| blob | f9f3a64943363adb4121d8672a0f20fb2ce53745 |
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,
3 1999, 2000, 2001, 2002 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. */
60 HOST_WIDE_INT));
63 HOST_WIDE_INT *));
88 HOST_WIDE_INT *,
109 static tree fold_binary_op_with_conditional_arg
113 #if defined(HOST_EBCDIC)
114 /* bit 8 is significant in EBCDIC */
115 #define CHARMASK 0xff
116 #else
117 #define CHARMASK 0x7f
118 #endif
120 /* The following constants represent a bit based encoding of GCC's
121 comparison operators. This encoding simplifies transformations
122 on relational comparison operators, such as AND and OR. */
123 #define COMPCODE_FALSE 0
124 #define COMPCODE_LT 1
125 #define COMPCODE_EQ 2
126 #define COMPCODE_LE 3
127 #define COMPCODE_GT 4
128 #define COMPCODE_NE 5
129 #define COMPCODE_GE 6
130 #define COMPCODE_TRUE 7
132 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
133 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
134 and SUM1. Then this yields nonzero if overflow occurred during the
135 addition.
137 Overflow occurs if A and B have the same sign, but A and SUM differ in
138 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
139 sign. */
140 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
141 \f
142 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
143 We do that by representing the two-word integer in 4 words, with only
144 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
145 number. The value of the word is LOWPART + HIGHPART * BASE. */
147 #define LOWPART(x) \
148 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
149 #define HIGHPART(x) \
150 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
151 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
153 /* Unpack a two-word integer into 4 words.
154 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
155 WORDS points to the array of HOST_WIDE_INTs. */
157 static void
161 HOST_WIDE_INT hi;
162 {
167 }
169 /* Pack an array of 4 words into a two-word integer.
170 WORDS points to the array of words.
171 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
173 static void
178 {
181 }
182 \f
183 /* Make the integer constant T valid for its type by setting to 0 or 1 all
184 the bits in the constant that don't belong in the type.
186 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
187 nonzero, a signed overflow has already occurred in calculating T, so
188 propagate it.
190 Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
191 if it exists. */
193 int
195 tree t;
197 {
199 HOST_WIDE_INT high;
203 {
204 #ifdef CHECK_FLOAT_VALUE
206 overflow);
207 #endif
209 }
219 else
222 /* First clear all bits that are beyond the type's precision. */
225 ;
229 else
230 {
234 }
236 /* Unsigned types do not suffer sign extension or overflow unless they
237 are a sizetype. */
243 /* If the value's sign bit is set, extend the sign. */
251 {
252 /* Value is negative:
253 set to 1 all the bits that are outside this type's precision. */
257 else
258 {
262 }
263 }
265 /* Return nonzero if signed overflow occurred. */
266 return
269 }
270 \f
271 /* Add two doubleword integers with doubleword result.
272 Each argument is given as two `HOST_WIDE_INT' pieces.
273 One argument is L1 and H1; the other, L2 and H2.
274 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
276 int
282 {
284 HOST_WIDE_INT h;
292 }
294 /* Negate a doubleword integer with doubleword result.
295 Return nonzero if the operation overflows, assuming it's signed.
296 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
297 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
299 int
302 HOST_WIDE_INT h1;
305 {
307 {
311 }
312 else
313 {
317 }
318 }
319 \f
320 /* Multiply two doubleword integers with doubleword result.
321 Return nonzero if the operation overflows, assuming it's signed.
322 Each argument is given as two `HOST_WIDE_INT' pieces.
323 One argument is L1 and H1; the other, L2 and H2.
324 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
326 int
332 {
347 {
350 {
352 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
354 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
358 }
360 }
364 /* Check for overflow by calculating the top half of the answer in full;
365 it should agree with the low half's sign bit. */
368 {
371 }
373 {
376 }
378 }
379 \f
380 /* Shift the doubleword integer in L1, H1 left by COUNT places
381 keeping only PREC bits of result.
382 Shift right if COUNT is negative.
383 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
384 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
386 void
394 {
398 {
401 }
403 #ifdef SHIFT_COUNT_TRUNCATED
406 #endif
409 {
410 /* Shifting by the host word size is undefined according to the
411 ANSI standard, so we must handle this as a special case. */
414 }
416 {
419 }
420 else
421 {
425 }
427 /* Sign extend all bits that are beyond the precision. */
435 ;
437 {
440 }
441 else
442 {
446 }
447 }
449 /* Shift the doubleword integer in L1, H1 right by COUNT places
450 keeping only PREC bits of result. COUNT must be positive.
451 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
452 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
454 void
462 {
465 signmask = (arith
469 #ifdef SHIFT_COUNT_TRUNCATED
472 #endif
475 {
476 /* Shifting by the host word size is undefined according to the
477 ANSI standard, so we must handle this as a special case. */
480 }
482 {
485 }
486 else
487 {
491 }
493 /* Zero / sign extend all bits that are beyond the precision. */
496 {
499 }
501 ;
503 {
506 }
507 else
508 {
512 }
513 }
514 \f
515 /* Rotate the doubleword integer in L1, H1 left by COUNT places
516 keeping only PREC bits of result.
517 Rotate right if COUNT is negative.
518 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
520 void
527 {
539 }
541 /* Rotate the doubleword integer in L1, H1 left by COUNT places
542 keeping only PREC bits of result. COUNT must be positive.
543 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
545 void
552 {
564 }
565 \f
566 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
567 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
568 CODE is a tree code for a kind of division, one of
569 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
570 or EXACT_DIV_EXPR
571 It controls how the quotient is rounded to an integer.
572 Return nonzero if the operation overflows.
573 UNS nonzero says do unsigned division. */
575 int
582 HOST_WIDE_INT hnum_orig;
584 HOST_WIDE_INT hden_orig;
587 {
603 /* calculate quotient sign and convert operands to unsigned. */
605 {
607 {
609 /* (minimum integer) / (-1) is the only overflow case. */
613 }
615 {
618 }
619 }
624 /* This unsigned division rounds toward zero. */
627 }
631 /* hden != 0 already checked. */
636 }
646 /* Special code for when the divisor < BASE. */
648 {
649 /* hnum != 0 already checked. */
651 {
655 }
656 }
657 else
658 {
659 /* Full double precision division,
660 with thanks to Don Knuth's "Seminumerical Algorithms". */
664 /* Find the highest non-zero divisor digit. */
667 {
670 }
672 /* Insure that the first digit of the divisor is at least BASE/2.
673 This is required by the quotient digit estimation algorithm. */
680 {
684 }
689 {
694 }
695 }
699 /* Main loop */
701 {
702 /* Guess the next quotient digit, quo_est, by dividing the first
703 two remaining dividend digits by the high order quotient digit.
704 quo_est is never low and is at most 2 high. */
711 else
714 /* Refine quo_est so it's usually correct, and at most one high. */
719 quo_est--;
721 /* Try QUO_EST as the quotient digit, by multiplying the
722 divisor by QUO_EST and subtracting from the remaining dividend.
723 Keep in mind that QUO_EST is the I - 1st digit. */
727 {
733 }
735 /* If quo_est was high by one, then num[i] went negative and
736 we need to correct things. */
738 {
739 quo_est--;
742 {
746 }
749 }
751 /* Store the quotient digit. */
753 }
754 }
758 finish_up:
759 /* if result is negative, make it so. */
763 /* compute trial remainder: rem = num - (quo * den) */
769 {
778 {
779 /* quo = quo - 1; */
782 }
783 else
790 {
793 }
794 else
800 {
806 /* Get absolute values */
812 /* If (2 * abs (lrem) >= abs (lden)) */
821 {
823 /* quo = quo - 1; */
826 else
827 /* quo = quo + 1; */
830 }
831 else
833 }
838 }
840 /* compute true remainder: rem = num - (quo * den) */
845 }
846 \f
847 /* Given T, an expression, return the negation of T. Allow for T to be
848 null, in which case return null. */
850 static tree
852 tree t;
853 {
854 tree type;
855 tree tem;
864 {
877 /* - (A - B) -> B - A */
887 }
890 }
891 \f
892 /* Split a tree IN into a constant, literal and variable parts that could be
893 combined with CODE to make IN. "constant" means an expression with
894 TREE_CONSTANT but that isn't an actual constant. CODE must be a
895 commutative arithmetic operation. Store the constant part into *CONP,
896 the literal in *LITP and return the variable part. If a part isn't
897 present, set it to null. If the tree does not decompose in this way,
898 return the entire tree as the variable part and the other parts as null.
900 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
901 case, we negate an operand that was subtracted. Except if it is a
902 literal for which we use *MINUS_LITP instead.
904 If NEGATE_P is true, we are negating all of IN, again except a literal
905 for which we use *MINUS_LITP instead.
907 If IN is itself a literal or constant, return it as appropriate.
909 Note that we do not guarantee that any of the three values will be the
910 same type as IN, but they will have the same signedness and mode. */
912 static tree
914 tree in;
918 {
925 /* Strip any conversions that don't change the machine mode or signedness. */
932 /* We can associate addition and subtraction together (even
933 though the C standard doesn't say so) for integers because
934 the value is not affected. For reals, the value might be
935 affected, so we can't. */
938 {
944 /* First see if either of the operands is a literal, then a constant. */
955 /* If we haven't dealt with either operand, this is not a case we can
956 decompose. Otherwise, VAR is either of the ones remaining, if any. */
961 else
964 /* Now do any needed negations. */
971 }
974 else
978 {
985 }
988 }
990 /* Re-associate trees split by the above function. T1 and T2 are either
991 expressions to associate or null. Return the new expression, if any. If
992 we build an operation, do it in TYPE and with CODE. */
994 static tree
998 tree type;
999 {
1005 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1006 try to fold this since we will have infinite recursion. But do
1007 deal with any NEGATE_EXPRs. */
1010 {
1017 else
1019 }
1022 }
1023 \f
1024 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1025 to produce a new constant.
1027 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1029 static tree
1034 {
1038 HOST_WIDE_INT hi;
1040 HOST_WIDE_INT garbageh;
1041 tree t;
1044 int is_sizetype
1055 {
1075 /* It's unclear from the C standard whether shifts can overflow.
1076 The following code ignores overflow; perhaps a C standard
1077 interpretation ruling is needed. */
1107 /* This is a shortcut for a common special case. */
1112 {
1118 }
1120 /* ... fall through ... */
1124 {
1127 }
1130 {
1133 }
1140 /* This is a shortcut for a common special case. */
1145 {
1150 }
1152 /* ... fall through ... */
1168 else
1174 else
1180 }
1182 /* If this is for a sizetype, can be represented as one (signed)
1183 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1184 constants. */
1190 else
1191 {
1194 }
1197 = ((notrunc
1204 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1205 So check if force_fit_type truncated the value. */
1216 }
1218 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1219 constant. We assume ARG1 and ARG2 have the same data type, or at least
1220 are the same kind of constant and the same machine mode.
1222 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1224 static tree
1229 {
1237 {
1238 REAL_VALUE_TYPE d1;
1239 REAL_VALUE_TYPE d2;
1240 REAL_VALUE_TYPE value;
1241 tree t;
1246 /* If either operand is a NaN, just return it. Otherwise, set up
1247 for floating-point trap; we return an overflow. */
1257 value));
1267 }
1269 {
1275 tree t;
1278 {
1298 notrunc),
1304 notrunc));
1308 {
1309 tree magsquared
1313 notrunc);
1316 const_binop
1321 notrunc),
1323 notrunc),
1324 notrunc),
1326 const_binop
1331 notrunc),
1333 notrunc),
1334 notrunc),
1336 }
1341 }
1343 }
1345 }
1347 /* These are the hash table functions for the hash table of INTEGER_CST
1348 nodes of a sizetype. */
1350 /* Return the hash code code X, an INTEGER_CST. */
1352 static hashval_t
1355 {
1361 }
1363 /* Return non-zero if the value represented by *X (an INTEGER_CST tree node)
1364 is the same as that given by *Y, which is the same. */
1366 static int
1370 {
1378 }
1379 \f
1380 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1381 bits are given by NUMBER and of the sizetype represented by KIND. */
1383 tree
1385 HOST_WIDE_INT number;
1387 {
1389 }
1391 /* Likewise, but the desired type is specified explicitly. */
1395 htab_t size_htab;
1397 tree
1399 HOST_WIDE_INT number;
1400 tree type;
1401 {
1405 {
1408 }
1410 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1411 hash table, we return the value from the hash table. Otherwise, we
1412 place that in the hash table and make a new node for the next time. */
1421 {
1427 }
1428 else
1430 }
1432 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1433 is a tree code. The type of the result is taken from the operands.
1434 Both must be the same type integer type and it must be a size type.
1435 If the operands are constant, so is the result. */
1437 tree
1441 {
1448 /* Handle the special case of two integer constants faster. */
1450 {
1451 /* And some specific cases even faster than that. */
1460 /* Handle general case of two integer constants. */
1462 }
1468 }
1470 /* Given two values, either both of sizetype or both of bitsizetype,
1471 compute the difference between the two values. Return the value
1472 in signed type corresponding to the type of the operands. */
1474 tree
1477 {
1479 tree ctype;
1485 /* If the type is already signed, just do the simple thing. */
1492 /* If either operand is not a constant, do the conversions to the signed
1493 type and subtract. The hardware will do the right thing with any
1494 overflow in the subtraction. */
1499 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1500 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1501 overflow) and negate (which can't either). Special-case a result
1502 of zero while we're here. */
1507 else
1510 }
1511 \f
1513 /* Given T, a tree representing type conversion of ARG1, a constant,
1514 return a constant tree representing the result of conversion. */
1516 static tree
1518 tree t;
1519 tree arg1;
1520 {
1525 {
1527 {
1528 /* If we would build a constant wider than GCC supports,
1529 leave the conversion unfolded. */
1533 /* If we are trying to make a sizetype for a small integer, use
1534 size_int to pick up cached types to reduce duplicate nodes. */
1540 /* Given an integer constant, make new constant with new type,
1541 appropriately sign-extended or truncated. */
1545 /* Indicate an overflow if (1) ARG1 already overflowed,
1546 or (2) force_fit_type indicates an overflow.
1547 Tell force_fit_type that an overflow has already occurred
1548 if ARG1 is a too-large unsigned value and T is signed.
1549 But don't indicate an overflow if converting a pointer. */
1559 }
1561 {
1562 /* Don't initialize these, use assignments.
1563 Initialized local aggregates don't work on old compilers. */
1564 REAL_VALUE_TYPE x;
1565 REAL_VALUE_TYPE l;
1566 REAL_VALUE_TYPE u;
1577 /* See if X will be in range after truncation towards 0.
1578 To compensate for truncation, move the bounds away from 0,
1579 but reject if X exactly equals the adjusted bounds. */
1583 /* If X is a NaN, use zero instead and show we have an overflow.
1584 Otherwise, range check. */
1588 && !no_upper_bound
1592 {
1596 }
1602 }
1604 }
1606 {
1610 {
1612 {
1613 /* We make a copy of ARG1 so that we don't modify an
1614 existing constant tree. */
1618 }
1629 }
1630 }
1633 }
1634 \f
1635 /* Return an expr equal to X but certainly not valid as an lvalue. */
1637 tree
1639 tree x;
1640 {
1641 tree result;
1643 /* These things are certainly not lvalues. */
1654 }
1656 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
1657 Zero means allow extended lvalues. */
1661 /* When pedantic, return an expr equal to X but certainly not valid as a
1662 pedantic lvalue. Otherwise, return X. */
1664 tree
1666 tree x;
1667 {
1670 else
1672 }
1673 \f
1674 /* Given a tree comparison code, return the code that is the logical inverse
1675 of the given code. It is not safe to do this for floating-point
1676 comparisons, except for NE_EXPR and EQ_EXPR. */
1678 static enum tree_code
1681 {
1683 {
1698 }
1699 }
1701 /* Similar, but return the comparison that results if the operands are
1702 swapped. This is safe for floating-point. */
1704 static enum tree_code
1707 {
1709 {
1723 }
1724 }
1727 /* Convert a comparison tree code from an enum tree_code representation
1728 into a compcode bit-based encoding. This function is the inverse of
1729 compcode_to_comparison. */
1731 static int
1734 {
1736 {
1751 }
1752 }
1754 /* Convert a compcode bit-based encoding of a comparison operator back
1755 to GCC's enum tree_code representation. This function is the
1756 inverse of comparison_to_compcode. */
1758 static enum tree_code
1761 {
1763 {
1778 }
1779 }
1781 /* Return nonzero if CODE is a tree code that represents a truth value. */
1783 static int
1786 {
1791 }
1792 \f
1793 /* Return nonzero if two operands are necessarily equal.
1794 If ONLY_CONST is non-zero, only return non-zero for constants.
1795 This function tests whether the operands are indistinguishable;
1796 it does not test whether they are equal using C's == operation.
1797 The distinction is important for IEEE floating point, because
1798 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
1799 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
1801 int
1805 {
1806 /* If both types don't have the same signedness, then we can't consider
1807 them equal. We must check this before the STRIP_NOPS calls
1808 because they may change the signedness of the arguments. */
1816 /* This is needed for conversions and for COMPONENT_REF.
1817 Might as well play it safe and always test this. */
1823 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
1824 We don't care about side effects in that case because the SAVE_EXPR
1825 takes care of that for us. In all other cases, two expressions are
1826 equal if they have no side effects. If we have two identical
1827 expressions with side effects that should be treated the same due
1828 to the only side effects being identical SAVE_EXPR's, that will
1829 be detected in the recursive calls below. */
1835 /* Next handle constant cases, those for which we can return 1 even
1836 if ONLY_CONST is set. */
1839 {
1852 {
1862 {
1867 }
1870 }
1874 only_const)
1876 only_const));
1889 }
1895 {
1897 /* Two conversions are equal only if signedness and modes match. */
1913 /* For commutative ops, allow the other order. */
1926 /* If either of the pointer (or reference) expressions we are dereferencing
1927 contain a side effect, these cannot be equal. */
1933 {
1955 }
1964 }
1965 }
1966 \f
1967 /* Similar to operand_equal_p, but see if ARG0 might have been made by
1968 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
1970 When in doubt, return 0. */
1972 static int
1975 tree other;
1976 {
1988 /* Discard any conversions that don't change the modes of ARG0 and ARG1
1989 and see if the inner values are the same. This removes any
1990 signedness comparison, which doesn't matter here. */
1997 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
1998 actual comparison operand, ARG0.
2000 First throw away any conversions to wider types
2001 already present in the operands. */
2010 {
2013 /* Make sure shorter operand is extended the right way
2014 to match the longer operand. */
2020 }
2023 }
2024 \f
2025 /* See if ARG is an expression that is either a comparison or is performing
2026 arithmetic on comparisons. The comparisons must only be comparing
2027 two different values, which will be stored in *CVAL1 and *CVAL2; if
2028 they are non-zero it means that some operands have already been found.
2029 No variables may be used anywhere else in the expression except in the
2030 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2031 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2033 If this is true, return 1. Otherwise, return zero. */
2035 static int
2037 tree arg;
2040 {
2044 /* We can handle some of the 'e' cases here. */
2054 {
2055 /* If we've already found a CVAL1 or CVAL2, this expression is
2056 two complex to handle. */
2062 }
2065 {
2088 /* First see if we can handle the first operand, then the second. For
2089 the second operand, we know *CVAL1 can't be zero. It must be that
2090 one side of the comparison is each of the values; test for the
2091 case where this isn't true by failing if the two operands
2092 are the same. */
2101 ;
2105 ;
2106 else
2110 ;
2114 ;
2115 else
2122 }
2123 }
2124 \f
2125 /* ARG is a tree that is known to contain just arithmetic operations and
2126 comparisons. Evaluate the operations in the tree substituting NEW0 for
2127 any occurrence of OLD0 as an operand of a comparison and likewise for
2128 NEW1 and OLD1. */
2130 static tree
2132 tree arg;
2134 {
2139 /* We can handle some of the 'e' cases here. */
2147 {
2162 {
2179 }
2180 /* fall through - ??? */
2183 {
2187 /* We need to check both for exact equality and tree equality. The
2188 former will be true if the operand has a side-effect. In that
2189 case, we know the operand occurred exactly once. */
2202 }
2206 }
2207 }
2208 \f
2209 /* Return a tree for the case when the result of an expression is RESULT
2210 converted to TYPE and OMITTED was previously an operand of the expression
2211 but is now not needed (e.g., we folded OMITTED * 0).
2213 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2214 the conversion of RESULT to TYPE. */
2216 static tree
2219 {
2226 }
2228 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2230 static tree
2233 {
2240 }
2241 \f
2242 /* Return a simplified tree node for the truth-negation of ARG. This
2243 never alters ARG itself. We assume that ARG is an operation that
2244 returns a truth value (0 or 1). */
2246 tree
2248 tree arg;
2249 {
2256 /* If this is a comparison, we can simply invert it, except for
2257 floating-point non-equality comparisons, in which case we just
2258 enclose a TRUTH_NOT_EXPR around what we have. */
2261 {
2263 && !flag_unsafe_math_optimizations
2267 else
2270 }
2273 {
2288 /* Here we can invert either operand. We invert the first operand
2289 unless the second operand is a TRUTH_NOT_EXPR in which case our
2290 result is the XOR of the first operand with the inside of the
2291 negation of the second operand. */
2296 else
2351 }
2355 }
2357 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2358 operands are another bit-wise operation with a common input. If so,
2359 distribute the bit operations to save an operation and possibly two if
2360 constants are involved. For example, convert
2361 (A | B) & (A | C) into A | (B & C)
2362 Further simplification will occur if B and C are constants.
2364 If this optimization cannot be done, 0 will be returned. */
2366 static tree
2369 tree type;
2371 {
2372 tree common;
2382 {
2386 }
2388 {
2392 }
2394 {
2398 }
2400 {
2404 }
2405 else
2410 }
2411 \f
2412 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2413 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2415 static tree
2417 tree inner;
2418 tree type;
2421 {
2428 }
2430 /* Optimize a bit-field compare.
2432 There are two cases: First is a compare against a constant and the
2433 second is a comparison of two items where the fields are at the same
2434 bit position relative to the start of a chunk (byte, halfword, word)
2435 large enough to contain it. In these cases we can avoid the shift
2436 implicit in bitfield extractions.
2438 For constants, we emit a compare of the shifted constant with the
2439 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2440 compared. For two fields at the same position, we do the ANDs with the
2441 similar mask and compare the result of the ANDs.
2443 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2444 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2445 are the left and right operands of the comparison, respectively.
2447 If the optimization described above can be done, we return the resulting
2448 tree. Otherwise we return zero. */
2450 static tree
2453 tree compare_type;
2455 {
2464 tree mask;
2465 tree offset;
2467 /* Get all the information about the extractions being done. If the bit size
2468 if the same as the size of the underlying object, we aren't doing an
2469 extraction at all and so can do nothing. We also don't want to
2470 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2471 then will no longer be able to replace it. */
2479 {
2480 /* If this is not a constant, we can only do something if bit positions,
2481 sizes, and signedness are the same. */
2489 }
2491 /* See if we can find a mode to refer to this field. We should be able to,
2492 but fail if we can't. */
2501 /* Set signed and unsigned types of the precision of this mode for the
2502 shifts below. */
2506 /* Compute the bit position and size for the new reference and our offset
2507 within it. If the new reference is the same size as the original, we
2508 won't optimize anything, so return zero. */
2518 /* Make the mask to be used against the extracted field. */
2528 /* If not comparing with constant, just rework the comparison
2529 and return. */
2534 mask),
2538 mask));
2540 /* Otherwise, we are handling the constant case. See if the constant is too
2541 big for the field. Warn and return a tree of for 0 (false) if so. We do
2542 this not only for its own sake, but to avoid having to test for this
2543 error case below. If we didn't, we might generate wrong code.
2545 For unsigned fields, the constant shifted right by the field length should
2546 be all zero. For signed fields, the high-order bits should agree with
2547 the sign bit. */
2550 {
2554 {
2560 }
2561 }
2562 else
2563 {
2567 {
2573 }
2574 }
2576 /* Single-bit compares should always be against zero. */
2578 {
2581 }
2583 /* Make a new bitfield reference, shift the constant over the
2584 appropriate number of bits and mask it with the computed mask
2585 (in case this was a signed field). If we changed it, make a new one. */
2588 {
2591 }
2601 rhs);
2602 }
2603 \f
2604 /* Subroutine for fold_truthop: decode a field reference.
2606 If EXP is a comparison reference, we return the innermost reference.
2608 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
2609 set to the starting bit number.
2611 If the innermost field can be completely contained in a mode-sized
2612 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
2614 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
2615 otherwise it is not changed.
2617 *PUNSIGNEDP is set to the signedness of the field.
2619 *PMASK is set to the mask used. This is either contained in a
2620 BIT_AND_EXPR or derived from the width of the field.
2622 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
2624 Return 0 if this is not a component reference or is one that we can't
2625 do anything with. */
2627 static tree
2630 tree exp;
2636 {
2639 tree unsigned_type;
2642 /* All the optimizations using this function assume integer fields.
2643 There are problems with FP fields since the type_for_size call
2644 below can fail for, e.g., XFmode. */
2651 {
2657 }
2666 /* Compute the mask to access the bitfield. */
2676 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
2684 }
2686 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
2687 bit positions. */
2689 static int
2691 tree mask;
2693 {
2696 tree tmask;
2701 return
2708 }
2710 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
2711 represents the sign bit of EXP's type. If EXP represents a sign
2712 or zero extension, also test VAL against the unextended type.
2713 The return value is the (sub)expression whose sign bit is VAL,
2714 or NULL_TREE otherwise. */
2716 static tree
2718 tree exp;
2719 tree val;
2720 {
2722 HOST_WIDE_INT hi;
2724 tree t;
2726 /* Tree EXP must have a integral type. */
2731 /* Tree VAL must be an integer constant. */
2738 {
2741 }
2742 else
2743 {
2746 }
2751 /* Handle extension from a narrower type. */
2757 }
2759 /* Subroutine for fold_truthop: determine if an operand is simple enough
2760 to be evaluated unconditionally. */
2762 static int
2764 tree exp;
2765 {
2766 /* Strip any conversions that don't change the machine mode. */
2778 /* Don't regard global variables as simple. They may be
2779 allocated in ways unknown to the compiler (shared memory,
2780 #pragma weak, etc). */
2783 /* Loading a static variable is unduly expensive, but global
2784 registers aren't expensive. */
2786 }
2787 \f
2788 /* The following functions are subroutines to fold_range_test and allow it to
2789 try to change a logical combination of comparisons into a range test.
2791 For example, both
2792 X == 2 || X == 3 || X == 4 || X == 5
2793 and
2794 X >= 2 && X <= 5
2795 are converted to
2796 (unsigned) (X - 2) <= 3
2798 We describe each set of comparisons as being either inside or outside
2799 a range, using a variable named like IN_P, and then describe the
2800 range with a lower and upper bound. If one of the bounds is omitted,
2801 it represents either the highest or lowest value of the type.
2803 In the comments below, we represent a range by two numbers in brackets
2804 preceded by a "+" to designate being inside that range, or a "-" to
2805 designate being outside that range, so the condition can be inverted by
2806 flipping the prefix. An omitted bound is represented by a "-". For
2807 example, "- [-, 10]" means being outside the range starting at the lowest
2808 possible value and ending at 10, in other words, being greater than 10.
2809 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
2810 always false.
2812 We set up things so that the missing bounds are handled in a consistent
2813 manner so neither a missing bound nor "true" and "false" need to be
2814 handled using a special case. */
2816 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
2817 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
2818 and UPPER1_P are nonzero if the respective argument is an upper bound
2819 and zero for a lower. TYPE, if nonzero, is the type of the result; it
2820 must be specified for a comparison. ARG1 will be converted to ARG0's
2821 type if both are specified. */
2823 static tree
2826 tree type;
2829 {
2830 tree tem;
2834 /* If neither arg represents infinity, do the normal operation.
2835 Else, if not a comparison, return infinity. Else handle the special
2836 comparison rules. Note that most of the cases below won't occur, but
2837 are handled for consistency. */
2840 {
2845 }
2850 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
2851 for neither. In real maths, we cannot assume open ended ranges are
2852 the same. But, this is computer arithmetic, where numbers are finite.
2853 We can therefore make the transformation of any unbounded range with
2854 the value Z, Z being greater than any representable number. This permits
2855 us to treat unbounded ranges as equal. */
2859 {
2880 }
2883 }
2884 \f
2885 /* Given EXP, a logical expression, set the range it is testing into
2886 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
2887 actually being tested. *PLOW and *PHIGH will be made of the same type
2888 as the returned expression. If EXP is not a comparison, we will most
2889 likely not be returning a useful value and range. */
2891 static tree
2893 tree exp;
2896 {
2903 /* Start with simply saying "EXP != 0" and then look at the code of EXP
2904 and see if we can refine the range. Some of the cases below may not
2905 happen, but it doesn't seem worth worrying about this. We "continue"
2906 the outer loop when we've changed something; otherwise we "break"
2907 the switch, which will "break" the while. */
2912 {
2916 {
2927 }
2929 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
2930 lose a cast by accident. */
2935 {
2942 /* We can only do something if the range is testing for zero
2943 and if the second operand is an integer constant. Note that
2944 saying something is "in" the range we make is done by
2945 complementing IN_P since it will set in the initial case of
2946 being not equal to zero; "out" is leaving it alone. */
2953 {
2974 }
2978 /* If this is an unsigned comparison, we also know that EXP is
2979 greater than or equal to zero. We base the range tests we make
2980 on that fact, so we record it here so we can parse existing
2981 range tests. */
2983 {
2986 NULL_TREE))
2991 /* If the high bound is missing, but we
2992 have a low bound, reverse the range so
2993 it goes from zero to the low bound minus 1. */
2995 {
3000 }
3001 }
3005 /* (-x) IN [a,b] -> x in [-b, -a] */
3015 /* ~ X -> -X - 1 */
3024 /* If EXP is signed, any overflow in the computation is undefined,
3025 so we don't worry about it so long as our computations on
3026 the bounds don't overflow. For unsigned, overflow is defined
3027 and this is exactly the right thing. */
3036 /* Check for an unsigned range which has wrapped around the maximum
3037 value thus making n_high < n_low, and normalize it. */
3039 {
3045 /* If the range is of the form +/- [ x+1, x ], we won't
3046 be able to normalize it. But then, it represents the
3047 whole range or the empty set, so make it
3048 +/- [ -, - ]. */
3052 else
3054 }
3055 else
3078 /* If we're converting from an unsigned to a signed type,
3079 we will be doing the comparison as unsigned. The tests above
3080 have already verified that LOW and HIGH are both positive.
3082 So we have to make sure that the original unsigned value will
3083 be interpreted as positive. */
3085 {
3088 tree high_positive;
3090 /* A range without an upper bound is, naturally, unbounded.
3091 Since convert would have cropped a very large value, use
3092 the max value for the destination type. */
3093 high_positive
3101 /* If the low bound is specified, "and" the range with the
3102 range for which the original unsigned value will be
3103 positive. */
3105 {
3109 high_positive))
3113 }
3114 else
3115 {
3116 /* Otherwise, "or" the range with the range of the input
3117 that will be interpreted as negative. */
3121 high_positive))
3125 }
3126 }
3134 }
3137 }
3139 /* If EXP is a constant, we can evaluate whether this is true or false. */
3141 {
3148 }
3152 }
3153 \f
3154 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3155 type, TYPE, return an expression to test if EXP is in (or out of, depending
3156 on IN_P) the range. */
3158 static tree
3160 tree type;
3161 tree exp;
3164 {
3166 tree value;
3185 {
3187 {
3191 }
3193 }
3195 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3197 {
3199 HOST_WIDE_INT hi;
3204 {
3207 }
3208 else
3209 {
3212 }
3215 {
3217 {
3220 }
3223 }
3224 }
3233 }
3234 \f
3235 /* Given two ranges, see if we can merge them into one. Return 1 if we
3236 can, 0 if we can't. Set the output range into the specified parameters. */
3238 static int
3244 {
3248 tree tem;
3258 /* Make range 0 be the range that starts first, or ends last if they
3259 start at the same value. Swap them if it isn't. */
3262 || (lowequal
3265 {
3269 }
3271 /* Now flag two cases, whether the ranges are disjoint or whether the
3272 second range is totally subsumed in the first. Note that the tests
3273 below are simplified by the ones above. */
3279 /* We now have four cases, depending on whether we are including or
3280 excluding the two ranges. */
3282 {
3283 /* If they don't overlap, the result is false. If the second range
3284 is a subset it is the result. Otherwise, the range is from the start
3285 of the second to the end of the first. */
3290 else
3292 }
3295 {
3296 /* If they don't overlap, the result is the first range. If they are
3297 equal, the result is false. If the second range is a subset of the
3298 first, and the ranges begin at the same place, we go from just after
3299 the end of the first range to the end of the second. If the second
3300 range is not a subset of the first, or if it is a subset and both
3301 ranges end at the same place, the range starts at the start of the
3302 first range and ends just before the second range.
3303 Otherwise, we can't describe this as a single range. */
3309 {
3313 }
3315 {
3319 }
3320 else
3322 }
3325 {
3326 /* If they don't overlap, the result is the second range. If the second
3327 is a subset of the first, the result is false. Otherwise,
3328 the range starts just after the first range and ends at the
3329 end of the second. */
3334 else
3335 {
3339 }
3340 }
3342 else
3343 {
3344 /* The case where we are excluding both ranges. Here the complex case
3345 is if they don't overlap. In that case, the only time we have a
3346 range is if they are adjacent. If the second is a subset of the
3347 first, the result is the first. Otherwise, the range to exclude
3348 starts at the beginning of the first range and ends at the end of the
3349 second. */
3351 {
3358 else
3360 }
3363 else
3365 }
3369 }
3370 \f
3371 /* EXP is some logical combination of boolean tests. See if we can
3372 merge it into some range test. Return the new tree if so. */
3374 static tree
3376 tree exp;
3377 {
3384 tree tem;
3386 /* If this is an OR operation, invert both sides; we will invert
3387 again at the end. */
3391 /* If both expressions are the same, if we can merge the ranges, and we
3392 can build the range test, return it or it inverted. If one of the
3393 ranges is always true or always false, consider it to be the same
3394 expression as the other. */
3404 /* On machines where the branch cost is expensive, if this is a
3405 short-circuited branch and the underlying object on both sides
3406 is the same, make a non-short-circuit operation. */
3412 {
3413 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3414 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3415 which cases we can't do this. */
3424 {
3436 }
3437 }
3440 }
3441 \f
3442 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3443 bit value. Arrange things so the extra bits will be set to zero if and
3444 only if C is signed-extended to its full width. If MASK is nonzero,
3445 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3447 static tree
3449 tree c;
3452 tree mask;
3453 {
3456 tree temp;
3461 /* We work by getting just the sign bit into the low-order bit, then
3462 into the high-order bit, then sign-extend. We then XOR that value
3463 with C. */
3467 /* We must use a signed type in order to get an arithmetic right shift.
3468 However, we must also avoid introducing accidental overflows, so that
3469 a subsequent call to integer_zerop will work. Hence we must
3470 do the type conversion here. At this point, the constant is either
3471 zero or one, and the conversion to a signed type can never overflow.
3472 We could get an overflow if this conversion is done anywhere else. */
3480 /* If necessary, convert the type back to match the type of C. */
3485 }
3486 \f
3487 /* Find ways of folding logical expressions of LHS and RHS:
3488 Try to merge two comparisons to the same innermost item.
3489 Look for range tests like "ch >= '0' && ch <= '9'".
3490 Look for combinations of simple terms on machines with expensive branches
3491 and evaluate the RHS unconditionally.
3493 For example, if we have p->a == 2 && p->b == 4 and we can make an
3494 object large enough to span both A and B, we can do this with a comparison
3495 against the object ANDed with the a mask.
3497 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3498 operations to do this with one comparison.
3500 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3501 function and the one above.
3503 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3504 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3506 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3507 two operands.
3509 We return the simplified tree or 0 if no optimization is possible. */
3511 static tree
3515 {
3516 /* If this is the "or" of two comparisons, we can do something if
3517 the comparisons are NE_EXPR. If this is the "and", we can do something
3518 if the comparisons are EQ_EXPR. I.e.,
3519 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3521 WANTED_CODE is this operation code. For single bit fields, we can
3522 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3523 comparison for one-bit fields. */
3543 /* Start by getting the comparison codes. Fail if anything is volatile.
3544 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3545 it were surrounded with a NE_EXPR. */
3570 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3574 {
3579 {
3587 }
3590 {
3599 }
3600 else
3610 }
3612 /* If the RHS can be evaluated unconditionally and its operands are
3613 simple, it wins to evaluate the RHS unconditionally on machines
3614 with expensive branches. In this case, this isn't a comparison
3615 that can be merged. Avoid doing this if the RHS is a floating-point
3616 comparison since those can trap. */
3622 {
3623 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
3631 integer_zero_node);
3633 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
3641 integer_zero_node);
3644 }
3646 /* See if the comparisons can be merged. Then get all the parameters for
3647 each side. */
3671 /* It must be true that the inner operation on the lhs of each
3672 comparison must be the same if we are to be able to do anything.
3673 Then see if we have constants. If not, the same must be true for
3674 the rhs's. */
3685 else
3688 /* If either comparison code is not correct for our logical operation,
3689 fail. However, we can convert a one-bit comparison against zero into
3690 the opposite comparison against that bit being set in the field. */
3694 {
3696 {
3697 /* Make the left operand unsigned, since we are only interested
3698 in the value of one bit. Otherwise we are doing the wrong
3699 thing below. */
3702 }
3703 else
3705 }
3707 /* This is analogous to the code for l_const above. */
3709 {
3711 {
3714 }
3715 else
3717 }
3719 /* See if we can find a mode that contains both fields being compared on
3720 the left. If we can't, fail. Otherwise, update all constants and masks
3721 to be relative to a field of that size. */
3726 volatilep);
3736 {
3739 }
3747 {
3755 {
3759 wanted_code == NE_EXPR
3761 }
3762 }
3764 {
3772 {
3776 wanted_code == NE_EXPR
3778 }
3779 }
3781 /* If the right sides are not constant, do the same for it. Also,
3782 disallow this optimization if a size or signedness mismatch occurs
3783 between the left and right sides. */
3785 {
3788 /* Make sure the two fields on the right
3789 correspond to the left without being swapped. */
3797 volatilep);
3807 {
3810 }
3817 /* Make a mask that corresponds to both fields being compared.
3818 Do this for both items being compared. If the operands are the
3819 same size and the bits being compared are in the same position
3820 then we can do this by masking both and comparing the masked
3821 results. */
3825 {
3837 }
3839 /* There is still another way we can do something: If both pairs of
3840 fields being compared are adjacent, we may be able to make a wider
3841 field containing them both.
3843 Note that we still must mask the lhs/rhs expressions. Furthermore,
3844 the mask must be shifted to account for the shift done by
3845 make_bit_field_ref. */
3850 {
3851 tree type;
3863 /* Convert to the smaller type before masking out unwanted bits. */
3866 {
3868 {
3872 }
3874 {
3878 }
3879 }
3888 }
3891 }
3893 /* Handle the case of comparisons with constants. If there is something in
3894 common between the masks, those bits of the constants must be the same.
3895 If not, the condition is always false. Test for this to avoid generating
3896 incorrect code below. */
3901 {
3903 {
3906 }
3907 else
3908 {
3911 }
3912 }
3914 /* Construct the expression we will return. First get the component
3915 reference we will make. Unless the mask is all ones the width of
3916 that field, perform the mask operation. Then compare with the
3917 merged constant. */
3927 }
3928 \f
3929 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
3930 constant. */
3932 static tree
3934 tree t;
3935 {
3940 tree minmax_const;
3942 tree inner;
3952 /* If something does not permit us to optimize, return the original tree. */
3960 /* Now handle all the various comparison codes. We only handle EQ_EXPR
3961 and GT_EXPR, doing the rest with recursive calls using logical
3962 simplifications. */
3964 {
3966 return
3970 return
3972 optimize_minmax_comparison
3974 optimize_minmax_comparison
3979 /* MAX (X, 0) == 0 -> X <= 0 */
3983 /* MAX (X, 0) == 5 -> X == 5 */
3987 /* MAX (X, 0) == -1 -> false */
3991 /* MIN (X, 0) == 0 -> X >= 0 */
3995 /* MIN (X, 0) == 5 -> false */
3998 else
3999 /* MIN (X, 0) == -1 -> X == -1 */
4004 /* MAX (X, 0) > 0 -> X > 0
4005 MAX (X, 0) > 5 -> X > 5 */
4009 /* MAX (X, 0) > -1 -> true */
4013 /* MIN (X, 0) > 0 -> false
4014 MIN (X, 0) > 5 -> false */
4017 else
4018 /* MIN (X, 0) > -1 -> X > -1 */
4023 }
4024 }
4025 \f
4026 /* T is an integer expression that is being multiplied, divided, or taken a
4027 modulus (CODE says which and what kind of divide or modulus) by a
4028 constant C. See if we can eliminate that operation by folding it with
4029 other operations already in T. WIDE_TYPE, if non-null, is a type that
4030 should be used for the computation if wider than our type.
4032 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4033 (X * 2) + (Y * 4). We must, however, be assured that either the original
4034 expression would not overflow or that overflow is undefined for the type
4035 in the language in question.
4037 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4038 the machine has a multiply-accumulate insn or that this is part of an
4039 addressing calculation.
4041 If we return a non-null expression, it is an equivalent form of the
4042 original computation, but need not be in the original type. */
4044 static tree
4046 tree t;
4047 tree c;
4049 tree wide_type;
4050 {
4060 /* Don't deal with constants of zero here; they confuse the code below. */
4070 /* Note that we need not handle conditional operations here since fold
4071 already handles those cases. So just do arithmetic here. */
4073 {
4075 /* For a constant, we can always simplify if we are a multiply
4076 or (for divide and modulus) if it is a multiple of our constant. */
4083 /* If op0 is an expression ... */
4088 /* ... and is unsigned, and its type is smaller than ctype,
4089 then we cannot pass through as widening. */
4095 /* ... or its type is larger than ctype,
4096 then we cannot pass through this truncation. */
4101 /* Pass the constant down and see if we can make a simplification. If
4102 we can, replace this expression with the inner simplification for
4103 possible later conversion to our or some other type. */
4115 /* If widening the type changes the signedness, then we can't perform
4116 this optimization as that changes the result. */
4120 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4123 {
4129 }
4139 /* If this has not been evaluated and the operand has no side effects,
4140 we can see if we can do something inside it and make a new one.
4141 Note that this test is overly conservative since we can do this
4142 if the only reason it had side effects is that it was another
4143 similar SAVE_EXPR, but that isn't worth bothering with. */
4146 wide_type)))
4147 {
4154 }
4158 /* If the second operand is constant, this is a multiplication
4159 or floor division, by a power of two, so we can treat it that
4160 way unless the multiplier or divisor overflows. */
4162 /* const_binop may not detect overflow correctly,
4163 so check for it explicitly here. */
4177 /* See if we can eliminate the operation on both sides. If we can, we
4178 can return a new PLUS or MINUS. If we can't, the only remaining
4179 cases where we can do anything are if the second operand is a
4180 constant. */
4185 /* If not multiplication, we can only do this if either operand
4186 is divisible by c. */
4192 /* If this was a subtraction, negate OP1 and set it to be an addition.
4193 This simplifies the logic below. */
4200 /* If either OP1 or C are negative, this optimization is not safe for
4201 some of the division and remainder types while for others we need
4202 to change the code. */
4204 {
4212 }
4214 /* If it's a multiply or a division/modulus operation of a multiple
4215 of our constant, do the operation and verify it doesn't overflow. */
4218 {
4222 }
4223 else
4226 /* If we have an unsigned type is not a sizetype, we cannot widen
4227 the operation since it will change the result if the original
4228 computation overflowed. */
4234 /* If we were able to eliminate our operation from the first side,
4235 apply our operation to the second side and reform the PLUS. */
4239 /* The last case is if we are a multiply. In that case, we can
4240 apply the distributive law to commute the multiply and addition
4241 if the multiplication of the constants doesn't overflow. */
4246 op1));
4251 /* We have a special case here if we are doing something like
4252 (C * 8) % 4 since we know that's zero. */
4259 /* ... fall through ... */
4263 /* If we can extract our operation from the LHS, do so and return a
4264 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4265 do something only if the second operand is a constant. */
4277 /* If these are the same operation types, we can associate them
4278 assuming no overflow. */
4285 /* If these operations "cancel" each other, we have the main
4286 optimizations of this pass, which occur when either constant is a
4287 multiple of the other, in which case we replace this with either an
4288 operation or CODE or TCODE.
4290 If we have an unsigned type that is not a sizetype, we cannot do
4291 this since it will change the result if the original computation
4292 overflowed. */
4299 {
4310 }
4315 }
4318 }
4319 \f
4320 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4321 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4322 that we may sometimes modify the tree. */
4324 static tree
4326 tree t;
4327 tree s;
4328 {
4331 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4336 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4337 don't bother handling any other types. */
4339 {
4343 }
4348 {
4351 }
4354 }
4355 \f
4356 /* Return a node which has the indicated constant VALUE (either 0 or
4357 1), and is of the indicated TYPE. */
4359 static tree
4362 tree type;
4363 {
4368 integer_zero_node);
4369 else
4370 {
4375 }
4376 }
4378 /* Utility function for the following routine, to see how complex a nesting of
4379 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4380 we don't care (to avoid spending too much time on complex expressions.). */
4382 static int
4384 tree expr;
4386 {
4397 }
4399 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4400 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4401 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4402 expression, and ARG to `a'. If COND_FIRST_P is non-zero, then the
4403 COND is the first argument to CODE; otherwise (as in the example
4404 given here), it is the second argument. TYPE is the type of the
4405 original expression. */
4407 static tree
4410 tree type;
4411 tree cond;
4412 tree arg;
4414 {
4418 /* In the end, we'll produce a COND_EXPR. Both arms of the
4419 conditional expression will be binary operations. The left-hand
4420 side of the expression to be executed if the condition is true
4421 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4422 of the expression to be executed if the condition is true will be
4423 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4424 but apply to the expression to be executed if the conditional is
4425 false. */
4430 /* These are the codes to use for the left-hand side and right-hand
4431 side of the COND_EXPR. Normally, they are the same as CODE. */
4434 /* And these are the types of the expressions. */
4439 {
4443 }
4444 else
4445 {
4449 }
4452 {
4456 /* If this operand throws an expression, then it does not make
4457 sense to try to perform a logical or arithmetic operation
4458 involving it. Instead of building `a + throw 3' for example,
4459 we simply build `a, throw 3'. */
4461 {
4465 }
4467 {
4471 }
4472 }
4473 else
4474 {
4479 }
4481 /* If ARG is complex we want to make sure we only evaluate
4482 it once. Though this is only required if it is volatile, it
4483 might be more efficient even if it is not. However, if we
4484 succeed in folding one part to a constant, we do not need
4485 to make this SAVE_EXPR. Since we do this optimization
4486 primarily to see if we do end up with constant and this
4487 SAVE_EXPR interferes with later optimizations, suppressing
4488 it when we can is important.
4490 If we are not in a function, we can't make a SAVE_EXPR, so don't
4491 try to do so. Don't try to see if the result is a constant
4492 if an arm is a COND_EXPR since we get exponential behavior
4493 in that case. */
4500 {
4510 }
4523 else
4525 }
4527 \f
4528 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4530 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4531 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4532 ADDEND is the same as X.
4534 X + 0 and X - 0 both give X when X is NaN, infinite, or non-zero
4535 and finite. The problematic cases are when X is zero, and its mode
4536 has signed zeros. In the case of rounding towards -infinity,
4537 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4538 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4540 static bool
4544 {
4548 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4552 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4557 /* The mode has signed zeros, and we have to honor their sign.
4558 In this situation, there is only one case we can return true for.
4559 X - 0 is the same as X unless rounding towards -infinity is
4560 supported. */
4562 }
4565 /* Perform constant folding and related simplification of EXPR.
4566 The related simplifications include x*1 => x, x*0 => 0, etc.,
4567 and application of the associative law.
4568 NOP_EXPR conversions may be removed freely (as long as we
4569 are careful not to change the C type of the overall expression)
4570 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4571 but we can constant-fold them if they have constant operands. */
4573 tree
4575 tree expr;
4576 {
4579 tree tem;
4585 /* WINS will be nonzero when the switch is done
4586 if all operands are constant. */
4589 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4590 Likewise for a SAVE_EXPR that's already been evaluated. */
4594 /* Return right away if a constant. */
4598 #ifdef MAX_INTEGER_COMPUTATION_MODE
4600 #endif
4603 {
4604 tree subop;
4606 /* Special case for conversion ops that can have fixed point args. */
4609 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4615 else
4620 )
4621 /* Note that TREE_CONSTANT isn't enough:
4622 static var addresses are constant but we can't
4623 do arithmetic on them. */
4625 }
4627 {
4631 {
4633 tree subop;
4639 {
4640 /* Signedness matters here. Perhaps we can refine this
4641 later. */
4643 }
4644 else
4645 /* Strip any conversions that don't change the mode. */
4650 else
4655 /* Note that TREE_CONSTANT isn't enough:
4656 static var addresses are constant but we can't
4657 do arithmetic on them. */
4664 }
4665 }
4667 /* If this is a commutative operation, and ARG0 is a constant, move it
4668 to ARG1 to reduce the number of tests below. */
4673 {
4678 }
4680 /* Now WINS is set as described above,
4681 ARG0 is the first operand of EXPR,
4682 and ARG1 is the second operand (if it has more than one operand).
4684 First check for cases where an arithmetic operation is applied to a
4685 compound, conditional, or comparison operation. Push the arithmetic
4686 operation inside the compound or conditional to see if any folding
4687 can then be done. Convert comparison to conditional for this purpose.
4688 The also optimizes non-constant cases that used to be done in
4689 expand_expr.
4691 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
4692 one of the operands is a comparison and the other is a comparison, a
4693 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4694 code below would make the expression more complex. Change it to a
4695 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
4696 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
4708 {
4718 }
4721 {
4726 {
4731 /* If this was a conversion, and all we did was to move into
4732 inside the COND_EXPR, bring it back out. But leave it if
4733 it is a conversion from integer to integer and the
4734 result precision is no wider than a word since such a
4735 conversion is cheap and may be optimized away by combine,
4736 while it couldn't if it were outside the COND_EXPR. Then return
4737 so we don't get into an infinite recursion loop taking the
4738 conversion out and then back in. */
4748 && (INTEGRAL_TYPE_P
4759 }
4764 }
4767 {
4780 return
4794 return
4797 }
4808 {
4824 /* Other kinds of FIX are not handled properly by fold_convert. */
4829 /* Handle cases of two conversions in a row. */
4832 {
4852 /* In addition to the cases of two conversions in a row
4853 handled below, if we are converting something to its own
4854 type via an object of identical or wider precision, neither
4855 conversion is needed. */
4861 /* Likewise, if the intermediate and final types are either both
4862 float or both integer, we don't need the middle conversion if
4863 it is wider than the final type and doesn't change the signedness
4864 (for integers). Avoid this if the final type is a pointer
4865 since then we sometimes need the inner conversion. Likewise if
4866 the outer has a precision not equal to the size of its mode. */
4876 /* If we have a sign-extension of a zero-extended value, we can
4877 replace that by a single zero-extension. */
4883 /* Two conversions in a row are not needed unless:
4884 - some conversion is floating-point (overstrict for now), or
4885 - the intermediate type is narrower than both initial and
4886 final, or
4887 - the intermediate type and innermost type differ in signedness,
4888 and the outermost type is wider than the intermediate, or
4889 - the initial type is a pointer type and the precisions of the
4890 intermediate and final types differ, or
4891 - the final type is a pointer type and the precisions of the
4892 initial and intermediate types differ. */
4906 }
4910 /* Detect assigning a bitfield. */
4913 {
4914 /* Don't leave an assignment inside a conversion
4915 unless assigning a bitfield. */
4918 /* First do the assignment, then return converted constant. */
4922 }
4924 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
4925 constants (if x has signed type, the sign bit cannot be set
4926 in c). This folds extension into the BIT_AND_EXPR. */
4931 {
4941 <= HOST_BITS_PER_WIDE_INT
4943 {
4950 #ifdef LOAD_EXTEND_OP
4954 {
4958 }
4959 #endif
4960 }
4965 }
4968 {
4971 }
4982 {
4986 }
4995 {
4997 {
4999 HOST_WIDE_INT high;
5010 }
5013 }
5017 /* Convert - (a - b) to (b - a) for non-floating-point. */
5027 {
5029 {
5030 /* If the value is unsigned, then the absolute value is
5031 the same as the ordinary value. */
5034 /* Similarly, if the value is non-negative. */
5037 /* If the value is negative, then the absolute value is
5038 its negation. */
5039 else
5040 {
5042 HOST_WIDE_INT high;
5053 }
5054 }
5056 {
5060 }
5061 }
5088 {
5095 }
5101 /* A + (-B) -> A - B */
5104 /* (-A) + B -> B - A */
5108 {
5112 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5113 with a constant, and the two constants have no bits in common,
5114 we should treat this as a BIT_IOR_EXPR since this may produce more
5115 simplifications. */
5123 {
5126 }
5128 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5129 (plus (plus (mult) (mult)) (foo)) so that we can
5130 take advantage of the factoring cases below. */
5135 {
5140 else
5151 parg1));
5156 parg0));
5157 }
5160 {
5164 /* (A * C) + (B * C) -> (A+B) * C.
5165 We are most concerned about the case where C is a constant,
5166 but other combinations show up during loop reduction. Since
5167 it is not difficult, try all four possibilities. */
5184 /* No identical multiplicands; see if we can find a common
5185 power-of-two factor in non-power-of-two multiplies. This
5186 can help in multi-dimensional array access. */
5191 {
5196 /* Move min of absolute values to int11. */
5199 {
5203 }
5206 {
5211 }
5212 }
5217 same));
5218 }
5219 }
5221 /* See if ARG1 is zero and X + ARG1 reduces to X. */
5225 /* Likewise if the operands are reversed. */
5229 bit_rotate:
5230 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5231 is a rotate of A by C1 bits. */
5232 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5233 is a rotate of A by B bits. */
5234 {
5243 {
5262 {
5270 TYPE_PRECISION
5275 ? LROTATE_EXPR
5278 }
5280 {
5288 TYPE_PRECISION
5293 ? LROTATE_EXPR
5296 }
5297 }
5298 }
5300 associate:
5301 /* In most languages, can't associate operations on floats through
5302 parentheses. Rather than remember where the parentheses were, we
5303 don't associate floats at all. It shouldn't matter much. However,
5304 associating multiplications is only very slightly inaccurate, so do
5305 that if -funsafe-math-optimizations is specified. */
5310 {
5314 /* Split both trees into variables, constants, and literals. Then
5315 associate each group together, the constants with literals,
5316 then the result with variables. This increases the chances of
5317 literals being recombined later and of generating relocatable
5318 expressions for the sum of a constant and literal. */
5323 /* Only do something if we found more than two objects. Otherwise,
5324 nothing has changed and we risk infinite recursion. */
5329 {
5330 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
5339 /* Preserve the MINUS_EXPR if the negative part of the literal is
5340 greater than the positive part. Otherwise, the multiplicative
5341 folding code (i.e extract_muldiv) may be fooled in case
5342 unsigned constants are substracted, like in the following
5343 example: ((X*2 + 4) - 8U)/2. */
5345 {
5347 {
5351 }
5352 else
5353 {
5357 }
5358 }
5360 {
5364 else
5365 {
5370 }
5371 }
5375 }
5376 }
5378 binary:
5382 {
5383 /* The return value should always have
5384 the same type as the original expression. */
5389 }
5393 /* A - (-B) -> A + B */
5396 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5398 return
5405 {
5411 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5412 about the case where C is a constant, just try one of the
5413 four possibilities. */
5423 }
5425 /* See if ARG1 is zero and X - ARG1 reduces to X. */
5429 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
5430 ARG0 is zero and X + ARG0 reduces to X, since that would mean
5431 (-ARG1 + ARG0) reduces to -ARG1. */
5435 /* Fold &x - &x. This can happen from &x.foo - &x.
5436 This is unsafe for certain floats even in non-IEEE formats.
5437 In IEEE, it is unsafe because it does wrong for NaNs.
5438 Also note that operand_equal_p is always false if an operand
5439 is volatile. */
5448 /* (-A) * (-B) -> A * B */
5454 {
5460 /* (a * (1 << b)) is (a << b) */
5475 }
5476 else
5477 {
5478 /* Maybe fold x * 0 to 0. The expressions aren't the same
5479 when x is NaN, since x * 0 is also NaN. Nor are they the
5480 same in modes with signed zeros, since multiplying a
5481 negative value by 0 gives -0, not +0. */
5486 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5487 However, ANSI says we can drop signals,
5488 so we can do this anyway. */
5492 /* Transform x * -1.0 into -x. This should be safe for NaNs,
5493 signed zeros and signed infinities, but is currently
5494 restricted to "unsafe math optimizations" just in case. */
5499 /* x*2 is x+x */
5503 {
5506 }
5507 }
5511 bit_ior:
5520 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5522 This results in more efficient code for machines without a NAND
5523 instruction. Combine will canonicalize to the first form
5524 which will allow use of NAND instructions provided by the
5525 backend if they exist. */
5528 {
5533 }
5535 /* See if this can be simplified into a rotate first. If that
5536 is unsuccessful continue in the association code. */
5545 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5546 with a constant, and the two constants have no bits in common,
5547 we should treat this as a BIT_IOR_EXPR since this may produce more
5548 simplifications. */
5556 {
5559 }
5561 /* See if this can be simplified into a rotate first. If that
5562 is unsuccessful continue in the association code. */
5566 bit_and:
5574 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5577 {
5578 unsigned int prec
5585 }
5587 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5589 This results in more efficient code for machines without a NOR
5590 instruction. Combine will canonicalize to the first form
5591 which will allow use of NOR instructions provided by the
5592 backend if they exist. */
5595 {
5600 }
5610 {
5614 }
5618 /* Don't touch a floating-point divide by zero unless the mode
5619 of the constant can represent infinity. */
5625 /* (-A) / (-B) -> A / B */
5630 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5631 However, ANSI says we can drop signals, so we can do this anyway. */
5635 /* If ARG1 is a constant, we can convert this to a multiply by the
5636 reciprocal. This does not have the same rounding properties,
5637 so only do this if -funsafe-math-optimizations. We can actually
5638 always safely do it if ARG1 is a power of two, but it's hard to
5639 tell if it is or not in a portable manner. */
5641 {
5646 /* Find the reciprocal if optimizing and the result is exact. */
5648 {
5649 REAL_VALUE_TYPE r;
5652 {
5655 }
5656 }
5657 }
5658 /* Convert A/B/C to A/(B*C). */
5661 {
5664 arg1)));
5665 }
5666 /* Convert A/(B/C) to (A/B)*C. */
5669 {
5674 }
5687 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5688 operation, EXACT_DIV_EXPR.
5690 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5691 At one time others generated faster code, it's not clear if they do
5692 after the last round to changes to the DIV code in expmed.c. */
5726 /* Since negative shift count is not well-defined,
5727 don't try to compute it in the compiler. */
5730 /* Rewrite an LROTATE_EXPR by a constant into an
5731 RROTATE_EXPR by a new constant. */
5733 {
5737 = const_binop
5744 }
5746 /* If we have a rotate of a bit operation with the rotate count and
5747 the second operand of the bit operation both constant,
5748 permute the two operations. */
5761 /* Two consecutive rotates adding up to the width of the mode can
5762 be ignored. */
5793 /* Note that the operand of this must be an int
5794 and its values must be 0 or 1.
5795 ("true" is a fixed value perhaps depending on the language,
5796 but we don't handle values other than 1 correctly yet.) */
5798 /* Avoid infinite recursion. */
5804 /* Note that the operands of this must be ints
5805 and their values must be 0 or 1.
5806 ("true" is a fixed value perhaps depending on the language.) */
5807 /* If first arg is constant zero, return it. */
5811 /* If either arg is constant true, drop it. */
5815 /* Preserve sequence points. */
5818 /* If second arg is constant zero, result is zero, but first arg
5819 must be evaluated. */
5822 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
5823 case will be handled here. */
5827 truth_andor:
5828 /* We only do these simplifications if we are optimizing. */
5832 /* Check for things like (A || B) && (A || C). We can convert this
5833 to A || (B && C). Note that either operator can be any of the four
5834 truth and/or operations and the transformation will still be
5835 valid. Also note that we only care about order for the
5836 ANDIF and ORIF operators. If B contains side effects, this
5837 might change the truth-value of A. */
5844 {
5864 /* This case if tricky because we must either have commutative
5865 operators or else A10 must not have side-effects. */
5871 a01));
5872 }
5874 /* See if we can build a range comparison. */
5878 /* Check for the possibility of merging component references. If our
5879 lhs is another similar operation, try to merge its rhs with our
5880 rhs. Then try to merge our lhs and rhs. */
5892 /* Note that the operands of this must be ints
5893 and their values must be 0 or true.
5894 ("true" is a fixed value perhaps depending on the language.) */
5895 /* If first arg is constant true, return it. */
5899 /* If either arg is constant zero, drop it. */
5903 /* Preserve sequence points. */
5906 /* If second arg is constant true, result is true, but we must
5907 evaluate first arg. */
5910 /* Likewise for first arg, but note this only occurs here for
5911 TRUTH_OR_EXPR. */
5917 /* If either arg is constant zero, drop it. */
5922 /* If either arg is constant true, this is a logical inversion. */
5935 /* If one arg is a real or integer constant, put it last. */
5940 {
5947 }
5950 {
5951 /* (-a) CMP (-b) -> b CMP a */
5956 /* (-a) CMP CST -> a swap(CMP) (-CST) */
5958 return
5964 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
5965 /* a CMP (-0) -> a CMP 0 */
5971 /* If this is a comparison of a real constant with a PLUS_EXPR
5972 or a MINUS_EXPR of a real constant, we can convert it into a
5973 comparison with a revised real constant as long as no overflow
5974 occurs when unsafe_math_optimizations are enabled. */
5985 }
5987 /* Convert foo++ == CONST into ++foo == CONST + INCR.
5988 First, see if one arg is constant; find the constant arg
5989 and the other one. */
5990 {
6000 {
6001 /* This optimization is invalid for ordered comparisons
6002 if CONST+INCR overflows or if foo+incr might overflow.
6003 This optimization is invalid for floating point due to rounding.
6004 For pointer types we assume overflow doesn't happen. */
6008 {
6009 tree newconst
6013 /* Do not overwrite the current varop to be a preincrement,
6014 create a new node so that we won't confuse our caller who
6015 might create trees and throw them away, reusing the
6016 arguments that they passed to build. This shows up in
6017 the THEN or ELSE parts of ?: being postincrements. */
6022 /* If VAROP is a reference to a bitfield, we must mask
6023 the constant by the width of the field. */
6027 {
6028 int size
6030 (TREE_OPERAND
6034 tree folded_compare;
6036 /* First check whether the comparison would come out
6037 always the same. If we don't do that we would
6038 change the meaning with the masking. */
6042 else
6045 constop));
6060 mask)));
6061 }
6067 }
6068 }
6070 {
6074 {
6075 tree newconst
6079 /* Do not overwrite the current varop to be a predecrement,
6080 create a new node so that we won't confuse our caller who
6081 might create trees and throw them away, reusing the
6082 arguments that they passed to build. This shows up in
6083 the THEN or ELSE parts of ?: being postdecrements. */
6091 {
6092 int size
6094 (TREE_OPERAND
6098 tree folded_compare;
6103 else
6106 constop));
6121 mask)));
6122 }
6128 }
6129 }
6130 }
6132 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
6133 This transformation affects the cases which are handled in later
6134 optimizations involving comparisons with non-negative constants. */
6138 {
6140 {
6155 }
6156 }
6158 /* Comparisons with the highest or lowest possible integer of
6159 the specified size will have known values. */
6160 {
6168 {
6175 {
6178 }
6179 else
6180 {
6183 }
6188 {
6192 arg0);
6200 arg0);
6206 /* The GE_EXPR and LT_EXPR cases above are not normally
6207 reached because of previous transformations. */
6211 }
6215 {
6228 }
6232 {
6236 arg0);
6245 arg0);
6253 }
6257 {
6270 }
6275 /* signed_type does not work on pointer types. */
6277 {
6278 /* The following case also applies to X < signed_max+1
6279 and X >= signed_max+1 because previous transformations. */
6281 {
6285 return fold
6289 }
6290 }
6291 }
6292 }
6294 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6295 a MINUS_EXPR of a constant, we can convert it into a comparison with
6296 a revised constant as long as no overflow occurs. */
6308 /* Similarly for a NEGATE_EXPR. */
6317 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6318 for !=. Don't do this for ordered comparisons due to overflow. */
6324 /* If we are widening one operand of an integer comparison,
6325 see if the other operand is similarly being widened. Perhaps we
6326 can do the comparison in the narrower type. */
6336 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6337 constant, we can simplify it. */
6344 /* If we are comparing an ABS_EXPR with a constant, we can
6345 convert all the cases into explicit comparisons, but they may
6346 well not be faster than doing the ABS and one comparison.
6347 But ABS (X) <= C is a range comparison, which becomes a subtraction
6348 and a comparison, and is probably faster. */
6360 /* If this is an EQ or NE comparison with zero and ARG0 is
6361 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6362 two operations, but the latter can be done in one less insn
6363 on machines that have only two-operand insns or on which a
6364 constant cannot be the first operand. */
6367 {
6370 return
6378 integer_one_node)),
6379 arg1));
6382 return
6390 integer_one_node)),
6391 arg1));
6392 }
6394 /* If this is an NE or EQ comparison of zero against the result of a
6395 signed MOD operation whose second operand is a power of 2, make
6396 the MOD operation unsigned since it is simpler and equivalent. */
6405 {
6412 }
6414 /* If this is an NE comparison of zero with an AND of one, remove the
6415 comparison since the AND will give the correct value. */
6421 /* If we have (A & C) == C where C is a power of 2, convert this into
6422 (A & C) != 0. Similarly for NE_EXPR. */
6430 /* If we have (A & C) != 0 where C is the sign bit of A, convert
6431 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
6435 {
6439 {
6444 }
6445 }
6447 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6448 and similarly for >= into !=. */
6464 return
6471 /* Simplify comparison of something with itself. (For IEEE
6472 floating-point, we can only do some of these simplifications.) */
6474 {
6476 {
6487 /* For NE, we can only do this simplification if integer. */
6490 /* ... fall through ... */
6496 }
6497 }
6499 /* If we are comparing an expression that just has comparisons
6500 of two integer values, arithmetic expressions of those comparisons,
6501 and constants, we can simplify it. There are only three cases
6502 to check: the two values can either be equal, the first can be
6503 greater, or the second can be greater. Fold the expression for
6504 those three values. Since each value must be 0 or 1, we have
6505 eight possibilities, each of which corresponds to the constant 0
6506 or 1 or one of the six possible comparisons.
6508 This handles common cases like (a > b) == 0 but also handles
6509 expressions like ((x > y) - (y > x)) > 0, which supposedly
6510 occur in macroized code. */
6513 {
6518 /* Don't handle degenerate cases here; they should already
6519 have been handled anyway. */
6528 {
6532 /* We can't just pass T to eval_subst in case cval1 or cval2
6533 was the same as ARG1. */
6535 tree high_result
6538 arg1));
6539 tree equal_result
6542 arg1));
6543 tree low_result
6546 arg1));
6548 /* All three of these results should be 0 or 1. Confirm they
6549 are. Then use those values to select the proper code
6550 to use. */
6558 {
6559 /* Make a 3-bit mask with the high-order bit being the
6560 value for `>', the next for '=', and the low for '<'. */
6564 {
6566 /* Always false. */
6587 /* Always true. */
6589 }
6594 else
6596 }
6597 }
6598 }
6600 /* If this is a comparison of a field, we may be able to simplify it. */
6604 /* Handle the constant case even without -O
6605 to make sure the warnings are given. */
6607 {
6610 }
6612 /* If this is a comparison of complex values and either or both sides
6613 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6614 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6615 This may prevent needless evaluations. */
6622 {
6635 type,
6638 }
6640 /* Optimize comparisons of strlen vs zero to a compare of the
6641 first character of the string vs zero. To wit,
6642 strlen(ptr) == 0 => *ptr == 0
6643 strlen(ptr) != 0 => *ptr != 0
6644 Other cases should reduce to one of these two (or a constant)
6645 due to the return value of strlen being unsigned. */
6650 {
6652 tree arglist;
6664 integer_zero_node));
6665 }
6667 /* From here on, the only cases we handle are when the result is
6668 known to be a constant.
6670 To compute GT, swap the arguments and do LT.
6671 To compute GE, do LT and invert the result.
6672 To compute LE, swap the arguments, do LT and invert the result.
6673 To compute NE, do EQ and invert the result.
6675 Therefore, the code below must handle only EQ and LT. */
6678 {
6681 }
6683 /* Note that it is safe to invert for real values here because we
6684 will check below in the one case that it matters. */
6689 {
6692 }
6694 /* Compute a result for LT or EQ if args permit;
6695 otherwise return T. */
6697 {
6700 else
6705 }
6708 /* Assume a nonexplicit constant cannot equal an explicit one,
6709 since such code would be undefined anyway.
6710 Exception: on sysvr4, using #pragma weak,
6711 a label can come out as 0. */
6718 #endif
6719 /* Two real constants can be compared explicitly. */
6721 {
6722 /* If either operand is a NaN, the result is false with two
6723 exceptions: First, an NE_EXPR is true on NaNs, but that case
6724 is already handled correctly since we will be inverting the
6725 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6726 or a GE_EXPR into a LT_EXPR, we must return true so that it
6727 will be inverted into false. */
6737 else
6741 }
6755 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6756 so all simple results must be passed through pedantic_non_lvalue. */
6758 return pedantic_non_lvalue
6763 /* If the second operand is zero, invert the comparison and swap
6764 the second and third operands. Likewise if the second operand
6765 is constant and the third is not or if the third operand is
6766 equivalent to the first operand of the comparison. */
6774 {
6775 /* See if this can be inverted. If it can't, possibly because
6776 it was a floating-point inequality comparison, don't do
6777 anything. */
6781 {
6785 /* arg1 should be the first argument of the new T. */
6788 }
6789 }
6791 /* If we have A op B ? A : C, we may be able to convert this to a
6792 simpler expression, depending on the operation and the values
6793 of B and C. Signed zeros prevent all of these transformations,
6794 for reasons given above each one. */
6800 {
6806 /* If we have A op 0 ? A : -A, consider applying the following
6807 transformations:
6809 A == 0? A : -A same as -A
6810 A != 0? A : -A same as A
6811 A >= 0? A : -A same as abs (A)
6812 A > 0? A : -A same as abs (A)
6813 A <= 0? A : -A same as -abs (A)
6814 A < 0? A : -A same as -abs (A)
6816 None of these transformations work for modes with signed
6817 zeros. If A is +/-0, the first two transformations will
6818 change the sign of the result (from +0 to -0, or vice
6819 versa). The last four will fix the sign of the result,
6820 even though the original expressions could be positive or
6821 negative, depending on the sign of A.
6823 Note that all these transformations are correct if A is
6824 NaN, since the two alternatives (A and -A) are also NaNs. */
6831 {
6833 return
6834 pedantic_non_lvalue
6836 negate_expr
6838 arg1))));
6846 return pedantic_non_lvalue
6854 return pedantic_non_lvalue
6858 arg1)))));
6861 }
6863 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
6864 A == 0 ? A : 0 is always 0 unless A is -0. Note that
6865 both transformations are correct when A is NaN: A != 0
6866 is then true, and A == 0 is false. */
6869 {
6874 }
6876 /* Try some transformations of A op B ? A : B.
6878 A == B? A : B same as B
6879 A != B? A : B same as A
6880 A >= B? A : B same as max (A, B)
6881 A > B? A : B same as max (B, A)
6882 A <= B? A : B same as min (A, B)
6883 A < B? A : B same as min (B, A)
6885 As above, these transformations don't work in the presence
6886 of signed zeros. For example, if A and B are zeros of
6887 opposite sign, the first two transformations will change
6888 the sign of the result. In the last four, the original
6889 expressions give different results for (A=+0, B=-0) and
6890 (A=-0, B=+0), but the transformed expressions do not.
6892 The first two transformations are correct if either A or B
6893 is a NaN. In the first transformation, the condition will
6894 be false, and B will indeed be chosen. In the case of the
6895 second transformation, the condition A != B will be true,
6896 and A will be chosen.
6898 The conversions to max() and min() are not correct if B is
6899 a number and A is not. The conditions in the original
6900 expressions will be false, so all four give B. The min()
6901 and max() versions would give a NaN instead. */
6904 {
6909 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
6914 {
6921 /* In C++ a ?: expression can be an lvalue, so put the
6922 operand which will be used if they are equal first
6923 so that we can convert this back to the
6924 corresponding COND_EXPR. */
6926 return pedantic_non_lvalue
6936 return pedantic_non_lvalue
6945 }
6946 }
6948 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
6949 we might still be able to simplify this. For example,
6950 if C1 is one less or one more than C2, this might have started
6951 out as a MIN or MAX and been transformed by this function.
6952 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
6958 {
6960 /* We can replace A with C1 in this case. */
6967 /* If C1 is C2 + 1, this is min(A, C2). */
6972 return pedantic_non_lvalue
6977 /* If C1 is C2 - 1, this is min(A, C2). */
6982 return pedantic_non_lvalue
6987 /* If C1 is C2 - 1, this is max(A, C2). */
6992 return pedantic_non_lvalue
6997 /* If C1 is C2 + 1, this is max(A, C2). */
7002 return pedantic_non_lvalue
7009 }
7010 }
7012 /* If the second operand is simpler than the third, swap them
7013 since that produces better jump optimization results. */
7019 {
7020 /* See if this can be inverted. If it can't, possibly because
7021 it was a floating-point inequality comparison, don't do
7022 anything. */
7026 {
7030 /* arg1 should be the first argument of the new T. */
7033 }
7034 }
7036 /* Convert A ? 1 : 0 to simply A. */
7039 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7040 call to fold will try to move the conversion inside
7041 a COND, which will recurse. In that case, the COND_EXPR
7042 is probably the best choice, so leave it alone. */
7046 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7047 operation is simply A & 2. */
7061 /* When pedantic, a compound expression can be neither an lvalue
7062 nor an integer constant expression. */
7065 /* Don't let (0, 0) be null pointer constant. */
7107 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7108 appropriate. */
7113 {
7117 tree arg01;
7128 {
7142 arg01));
7143 }
7146 }
7149 /* Check for a built-in function. */
7154 {
7158 }
7164 }
7166 /* Determine if first argument is a multiple of second argument. Return 0 if
7167 it is not, or we cannot easily determined it to be.
7169 An example of the sort of thing we care about (at this point; this routine
7170 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7171 fold cases do now) is discovering that
7173 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7175 is a multiple of
7177 SAVE_EXPR (J * 8)
7179 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7181 This code also handles discovering that
7183 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7185 is a multiple of 8 so we don't have to worry about dealing with a
7186 possible remainder.
7188 Note that we *look* inside a SAVE_EXPR only to determine how it was
7189 calculated; it is not safe for fold to do much of anything else with the
7190 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7191 at run time. For example, the latter example above *cannot* be implemented
7192 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7193 evaluation time of the original SAVE_EXPR is not necessarily the same at
7194 the time the new expression is evaluated. The only optimization of this
7195 sort that would be valid is changing
7197 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7199 divided by 8 to
7201 SAVE_EXPR (I) * SAVE_EXPR (J)
7203 (where the same SAVE_EXPR (J) is used in the original and the
7204 transformed version). */
7206 static int
7208 tree type;
7209 tree top;
7210 tree bottom;
7211 {
7219 {
7231 {
7235 /* const_binop may not detect overflow correctly,
7236 so check for it explicitly here. */
7245 }
7249 /* Can't handle conversions from non-integral or wider integral type. */
7255 /* .. fall through ... */
7271 }
7272 }
7274 /* Return true if `t' is known to be non-negative. */
7276 int
7278 tree t;
7279 {
7281 {
7322 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7324 else
7325 /* We don't know sign of `t', so be conservative and return false. */
7327 }
7328 }
7330 /* Return true if `r' is known to be non-negative.
7331 Only handles constants at the moment. */
7333 int
7335 rtx r;
7336 {
7338 {
7348 {
7350 rtx elt;
7355 {
7359 }
7362 }
7366 /* These are always nonnegative. */
7371 }
7372 }