or it inverted. If one of the
3800 ranges is always true or always false, consider it to be the same
3801 expression as the other. */
3811 /* On machines where the branch cost is expensive, if this is a
3812 short-circuited branch and the underlying object on both sides
3813 is the same, make a non-short-circuit operation. */
3819 {
3820 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3821 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3822 which cases we can't do this. */
3831 {
3843 }
3844 }
3847 }
3848 \f
3849 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3850 bit value. Arrange things so the extra bits will be set to zero if and
3851 only if C is signed-extended to its full width. If MASK is nonzero,
3852 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3854 static tree
3856 {
3859 tree temp;
3864 /* We work by getting just the sign bit into the low-order bit, then
3865 into the high-order bit, then sign-extend. We then XOR that value
3866 with C. */
3870 /* We must use a signed type in order to get an arithmetic right shift.
3871 However, we must also avoid introducing accidental overflows, so that
3872 a subsequent call to integer_zerop will work. Hence we must
3873 do the type conversion here. At this point, the constant is either
3874 zero or one, and the conversion to a signed type can never overflow.
3875 We could get an overflow if this conversion is done anywhere else. */
3884 /* If necessary, convert the type back to match the type of C. */
3889 }
3890 \f
3891 /* Find ways of folding logical expressions of LHS and RHS:
3892 Try to merge two comparisons to the same innermost item.
3893 Look for range tests like "ch >= '0' && ch <= '9'".
3894 Look for combinations of simple terms on machines with expensive branches
3895 and evaluate the RHS unconditionally.
3897 For example, if we have p->a == 2 && p->b == 4 and we can make an
3898 object large enough to span both A and B, we can do this with a comparison
3899 against the object ANDed with the a mask.
3901 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3902 operations to do this with one comparison.
3904 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3905 function and the one above.
3907 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3908 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3910 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3911 two operands.
3913 We return the simplified tree or 0 if no optimization is possible. */
3915 static tree
3917 {
3918 /* If this is the "or" of two comparisons, we can do something if
3919 the comparisons are NE_EXPR. If this is the "and", we can do something
3920 if the comparisons are EQ_EXPR. I.e.,
3921 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3923 WANTED_CODE is this operation code. For single bit fields, we can
3924 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3925 comparison for one-bit fields. */
3945 /* Start by getting the comparison codes. Fail if anything is volatile.
3946 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3947 it were surrounded with a NE_EXPR. */
3972 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3976 {
3981 {
3989 }
3992 {
4001 }
4002 else
4012 }
4014 /* If the RHS can be evaluated unconditionally and its operands are
4015 simple, it wins to evaluate the RHS unconditionally on machines
4016 with expensive branches. In this case, this isn't a comparison
4017 that can be merged. Avoid doing this if the RHS is a floating-point
4018 comparison since those can trap. */
4024 {
4025 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4033 integer_zero_node);
4035 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4043 integer_zero_node);
4046 }
4048 /* See if the comparisons can be merged. Then get all the parameters for
4049 each side. */
4073 /* It must be true that the inner operation on the lhs of each
4074 comparison must be the same if we are to be able to do anything.
4075 Then see if we have constants. If not, the same must be true for
4076 the rhs's. */
4087 else
4090 /* If either comparison code is not correct for our logical operation,
4091 fail. However, we can convert a one-bit comparison against zero into
4092 the opposite comparison against that bit being set in the field. */
4096 {
4098 {
4099 /* Make the left operand unsigned, since we are only interested
4100 in the value of one bit. Otherwise we are doing the wrong
4101 thing below. */
4104 }
4105 else
4107 }
4109 /* This is analogous to the code for l_const above. */
4111 {
4113 {
4116 }
4117 else
4119 }
4121 /* After this point all optimizations will generate bit-field
4122 references, which we might not want. */
4126 /* See if we can find a mode that contains both fields being compared on
4127 the left. If we can't, fail. Otherwise, update all constants and masks
4128 to be relative to a field of that size. */
4133 volatilep);
4143 {
4146 }
4154 {
4162 {
4166 wanted_code == NE_EXPR
4168 }
4169 }
4171 {
4179 {
4183 wanted_code == NE_EXPR
4185 }
4186 }
4188 /* If the right sides are not constant, do the same for it. Also,
4189 disallow this optimization if a size or signedness mismatch occurs
4190 between the left and right sides. */
4192 {
4195 /* Make sure the two fields on the right
4196 correspond to the left without being swapped. */
4204 volatilep);
4214 {
4217 }
4224 /* Make a mask that corresponds to both fields being compared.
4225 Do this for both items being compared. If the operands are the
4226 same size and the bits being compared are in the same position
4227 then we can do this by masking both and comparing the masked
4228 results. */
4232 {
4244 }
4246 /* There is still another way we can do something: If both pairs of
4247 fields being compared are adjacent, we may be able to make a wider
4248 field containing them both.
4250 Note that we still must mask the lhs/rhs expressions. Furthermore,
4251 the mask must be shifted to account for the shift done by
4252 make_bit_field_ref. */
4257 {
4258 tree type;
4270 /* Convert to the smaller type before masking out unwanted bits. */
4273 {
4275 {
4279 }
4281 {
4285 }
4286 }
4295 }
4298 }
4300 /* Handle the case of comparisons with constants. If there is something in
4301 common between the masks, those bits of the constants must be the same.
4302 If not, the condition is always false. Test for this to avoid generating
4303 incorrect code below. */
4308 {
4310 {
4313 }
4314 else
4315 {
4318 }
4319 }
4321 /* Construct the expression we will return. First get the component
4322 reference we will make. Unless the mask is all ones the width of
4323 that field, perform the mask operation. Then compare with the
4324 merged constant. */
4334 }
4335 \f
4336 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4337 constant. */
4339 static tree
4341 {
4346 tree minmax_const;
4348 tree inner;
4358 /* If something does not permit us to optimize, return the original tree. */
4366 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4367 and GT_EXPR, doing the rest with recursive calls using logical
4368 simplifications. */
4370 {
4372 return
4376 return
4378 optimize_minmax_comparison
4380 optimize_minmax_comparison
4385 /* MAX (X, 0) == 0 -> X <= 0 */
4389 /* MAX (X, 0) == 5 -> X == 5 */
4393 /* MAX (X, 0) == -1 -> false */
4397 /* MIN (X, 0) == 0 -> X >= 0 */
4401 /* MIN (X, 0) == 5 -> false */
4404 else
4405 /* MIN (X, 0) == -1 -> X == -1 */
4410 /* MAX (X, 0) > 0 -> X > 0
4411 MAX (X, 0) > 5 -> X > 5 */
4415 /* MAX (X, 0) > -1 -> true */
4419 /* MIN (X, 0) > 0 -> false
4420 MIN (X, 0) > 5 -> false */
4423 else
4424 /* MIN (X, 0) > -1 -> X > -1 */
4429 }
4430 }
4431 \f
4432 /* T is an integer expression that is being multiplied, divided, or taken a
4433 modulus (CODE says which and what kind of divide or modulus) by a
4434 constant C. See if we can eliminate that operation by folding it with
4435 other operations already in T. WIDE_TYPE, if non-null, is a type that
4436 should be used for the computation if wider than our type.
4438 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4439 (X * 2) + (Y * 4). We must, however, be assured that either the original
4440 expression would not overflow or that overflow is undefined for the type
4441 in the language in question.
4443 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4444 the machine has a multiply-accumulate insn or that this is part of an
4445 addressing calculation.
4447 If we return a non-null expression, it is an equivalent form of the
4448 original computation, but need not be in the original type. */
4450 static tree
4452 {
4453 /* To avoid exponential search depth, refuse to allow recursion past
4454 three levels. Beyond that (1) it's highly unlikely that we'll find
4455 something interesting and (2) we've probably processed it before
4456 when we built the inner expression. */
4459 tree ret;
4464 depth++;
4466 depth--;
4469 }
4471 static tree
4473 {
4483 /* Don't deal with constants of zero here; they confuse the code below. */
4493 /* Note that we need not handle conditional operations here since fold
4494 already handles those cases. So just do arithmetic here. */
4496 {
4498 /* For a constant, we can always simplify if we are a multiply
4499 or (for divide and modulus) if it is a multiple of our constant. */
4507 /* If op0 is an expression ... */
4512 /* ... and is unsigned, and its type is smaller than ctype,
4513 then we cannot pass through as widening. */
4519 /* ... or its type is larger than ctype,
4520 then we cannot pass through this truncation. */
4523 /* ... or signedness changes for division or modulus,
4524 then we cannot pass through this conversion. */
4530 /* Pass the constant down and see if we can make a simplification. If
4531 we can, replace this expression with the inner simplification for
4532 possible later conversion to our or some other type. */
4537 code == MULT_EXPR
4548 /* If widening the type changes the signedness, then we can't perform
4549 this optimization as that changes the result. */
4553 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4556 {
4562 }
4566 /* If the second operand is constant, this is a multiplication
4567 or floor division, by a power of two, so we can treat it that
4568 way unless the multiplier or divisor overflows. */
4570 /* const_binop may not detect overflow correctly,
4571 so check for it explicitly here. */
4576 size_one_node,
4586 /* See if we can eliminate the operation on both sides. If we can, we
4587 can return a new PLUS or MINUS. If we can't, the only remaining
4588 cases where we can do anything are if the second operand is a
4589 constant. */
4594 /* If not multiplication, we can only do this if both operands
4595 are divisible by c. */
4601 /* If this was a subtraction, negate OP1 and set it to be an addition.
4602 This simplifies the logic below. */
4609 /* If either OP1 or C are negative, this optimization is not safe for
4610 some of the division and remainder types while for others we need
4611 to change the code. */
4613 {
4621 }
4623 /* If it's a multiply or a division/modulus operation of a multiple
4624 of our constant, do the operation and verify it doesn't overflow. */
4627 {
4630 /* We allow the constant to overflow with wrapping semantics. */
4634 }
4635 else
4638 /* If we have an unsigned type is not a sizetype, we cannot widen
4639 the operation since it will change the result if the original
4640 computation overflowed. */
4646 /* If we were able to eliminate our operation from the first side,
4647 apply our operation to the second side and reform the PLUS. */
4651 /* The last case is if we are a multiply. In that case, we can
4652 apply the distributive law to commute the multiply and addition
4653 if the multiplication of the constants doesn't overflow. */
4659 op1));
4664 /* We have a special case here if we are doing something like
4665 (C * 8) % 4 since we know that's zero. */
4672 /* ... fall through ... */
4676 /* If we can extract our operation from the LHS, do so and return a
4677 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4678 do something only if the second operand is a constant. */
4690 /* If these are the same operation types, we can associate them
4691 assuming no overflow. */
4698 /* If these operations "cancel" each other, we have the main
4699 optimizations of this pass, which occur when either constant is a
4700 multiple of the other, in which case we replace this with either an
4701 operation or CODE or TCODE.
4703 If we have an unsigned type that is not a sizetype, we cannot do
4704 this since it will change the result if the original computation
4705 overflowed. */
4708 && ! flag_wrapv
4713 {
4724 }
4729 }
4732 }
4733 \f
4734 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4735 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4736 that we may sometimes modify the tree. */
4738 static tree
4740 {
4743 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4748 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4749 don't bother handling any other types. */
4751 {
4755 }
4760 {
4763 }
4766 }
4767 \f
4768 /* Return a node which has the indicated constant VALUE (either 0 or
4769 1), and is of the indicated TYPE. */
4771 static tree
4773 {
4779 else
4780 {
4785 }
4786 }
4788 /* Utility function for the following routine, to see how complex a nesting of
4789 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4790 we don't care (to avoid spending too much time on complex expressions.). */
4792 static int
4794 {
4805 }
4807 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4808 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4809 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4810 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4811 COND is the first argument to CODE; otherwise (as in the example
4812 given here), it is the second argument. TYPE is the type of the
4813 original expression. Return NULL_TREE if no simplification is
4814 possible. */
4816 static tree
4819 {
4823 /* In the end, we'll produce a COND_EXPR. Both arms of the
4824 conditional expression will be binary operations. The left-hand
4825 side of the expression to be executed if the condition is true
4826 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4827 of the expression to be executed if the condition is true will be
4828 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4829 but apply to the expression to be executed if the conditional is
4830 false. */
4835 /* These are the codes to use for the left-hand side and right-hand
4836 side of the COND_EXPR. Normally, they are the same as CODE. */
4839 /* And these are the types of the expressions. */
4858 {
4862 }
4863 else
4864 {
4868 }
4871 {
4875 /* If this operand throws an expression, then it does not make
4876 sense to try to perform a logical or arithmetic operation
4877 involving it. Instead of building `a + throw 3' for example,
4878 we simply build `a, throw 3'. */
4880 {
4882 {
4885 }
4886 else
4888 }
4890 {
4892 {
4895 }
4896 else
4898 }
4899 }
4900 else
4901 {
4906 }
4908 /* If ARG is complex we want to make sure we only evaluate it once. Though
4909 this is only required if it is volatile, it might be more efficient even
4910 if it is not. However, if we succeed in folding one part to a constant,
4911 we do not need to make this SAVE_EXPR. Since we do this optimization
4912 primarily to see if we do end up with constant and this SAVE_EXPR
4913 interferes with later optimizations, suppressing it when we can is
4914 important.
4916 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4917 do so. Don't try to see if the result is a constant if an arm is a
4918 COND_EXPR since we get exponential behavior in that case. */
4927 {
4936 {
4940 }
4941 }
4950 /* If ARG involves a SAVE_EXPR, we need to ensure it is evaluated
4951 ahead of the COND_EXPR we made. Otherwise we would have it only
4952 evaluated in one branch, with the other branch using the result
4953 but missing the evaluation code. Beware that the save_expr call
4954 above might not return a SAVE_EXPR, so testing the TREE_CODE
4955 of ARG is not enough to decide here. Â */
4960 else
4962 }
4964 \f
4965 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4967 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4968 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4969 ADDEND is the same as X.
4971 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4972 and finite. The problematic cases are when X is zero, and its mode
4973 has signed zeros. In the case of rounding towards -infinity,
4974 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4975 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4977 static bool
4979 {
4983 /* Don't allow the fold with -fsignaling-nans. */
4987 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4991 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4996 /* The mode has signed zeros, and we have to honor their sign.
4997 In this situation, there is only one case we can return true for.
4998 X - 0 is the same as X unless rounding towards -infinity is
4999 supported. */
5001 }
5003 /* Subroutine of fold() that checks comparisons of built-in math
5004 functions against real constants.
5006 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
5007 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
5008 is the type of the result and ARG0 and ARG1 are the operands of the
5009 comparison. ARG1 must be a TREE_REAL_CST.
5011 The function returns the constant folded tree if a simplification
5012 can be made, and NULL_TREE otherwise. */
5014 static tree
5017 {
5018 REAL_VALUE_TYPE c;
5021 {
5027 {
5028 /* sqrt(x) < y is always false, if y is negative. */
5032 arg);
5034 /* sqrt(x) > y is always true, if y is negative and we
5035 don't care about NaNs, i.e. negative values of x. */
5039 arg);
5041 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5044 }
5046 {
5047 REAL_VALUE_TYPE c2;
5053 {
5054 /* sqrt(x) > y is x == +Inf, when y is very large. */
5059 /* sqrt(x) > y is always false, when y is very large
5060 and we don't care about infinities. */
5063 arg);
5064 }
5066 /* sqrt(x) > c is the same as x > c*c. */
5069 }
5071 {
5072 REAL_VALUE_TYPE c2;
5078 {
5079 /* sqrt(x) < y is always true, when y is a very large
5080 value and we don't care about NaNs or Infinities. */
5084 arg);
5086 /* sqrt(x) < y is x != +Inf when y is very large and we
5087 don't care about NaNs. */
5092 /* sqrt(x) < y is x >= 0 when y is very large and we
5093 don't care about Infinities. */
5098 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5107 dconst0))),
5110 c2)))));
5111 }
5113 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5118 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5121 {
5126 dconst0))),
5129 c2)))));
5130 }
5131 }
5132 }
5135 }
5137 /* Subroutine of fold() that optimizes comparisons against Infinities,
5138 either +Inf or -Inf.
5140 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5141 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5142 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5144 The function returns the constant folded tree if a simplification
5145 can be made, and NULL_TREE otherwise. */
5147 static tree
5149 {
5151 REAL_VALUE_TYPE max;
5152 tree temp;
5157 /* For negative infinity swap the sense of the comparison. */
5163 {
5165 /* x > +Inf is always false, if with ignore sNANs. */
5170 arg0);
5173 /* x <= +Inf is always true, if we don't case about NaNs. */
5177 arg0);
5179 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5182 {
5185 }
5190 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5196 /* x < +Inf is always equal to x <= DBL_MAX. */
5202 /* x != +Inf is always equal to !(x > DBL_MAX). */
5213 }
5216 }
5218 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5219 equality/inequality test, then return a simplified form of
5220 the test using shifts and logical operations. Otherwise return
5221 NULL. TYPE is the desired result type. */
5223 tree
5225 tree result_type)
5226 {
5227 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5228 operand 0. */
5230 {
5235 /* Extract the arguments of the EQ/NE. */
5239 /* This requires us to invert the code. */
5241 }
5243 /* If this is testing a single bit, we can optimize the test. */
5247 {
5254 tree arg00;
5256 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5257 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5260 {
5265 }
5267 /* At this point, we know that arg0 is not testing the sign bit. */
5271 /* Otherwise we have (A & C) != 0 where C is a single bit,
5272 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5273 Similarly for (A & C) == 0. */
5275 /* If INNER is a right shift of a constant and it plus BITNUM does
5276 not overflow, adjust BITNUM and INNER. */
5283 {
5286 }
5288 /* If we are going to be able to omit the AND below, we must do our
5289 operations as unsigned. If we must use the AND, we have a choice.
5290 Normally unsigned is faster, but for some machines signed is. */
5291 #ifdef LOAD_EXTEND_OP
5293 #else
5295 #endif
5310 /* Put the AND last so it can combine with more things. */
5314 /* Make sure to return the proper type. */
5318 }
5320 }
5322 /* Check whether we are allowed to reorder operands arg0 and arg1,
5323 such that the evaluation of arg1 occurs before arg0. */
5325 static bool
5327 {
5334 }
5336 /* Test whether it is preferable two swap two operands, ARG0 and
5337 ARG1, for example because ARG0 is an integer constant and ARG1
5338 isn't. If REORDER is true, only recommend swapping if we can
5339 evaluate the operands in reverse order. */
5341 static bool
5343 {
5380 }
5382 /* Perform constant folding and related simplification of EXPR.
5383 The related simplifications include x*1 => x, x*0 => 0, etc.,
5384 and application of the associative law.
5385 NOP_EXPR conversions may be removed freely (as long as we
5386 are careful not to change the type of the overall expression).
5387 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5388 but we can constant-fold them if they have constant operands. */
5390 #ifdef ENABLE_FOLD_CHECKING
5391 # define fold(x) fold_1 (x)
5393 static
5394 #endif
5395 tree
5397 {
5401 tree tem;
5405 /* WINS will be nonzero when the switch is done
5406 if all operands are constant. */
5409 /* Don't try to process an RTL_EXPR since its operands aren't trees.
5410 Likewise for a SAVE_EXPR that's already been evaluated. */
5414 /* Return right away if a constant. */
5419 {
5420 tree subop;
5422 /* Special case for conversion ops that can have fixed point args. */
5425 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
5431 else
5436 /* Note that TREE_CONSTANT isn't enough:
5437 static var addresses are constant but we can't
5438 do arithmetic on them. */
5440 }
5442 {
5446 {
5448 tree subop;
5453 /* Strip any conversions that don't change the mode. This is
5454 safe for every expression, except for a comparison expression
5455 because its signedness is derived from its operands. So, in
5456 the latter case, only strip conversions that don't change the
5457 signedness.
5459 Note that this is done as an internal manipulation within the
5460 constant folder, in order to find the simplest representation
5461 of the arguments so that their form can be studied. In any
5462 cases, the appropriate type conversions should be put back in
5463 the tree that will get out of the constant folder. */
5466 else
5471 else
5476 /* Note that TREE_CONSTANT isn't enough:
5477 static var addresses are constant but we can't
5478 do arithmetic on them. */
5485 }
5486 }
5488 /* If this is a commutative operation, and ARG0 is a constant, move it
5489 to ARG1 to reduce the number of tests below. */
5495 /* Now WINS is set as described above,
5496 ARG0 is the first operand of EXPR,
5497 and ARG1 is the second operand (if it has more than one operand).
5499 First check for cases where an arithmetic operation is applied to a
5500 compound, conditional, or comparison operation. Push the arithmetic
5501 operation inside the compound or conditional to see if any folding
5502 can then be done. Convert comparison to conditional for this purpose.
5503 The also optimizes non-constant cases that used to be done in
5504 expand_expr.
5506 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5507 one of the operands is a comparison and the other is a comparison, a
5508 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5509 code below would make the expression more complex. Change it to a
5510 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5511 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5523 {
5533 }
5536 {
5541 {
5551 /* If this was a conversion, and all we did was to move into
5552 inside the COND_EXPR, bring it back out. But leave it if
5553 it is a conversion from integer to integer and the
5554 result precision is no wider than a word since such a
5555 conversion is cheap and may be optimized away by combine,
5556 while it couldn't if it were outside the COND_EXPR. Then return
5557 so we don't get into an infinite recursion loop taking the
5558 conversion out and then back in. */
5570 && (INTEGRAL_TYPE_P
5581 }
5586 }
5597 {
5609 {
5614 }
5618 {
5623 }
5624 }
5627 {
5641 /* Handle cases of two conversions in a row. */
5644 {
5663 /* In addition to the cases of two conversions in a row
5664 handled below, if we are converting something to its own
5665 type via an object of identical or wider precision, neither
5666 conversion is needed. */
5673 /* Likewise, if the intermediate and final types are either both
5674 float or both integer, we don't need the middle conversion if
5675 it is wider than the final type and doesn't change the signedness
5676 (for integers). Avoid this if the final type is a pointer
5677 since then we sometimes need the inner conversion. Likewise if
5678 the outer has a precision not equal to the size of its mode. */
5689 /* If we have a sign-extension of a zero-extended value, we can
5690 replace that by a single zero-extension. */
5697 /* Two conversions in a row are not needed unless:
5698 - some conversion is floating-point (overstrict for now), or
5699 - the intermediate type is narrower than both initial and
5700 final, or
5701 - the intermediate type and innermost type differ in signedness,
5702 and the outermost type is wider than the intermediate, or
5703 - the initial type is a pointer type and the precisions of the
5704 intermediate and final types differ, or
5705 - the final type is a pointer type and the precisions of the
5706 initial and intermediate types differ. */
5721 }
5725 /* Detect assigning a bitfield. */
5728 {
5729 /* Don't leave an assignment inside a conversion
5730 unless assigning a bitfield. */
5734 /* First do the assignment, then return converted constant. */
5739 }
5741 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5742 constants (if x has signed type, the sign bit cannot be set
5743 in c). This folds extension into the BIT_AND_EXPR. */
5748 {
5758 <= HOST_BITS_PER_WIDE_INT
5760 {
5767 #ifdef LOAD_EXTEND_OP
5771 {
5775 }
5776 #endif
5777 }
5782 }
5796 {
5800 }
5805 {
5809 }
5823 /* Convert fabs((double)float) into (double)fabsf(float). */
5826 {
5831 targ0)));
5832 }
5859 {
5867 }
5873 /* A + (-B) -> A - B */
5876 /* (-A) + B -> B - A */
5881 {
5885 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5886 with a constant, and the two constants have no bits in common,
5887 we should treat this as a BIT_IOR_EXPR since this may produce more
5888 simplifications. */
5896 {
5899 }
5901 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5902 (plus (plus (mult) (mult)) (foo)) so that we can
5903 take advantage of the factoring cases below. */
5908 {
5913 else
5934 }
5937 {
5941 /* (A * C) + (B * C) -> (A+B) * C.
5942 We are most concerned about the case where C is a constant,
5943 but other combinations show up during loop reduction. Since
5944 it is not difficult, try all four possibilities. */
5961 /* No identical multiplicands; see if we can find a common
5962 power-of-two factor in non-power-of-two multiplies. This
5963 can help in multi-dimensional array access. */
5968 {
5973 /* Move min of absolute values to int11. */
5976 {
5980 }
5983 {
5988 }
5989 }
5994 same));
5995 }
5996 }
5997 else
5998 {
5999 /* See if ARG1 is zero and X + ARG1 reduces to X. */
6003 /* Likewise if the operands are reversed. */
6007 /* Convert x+x into x*2.0. */
6013 /* Convert x*c+x into x*(c+1). */
6019 {
6020 REAL_VALUE_TYPE c;
6026 }
6028 /* Convert x+x*c into x*(c+1). */
6034 {
6035 REAL_VALUE_TYPE c;
6041 }
6043 /* Convert x*c1+x*c2 into x*(c1+c2). */
6053 {
6062 }
6063 /* Convert a + (b*c + d*e) into (a + b*c) + d*e */
6067 {
6072 {
6073 tree tree0;
6076 }
6077 }
6078 /* Convert (b*c + d*e) + a into b*c + (d*e +a) */
6082 {
6087 {
6088 tree tree0;
6091 }
6092 }
6093 }
6095 bit_rotate:
6096 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
6097 is a rotate of A by C1 bits. */
6098 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
6099 is a rotate of A by B bits. */
6100 {
6109 {
6128 {
6136 TYPE_PRECISION
6141 ? LROTATE_EXPR
6144 }
6146 {
6154 TYPE_PRECISION
6159 ? LROTATE_EXPR
6162 }
6163 }
6164 }
6166 associate:
6167 /* In most languages, can't associate operations on floats through
6168 parentheses. Rather than remember where the parentheses were, we
6169 don't associate floats at all, unless the user has specified
6170 -funsafe-math-optimizations. */
6174 {
6178 /* Split both trees into variables, constants, and literals. Then
6179 associate each group together, the constants with literals,
6180 then the result with variables. This increases the chances of
6181 literals being recombined later and of generating relocatable
6182 expressions for the sum of a constant and literal. */
6187 /* Only do something if we found more than two objects. Otherwise,
6188 nothing has changed and we risk infinite recursion. */
6193 {
6194 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6203 /* Preserve the MINUS_EXPR if the negative part of the literal is
6204 greater than the positive part. Otherwise, the multiplicative
6205 folding code (i.e extract_muldiv) may be fooled in case
6206 unsigned constants are subtracted, like in the following
6207 example: ((X*2 + 4) - 8U)/2. */
6209 {
6213 {
6217 }
6218 else
6219 {
6223 }
6224 }
6226 {
6231 else
6232 {
6238 }
6239 }
6244 }
6245 }
6247 binary:
6251 {
6252 /* The return value should always have
6253 the same type as the original expression. */
6258 }
6262 /* A - (-B) -> A + B */
6265 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6275 {
6281 /* Fold A - (A & B) into ~B & A. */
6284 {
6289 arg0));
6294 arg0));
6295 }
6297 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6298 any power of 2 minus 1. */
6303 {
6309 {
6313 }
6314 }
6315 }
6317 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6321 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6322 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6323 (-ARG1 + ARG0) reduces to -ARG1. */
6327 /* Fold &x - &x. This can happen from &x.foo - &x.
6328 This is unsafe for certain floats even in non-IEEE formats.
6329 In IEEE, it is unsafe because it does wrong for NaNs.
6330 Also note that operand_equal_p is always false if an operand
6331 is volatile. */
6337 /* A - B -> A + (-B) if B is easily negatable. */
6346 {
6347 /* (A * C) - (B * C) -> (A-B) * C. */
6355 /* (A * C1) - (A * C2) -> A * (C1-C2). */
6363 }
6368 /* (-A) * (-B) -> A * B */
6379 {
6385 /* (a * (1 << b)) is (a << b) */
6401 }
6402 else
6403 {
6404 /* Maybe fold x * 0 to 0. The expressions aren't the same
6405 when x is NaN, since x * 0 is also NaN. Nor are they the
6406 same in modes with signed zeros, since multiplying a
6407 negative value by 0 gives -0, not +0. */
6412 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
6417 /* Transform x * -1.0 into -x. */
6422 /* Convert (C1/X)*C2 into (C1*C2)/X. */
6427 {
6433 }
6436 {
6440 /* Optimizations of root(...)*root(...). */
6442 {
6447 /* Optimize sqrt(x)*sqrt(x) as x. */
6453 /* Optimize root(x)*root(y) as root(x*y). */
6458 }
6460 /* Optimize expN(x)*expN(y) as expN(x+y). */
6462 {
6469 }
6471 /* Optimizations of pow(...)*pow(...). */
6475 {
6483 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
6485 {
6490 arg01));
6492 }
6494 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
6496 {
6501 arg));
6503 }
6504 }
6506 /* Optimize tan(x)*cos(x) as sin(x). */
6515 {
6521 }
6523 /* Optimize x*pow(x,c) as pow(x,c+1). */
6527 {
6534 {
6536 REAL_VALUE_TYPE c;
6545 }
6546 }
6548 /* Optimize pow(x,c)*x as pow(x,c+1). */
6552 {
6559 {
6561 REAL_VALUE_TYPE c;
6570 }
6571 }
6573 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
6576 {
6580 {
6585 }
6586 }
6587 }
6588 }
6592 bit_ior:
6603 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6605 This results in more efficient code for machines without a NAND
6606 instruction. Combine will canonicalize to the first form
6607 which will allow use of NAND instructions provided by the
6608 backend if they exist. */
6611 {
6616 }
6618 /* See if this can be simplified into a rotate first. If that
6619 is unsuccessful continue in the association code. */
6630 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6631 with a constant, and the two constants have no bits in common,
6632 we should treat this as a BIT_IOR_EXPR since this may produce more
6633 simplifications. */
6641 {
6644 }
6646 /* See if this can be simplified into a rotate first. If that
6647 is unsuccessful continue in the association code. */
6660 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6663 {
6664 unsigned int prec
6671 }
6673 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6675 This results in more efficient code for machines without a NOR
6676 instruction. Combine will canonicalize to the first form
6677 which will allow use of NOR instructions provided by the
6678 backend if they exist. */
6681 {
6686 }
6691 /* Don't touch a floating-point divide by zero unless the mode
6692 of the constant can represent infinity. */
6698 /* (-A) / (-B) -> A / B */
6708 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6713 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
6718 /* If ARG1 is a constant, we can convert this to a multiply by the
6719 reciprocal. This does not have the same rounding properties,
6720 so only do this if -funsafe-math-optimizations. We can actually
6721 always safely do it if ARG1 is a power of two, but it's hard to
6722 tell if it is or not in a portable manner. */
6724 {
6729 /* Find the reciprocal if optimizing and the result is exact. */
6731 {
6732 REAL_VALUE_TYPE r;
6735 {
6738 }
6739 }
6740 }
6741 /* Convert A/B/C to A/(B*C). */
6748 /* Convert A/(B/C) to (A/B)*C. */
6756 /* Convert C1/(X*C2) into (C1/C2)/X. */
6761 {
6767 }
6770 {
6772 /* Optimize x/expN(y) into x*expN(-y). */
6774 {
6781 }
6783 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6787 {
6796 }
6797 }
6800 {
6804 /* Optimize sin(x)/cos(x) as tan(x). */
6810 {
6816 }
6818 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
6824 {
6828 {
6833 tmp));
6834 }
6835 }
6837 /* Optimize pow(x,c)/x as pow(x,c-1). */
6841 {
6847 {
6849 REAL_VALUE_TYPE c;
6858 }
6859 }
6860 }
6872 /* X / -1 is -X. */
6879 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
6880 operation, EXACT_DIV_EXPR.
6882 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
6883 At one time others generated faster code, it's not clear if they do
6884 after the last round to changes to the DIV code in expmed.c. */
6904 /* X % -1 is zero. */
6925 /* Optimize -1 >> x for arithmetic right shifts. */
6928 /* ... fall through ... */
6931 shift:
6937 /* Since negative shift count is not well-defined,
6938 don't try to compute it in the compiler. */
6941 /* Rewrite an LROTATE_EXPR by a constant into an
6942 RROTATE_EXPR by a new constant. */
6944 {
6949 }
6951 /* If we have a rotate of a bit operation with the rotate count and
6952 the second operand of the bit operation both constant,
6953 permute the two operations. */
6965 /* Two consecutive rotates adding up to the width of the mode can
6966 be ignored. */
6997 /* Note that the operand of this must be an int
6998 and its values must be 0 or 1.
6999 ("true" is a fixed value perhaps depending on the language,
7000 but we don't handle values other than 1 correctly yet.) */
7002 /* Avoid infinite recursion. */
7004 {
7009 }
7013 /* Note that the operands of this must be ints
7014 and their values must be 0 or 1.
7015 ("true" is a fixed value perhaps depending on the language.) */
7016 /* If first arg is constant zero, return it. */
7020 /* If either arg is constant true, drop it. */
7024 /* Preserve sequence points. */
7027 /* If second arg is constant zero, result is zero, but first arg
7028 must be evaluated. */
7031 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
7032 case will be handled here. */
7036 truth_andor:
7037 /* We only do these simplifications if we are optimizing. */
7041 /* Check for things like (A || B) && (A || C). We can convert this
7042 to A || (B && C). Note that either operator can be any of the four
7043 truth and/or operations and the transformation will still be
7044 valid. Also note that we only care about order for the
7045 ANDIF and ORIF operators. If B contains side effects, this
7046 might change the truth-value of A. */
7053 {
7073 /* This case if tricky because we must either have commutative
7074 operators or else A10 must not have side-effects. */
7080 a01));
7081 }
7083 /* See if we can build a range comparison. */
7087 /* Check for the possibility of merging component references. If our
7088 lhs is another similar operation, try to merge its rhs with our
7089 rhs. Then try to merge our lhs and rhs. */
7101 /* Note that the operands of this must be ints
7102 and their values must be 0 or true.
7103 ("true" is a fixed value perhaps depending on the language.) */
7104 /* If first arg is constant true, return it. */
7108 /* If either arg is constant zero, drop it. */
7112 /* Preserve sequence points. */
7115 /* If second arg is constant true, result is true, but we must
7116 evaluate first arg. */
7119 /* Likewise for first arg, but note this only occurs here for
7120 TRUTH_OR_EXPR. */
7126 /* If either arg is constant zero, drop it. */
7131 /* If either arg is constant true, this is a logical inversion. */
7144 /* If one arg is a real or integer constant, put it last. */
7148 /* If this is an equality comparison of the address of a non-weak
7149 object against zero, then we know the result. */
7155 {
7158 else
7160 }
7162 /* If this is an equality comparison of the address of two non-weak,
7163 unaliased symbols neither of which are extern (since we do not
7164 have access to attributes for externs), then we know the result. */
7178 {
7182 else
7185 }
7188 {
7196 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7201 /* (-a) CMP (-b) -> b CMP a */
7208 {
7209 REAL_VALUE_TYPE cst;
7212 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7214 return
7220 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7221 /* a CMP (-0) -> a CMP 0 */
7226 /* x != NaN is always true, other ops are always false. */
7229 {
7232 }
7234 /* Fold comparisons against infinity. */
7236 {
7240 }
7241 }
7243 /* If this is a comparison of a real constant with a PLUS_EXPR
7244 or a MINUS_EXPR of a real constant, we can convert it into a
7245 comparison with a revised real constant as long as no overflow
7246 occurs when unsafe_math_optimizations are enabled. */
7258 /* Likewise, we can simplify a comparison of a real constant with
7259 a MINUS_EXPR whose first operand is also a real constant, i.e.
7260 (c1 - x) < c2 becomes x > c1-c2. */
7271 /* Fold comparisons against built-in math functions. */
7273 && flag_unsafe_math_optimizations
7275 {
7279 {
7283 }
7284 }
7285 }
7287 /* Convert foo++ == CONST into ++foo == CONST + INCR. */
7291 /* This optimization is invalid for ordered comparisons
7292 if CONST+INCR overflows or if foo+incr might overflow.
7293 This optimization is invalid for floating point due to rounding.
7294 For pointer types we assume overflow doesn't happen. */
7298 {
7302 {
7308 }
7309 else
7310 {
7316 }
7319 /* If VAROP is a reference to a bitfield, we must mask
7320 the constant by the width of the field. */
7323 {
7328 /* First check whether the comparison would come out
7329 always the same. If we don't do that we would
7330 change the meaning with the masking. */
7333 arg1));
7344 }
7347 }
7349 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
7350 This transformation affects the cases which are handled in later
7351 optimizations involving comparisons with non-negative constants. */
7355 {
7357 {
7368 }
7369 }
7371 /* Comparisons with the highest or lowest possible integer of
7372 the specified size will have known values. */
7373 {
7381 {
7388 {
7391 }
7392 else
7393 {
7396 }
7401 {
7405 integer_zero_node),
7406 arg0);
7413 integer_one_node),
7414 arg0);
7418 /* The GE_EXPR and LT_EXPR cases above are not normally
7419 reached because of previous transformations. */
7423 }
7427 {
7436 }
7440 {
7444 integer_zero_node),
7445 arg0);
7452 integer_one_node),
7453 arg0);
7459 }
7463 {
7472 }
7477 /* signed_type does not work on pointer types. */
7479 {
7480 /* The following case also applies to X < signed_max+1
7481 and X >= signed_max+1 because previous transformations. */
7483 {
7487 return fold
7491 }
7492 }
7493 }
7494 }
7496 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
7497 a MINUS_EXPR of a constant, we can convert it into a comparison with
7498 a revised constant as long as no overflow occurs. */
7510 /* Similarly for a NEGATE_EXPR. */
7519 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7520 for !=. Don't do this for ordered comparisons due to overflow. */
7526 /* If we are widening one operand of an integer comparison,
7527 see if the other operand is similarly being widened. Perhaps we
7528 can do the comparison in the narrower type. */
7542 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7543 constant, we can simplify it. */
7550 /* If we are comparing an ABS_EXPR with a constant, we can
7551 convert all the cases into explicit comparisons, but they may
7552 well not be faster than doing the ABS and one comparison.
7553 But ABS (X) <= C is a range comparison, which becomes a subtraction
7554 and a comparison, and is probably faster. */
7566 /* If this is an EQ or NE comparison with zero and ARG0 is
7567 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7568 two operations, but the latter can be done in one less insn
7569 on machines that have only two-operand insns or on which a
7570 constant cannot be the first operand. */
7573 {
7576 return
7584 integer_one_node)),
7585 arg1));
7588 return
7596 integer_one_node)),
7597 arg1));
7598 }
7600 /* If this is an NE or EQ comparison of zero against the result of a
7601 signed MOD operation whose second operand is a power of 2, make
7602 the MOD operation unsigned since it is simpler and equivalent. */
7611 {
7620 }
7622 /* If this is an NE comparison of zero with an AND of one, remove the
7623 comparison since the AND will give the correct value. */
7629 /* If we have (A & C) == C where C is a power of 2, convert this into
7630 (A & C) != 0. Similarly for NE_EXPR. */
7638 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7639 2, then fold the expression into shifts and logical operations. */
7644 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
7645 Similarly for NE_EXPR. */
7650 {
7651 tree dandnotc
7659 }
7661 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
7662 Similarly for NE_EXPR. */
7667 {
7668 tree candnotd
7675 }
7677 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7678 and similarly for >= into !=. */
7694 return
7702 /* Simplify comparison of something with itself. (For IEEE
7703 floating-point, we can only do some of these simplifications.) */
7705 {
7707 {
7722 /* For NE, we can only do this simplification if integer
7723 or we don't honor IEEE floating point NaNs. */
7727 /* ... fall through ... */
7733 }
7734 }
7736 /* If we are comparing an expression that just has comparisons
7737 of two integer values, arithmetic expressions of those comparisons,
7738 and constants, we can simplify it. There are only three cases
7739 to check: the two values can either be equal, the first can be
7740 greater, or the second can be greater. Fold the expression for
7741 those three values. Since each value must be 0 or 1, we have
7742 eight possibilities, each of which corresponds to the constant 0
7743 or 1 or one of the six possible comparisons.
7745 This handles common cases like (a > b) == 0 but also handles
7746 expressions like ((x > y) - (y > x)) > 0, which supposedly
7747 occur in macroized code. */
7750 {
7755 /* Don't handle degenerate cases here; they should already
7756 have been handled anyway. */
7765 {
7769 /* We can't just pass T to eval_subst in case cval1 or cval2
7770 was the same as ARG1. */
7772 tree high_result
7775 arg1));
7776 tree equal_result
7779 arg1));
7780 tree low_result
7783 arg1));
7785 /* All three of these results should be 0 or 1. Confirm they
7786 are. Then use those values to select the proper code
7787 to use. */
7795 {
7796 /* Make a 3-bit mask with the high-order bit being the
7797 value for `>', the next for '=', and the low for '<'. */
7801 {
7803 /* Always false. */
7824 /* Always true. */
7826 }
7831 else
7833 }
7834 }
7835 }
7837 /* If this is a comparison of a field, we may be able to simplify it. */
7842 /* Handle the constant case even without -O
7843 to make sure the warnings are given. */
7845 {
7849 }
7851 /* If this is a comparison of complex values and either or both sides
7852 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
7853 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
7854 This may prevent needless evaluations. */
7861 {
7874 type,
7877 }
7879 /* Optimize comparisons of strlen vs zero to a compare of the
7880 first character of the string vs zero. To wit,
7881 strlen(ptr) == 0 => *ptr == 0
7882 strlen(ptr) != 0 => *ptr != 0
7883 Other cases should reduce to one of these two (or a constant)
7884 due to the return value of strlen being unsigned. */
7888 {
7890 tree arglist;
7902 integer_zero_node));
7903 }
7905 /* Both ARG0 and ARG1 are known to be constants at this point. */
7910 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
7911 so all simple results must be passed through pedantic_non_lvalue. */
7913 {
7915 /* Only optimize constant conditions when the selected branch
7916 has the same type as the COND_EXPR. This avoids optimizing
7917 away "c ? x : throw", where the throw has a void type. */
7922 }
7926 /* If we have A op B ? A : C, we may be able to convert this to a
7927 simpler expression, depending on the operation and the values
7928 of B and C. Signed zeros prevent all of these transformations,
7929 for reasons given above each one. */
7935 {
7941 /* If we have A op 0 ? A : -A, consider applying the following
7942 transformations:
7944 A == 0? A : -A same as -A
7945 A != 0? A : -A same as A
7946 A >= 0? A : -A same as abs (A)
7947 A > 0? A : -A same as abs (A)
7948 A <= 0? A : -A same as -abs (A)
7949 A < 0? A : -A same as -abs (A)
7951 None of these transformations work for modes with signed
7952 zeros. If A is +/-0, the first two transformations will
7953 change the sign of the result (from +0 to -0, or vice
7954 versa). The last four will fix the sign of the result,
7955 even though the original expressions could be positive or
7956 negative, depending on the sign of A.
7958 Note that all these transformations are correct if A is
7959 NaN, since the two alternatives (A and -A) are also NaNs. */
7966 {
7990 }
7992 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
7993 A == 0 ? A : 0 is always 0 unless A is -0. Note that
7994 both transformations are correct when A is NaN: A != 0
7995 is then true, and A == 0 is false. */
7998 {
8003 }
8005 /* Try some transformations of A op B ? A : B.
8007 A == B? A : B same as B
8008 A != B? A : B same as A
8009 A >= B? A : B same as max (A, B)
8010 A > B? A : B same as max (B, A)
8011 A <= B? A : B same as min (A, B)
8012 A < B? A : B same as min (B, A)
8014 As above, these transformations don't work in the presence
8015 of signed zeros. For example, if A and B are zeros of
8016 opposite sign, the first two transformations will change
8017 the sign of the result. In the last four, the original
8018 expressions give different results for (A=+0, B=-0) and
8019 (A=-0, B=+0), but the transformed expressions do not.
8021 The first two transformations are correct if either A or B
8022 is a NaN. In the first transformation, the condition will
8023 be false, and B will indeed be chosen. In the case of the
8024 second transformation, the condition A != B will be true,
8025 and A will be chosen.
8027 The conversions to max() and min() are not correct if B is
8028 a number and A is not. The conditions in the original
8029 expressions will be false, so all four give B. The min()
8030 and max() versions would give a NaN instead. */
8033 {
8038 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
8040 {
8044 }
8047 {
8054 /* In C++ a ?: expression can be an lvalue, so put the
8055 operand which will be used if they are equal first
8056 so that we can convert this back to the
8057 corresponding COND_EXPR. */
8078 }
8079 }
8081 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
8082 we might still be able to simplify this. For example,
8083 if C1 is one less or one more than C2, this might have started
8084 out as a MIN or MAX and been transformed by this function.
8085 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
8091 {
8093 /* We can replace A with C1 in this case. */
8099 /* If C1 is C2 + 1, this is min(A, C2). */
8104 return pedantic_non_lvalue
8109 /* If C1 is C2 - 1, this is min(A, C2). */
8114 return pedantic_non_lvalue
8119 /* If C1 is C2 - 1, this is max(A, C2). */
8124 return pedantic_non_lvalue
8129 /* If C1 is C2 + 1, this is max(A, C2). */
8134 return pedantic_non_lvalue
8141 }
8142 }
8144 /* If the second operand is simpler than the third, swap them
8145 since that produces better jump optimization results. */
8148 {
8149 /* See if this can be inverted. If it can't, possibly because
8150 it was a floating-point inequality comparison, don't do
8151 anything. */
8157 }
8159 /* Convert A ? 1 : 0 to simply A. */
8162 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8163 call to fold will try to move the conversion inside
8164 a COND, which will recurse. In that case, the COND_EXPR
8165 is probably the best choice, so leave it alone. */
8169 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8170 over COND_EXPR in cases such as floating point comparisons. */
8177 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
8178 operation is simply A & 2. */
8190 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8197 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8201 {
8202 /* Only perform transformation if ARG0 is easily inverted. */
8207 }
8212 /* When pedantic, a compound expression can be neither an lvalue
8213 nor an integer constant expression. */
8216 /* Don't let (0, 0) be null pointer constant. */
8258 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8259 appropriate. */
8264 {
8268 tree arg01;
8279 {
8293 arg01));
8294 }
8297 }
8300 /* Check for a built-in function. */
8305 {
8309 }
8315 }
8317 #ifdef ENABLE_FOLD_CHECKING
8318 #undef fold
8324 /* When --enable-checking=fold, compute a digest of expr before
8325 and after actual fold call to see if fold did not accidentally
8326 change original expr. */
8328 tree
8330 {
8331 tree ret;
8334 htab_t ht;
8353 }
8355 void
8357 {
8360 htab_t ht;
8370 }
8372 static void
8374 {
8376 }
8378 static void
8380 {
8398 {
8399 /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified. */
8403 }
8405 {
8406 /* Allow DECL_ASSEMBLER_NAME to be modified. */
8410 }
8413 {
8414 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
8419 }
8426 {
8429 {
8443 }
8447 {
8458 }
8462 {
8468 }
8469 /* Fall through. */
8505 }
8506 }
8508 #endif
8510 /* Perform constant folding and related simplification of initializer
8511 expression EXPR. This behaves identically to "fold" but ignores
8512 potential run-time traps and exceptions that fold must preserve. */
8514 tree
8516 {
8520 tree result;
8533 }
8535 /* Determine if first argument is a multiple of second argument. Return 0 if
8536 it is not, or we cannot easily determined it to be.
8538 An example of the sort of thing we care about (at this point; this routine
8539 could surely be made more general, and expanded to do what the *_DIV_EXPR's
8540 fold cases do now) is discovering that
8542 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8544 is a multiple of
8546 SAVE_EXPR (J * 8)
8548 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
8550 This code also handles discovering that
8552 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8554 is a multiple of 8 so we don't have to worry about dealing with a
8555 possible remainder.
8557 Note that we *look* inside a SAVE_EXPR only to determine how it was
8558 calculated; it is not safe for fold to do much of anything else with the
8559 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
8560 at run time. For example, the latter example above *cannot* be implemented
8561 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
8562 evaluation time of the original SAVE_EXPR is not necessarily the same at
8563 the time the new expression is evaluated. The only optimization of this
8564 sort that would be valid is changing
8566 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
8568 divided by 8 to
8570 SAVE_EXPR (I) * SAVE_EXPR (J)
8572 (where the same SAVE_EXPR (J) is used in the original and the
8573 transformed version). */
8575 static int
8577 {
8585 {
8597 {
8601 /* const_binop may not detect overflow correctly,
8602 so check for it explicitly here. */
8608 size_one_node,
8612 }
8616 /* Can't handle conversions from non-integral or wider integral type. */
8622 /* .. fall through ... */
8638 }
8639 }
8641 /* Return true if `t' is known to be non-negative. */
8643 int
8645 {
8647 {
8662 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8663 both unsigned and at least 2 bits shorter than the result. */
8667 {
8672 {
8676 }
8677 }
8682 {
8683 /* x * x for floating point x is always non-negative. */
8688 }
8690 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8691 both unsigned and their total bits is shorter than the result. */
8695 {
8702 }
8731 {
8736 {
8740 {
8744 }
8745 }
8747 {
8753 }
8754 }
8782 {
8789 {
8790 #define CASE_BUILTIN_F(BUILT_IN_FN) \
8791 case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
8792 #define CASE_BUILTIN_I(BUILT_IN_FN) \
8793 case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:
8812 /* Always true. */
8838 /* True if the 1st argument is nonnegative. */
8842 /* True if the 1st OR 2nd arguments are nonnegative. */
8847 /* True if the 1st AND 2nd arguments are nonnegative. */
8852 /* True if the 2nd argument is nonnegative. */
8857 #undef CASE_BUILTIN_F
8858 #undef CASE_BUILTIN_I
8859 }
8860 }
8862 /* ... fall through ... */
8866 /* Truth values evaluate to 0 or 1, which is nonnegative. */
8868 }
8870 /* We don't know sign of `t', so be conservative and return false. */
8872 }
8874 /* Return true when T is an address and is known to be nonzero.
8875 For floating point we further ensure that T is not denormal.
8876 Similar logic is present in nonzero_address in rtlanal.h */
8878 static bool
8880 {
8883 /* Doing something useful for floating point would need more work. */
8888 {
8898 {
8899 /* With the presence of negative values it is hard
8900 to say something. */
8904 /* One of operands must be positive and the other non-negative. */
8907 }
8912 {
8915 }
8919 {
8925 }
8929 /* Weak declarations may link to NULL. */
8932 /* Constants and all other cases are never weak. */
8945 {
8946 /* When both operands are nonzero, then MAX must be too. */
8950 /* MAX where operand 0 is positive is positive. */
8952 }
8953 /* MAX where operand 1 is positive is positive. */
8974 }
8976 }
8978 /* Return true if `r' is known to be non-negative.
8979 Only handles constants at the moment. */
8981 int
8983 {
8985 {
8995 {
8997 rtx elt;
9002 {
9006 }
9009 }
9013 /* These are always nonnegative. */
9018 }
9019 }
9021 /* Return the tree for neg (ARG0) when ARG0 is known to be either
9022 an integer constant or real constant.
9024 TYPE is the type of the result. */
9026 static tree
9028 {
9032 {
9034 HOST_WIDE_INT high;
9045 }
9048 #ifdef ENABLE_CHECKING
9049 else
9051 #endif
9054 }
9056 /* Return the tree for abs (ARG0) when ARG0 is known to be either
9057 an integer constant or real constant.
9059 TYPE is the type of the result. */
9061 static tree
9063 {
9067 {
9068 /* If the value is unsigned, then the absolute value is
9069 the same as the ordinary value. */
9072 /* Similarly, if the value is non-negative. */
9075 /* If the value is negative, then the absolute value is
9076 its negation. */
9077 else
9078 {
9080 HOST_WIDE_INT high;
9092 }
9093 }
9095 {
9098 else
9100 }
9101 #ifdef ENABLE_CHECKING
9102 else
9104 #endif
9107 }
9109 /* Given CODE, a relational operator, the target type, TYPE and two
9110 constant operands OP0 and OP1, return the result of the
9111 relational operation. If the result is not a compile time
9112 constant, then return NULL_TREE. */
9114 static tree
9116 {
9117 tree tem;
9120 /* From here on, the only cases we handle are when the result is
9121 known to be a constant.
9123 To compute GT, swap the arguments and do LT.
9124 To compute GE, do LT and invert the result.
9125 To compute LE, swap the arguments, do LT and invert the result.
9126 To compute NE, do EQ and invert the result.
9128 Therefore, the code below must handle only EQ and LT. */
9131 {
9134 }
9136 /* Note that it is safe to invert for real values here because we
9137 will check below in the one case that it matters. */
9142 {
9145 }
9147 /* Compute a result for LT or EQ if args permit;
9148 Otherwise return T. */
9150 {
9153 else
9158 }
9164 /* Two real constants can be compared explicitly. */
9166 {
9167 /* If either operand is a NaN, the result is false with two
9168 exceptions: First, an NE_EXPR is true on NaNs, but that case
9169 is already handled correctly since we will be inverting the
9170 result for NE_EXPR. Second, if we had inverted a LE_EXPR
9171 or a GE_EXPR into a LT_EXPR, we must return true so that it
9172 will be inverted into false. */
9182 else
9186 }
9198 }