| blob | 95a68bcbeee4a7b0324e4800a8d8653cb939b8ad |
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 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. */
93 tree);
111 /* The following constants represent a bit based encoding of GCC's
112 comparison operators. This encoding simplifies transformations
113 on relational comparison operators, such as AND and OR. */
114 #define COMPCODE_FALSE 0
115 #define COMPCODE_LT 1
116 #define COMPCODE_EQ 2
117 #define COMPCODE_LE 3
118 #define COMPCODE_GT 4
119 #define COMPCODE_NE 5
120 #define COMPCODE_GE 6
121 #define COMPCODE_TRUE 7
123 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
124 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
125 and SUM1. Then this yields nonzero if overflow occurred during the
126 addition.
128 Overflow occurs if A and B have the same sign, but A and SUM differ in
129 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
130 sign. */
131 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
132 \f
133 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
134 We do that by representing the two-word integer in 4 words, with only
135 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
136 number. The value of the word is LOWPART + HIGHPART * BASE. */
138 #define LOWPART(x) \
139 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
140 #define HIGHPART(x) \
141 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
142 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
144 /* Unpack a two-word integer into 4 words.
145 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
146 WORDS points to the array of HOST_WIDE_INTs. */
148 static void
150 {
155 }
157 /* Pack an array of 4 words into a two-word integer.
158 WORDS points to the array of words.
159 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
161 static void
164 {
167 }
168 \f
169 /* Make the integer constant T valid for its type by setting to 0 or 1 all
170 the bits in the constant that don't belong in the type.
172 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
173 nonzero, a signed overflow has already occurred in calculating T, so
174 propagate it. */
176 int
178 {
180 HOST_WIDE_INT high;
184 {
185 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
186 Consider doing it via real_convert now. */
188 }
198 else
201 /* First clear all bits that are beyond the type's precision. */
204 ;
208 else
209 {
213 }
215 /* Unsigned types do not suffer sign extension or overflow unless they
216 are a sizetype. */
222 /* If the value's sign bit is set, extend the sign. */
230 {
231 /* Value is negative:
232 set to 1 all the bits that are outside this type's precision. */
236 else
237 {
241 }
242 }
244 /* Return nonzero if signed overflow occurred. */
245 return
248 }
249 \f
250 /* Add two doubleword integers with doubleword result.
251 Each argument is given as two `HOST_WIDE_INT' pieces.
252 One argument is L1 and H1; the other, L2 and H2.
253 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
255 int
259 {
261 HOST_WIDE_INT h;
269 }
271 /* Negate a doubleword integer with doubleword result.
272 Return nonzero if the operation overflows, assuming it's signed.
273 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
274 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
276 int
279 {
281 {
285 }
286 else
287 {
291 }
292 }
293 \f
294 /* Multiply two doubleword integers with doubleword result.
295 Return nonzero if the operation overflows, assuming it's signed.
296 Each argument is given as two `HOST_WIDE_INT' pieces.
297 One argument is L1 and H1; the other, L2 and H2.
298 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
300 int
304 {
319 {
322 {
324 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
326 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
330 }
332 }
336 /* Check for overflow by calculating the top half of the answer in full;
337 it should agree with the low half's sign bit. */
340 {
343 }
345 {
348 }
350 }
351 \f
352 /* Shift the doubleword integer in L1, H1 left by COUNT places
353 keeping only PREC bits of result.
354 Shift right if COUNT is negative.
355 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
356 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
358 void
362 {
366 {
369 }
371 #ifdef SHIFT_COUNT_TRUNCATED
374 #endif
377 {
378 /* Shifting by the host word size is undefined according to the
379 ANSI standard, so we must handle this as a special case. */
382 }
384 {
387 }
388 else
389 {
393 }
395 /* Sign extend all bits that are beyond the precision. */
403 ;
405 {
408 }
409 else
410 {
414 }
415 }
417 /* Shift the doubleword integer in L1, H1 right by COUNT places
418 keeping only PREC bits of result. COUNT must be positive.
419 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
420 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
422 void
427 {
430 signmask = (arith
434 #ifdef SHIFT_COUNT_TRUNCATED
437 #endif
440 {
441 /* Shifting by the host word size is undefined according to the
442 ANSI standard, so we must handle this as a special case. */
445 }
447 {
450 }
451 else
452 {
456 }
458 /* Zero / sign extend all bits that are beyond the precision. */
461 {
464 }
466 ;
468 {
471 }
472 else
473 {
477 }
478 }
479 \f
480 /* Rotate the doubleword integer in L1, H1 left by COUNT places
481 keeping only PREC bits of result.
482 Rotate right if COUNT is negative.
483 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
485 void
489 {
501 }
503 /* Rotate the doubleword integer in L1, H1 left by COUNT places
504 keeping only PREC bits of result. COUNT must be positive.
505 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
507 void
511 {
523 }
524 \f
525 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
526 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
527 CODE is a tree code for a kind of division, one of
528 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
529 or EXACT_DIV_EXPR
530 It controls how the quotient is rounded to an integer.
531 Return nonzero if the operation overflows.
532 UNS nonzero says do unsigned division. */
534 int
537 HOST_WIDE_INT hnum_orig,
539 HOST_WIDE_INT hden_orig,
543 {
559 /* calculate quotient sign and convert operands to unsigned. */
561 {
563 {
565 /* (minimum integer) / (-1) is the only overflow case. */
569 }
571 {
574 }
575 }
580 /* This unsigned division rounds toward zero. */
583 }
587 /* hden != 0 already checked. */
592 }
602 /* Special code for when the divisor < BASE. */
604 {
605 /* hnum != 0 already checked. */
607 {
611 }
612 }
613 else
614 {
615 /* Full double precision division,
616 with thanks to Don Knuth's "Seminumerical Algorithms". */
620 /* Find the highest nonzero divisor digit. */
623 {
626 }
628 /* Insure that the first digit of the divisor is at least BASE/2.
629 This is required by the quotient digit estimation algorithm. */
636 {
640 }
645 {
650 }
651 }
655 /* Main loop */
657 {
658 /* Guess the next quotient digit, quo_est, by dividing the first
659 two remaining dividend digits by the high order quotient digit.
660 quo_est is never low and is at most 2 high. */
667 else
670 /* Refine quo_est so it's usually correct, and at most one high. */
675 quo_est--;
677 /* Try QUO_EST as the quotient digit, by multiplying the
678 divisor by QUO_EST and subtracting from the remaining dividend.
679 Keep in mind that QUO_EST is the I - 1st digit. */
683 {
689 }
691 /* If quo_est was high by one, then num[i] went negative and
692 we need to correct things. */
694 {
695 quo_est--;
698 {
702 }
705 }
707 /* Store the quotient digit. */
709 }
710 }
714 finish_up:
715 /* if result is negative, make it so. */
719 /* compute trial remainder: rem = num - (quo * den) */
725 {
734 {
735 /* quo = quo - 1; */
738 }
739 else
746 {
749 }
750 else
756 {
762 /* Get absolute values. */
768 /* If (2 * abs (lrem) >= abs (lden)) */
777 {
779 /* quo = quo - 1; */
782 else
783 /* quo = quo + 1; */
786 }
787 else
789 }
794 }
796 /* compute true remainder: rem = num - (quo * den) */
801 }
802 \f
803 /* Determine whether an expression T can be cheaply negated using
804 the function negate_expr. */
806 static bool
808 {
811 tree type;
820 {
825 /* Check that -CST will not overflow type. */
828 {
833 }
834 else
847 }
849 }
851 /* Given T, an expression, return the negation of T. Allow for T to be
852 null, in which case return null. */
854 static tree
856 {
857 tree type;
858 tree tem;
867 {
880 /* - (A - B) -> B - A */
890 }
893 }
894 \f
895 /* Split a tree IN into a constant, literal and variable parts that could be
896 combined with CODE to make IN. "constant" means an expression with
897 TREE_CONSTANT but that isn't an actual constant. CODE must be a
898 commutative arithmetic operation. Store the constant part into *CONP,
899 the literal in *LITP and return the variable part. If a part isn't
900 present, set it to null. If the tree does not decompose in this way,
901 return the entire tree as the variable part and the other parts as null.
903 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
904 case, we negate an operand that was subtracted. Except if it is a
905 literal for which we use *MINUS_LITP instead.
907 If NEGATE_P is true, we are negating all of IN, again except a literal
908 for which we use *MINUS_LITP instead.
910 If IN is itself a literal or constant, return it as appropriate.
912 Note that we do not guarantee that any of the three values will be the
913 same type as IN, but they will have the same signedness and mode. */
915 static tree
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
996 {
1002 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1003 try to fold this since we will have infinite recursion. But do
1004 deal with any NEGATE_EXPRs. */
1007 {
1009 {
1016 }
1018 }
1021 }
1022 \f
1023 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1024 to produce a new constant.
1026 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1028 static tree
1030 {
1034 HOST_WIDE_INT hi;
1036 HOST_WIDE_INT garbageh;
1037 tree t;
1040 int is_sizetype
1051 {
1071 /* It's unclear from the C standard whether shifts can overflow.
1072 The following code ignores overflow; perhaps a C standard
1073 interpretation ruling is needed. */
1103 /* This is a shortcut for a common special case. */
1108 {
1114 }
1116 /* ... fall through ... */
1120 {
1123 }
1126 {
1129 }
1136 /* This is a shortcut for a common special case. */
1141 {
1146 }
1148 /* ... fall through ... */
1164 else
1170 else
1176 }
1178 /* If this is for a sizetype, can be represented as one (signed)
1179 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1180 constants. */
1186 else
1187 {
1190 }
1193 = ((notrunc
1200 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1201 So check if force_fit_type truncated the value. */
1212 }
1214 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1215 constant. We assume ARG1 and ARG2 have the same data type, or at least
1216 are the same kind of constant and the same machine mode.
1218 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1220 static tree
1222 {
1230 {
1231 REAL_VALUE_TYPE d1;
1232 REAL_VALUE_TYPE d2;
1233 REAL_VALUE_TYPE value;
1234 tree t;
1239 /* If either operand is a NaN, just return it. Otherwise, set up
1240 for floating-point trap; we return an overflow. */
1250 value));
1260 }
1262 {
1268 tree t;
1271 {
1291 notrunc),
1297 notrunc));
1301 {
1302 tree magsquared
1306 notrunc);
1309 const_binop
1314 notrunc),
1316 notrunc),
1317 notrunc),
1319 const_binop
1324 notrunc),
1326 notrunc),
1327 notrunc),
1329 }
1334 }
1336 }
1338 }
1340 /* These are the hash table functions for the hash table of INTEGER_CST
1341 nodes of a sizetype. */
1343 /* Return the hash code code X, an INTEGER_CST. */
1345 static hashval_t
1347 {
1353 }
1355 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1356 is the same as that given by *Y, which is the same. */
1358 static int
1360 {
1368 }
1369 \f
1370 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1371 bits are given by NUMBER and of the sizetype represented by KIND. */
1373 tree
1375 {
1377 }
1379 /* Likewise, but the desired type is specified explicitly. */
1383 htab_t size_htab;
1385 tree
1387 {
1391 {
1394 }
1396 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1397 hash table, we return the value from the hash table. Otherwise, we
1398 place that in the hash table and make a new node for the next time. */
1407 {
1413 }
1414 else
1416 }
1418 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1419 is a tree code. The type of the result is taken from the operands.
1420 Both must be the same type integer type and it must be a size type.
1421 If the operands are constant, so is the result. */
1423 tree
1425 {
1432 /* Handle the special case of two integer constants faster. */
1434 {
1435 /* And some specific cases even faster than that. */
1444 /* Handle general case of two integer constants. */
1446 }
1452 }
1454 /* Given two values, either both of sizetype or both of bitsizetype,
1455 compute the difference between the two values. Return the value
1456 in signed type corresponding to the type of the operands. */
1458 tree
1460 {
1462 tree ctype;
1468 /* If the type is already signed, just do the simple thing. */
1475 /* If either operand is not a constant, do the conversions to the signed
1476 type and subtract. The hardware will do the right thing with any
1477 overflow in the subtraction. */
1482 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1483 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1484 overflow) and negate (which can't either). Special-case a result
1485 of zero while we're here. */
1490 else
1493 }
1494 \f
1496 /* Given T, a tree representing type conversion of ARG1, a constant,
1497 return a constant tree representing the result of conversion. */
1499 static tree
1501 {
1506 {
1508 {
1509 /* If we would build a constant wider than GCC supports,
1510 leave the conversion unfolded. */
1514 /* If we are trying to make a sizetype for a small integer, use
1515 size_int to pick up cached types to reduce duplicate nodes. */
1521 /* Given an integer constant, make new constant with new type,
1522 appropriately sign-extended or truncated. */
1526 /* Indicate an overflow if (1) ARG1 already overflowed,
1527 or (2) force_fit_type indicates an overflow.
1528 Tell force_fit_type that an overflow has already occurred
1529 if ARG1 is a too-large unsigned value and T is signed.
1530 But don't indicate an overflow if converting a pointer. */
1540 }
1542 {
1543 /* Don't initialize these, use assignments.
1544 Initialized local aggregates don't work on old compilers. */
1545 REAL_VALUE_TYPE x;
1546 REAL_VALUE_TYPE l;
1547 REAL_VALUE_TYPE u;
1558 /* See if X will be in range after truncation towards 0.
1559 To compensate for truncation, move the bounds away from 0,
1560 but reject if X exactly equals the adjusted bounds. */
1564 /* If X is a NaN, use zero instead and show we have an overflow.
1565 Otherwise, range check. */
1569 && !no_upper_bound
1573 {
1577 }
1583 }
1585 }
1587 {
1591 {
1593 {
1594 /* We make a copy of ARG1 so that we don't modify an
1595 existing constant tree. */
1599 }
1610 }
1611 }
1614 }
1615 \f
1616 /* Return an expr equal to X but certainly not valid as an lvalue. */
1618 tree
1620 {
1621 tree result;
1623 /* These things are certainly not lvalues. */
1634 }
1636 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
1637 Zero means allow extended lvalues. */
1641 /* When pedantic, return an expr equal to X but certainly not valid as a
1642 pedantic lvalue. Otherwise, return X. */
1644 tree
1646 {
1649 else
1651 }
1652 \f
1653 /* Given a tree comparison code, return the code that is the logical inverse
1654 of the given code. It is not safe to do this for floating-point
1655 comparisons, except for NE_EXPR and EQ_EXPR. */
1657 static enum tree_code
1659 {
1661 {
1676 }
1677 }
1679 /* Similar, but return the comparison that results if the operands are
1680 swapped. This is safe for floating-point. */
1682 static enum tree_code
1684 {
1686 {
1700 }
1701 }
1704 /* Convert a comparison tree code from an enum tree_code representation
1705 into a compcode bit-based encoding. This function is the inverse of
1706 compcode_to_comparison. */
1708 static int
1710 {
1712 {
1727 }
1728 }
1730 /* Convert a compcode bit-based encoding of a comparison operator back
1731 to GCC's enum tree_code representation. This function is the
1732 inverse of comparison_to_compcode. */
1734 static enum tree_code
1736 {
1738 {
1753 }
1754 }
1756 /* Return nonzero if CODE is a tree code that represents a truth value. */
1758 static int
1760 {
1765 }
1766 \f
1767 /* Return nonzero if two operands are necessarily equal.
1768 If ONLY_CONST is nonzero, only return nonzero for constants.
1769 This function tests whether the operands are indistinguishable;
1770 it does not test whether they are equal using C's == operation.
1771 The distinction is important for IEEE floating point, because
1772 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
1773 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
1775 int
1777 {
1778 /* If both types don't have the same signedness, then we can't consider
1779 them equal. We must check this before the STRIP_NOPS calls
1780 because they may change the signedness of the arguments. */
1788 /* This is needed for conversions and for COMPONENT_REF.
1789 Might as well play it safe and always test this. */
1795 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
1796 We don't care about side effects in that case because the SAVE_EXPR
1797 takes care of that for us. In all other cases, two expressions are
1798 equal if they have no side effects. If we have two identical
1799 expressions with side effects that should be treated the same due
1800 to the only side effects being identical SAVE_EXPR's, that will
1801 be detected in the recursive calls below. */
1807 /* Next handle constant cases, those for which we can return 1 even
1808 if ONLY_CONST is set. */
1811 {
1824 {
1834 {
1839 }
1842 }
1846 only_const)
1848 only_const));
1861 }
1867 {
1869 /* Two conversions are equal only if signedness and modes match. */
1885 /* For commutative ops, allow the other order. */
1898 /* If either of the pointer (or reference) expressions we are
1899 dereferencing contain a side effect, these cannot be equal. */
1905 {
1927 }
1931 {
1941 /* If the CALL_EXPRs call different functions, then they
1942 clearly can not be equal. */
1947 /* Only consider const functions equivalent. */
1949 {
1953 }
1954 else
1957 /* Now see if all the arguments are the same. operand_equal_p
1958 does not handle TREE_LIST, so we walk the operands here
1959 feeding them to operand_equal_p. */
1963 {
1969 }
1971 /* If we get here and both argument lists are exhausted
1972 then the CALL_EXPRs are equal. */
1977 }
1980 /* Consider __builtin_sqrt equal to sqrt. */
1988 }
1989 }
1990 \f
1991 /* Similar to operand_equal_p, but see if ARG0 might have been made by
1992 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
1994 When in doubt, return 0. */
1996 static int
1998 {
2010 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2011 and see if the inner values are the same. This removes any
2012 signedness comparison, which doesn't matter here. */
2019 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2020 actual comparison operand, ARG0.
2022 First throw away any conversions to wider types
2023 already present in the operands. */
2032 {
2035 /* Make sure shorter operand is extended the right way
2036 to match the longer operand. */
2042 }
2045 }
2046 \f
2047 /* See if ARG is an expression that is either a comparison or is performing
2048 arithmetic on comparisons. The comparisons must only be comparing
2049 two different values, which will be stored in *CVAL1 and *CVAL2; if
2050 they are nonzero it means that some operands have already been found.
2051 No variables may be used anywhere else in the expression except in the
2052 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2053 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2055 If this is true, return 1. Otherwise, return zero. */
2057 static int
2059 {
2063 /* We can handle some of the 'e' cases here. */
2073 {
2074 /* If we've already found a CVAL1 or CVAL2, this expression is
2075 two complex to handle. */
2081 }
2084 {
2107 /* First see if we can handle the first operand, then the second. For
2108 the second operand, we know *CVAL1 can't be zero. It must be that
2109 one side of the comparison is each of the values; test for the
2110 case where this isn't true by failing if the two operands
2111 are the same. */
2120 ;
2124 ;
2125 else
2129 ;
2133 ;
2134 else
2141 }
2142 }
2143 \f
2144 /* ARG is a tree that is known to contain just arithmetic operations and
2145 comparisons. Evaluate the operations in the tree substituting NEW0 for
2146 any occurrence of OLD0 as an operand of a comparison and likewise for
2147 NEW1 and OLD1. */
2149 static tree
2151 {
2156 /* We can handle some of the 'e' cases here. */
2164 {
2179 {
2196 }
2197 /* fall through - ??? */
2200 {
2204 /* We need to check both for exact equality and tree equality. The
2205 former will be true if the operand has a side-effect. In that
2206 case, we know the operand occurred exactly once. */
2219 }
2223 }
2224 }
2225 \f
2226 /* Return a tree for the case when the result of an expression is RESULT
2227 converted to TYPE and OMITTED was previously an operand of the expression
2228 but is now not needed (e.g., we folded OMITTED * 0).
2230 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2231 the conversion of RESULT to TYPE. */
2233 tree
2235 {
2242 }
2244 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2246 static tree
2248 {
2255 }
2256 \f
2257 /* Return a simplified tree node for the truth-negation of ARG. This
2258 never alters ARG itself. We assume that ARG is an operation that
2259 returns a truth value (0 or 1). */
2261 tree
2263 {
2270 /* If this is a comparison, we can simply invert it, except for
2271 floating-point non-equality comparisons, in which case we just
2272 enclose a TRUTH_NOT_EXPR around what we have. */
2275 {
2277 && !flag_unsafe_math_optimizations
2281 else
2284 }
2287 {
2302 /* Here we can invert either operand. We invert the first operand
2303 unless the second operand is a TRUTH_NOT_EXPR in which case our
2304 result is the XOR of the first operand with the inside of the
2305 negation of the second operand. */
2310 else
2365 }
2369 }
2371 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2372 operands are another bit-wise operation with a common input. If so,
2373 distribute the bit operations to save an operation and possibly two if
2374 constants are involved. For example, convert
2375 (A | B) & (A | C) into A | (B & C)
2376 Further simplification will occur if B and C are constants.
2378 If this optimization cannot be done, 0 will be returned. */
2380 static tree
2382 {
2383 tree common;
2393 {
2397 }
2399 {
2403 }
2405 {
2409 }
2411 {
2415 }
2416 else
2421 }
2422 \f
2423 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2424 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2426 static tree
2429 {
2436 }
2438 /* Optimize a bit-field compare.
2440 There are two cases: First is a compare against a constant and the
2441 second is a comparison of two items where the fields are at the same
2442 bit position relative to the start of a chunk (byte, halfword, word)
2443 large enough to contain it. In these cases we can avoid the shift
2444 implicit in bitfield extractions.
2446 For constants, we emit a compare of the shifted constant with the
2447 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2448 compared. For two fields at the same position, we do the ANDs with the
2449 similar mask and compare the result of the ANDs.
2451 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2452 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2453 are the left and right operands of the comparison, respectively.
2455 If the optimization described above can be done, we return the resulting
2456 tree. Otherwise we return zero. */
2458 static tree
2461 {
2470 tree mask;
2471 tree offset;
2473 /* Get all the information about the extractions being done. If the bit size
2474 if the same as the size of the underlying object, we aren't doing an
2475 extraction at all and so can do nothing. We also don't want to
2476 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2477 then will no longer be able to replace it. */
2485 {
2486 /* If this is not a constant, we can only do something if bit positions,
2487 sizes, and signedness are the same. */
2495 }
2497 /* See if we can find a mode to refer to this field. We should be able to,
2498 but fail if we can't. */
2507 /* Set signed and unsigned types of the precision of this mode for the
2508 shifts below. */
2512 /* Compute the bit position and size for the new reference and our offset
2513 within it. If the new reference is the same size as the original, we
2514 won't optimize anything, so return zero. */
2524 /* Make the mask to be used against the extracted field. */
2534 /* If not comparing with constant, just rework the comparison
2535 and return. */
2540 mask),
2544 mask));
2546 /* Otherwise, we are handling the constant case. See if the constant is too
2547 big for the field. Warn and return a tree of for 0 (false) if so. We do
2548 this not only for its own sake, but to avoid having to test for this
2549 error case below. If we didn't, we might generate wrong code.
2551 For unsigned fields, the constant shifted right by the field length should
2552 be all zero. For signed fields, the high-order bits should agree with
2553 the sign bit. */
2556 {
2560 {
2566 }
2567 }
2568 else
2569 {
2573 {
2579 }
2580 }
2582 /* Single-bit compares should always be against zero. */
2584 {
2587 }
2589 /* Make a new bitfield reference, shift the constant over the
2590 appropriate number of bits and mask it with the computed mask
2591 (in case this was a signed field). If we changed it, make a new one. */
2594 {
2597 }
2607 rhs);
2608 }
2609 \f
2610 /* Subroutine for fold_truthop: decode a field reference.
2612 If EXP is a comparison reference, we return the innermost reference.
2614 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
2615 set to the starting bit number.
2617 If the innermost field can be completely contained in a mode-sized
2618 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
2620 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
2621 otherwise it is not changed.
2623 *PUNSIGNEDP is set to the signedness of the field.
2625 *PMASK is set to the mask used. This is either contained in a
2626 BIT_AND_EXPR or derived from the width of the field.
2628 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
2630 Return 0 if this is not a component reference or is one that we can't
2631 do anything with. */
2633 static tree
2638 {
2642 tree unsigned_type;
2645 /* All the optimizations using this function assume integer fields.
2646 There are problems with FP fields since the type_for_size call
2647 below can fail for, e.g., XFmode. */
2651 /* We are interested in the bare arrangement of bits, so strip everything
2652 that doesn't affect the machine mode. However, record the type of the
2653 outermost expression if it may matter below. */
2661 {
2667 }
2676 /* If the number of bits in the reference is the same as the bitsize of
2677 the outer type, then the outer type gives the signedness. Otherwise
2678 (in case of a small bitfield) the signedness is unchanged. */
2682 /* Compute the mask to access the bitfield. */
2692 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
2700 }
2702 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
2703 bit positions. */
2705 static int
2707 {
2710 tree tmask;
2715 return
2722 }
2724 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
2725 represents the sign bit of EXP's type. If EXP represents a sign
2726 or zero extension, also test VAL against the unextended type.
2727 The return value is the (sub)expression whose sign bit is VAL,
2728 or NULL_TREE otherwise. */
2730 static tree
2732 {
2736 tree t;
2738 /* Tree EXP must have an integral type. */
2743 /* Tree VAL must be an integer constant. */
2750 {
2757 }
2758 else
2759 {
2766 }
2768 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
2769 treat VAL as if it were unsigned. */
2774 /* Handle extension from a narrower type. */
2780 }
2782 /* Subroutine for fold_truthop: determine if an operand is simple enough
2783 to be evaluated unconditionally. */
2785 static int
2787 {
2788 /* Strip any conversions that don't change the machine mode. */
2800 /* Don't regard global variables as simple. They may be
2801 allocated in ways unknown to the compiler (shared memory,
2802 #pragma weak, etc). */
2805 /* Loading a static variable is unduly expensive, but global
2806 registers aren't expensive. */
2808 }
2809 \f
2810 /* The following functions are subroutines to fold_range_test and allow it to
2811 try to change a logical combination of comparisons into a range test.
2813 For example, both
2814 X == 2 || X == 3 || X == 4 || X == 5
2815 and
2816 X >= 2 && X <= 5
2817 are converted to
2818 (unsigned) (X - 2) <= 3
2820 We describe each set of comparisons as being either inside or outside
2821 a range, using a variable named like IN_P, and then describe the
2822 range with a lower and upper bound. If one of the bounds is omitted,
2823 it represents either the highest or lowest value of the type.
2825 In the comments below, we represent a range by two numbers in brackets
2826 preceded by a "+" to designate being inside that range, or a "-" to
2827 designate being outside that range, so the condition can be inverted by
2828 flipping the prefix. An omitted bound is represented by a "-". For
2829 example, "- [-, 10]" means being outside the range starting at the lowest
2830 possible value and ending at 10, in other words, being greater than 10.
2831 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
2832 always false.
2834 We set up things so that the missing bounds are handled in a consistent
2835 manner so neither a missing bound nor "true" and "false" need to be
2836 handled using a special case. */
2838 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
2839 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
2840 and UPPER1_P are nonzero if the respective argument is an upper bound
2841 and zero for a lower. TYPE, if nonzero, is the type of the result; it
2842 must be specified for a comparison. ARG1 will be converted to ARG0's
2843 type if both are specified. */
2845 static tree
2848 {
2849 tree tem;
2853 /* If neither arg represents infinity, do the normal operation.
2854 Else, if not a comparison, return infinity. Else handle the special
2855 comparison rules. Note that most of the cases below won't occur, but
2856 are handled for consistency. */
2859 {
2864 }
2869 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
2870 for neither. In real maths, we cannot assume open ended ranges are
2871 the same. But, this is computer arithmetic, where numbers are finite.
2872 We can therefore make the transformation of any unbounded range with
2873 the value Z, Z being greater than any representable number. This permits
2874 us to treat unbounded ranges as equal. */
2878 {
2899 }
2902 }
2903 \f
2904 /* Given EXP, a logical expression, set the range it is testing into
2905 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
2906 actually being tested. *PLOW and *PHIGH will be made of the same type
2907 as the returned expression. If EXP is not a comparison, we will most
2908 likely not be returning a useful value and range. */
2910 static tree
2912 {
2919 /* Start with simply saying "EXP != 0" and then look at the code of EXP
2920 and see if we can refine the range. Some of the cases below may not
2921 happen, but it doesn't seem worth worrying about this. We "continue"
2922 the outer loop when we've changed something; otherwise we "break"
2923 the switch, which will "break" the while. */
2928 {
2932 {
2944 }
2946 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
2947 lose a cast by accident. */
2952 {
2959 /* We can only do something if the range is testing for zero
2960 and if the second operand is an integer constant. Note that
2961 saying something is "in" the range we make is done by
2962 complementing IN_P since it will set in the initial case of
2963 being not equal to zero; "out" is leaving it alone. */
2970 {
2991 }
2995 /* If this is an unsigned comparison, we also know that EXP is
2996 greater than or equal to zero. We base the range tests we make
2997 on that fact, so we record it here so we can parse existing
2998 range tests. */
3000 {
3003 NULL_TREE))
3008 /* If the high bound is missing, but we
3009 have a low bound, reverse the range so
3010 it goes from zero to the low bound minus 1. */
3012 {
3017 }
3018 }
3022 /* (-x) IN [a,b] -> x in [-b, -a] */
3032 /* ~ X -> -X - 1 */
3041 /* If EXP is signed, any overflow in the computation is undefined,
3042 so we don't worry about it so long as our computations on
3043 the bounds don't overflow. For unsigned, overflow is defined
3044 and this is exactly the right thing. */
3053 /* Check for an unsigned range which has wrapped around the maximum
3054 value thus making n_high < n_low, and normalize it. */
3056 {
3062 /* If the range is of the form +/- [ x+1, x ], we won't
3063 be able to normalize it. But then, it represents the
3064 whole range or the empty set, so make it
3065 +/- [ -, - ]. */
3069 else
3071 }
3072 else
3095 /* If we're converting from an unsigned to a signed type,
3096 we will be doing the comparison as unsigned. The tests above
3097 have already verified that LOW and HIGH are both positive.
3099 So we have to make sure that the original unsigned value will
3100 be interpreted as positive. */
3102 {
3105 tree high_positive;
3107 /* A range without an upper bound is, naturally, unbounded.
3108 Since convert would have cropped a very large value, use
3109 the max value for the destination type. */
3110 high_positive
3119 /* If the low bound is specified, "and" the range with the
3120 range for which the original unsigned value will be
3121 positive. */
3123 {
3127 high_positive))
3131 }
3132 else
3133 {
3134 /* Otherwise, "or" the range with the range of the input
3135 that will be interpreted as negative. */
3139 high_positive))
3143 }
3144 }
3152 }
3155 }
3157 /* If EXP is a constant, we can evaluate whether this is true or false. */
3159 {
3166 }
3170 }
3171 \f
3172 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3173 type, TYPE, return an expression to test if EXP is in (or out of, depending
3174 on IN_P) the range. */
3176 static tree
3178 {
3180 tree value;
3199 {
3201 {
3205 }
3207 }
3209 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3211 {
3213 HOST_WIDE_INT hi;
3218 {
3221 }
3222 else
3223 {
3226 }
3229 {
3231 {
3234 }
3237 }
3238 }
3247 }
3248 \f
3249 /* Given two ranges, see if we can merge them into one. Return 1 if we
3250 can, 0 if we can't. Set the output range into the specified parameters. */
3252 static int
3255 {
3259 tree tem;
3269 /* Make range 0 be the range that starts first, or ends last if they
3270 start at the same value. Swap them if it isn't. */
3273 || (lowequal
3276 {
3280 }
3282 /* Now flag two cases, whether the ranges are disjoint or whether the
3283 second range is totally subsumed in the first. Note that the tests
3284 below are simplified by the ones above. */
3290 /* We now have four cases, depending on whether we are including or
3291 excluding the two ranges. */
3293 {
3294 /* If they don't overlap, the result is false. If the second range
3295 is a subset it is the result. Otherwise, the range is from the start
3296 of the second to the end of the first. */
3301 else
3303 }
3306 {
3307 /* If they don't overlap, the result is the first range. If they are
3308 equal, the result is false. If the second range is a subset of the
3309 first, and the ranges begin at the same place, we go from just after
3310 the end of the first range to the end of the second. If the second
3311 range is not a subset of the first, or if it is a subset and both
3312 ranges end at the same place, the range starts at the start of the
3313 first range and ends just before the second range.
3314 Otherwise, we can't describe this as a single range. */
3320 {
3324 }
3326 {
3330 }
3331 else
3333 }
3336 {
3337 /* If they don't overlap, the result is the second range. If the second
3338 is a subset of the first, the result is false. Otherwise,
3339 the range starts just after the first range and ends at the
3340 end of the second. */
3345 else
3346 {
3350 }
3351 }
3353 else
3354 {
3355 /* The case where we are excluding both ranges. Here the complex case
3356 is if they don't overlap. In that case, the only time we have a
3357 range is if they are adjacent. If the second is a subset of the
3358 first, the result is the first. Otherwise, the range to exclude
3359 starts at the beginning of the first range and ends at the end of the
3360 second. */
3362 {
3369 else
3371 }
3374 else
3376 }
3380 }
3381 \f
3382 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3383 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3384 #endif
3386 /* EXP is some logical combination of boolean tests. See if we can
3387 merge it into some range test. Return the new tree if so. */
3389 static tree
3391 {
3398 tree tem;
3400 /* If this is an OR operation, invert both sides; we will invert
3401 again at the end. */
3405 /* If both expressions are the same, if we can merge the ranges, and we
3406 can build the range test, return it or it inverted. If one of the
3407 ranges is always true or always false, consider it to be the same
3408 expression as the other. */
3418 /* On machines where the branch cost is expensive, if this is a
3419 short-circuited branch and the underlying object on both sides
3420 is the same, make a non-short-circuit operation. */
3426 {
3427 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3428 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3429 which cases we can't do this. */
3438 {
3450 }
3451 }
3454 }
3455 \f
3456 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3457 bit value. Arrange things so the extra bits will be set to zero if and
3458 only if C is signed-extended to its full width. If MASK is nonzero,
3459 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3461 static tree
3463 {
3466 tree temp;
3471 /* We work by getting just the sign bit into the low-order bit, then
3472 into the high-order bit, then sign-extend. We then XOR that value
3473 with C. */
3477 /* We must use a signed type in order to get an arithmetic right shift.
3478 However, we must also avoid introducing accidental overflows, so that
3479 a subsequent call to integer_zerop will work. Hence we must
3480 do the type conversion here. At this point, the constant is either
3481 zero or one, and the conversion to a signed type can never overflow.
3482 We could get an overflow if this conversion is done anywhere else. */
3490 /* If necessary, convert the type back to match the type of C. */
3495 }
3496 \f
3497 /* Find ways of folding logical expressions of LHS and RHS:
3498 Try to merge two comparisons to the same innermost item.
3499 Look for range tests like "ch >= '0' && ch <= '9'".
3500 Look for combinations of simple terms on machines with expensive branches
3501 and evaluate the RHS unconditionally.
3503 For example, if we have p->a == 2 && p->b == 4 and we can make an
3504 object large enough to span both A and B, we can do this with a comparison
3505 against the object ANDed with the a mask.
3507 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3508 operations to do this with one comparison.
3510 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3511 function and the one above.
3513 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3514 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3516 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3517 two operands.
3519 We return the simplified tree or 0 if no optimization is possible. */
3521 static tree
3523 {
3524 /* If this is the "or" of two comparisons, we can do something if
3525 the comparisons are NE_EXPR. If this is the "and", we can do something
3526 if the comparisons are EQ_EXPR. I.e.,
3527 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3529 WANTED_CODE is this operation code. For single bit fields, we can
3530 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3531 comparison for one-bit fields. */
3551 /* Start by getting the comparison codes. Fail if anything is volatile.
3552 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3553 it were surrounded with a NE_EXPR. */
3578 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3582 {
3587 {
3595 }
3598 {
3607 }
3608 else
3618 }
3620 /* If the RHS can be evaluated unconditionally and its operands are
3621 simple, it wins to evaluate the RHS unconditionally on machines
3622 with expensive branches. In this case, this isn't a comparison
3623 that can be merged. Avoid doing this if the RHS is a floating-point
3624 comparison since those can trap. */
3630 {
3631 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
3639 integer_zero_node);
3641 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
3649 integer_zero_node);
3652 }
3654 /* See if the comparisons can be merged. Then get all the parameters for
3655 each side. */
3679 /* It must be true that the inner operation on the lhs of each
3680 comparison must be the same if we are to be able to do anything.
3681 Then see if we have constants. If not, the same must be true for
3682 the rhs's. */
3693 else
3696 /* If either comparison code is not correct for our logical operation,
3697 fail. However, we can convert a one-bit comparison against zero into
3698 the opposite comparison against that bit being set in the field. */
3702 {
3704 {
3705 /* Make the left operand unsigned, since we are only interested
3706 in the value of one bit. Otherwise we are doing the wrong
3707 thing below. */
3710 }
3711 else
3713 }
3715 /* This is analogous to the code for l_const above. */
3717 {
3719 {
3722 }
3723 else
3725 }
3727 /* After this point all optimizations will generate bit-field
3728 references, which we might not want. */
3732 /* See if we can find a mode that contains both fields being compared on
3733 the left. If we can't, fail. Otherwise, update all constants and masks
3734 to be relative to a field of that size. */
3739 volatilep);
3749 {
3752 }
3760 {
3768 {
3772 wanted_code == NE_EXPR
3774 }
3775 }
3777 {
3785 {
3789 wanted_code == NE_EXPR
3791 }
3792 }
3794 /* If the right sides are not constant, do the same for it. Also,
3795 disallow this optimization if a size or signedness mismatch occurs
3796 between the left and right sides. */
3798 {
3801 /* Make sure the two fields on the right
3802 correspond to the left without being swapped. */
3810 volatilep);
3820 {
3823 }
3830 /* Make a mask that corresponds to both fields being compared.
3831 Do this for both items being compared. If the operands are the
3832 same size and the bits being compared are in the same position
3833 then we can do this by masking both and comparing the masked
3834 results. */
3838 {
3850 }
3852 /* There is still another way we can do something: If both pairs of
3853 fields being compared are adjacent, we may be able to make a wider
3854 field containing them both.
3856 Note that we still must mask the lhs/rhs expressions. Furthermore,
3857 the mask must be shifted to account for the shift done by
3858 make_bit_field_ref. */
3863 {
3864 tree type;
3876 /* Convert to the smaller type before masking out unwanted bits. */
3879 {
3881 {
3885 }
3887 {
3891 }
3892 }
3901 }
3904 }
3906 /* Handle the case of comparisons with constants. If there is something in
3907 common between the masks, those bits of the constants must be the same.
3908 If not, the condition is always false. Test for this to avoid generating
3909 incorrect code below. */
3914 {
3916 {
3919 }
3920 else
3921 {
3924 }
3925 }
3927 /* Construct the expression we will return. First get the component
3928 reference we will make. Unless the mask is all ones the width of
3929 that field, perform the mask operation. Then compare with the
3930 merged constant. */
3940 }
3941 \f
3942 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
3943 constant. */
3945 static tree
3947 {
3952 tree minmax_const;
3954 tree inner;
3964 /* If something does not permit us to optimize, return the original tree. */
3972 /* Now handle all the various comparison codes. We only handle EQ_EXPR
3973 and GT_EXPR, doing the rest with recursive calls using logical
3974 simplifications. */
3976 {
3978 return
3982 return
3984 optimize_minmax_comparison
3986 optimize_minmax_comparison
3991 /* MAX (X, 0) == 0 -> X <= 0 */
3995 /* MAX (X, 0) == 5 -> X == 5 */
3999 /* MAX (X, 0) == -1 -> false */
4003 /* MIN (X, 0) == 0 -> X >= 0 */
4007 /* MIN (X, 0) == 5 -> false */
4010 else
4011 /* MIN (X, 0) == -1 -> X == -1 */
4016 /* MAX (X, 0) > 0 -> X > 0
4017 MAX (X, 0) > 5 -> X > 5 */
4021 /* MAX (X, 0) > -1 -> true */
4025 /* MIN (X, 0) > 0 -> false
4026 MIN (X, 0) > 5 -> false */
4029 else
4030 /* MIN (X, 0) > -1 -> X > -1 */
4035 }
4036 }
4037 \f
4038 /* T is an integer expression that is being multiplied, divided, or taken a
4039 modulus (CODE says which and what kind of divide or modulus) by a
4040 constant C. See if we can eliminate that operation by folding it with
4041 other operations already in T. WIDE_TYPE, if non-null, is a type that
4042 should be used for the computation if wider than our type.
4044 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4045 (X * 2) + (Y * 4). We must, however, be assured that either the original
4046 expression would not overflow or that overflow is undefined for the type
4047 in the language in question.
4049 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4050 the machine has a multiply-accumulate insn or that this is part of an
4051 addressing calculation.
4053 If we return a non-null expression, it is an equivalent form of the
4054 original computation, but need not be in the original type. */
4056 static tree
4058 {
4059 /* To avoid exponential search depth, refuse to allow recursion past
4060 three levels. Beyond that (1) it's highly unlikely that we'll find
4061 something interesting and (2) we've probably processed it before
4062 when we built the inner expression. */
4065 tree ret;
4070 depth++;
4072 depth--;
4075 }
4077 static tree
4079 {
4089 /* Don't deal with constants of zero here; they confuse the code below. */
4099 /* Note that we need not handle conditional operations here since fold
4100 already handles those cases. So just do arithmetic here. */
4102 {
4104 /* For a constant, we can always simplify if we are a multiply
4105 or (for divide and modulus) if it is a multiple of our constant. */
4112 /* If op0 is an expression ... */
4117 /* ... and is unsigned, and its type is smaller than ctype,
4118 then we cannot pass through as widening. */
4124 /* ... or its type is larger than ctype,
4125 then we cannot pass through this truncation. */
4128 /* ... or signedness changes for division or modulus,
4129 then we cannot pass through this conversion. */
4135 /* Pass the constant down and see if we can make a simplification. If
4136 we can, replace this expression with the inner simplification for
4137 possible later conversion to our or some other type. */
4142 code == MULT_EXPR
4153 /* If widening the type changes the signedness, then we can't perform
4154 this optimization as that changes the result. */
4158 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4161 {
4167 }
4177 /* If the second operand is constant, this is a multiplication
4178 or floor division, by a power of two, so we can treat it that
4179 way unless the multiplier or divisor overflows. */
4181 /* const_binop may not detect overflow correctly,
4182 so check for it explicitly here. */
4196 /* See if we can eliminate the operation on both sides. If we can, we
4197 can return a new PLUS or MINUS. If we can't, the only remaining
4198 cases where we can do anything are if the second operand is a
4199 constant. */
4204 /* If not multiplication, we can only do this if both operands
4205 are divisible by c. */
4211 /* If this was a subtraction, negate OP1 and set it to be an addition.
4212 This simplifies the logic below. */
4219 /* If either OP1 or C are negative, this optimization is not safe for
4220 some of the division and remainder types while for others we need
4221 to change the code. */
4223 {
4231 }
4233 /* If it's a multiply or a division/modulus operation of a multiple
4234 of our constant, do the operation and verify it doesn't overflow. */
4237 {
4241 }
4242 else
4245 /* If we have an unsigned type is not a sizetype, we cannot widen
4246 the operation since it will change the result if the original
4247 computation overflowed. */
4253 /* If we were able to eliminate our operation from the first side,
4254 apply our operation to the second side and reform the PLUS. */
4258 /* The last case is if we are a multiply. In that case, we can
4259 apply the distributive law to commute the multiply and addition
4260 if the multiplication of the constants doesn't overflow. */
4265 op1));
4270 /* We have a special case here if we are doing something like
4271 (C * 8) % 4 since we know that's zero. */
4278 /* ... fall through ... */
4282 /* If we can extract our operation from the LHS, do so and return a
4283 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4284 do something only if the second operand is a constant. */
4296 /* If these are the same operation types, we can associate them
4297 assuming no overflow. */
4304 /* If these operations "cancel" each other, we have the main
4305 optimizations of this pass, which occur when either constant is a
4306 multiple of the other, in which case we replace this with either an
4307 operation or CODE or TCODE.
4309 If we have an unsigned type that is not a sizetype, we cannot do
4310 this since it will change the result if the original computation
4311 overflowed. */
4314 && ! flag_wrapv
4319 {
4330 }
4335 }
4338 }
4339 \f
4340 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4341 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4342 that we may sometimes modify the tree. */
4344 static tree
4346 {
4349 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4354 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4355 don't bother handling any other types. */
4357 {
4361 }
4366 {
4369 }
4372 }
4373 \f
4374 /* Return a node which has the indicated constant VALUE (either 0 or
4375 1), and is of the indicated TYPE. */
4377 static tree
4379 {
4384 integer_zero_node);
4385 else
4386 {
4391 }
4392 }
4394 /* Utility function for the following routine, to see how complex a nesting of
4395 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4396 we don't care (to avoid spending too much time on complex expressions.). */
4398 static int
4400 {
4411 }
4413 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4414 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4415 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4416 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4417 COND is the first argument to CODE; otherwise (as in the example
4418 given here), it is the second argument. TYPE is the type of the
4419 original expression. */
4421 static tree
4424 {
4428 /* In the end, we'll produce a COND_EXPR. Both arms of the
4429 conditional expression will be binary operations. The left-hand
4430 side of the expression to be executed if the condition is true
4431 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4432 of the expression to be executed if the condition is true will be
4433 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4434 but apply to the expression to be executed if the conditional is
4435 false. */
4440 /* These are the codes to use for the left-hand side and right-hand
4441 side of the COND_EXPR. Normally, they are the same as CODE. */
4444 /* And these are the types of the expressions. */
4450 {
4454 }
4455 else
4456 {
4460 }
4463 {
4467 /* If this operand throws an expression, then it does not make
4468 sense to try to perform a logical or arithmetic operation
4469 involving it. Instead of building `a + throw 3' for example,
4470 we simply build `a, throw 3'. */
4472 {
4474 {
4477 }
4478 else
4480 }
4482 {
4484 {
4487 }
4488 else
4490 }
4491 }
4492 else
4493 {
4498 }
4500 /* If ARG is complex we want to make sure we only evaluate it once. Though
4501 this is only required if it is volatile, it might be more efficient even
4502 if it is not. However, if we succeed in folding one part to a constant,
4503 we do not need to make this SAVE_EXPR. Since we do this optimization
4504 primarily to see if we do end up with constant and this SAVE_EXPR
4505 interferes with later optimizations, suppressing it when we can is
4506 important.
4508 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4509 do so. Don't try to see if the result is a constant if an arm is a
4510 COND_EXPR since we get exponential behavior in that case. */
4519 {
4528 {
4532 }
4533 }
4546 else
4548 }
4550 \f
4551 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4553 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4554 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4555 ADDEND is the same as X.
4557 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4558 and finite. The problematic cases are when X is zero, and its mode
4559 has signed zeros. In the case of rounding towards -infinity,
4560 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4561 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4563 static bool
4565 {
4569 /* Don't allow the fold with -fsignaling-nans. */
4573 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4577 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4582 /* The mode has signed zeros, and we have to honor their sign.
4583 In this situation, there is only one case we can return true for.
4584 X - 0 is the same as X unless rounding towards -infinity is
4585 supported. */
4587 }
4589 /* Subroutine of fold() that checks comparisons of built-in math
4590 functions against real constants.
4592 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
4593 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
4594 is the type of the result and ARG0 and ARG1 are the operands of the
4595 comparison. ARG1 must be a TREE_REAL_CST.
4597 The function returns the constant folded tree if a simplification
4598 can be made, and NULL_TREE otherwise. */
4600 static tree
4603 {
4604 REAL_VALUE_TYPE c;
4609 {
4615 {
4616 /* sqrt(x) < y is always false, if y is negative. */
4620 arg);
4622 /* sqrt(x) > y is always true, if y is negative and we
4623 don't care about NaNs, i.e. negative values of x. */
4627 arg);
4629 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
4632 }
4634 {
4635 REAL_VALUE_TYPE c2;
4641 {
4642 /* sqrt(x) > y is x == +Inf, when y is very large. */
4647 /* sqrt(x) > y is always false, when y is very large
4648 and we don't care about infinities. */
4651 arg);
4652 }
4654 /* sqrt(x) > c is the same as x > c*c. */
4657 }
4659 {
4660 REAL_VALUE_TYPE c2;
4666 {
4667 /* sqrt(x) < y is always true, when y is a very large
4668 value and we don't care about NaNs or Infinities. */
4672 arg);
4674 /* sqrt(x) < y is x != +Inf when y is very large and we
4675 don't care about NaNs. */
4680 /* sqrt(x) < y is x >= 0 when y is very large and we
4681 don't care about Infinities. */
4686 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
4695 dconst0))),
4698 c2)))));
4699 }
4701 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
4706 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
4709 {
4714 dconst0))),
4717 c2)))));
4718 }
4719 }
4720 }
4723 }
4725 /* Subroutine of fold() that optimizes comparisons against Infinities,
4726 either +Inf or -Inf.
4728 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
4729 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
4730 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
4732 The function returns the constant folded tree if a simplification
4733 can be made, and NULL_TREE otherwise. */
4735 static tree
4737 {
4739 REAL_VALUE_TYPE max;
4740 tree temp;
4745 /* For negative infinity swap the sense of the comparison. */
4751 {
4753 /* x > +Inf is always false, if with ignore sNANs. */
4758 arg0);
4761 /* x <= +Inf is always true, if we don't case about NaNs. */
4765 arg0);
4767 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
4770 {
4773 }
4778 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
4784 /* x < +Inf is always equal to x <= DBL_MAX. */
4790 /* x != +Inf is always equal to !(x > DBL_MAX). */
4801 }
4804 }
4806 /* If CODE with arguments ARG0 and ARG1 represents a single bit
4807 equality/inequality test, then return a simplified form of
4808 the test using shifts and logical operations. Otherwise return
4809 NULL. TYPE is the desired result type. */
4811 tree
4813 tree result_type)
4814 {
4815 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
4816 operand 0. */
4818 {
4823 /* Extract the arguments of the EQ/NE. */
4827 /* This requires us to invert the code. */
4829 }
4831 /* If this is testing a single bit, we can optimize the test. */
4835 {
4842 tree arg00;
4844 /* If we have (A & C) != 0 where C is the sign bit of A, convert
4845 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
4848 {
4853 }
4855 /* At this point, we know that arg0 is not testing the sign bit. */
4859 /* Otherwise we have (A & C) != 0 where C is a single bit,
4860 convert that into ((A >> C2) & 1). Where C2 = log2(C).
4861 Similarly for (A & C) == 0. */
4863 /* If INNER is a right shift of a constant and it plus BITNUM does
4864 not overflow, adjust BITNUM and INNER. */
4871 {
4874 }
4876 /* If we are going to be able to omit the AND below, we must do our
4877 operations as unsigned. If we must use the AND, we have a choice.
4878 Normally unsigned is faster, but for some machines signed is. */
4879 #ifdef LOAD_EXTEND_OP
4881 #else
4883 #endif
4896 /* Put the AND last so it can combine with more things. */
4900 /* Make sure to return the proper type. */
4905 }
4907 }
4909 /* Perform constant folding and related simplification of EXPR.
4910 The related simplifications include x*1 => x, x*0 => 0, etc.,
4911 and application of the associative law.
4912 NOP_EXPR conversions may be removed freely (as long as we
4913 are careful not to change the C type of the overall expression)
4914 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4915 but we can constant-fold them if they have constant operands. */
4917 tree
4919 {
4922 tree tem;
4928 /* WINS will be nonzero when the switch is done
4929 if all operands are constant. */
4932 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4933 Likewise for a SAVE_EXPR that's already been evaluated. */
4937 /* Return right away if a constant. */
4941 #ifdef MAX_INTEGER_COMPUTATION_MODE
4943 #endif
4946 {
4947 tree subop;
4949 /* Special case for conversion ops that can have fixed point args. */
4952 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4958 else
4963 )
4964 /* Note that TREE_CONSTANT isn't enough:
4965 static var addresses are constant but we can't
4966 do arithmetic on them. */
4968 }
4970 {
4974 {
4976 tree subop;
4982 {
4983 /* Signedness matters here. Perhaps we can refine this
4984 later. */
4986 }
4987 else
4988 /* Strip any conversions that don't change the mode. */
4993 else
4998 /* Note that TREE_CONSTANT isn't enough:
4999 static var addresses are constant but we can't
5000 do arithmetic on them. */
5007 }
5008 }
5010 /* If this is a commutative operation, and ARG0 is a constant, move it
5011 to ARG1 to reduce the number of tests below. */
5016 {
5021 }
5023 /* Now WINS is set as described above,
5024 ARG0 is the first operand of EXPR,
5025 and ARG1 is the second operand (if it has more than one operand).
5027 First check for cases where an arithmetic operation is applied to a
5028 compound, conditional, or comparison operation. Push the arithmetic
5029 operation inside the compound or conditional to see if any folding
5030 can then be done. Convert comparison to conditional for this purpose.
5031 The also optimizes non-constant cases that used to be done in
5032 expand_expr.
5034 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5035 one of the operands is a comparison and the other is a comparison, a
5036 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5037 code below would make the expression more complex. Change it to a
5038 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5039 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5051 {
5061 }
5064 {
5069 {
5079 /* If this was a conversion, and all we did was to move into
5080 inside the COND_EXPR, bring it back out. But leave it if
5081 it is a conversion from integer to integer and the
5082 result precision is no wider than a word since such a
5083 conversion is cheap and may be optimized away by combine,
5084 while it couldn't if it were outside the COND_EXPR. Then return
5085 so we don't get into an infinite recursion loop taking the
5086 conversion out and then back in. */
5098 && (INTEGRAL_TYPE_P
5109 }
5114 }
5125 {
5140 return
5154 return
5157 }
5160 {
5176 /* Other kinds of FIX are not handled properly by fold_convert. */
5181 /* Handle cases of two conversions in a row. */
5184 {
5204 /* In addition to the cases of two conversions in a row
5205 handled below, if we are converting something to its own
5206 type via an object of identical or wider precision, neither
5207 conversion is needed. */
5213 /* Likewise, if the intermediate and final types are either both
5214 float or both integer, we don't need the middle conversion if
5215 it is wider than the final type and doesn't change the signedness
5216 (for integers). Avoid this if the final type is a pointer
5217 since then we sometimes need the inner conversion. Likewise if
5218 the outer has a precision not equal to the size of its mode. */
5228 /* If we have a sign-extension of a zero-extended value, we can
5229 replace that by a single zero-extension. */
5235 /* Two conversions in a row are not needed unless:
5236 - some conversion is floating-point (overstrict for now), or
5237 - the intermediate type is narrower than both initial and
5238 final, or
5239 - the intermediate type and innermost type differ in signedness,
5240 and the outermost type is wider than the intermediate, or
5241 - the initial type is a pointer type and the precisions of the
5242 intermediate and final types differ, or
5243 - the final type is a pointer type and the precisions of the
5244 initial and intermediate types differ. */
5258 }
5262 /* Detect assigning a bitfield. */
5265 {
5266 /* Don't leave an assignment inside a conversion
5267 unless assigning a bitfield. */
5270 /* First do the assignment, then return converted constant. */
5274 }
5276 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5277 constants (if x has signed type, the sign bit cannot be set
5278 in c). This folds extension into the BIT_AND_EXPR. */
5283 {
5293 <= HOST_BITS_PER_WIDE_INT
5295 {
5302 #ifdef LOAD_EXTEND_OP
5306 {
5310 }
5311 #endif
5312 }
5317 }
5320 {
5323 }
5335 {
5339 }
5348 {
5350 {
5352 HOST_WIDE_INT high;
5363 }
5366 }
5369 /* Convert -((double)float) into (double)(-float). */
5372 {
5377 }
5379 /* Convert - (a - b) to (b - a) for non-floating-point. */
5385 /* Convert -f(x) into f(-x) where f is sin, tan or atan. */
5387 {
5398 {
5406 }
5411 }
5416 {
5418 {
5419 /* If the value is unsigned, then the absolute value is
5420 the same as the ordinary value. */
5423 /* Similarly, if the value is non-negative. */
5426 /* If the value is negative, then the absolute value is
5427 its negation. */
5428 else
5429 {
5431 HOST_WIDE_INT high;
5442 }
5443 }
5445 {
5449 }
5450 }
5453 /* Convert fabs((double)float) into (double)fabsf(float). */
5456 {
5460 targ0)));
5461 }
5488 {
5495 }
5501 /* A + (-B) -> A - B */
5504 /* (-A) + B -> B - A */
5508 {
5512 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5513 with a constant, and the two constants have no bits in common,
5514 we should treat this as a BIT_IOR_EXPR since this may produce more
5515 simplifications. */
5523 {
5526 }
5528 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5529 (plus (plus (mult) (mult)) (foo)) so that we can
5530 take advantage of the factoring cases below. */
5535 {
5540 else
5561 }
5564 {
5568 /* (A * C) + (B * C) -> (A+B) * C.
5569 We are most concerned about the case where C is a constant,
5570 but other combinations show up during loop reduction. Since
5571 it is not difficult, try all four possibilities. */
5588 /* No identical multiplicands; see if we can find a common
5589 power-of-two factor in non-power-of-two multiplies. This
5590 can help in multi-dimensional array access. */
5595 {
5600 /* Move min of absolute values to int11. */
5603 {
5607 }
5610 {
5615 }
5616 }
5621 same));
5622 }
5623 }
5625 /* See if ARG1 is zero and X + ARG1 reduces to X. */
5629 /* Likewise if the operands are reversed. */
5633 bit_rotate:
5634 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5635 is a rotate of A by C1 bits. */
5636 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5637 is a rotate of A by B bits. */
5638 {
5647 {
5666 {
5674 TYPE_PRECISION
5679 ? LROTATE_EXPR
5682 }
5684 {
5692 TYPE_PRECISION
5697 ? LROTATE_EXPR
5700 }
5701 }
5702 }
5704 associate:
5705 /* In most languages, can't associate operations on floats through
5706 parentheses. Rather than remember where the parentheses were, we
5707 don't associate floats at all. It shouldn't matter much. However,
5708 associating multiplications is only very slightly inaccurate, so do
5709 that if -funsafe-math-optimizations is specified. */
5714 {
5718 /* Split both trees into variables, constants, and literals. Then
5719 associate each group together, the constants with literals,
5720 then the result with variables. This increases the chances of
5721 literals being recombined later and of generating relocatable
5722 expressions for the sum of a constant and literal. */
5727 /* Only do something if we found more than two objects. Otherwise,
5728 nothing has changed and we risk infinite recursion. */
5733 {
5734 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
5743 /* Preserve the MINUS_EXPR if the negative part of the literal is
5744 greater than the positive part. Otherwise, the multiplicative
5745 folding code (i.e extract_muldiv) may be fooled in case
5746 unsigned constants are subtracted, like in the following
5747 example: ((X*2 + 4) - 8U)/2. */
5749 {
5751 {
5755 }
5756 else
5757 {
5761 }
5762 }
5764 {
5768 else
5769 {
5774 }
5775 }
5779 }
5780 }
5782 binary:
5786 {
5787 /* The return value should always have
5788 the same type as the original expression. */
5793 }
5797 /* A - (-B) -> A + B */
5800 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
5811 {
5817 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5818 about the case where C is a constant, just try one of the
5819 four possibilities. */
5830 /* Fold A - (A & B) into ~B & A. */
5833 {
5838 arg0));
5843 arg0));
5844 }
5845 }
5847 /* See if ARG1 is zero and X - ARG1 reduces to X. */
5851 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
5852 ARG0 is zero and X + ARG0 reduces to X, since that would mean
5853 (-ARG1 + ARG0) reduces to -ARG1. */
5857 /* Fold &x - &x. This can happen from &x.foo - &x.
5858 This is unsafe for certain floats even in non-IEEE formats.
5859 In IEEE, it is unsafe because it does wrong for NaNs.
5860 Also note that operand_equal_p is always false if an operand
5861 is volatile. */
5870 /* (-A) * (-B) -> A * B */
5876 {
5882 /* (a * (1 << b)) is (a << b) */
5898 }
5899 else
5900 {
5901 /* Maybe fold x * 0 to 0. The expressions aren't the same
5902 when x is NaN, since x * 0 is also NaN. Nor are they the
5903 same in modes with signed zeros, since multiplying a
5904 negative value by 0 gives -0, not +0. */
5909 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
5914 /* Transform x * -1.0 into -x. */
5919 /* x*2 is x+x */
5923 {
5926 }
5929 {
5933 /* Optimizations of sqrt(...)*sqrt(...). */
5937 {
5942 /* Optimize sqrt(x)*sqrt(x) as x. */
5947 /* Optimize sqrt(x)*sqrt(y) as sqrt(x*y). */
5952 }
5954 /* Optimize exp(x)*exp(y) as exp(x+y). */
5958 {
5965 }
5967 /* Optimizations of pow(...)*pow(...). */
5971 {
5979 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
5981 {
5986 arg01));
5988 }
5990 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
5992 {
5997 arg));
5999 }
6000 }
6002 /* Optimize tan(x)*cos(x) as sin(x). */
6011 {
6012 tree sinfn;
6015 {
6030 }
6035 }
6036 }
6037 }
6041 bit_ior:
6050 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6052 This results in more efficient code for machines without a NAND
6053 instruction. Combine will canonicalize to the first form
6054 which will allow use of NAND instructions provided by the
6055 backend if they exist. */
6058 {
6063 }
6065 /* See if this can be simplified into a rotate first. If that
6066 is unsuccessful continue in the association code. */
6075 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6076 with a constant, and the two constants have no bits in common,
6077 we should treat this as a BIT_IOR_EXPR since this may produce more
6078 simplifications. */
6086 {
6089 }
6091 /* See if this can be simplified into a rotate first. If that
6092 is unsuccessful continue in the association code. */
6096 bit_and:
6104 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6107 {
6108 unsigned int prec
6115 }
6117 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6119 This results in more efficient code for machines without a NOR
6120 instruction. Combine will canonicalize to the first form
6121 which will allow use of NOR instructions provided by the
6122 backend if they exist. */
6125 {
6130 }
6140 {
6144 }
6148 /* Don't touch a floating-point divide by zero unless the mode
6149 of the constant can represent infinity. */
6155 /* (-A) / (-B) -> A / B */
6160 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6165 /* If ARG1 is a constant, we can convert this to a multiply by the
6166 reciprocal. This does not have the same rounding properties,
6167 so only do this if -funsafe-math-optimizations. We can actually
6168 always safely do it if ARG1 is a power of two, but it's hard to
6169 tell if it is or not in a portable manner. */
6171 {
6176 /* Find the reciprocal if optimizing and the result is exact. */
6178 {
6179 REAL_VALUE_TYPE r;
6182 {
6185 }
6186 }
6187 }
6188 /* Convert A/B/C to A/(B*C). */
6191 {
6194 arg1)));
6195 }
6196 /* Convert A/(B/C) to (A/B)*C. */
6199 {
6204 }
6207 {
6209 /* Optimize x/exp(y) into x*exp(-y). */
6213 {
6220 }
6222 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6226 {
6235 }
6236 }
6239 {
6243 /* Optimize sin(x)/cos(x) as tan(x). */
6249 {
6250 tree tanfn;
6258 else
6264 }
6266 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
6272 {
6273 tree tanfn;
6281 else
6285 {
6290 tmp));
6291 }
6292 }
6293 }
6306 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
6307 operation, EXACT_DIV_EXPR.
6309 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
6310 At one time others generated faster code, it's not clear if they do
6311 after the last round to changes to the DIV code in expmed.c. */
6346 /* Optimize -1 >> x for arithmetic right shifts. */
6349 /* ... fall through ... */
6352 shift:
6358 /* Since negative shift count is not well-defined,
6359 don't try to compute it in the compiler. */
6362 /* Rewrite an LROTATE_EXPR by a constant into an
6363 RROTATE_EXPR by a new constant. */
6365 {
6369 = const_binop
6376 }
6378 /* If we have a rotate of a bit operation with the rotate count and
6379 the second operand of the bit operation both constant,
6380 permute the two operations. */
6393 /* Two consecutive rotates adding up to the width of the mode can
6394 be ignored. */
6425 /* Note that the operand of this must be an int
6426 and its values must be 0 or 1.
6427 ("true" is a fixed value perhaps depending on the language,
6428 but we don't handle values other than 1 correctly yet.) */
6430 /* Avoid infinite recursion. */
6432 {
6437 }
6441 /* Note that the operands of this must be ints
6442 and their values must be 0 or 1.
6443 ("true" is a fixed value perhaps depending on the language.) */
6444 /* If first arg is constant zero, return it. */
6448 /* If either arg is constant true, drop it. */
6452 /* Preserve sequence points. */
6455 /* If second arg is constant zero, result is zero, but first arg
6456 must be evaluated. */
6459 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6460 case will be handled here. */
6464 truth_andor:
6465 /* We only do these simplifications if we are optimizing. */
6469 /* Check for things like (A || B) && (A || C). We can convert this
6470 to A || (B && C). Note that either operator can be any of the four
6471 truth and/or operations and the transformation will still be
6472 valid. Also note that we only care about order for the
6473 ANDIF and ORIF operators. If B contains side effects, this
6474 might change the truth-value of A. */
6481 {
6501 /* This case if tricky because we must either have commutative
6502 operators or else A10 must not have side-effects. */
6508 a01));
6509 }
6511 /* See if we can build a range comparison. */
6515 /* Check for the possibility of merging component references. If our
6516 lhs is another similar operation, try to merge its rhs with our
6517 rhs. Then try to merge our lhs and rhs. */
6529 /* Note that the operands of this must be ints
6530 and their values must be 0 or true.
6531 ("true" is a fixed value perhaps depending on the language.) */
6532 /* If first arg is constant true, return it. */
6536 /* If either arg is constant zero, drop it. */
6540 /* Preserve sequence points. */
6543 /* If second arg is constant true, result is true, but we must
6544 evaluate first arg. */
6547 /* Likewise for first arg, but note this only occurs here for
6548 TRUTH_OR_EXPR. */
6554 /* If either arg is constant zero, drop it. */
6559 /* If either arg is constant true, this is a logical inversion. */
6572 /* If one arg is a real or integer constant, put it last. */
6577 {
6584 }
6587 {
6595 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
6600 /* (-a) CMP (-b) -> b CMP a */
6607 {
6608 REAL_VALUE_TYPE cst;
6611 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6613 return
6619 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6620 /* a CMP (-0) -> a CMP 0 */
6625 /* x != NaN is always true, other ops are always false. */
6628 {
6631 }
6633 /* Fold comparisons against infinity. */
6635 {
6639 }
6640 }
6642 /* If this is a comparison of a real constant with a PLUS_EXPR
6643 or a MINUS_EXPR of a real constant, we can convert it into a
6644 comparison with a revised real constant as long as no overflow
6645 occurs when unsafe_math_optimizations are enabled. */
6657 /* Likewise, we can simplify a comparison of a real constant with
6658 a MINUS_EXPR whose first operand is also a real constant, i.e.
6659 (c1 - x) < c2 becomes x > c1-c2. */
6670 /* Fold comparisons against built-in math functions. */
6672 && flag_unsafe_math_optimizations
6674 {
6678 {
6682 }
6683 }
6684 }
6686 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6687 First, see if one arg is constant; find the constant arg
6688 and the other one. */
6689 {
6699 {
6700 /* This optimization is invalid for ordered comparisons
6701 if CONST+INCR overflows or if foo+incr might overflow.
6702 This optimization is invalid for floating point due to rounding.
6703 For pointer types we assume overflow doesn't happen. */
6707 {
6708 tree newconst
6712 /* Do not overwrite the current varop to be a preincrement,
6713 create a new node so that we won't confuse our caller who
6714 might create trees and throw them away, reusing the
6715 arguments that they passed to build. This shows up in
6716 the THEN or ELSE parts of ?: being postincrements. */
6721 /* If VAROP is a reference to a bitfield, we must mask
6722 the constant by the width of the field. */
6726 {
6727 int size
6729 (TREE_OPERAND
6733 tree folded_compare;
6735 /* First check whether the comparison would come out
6736 always the same. If we don't do that we would
6737 change the meaning with the masking. */
6741 else
6744 constop));
6759 mask)));
6760 }
6766 }
6767 }
6769 {
6773 {
6774 tree newconst
6778 /* Do not overwrite the current varop to be a predecrement,
6779 create a new node so that we won't confuse our caller who
6780 might create trees and throw them away, reusing the
6781 arguments that they passed to build. This shows up in
6782 the THEN or ELSE parts of ?: being postdecrements. */
6790 {
6791 int size
6793 (TREE_OPERAND
6797 tree folded_compare;
6802 else
6805 constop));
6820 mask)));
6821 }
6827 }
6828 }
6829 }
6831 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
6832 This transformation affects the cases which are handled in later
6833 optimizations involving comparisons with non-negative constants. */
6837 {
6839 {
6854 }
6855 }
6857 /* Comparisons with the highest or lowest possible integer of
6858 the specified size will have known values. */
6859 {
6867 {
6874 {
6877 }
6878 else
6879 {
6882 }
6887 {
6891 arg0);
6899 arg0);
6905 /* The GE_EXPR and LT_EXPR cases above are not normally
6906 reached because of previous transformations. */
6910 }
6914 {
6927 }
6931 {
6935 arg0);
6944 arg0);
6952 }
6956 {
6969 }
6974 /* signed_type does not work on pointer types. */
6976 {
6977 /* The following case also applies to X < signed_max+1
6978 and X >= signed_max+1 because previous transformations. */
6980 {
6984 return fold
6988 }
6989 }
6990 }
6991 }
6993 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6994 a MINUS_EXPR of a constant, we can convert it into a comparison with
6995 a revised constant as long as no overflow occurs. */
7007 /* Similarly for a NEGATE_EXPR. */
7016 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7017 for !=. Don't do this for ordered comparisons due to overflow. */
7023 /* If we are widening one operand of an integer comparison,
7024 see if the other operand is similarly being widened. Perhaps we
7025 can do the comparison in the narrower type. */
7035 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7036 constant, we can simplify it. */
7043 /* If we are comparing an ABS_EXPR with a constant, we can
7044 convert all the cases into explicit comparisons, but they may
7045 well not be faster than doing the ABS and one comparison.
7046 But ABS (X) <= C is a range comparison, which becomes a subtraction
7047 and a comparison, and is probably faster. */
7059 /* If this is an EQ or NE comparison with zero and ARG0 is
7060 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7061 two operations, but the latter can be done in one less insn
7062 on machines that have only two-operand insns or on which a
7063 constant cannot be the first operand. */
7066 {
7069 return
7077 integer_one_node)),
7078 arg1));
7081 return
7089 integer_one_node)),
7090 arg1));
7091 }
7093 /* If this is an NE or EQ comparison of zero against the result of a
7094 signed MOD operation whose second operand is a power of 2, make
7095 the MOD operation unsigned since it is simpler and equivalent. */
7104 {
7111 }
7113 /* If this is an NE comparison of zero with an AND of one, remove the
7114 comparison since the AND will give the correct value. */
7120 /* If we have (A & C) == C where C is a power of 2, convert this into
7121 (A & C) != 0. Similarly for NE_EXPR. */
7129 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7130 2, then fold the expression into shifts and logical operations. */
7135 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7136 and similarly for >= into !=. */
7152 return
7159 /* Simplify comparison of something with itself. (For IEEE
7160 floating-point, we can only do some of these simplifications.) */
7162 {
7164 {
7176 /* For NE, we can only do this simplification if integer
7177 or we don't honor IEEE floating point NaNs. */
7181 /* ... fall through ... */
7187 }
7188 }
7190 /* If we are comparing an expression that just has comparisons
7191 of two integer values, arithmetic expressions of those comparisons,
7192 and constants, we can simplify it. There are only three cases
7193 to check: the two values can either be equal, the first can be
7194 greater, or the second can be greater. Fold the expression for
7195 those three values. Since each value must be 0 or 1, we have
7196 eight possibilities, each of which corresponds to the constant 0
7197 or 1 or one of the six possible comparisons.
7199 This handles common cases like (a > b) == 0 but also handles
7200 expressions like ((x > y) - (y > x)) > 0, which supposedly
7201 occur in macroized code. */
7204 {
7209 /* Don't handle degenerate cases here; they should already
7210 have been handled anyway. */
7219 {
7223 /* We can't just pass T to eval_subst in case cval1 or cval2
7224 was the same as ARG1. */
7226 tree high_result
7229 arg1));
7230 tree equal_result
7233 arg1));
7234 tree low_result
7237 arg1));
7239 /* All three of these results should be 0 or 1. Confirm they
7240 are. Then use those values to select the proper code
7241 to use. */
7249 {
7250 /* Make a 3-bit mask with the high-order bit being the
7251 value for `>', the next for '=', and the low for '<'. */
7255 {
7257 /* Always false. */
7278 /* Always true. */
7280 }
7285 else
7287 }
7288 }
7289 }
7291 /* If this is a comparison of a field, we may be able to simplify it. */
7296 /* Handle the constant case even without -O
7297 to make sure the warnings are given. */
7299 {
7302 }
7304 /* If this is a comparison of complex values and either or both sides
7305 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
7306 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
7307 This may prevent needless evaluations. */
7314 {
7327 type,
7330 }
7332 /* Optimize comparisons of strlen vs zero to a compare of the
7333 first character of the string vs zero. To wit,
7334 strlen(ptr) == 0 => *ptr == 0
7335 strlen(ptr) != 0 => *ptr != 0
7336 Other cases should reduce to one of these two (or a constant)
7337 due to the return value of strlen being unsigned. */
7342 {
7344 tree arglist;
7356 integer_zero_node));
7357 }
7359 /* From here on, the only cases we handle are when the result is
7360 known to be a constant.
7362 To compute GT, swap the arguments and do LT.
7363 To compute GE, do LT and invert the result.
7364 To compute LE, swap the arguments, do LT and invert the result.
7365 To compute NE, do EQ and invert the result.
7367 Therefore, the code below must handle only EQ and LT. */
7370 {
7373 }
7375 /* Note that it is safe to invert for real values here because we
7376 will check below in the one case that it matters. */
7381 {
7384 }
7386 /* Compute a result for LT or EQ if args permit;
7387 otherwise return T. */
7389 {
7392 else
7397 }
7400 /* Assume a nonexplicit constant cannot equal an explicit one,
7401 since such code would be undefined anyway.
7402 Exception: on sysvr4, using #pragma weak,
7403 a label can come out as 0. */
7410 #endif
7411 /* Two real constants can be compared explicitly. */
7413 {
7414 /* If either operand is a NaN, the result is false with two
7415 exceptions: First, an NE_EXPR is true on NaNs, but that case
7416 is already handled correctly since we will be inverting the
7417 result for NE_EXPR. Second, if we had inverted a LE_EXPR
7418 or a GE_EXPR into a LT_EXPR, we must return true so that it
7419 will be inverted into false. */
7429 else
7433 }
7447 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
7448 so all simple results must be passed through pedantic_non_lvalue. */
7450 return pedantic_non_lvalue
7455 /* If the second operand is zero, invert the comparison and swap
7456 the second and third operands. Likewise if the second operand
7457 is constant and the third is not or if the third operand is
7458 equivalent to the first operand of the comparison. */
7466 {
7467 /* See if this can be inverted. If it can't, possibly because
7468 it was a floating-point inequality comparison, don't do
7469 anything. */
7473 {
7477 /* arg1 should be the first argument of the new T. */
7480 }
7481 }
7483 /* If we have A op B ? A : C, we may be able to convert this to a
7484 simpler expression, depending on the operation and the values
7485 of B and C. Signed zeros prevent all of these transformations,
7486 for reasons given above each one. */
7492 {
7498 /* If we have A op 0 ? A : -A, consider applying the following
7499 transformations:
7501 A == 0? A : -A same as -A
7502 A != 0? A : -A same as A
7503 A >= 0? A : -A same as abs (A)
7504 A > 0? A : -A same as abs (A)
7505 A <= 0? A : -A same as -abs (A)
7506 A < 0? A : -A same as -abs (A)
7508 None of these transformations work for modes with signed
7509 zeros. If A is +/-0, the first two transformations will
7510 change the sign of the result (from +0 to -0, or vice
7511 versa). The last four will fix the sign of the result,
7512 even though the original expressions could be positive or
7513 negative, depending on the sign of A.
7515 Note that all these transformations are correct if A is
7516 NaN, since the two alternatives (A and -A) are also NaNs. */
7523 {
7525 return
7526 pedantic_non_lvalue
7528 negate_expr
7530 arg1))));
7538 return pedantic_non_lvalue
7546 return pedantic_non_lvalue
7550 arg1)))));
7553 }
7555 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
7556 A == 0 ? A : 0 is always 0 unless A is -0. Note that
7557 both transformations are correct when A is NaN: A != 0
7558 is then true, and A == 0 is false. */
7561 {
7566 }
7568 /* Try some transformations of A op B ? A : B.
7570 A == B? A : B same as B
7571 A != B? A : B same as A
7572 A >= B? A : B same as max (A, B)
7573 A > B? A : B same as max (B, A)
7574 A <= B? A : B same as min (A, B)
7575 A < B? A : B same as min (B, A)
7577 As above, these transformations don't work in the presence
7578 of signed zeros. For example, if A and B are zeros of
7579 opposite sign, the first two transformations will change
7580 the sign of the result. In the last four, the original
7581 expressions give different results for (A=+0, B=-0) and
7582 (A=-0, B=+0), but the transformed expressions do not.
7584 The first two transformations are correct if either A or B
7585 is a NaN. In the first transformation, the condition will
7586 be false, and B will indeed be chosen. In the case of the
7587 second transformation, the condition A != B will be true,
7588 and A will be chosen.
7590 The conversions to max() and min() are not correct if B is
7591 a number and A is not. The conditions in the original
7592 expressions will be false, so all four give B. The min()
7593 and max() versions would give a NaN instead. */
7596 {
7601 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
7603 {
7607 }
7610 {
7617 /* In C++ a ?: expression can be an lvalue, so put the
7618 operand which will be used if they are equal first
7619 so that we can convert this back to the
7620 corresponding COND_EXPR. */
7622 return pedantic_non_lvalue
7632 return pedantic_non_lvalue
7641 }
7642 }
7644 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7645 we might still be able to simplify this. For example,
7646 if C1 is one less or one more than C2, this might have started
7647 out as a MIN or MAX and been transformed by this function.
7648 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7654 {
7656 /* We can replace A with C1 in this case. */
7663 /* If C1 is C2 + 1, this is min(A, C2). */
7668 return pedantic_non_lvalue
7673 /* If C1 is C2 - 1, this is min(A, C2). */
7678 return pedantic_non_lvalue
7683 /* If C1 is C2 - 1, this is max(A, C2). */
7688 return pedantic_non_lvalue
7693 /* If C1 is C2 + 1, this is max(A, C2). */
7698 return pedantic_non_lvalue
7705 }
7706 }
7708 /* If the second operand is simpler than the third, swap them
7709 since that produces better jump optimization results. */
7715 {
7716 /* See if this can be inverted. If it can't, possibly because
7717 it was a floating-point inequality comparison, don't do
7718 anything. */
7722 {
7726 /* arg1 should be the first argument of the new T. */
7729 }
7730 }
7732 /* Convert A ? 1 : 0 to simply A. */
7735 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7736 call to fold will try to move the conversion inside
7737 a COND, which will recurse. In that case, the COND_EXPR
7738 is probably the best choice, so leave it alone. */
7742 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
7743 over COND_EXPR in cases such as floating point comparisons. */
7750 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7751 operation is simply A & 2. */
7762 /* Convert A ? B : 0 into A && B if A and B are truth values. */
7769 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
7773 {
7774 /* Only perform transformation if ARG0 is easily inverted. */
7779 }
7784 /* When pedantic, a compound expression can be neither an lvalue
7785 nor an integer constant expression. */
7788 /* Don't let (0, 0) be null pointer constant. */
7830 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7831 appropriate. */
7836 {
7840 tree arg01;
7851 {
7865 arg01));
7866 }
7869 }
7872 /* Check for a built-in function. */
7877 {
7881 }
7887 }
7889 /* Determine if first argument is a multiple of second argument. Return 0 if
7890 it is not, or we cannot easily determined it to be.
7892 An example of the sort of thing we care about (at this point; this routine
7893 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7894 fold cases do now) is discovering that
7896 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7898 is a multiple of
7900 SAVE_EXPR (J * 8)
7902 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7904 This code also handles discovering that
7906 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7908 is a multiple of 8 so we don't have to worry about dealing with a
7909 possible remainder.
7911 Note that we *look* inside a SAVE_EXPR only to determine how it was
7912 calculated; it is not safe for fold to do much of anything else with the
7913 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7914 at run time. For example, the latter example above *cannot* be implemented
7915 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7916 evaluation time of the original SAVE_EXPR is not necessarily the same at
7917 the time the new expression is evaluated. The only optimization of this
7918 sort that would be valid is changing
7920 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7922 divided by 8 to
7924 SAVE_EXPR (I) * SAVE_EXPR (J)
7926 (where the same SAVE_EXPR (J) is used in the original and the
7927 transformed version). */
7929 static int
7931 {
7939 {
7951 {
7955 /* const_binop may not detect overflow correctly,
7956 so check for it explicitly here. */
7965 }
7969 /* Can't handle conversions from non-integral or wider integral type. */
7975 /* .. fall through ... */
7991 }
7992 }
7994 /* Return true if `t' is known to be non-negative. */
7996 int
7998 {
8000 {
8009 /* These are undefined at zero. This is true even if
8010 C[LT]Z_DEFINED_VALUE_AT_ZERO is set, since what we're
8011 computing here is a user-visible property. */
8025 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8026 both unsigned and at least 2 bits shorter than the result. */
8030 {
8035 {
8039 }
8040 }
8045 {
8046 /* x * x for floating point x is always non-negative. */
8051 }
8053 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8054 both unsigned and their total bits is shorter than the result. */
8058 {
8065 }
8086 {
8091 {
8095 {
8099 }
8100 }
8102 {
8108 }
8109 }
8138 {
8145 {
8187 }
8188 }
8190 /* ... fall through ... */
8194 /* Truth values evaluate to 0 or 1, which is nonnegative. */
8196 }
8198 /* We don't know sign of `t', so be conservative and return false. */
8200 }
8202 /* Return true if `r' is known to be non-negative.
8203 Only handles constants at the moment. */
8205 int
8207 {
8209 {
8219 {
8221 rtx elt;
8226 {
8230 }
8233 }
8237 /* These are always nonnegative. */
8242 }
8243 }