| blob | 3da0ebf6f46a82110a074da04266e969460d5913 |
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. */
95 tree);
115 /* The following constants represent a bit based encoding of GCC's
116 comparison operators. This encoding simplifies transformations
117 on relational comparison operators, such as AND and OR. */
118 #define COMPCODE_FALSE 0
119 #define COMPCODE_LT 1
120 #define COMPCODE_EQ 2
121 #define COMPCODE_LE 3
122 #define COMPCODE_GT 4
123 #define COMPCODE_NE 5
124 #define COMPCODE_GE 6
125 #define COMPCODE_TRUE 7
127 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
128 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
129 and SUM1. Then this yields nonzero if overflow occurred during the
130 addition.
132 Overflow occurs if A and B have the same sign, but A and SUM differ in
133 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
134 sign. */
135 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
136 \f
137 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
138 We do that by representing the two-word integer in 4 words, with only
139 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
140 number. The value of the word is LOWPART + HIGHPART * BASE. */
142 #define LOWPART(x) \
143 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
144 #define HIGHPART(x) \
145 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
146 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
148 /* Unpack a two-word integer into 4 words.
149 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
150 WORDS points to the array of HOST_WIDE_INTs. */
152 static void
154 {
159 }
161 /* Pack an array of 4 words into a two-word integer.
162 WORDS points to the array of words.
163 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
165 static void
168 {
171 }
172 \f
173 /* Make the integer constant T valid for its type by setting to 0 or 1 all
174 the bits in the constant that don't belong in the type.
176 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
177 nonzero, a signed overflow has already occurred in calculating T, so
178 propagate it. */
180 int
182 {
184 HOST_WIDE_INT high;
188 {
189 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
190 Consider doing it via real_convert now. */
192 }
203 else
206 /* First clear all bits that are beyond the type's precision. */
209 ;
213 else
214 {
218 }
220 /* Unsigned types do not suffer sign extension or overflow unless they
221 are a sizetype. */
227 /* If the value's sign bit is set, extend the sign. */
235 {
236 /* Value is negative:
237 set to 1 all the bits that are outside this type's precision. */
241 else
242 {
246 }
247 }
249 /* Return nonzero if signed overflow occurred. */
250 return
253 }
254 \f
255 /* Add two doubleword integers with doubleword result.
256 Each argument is given as two `HOST_WIDE_INT' pieces.
257 One argument is L1 and H1; the other, L2 and H2.
258 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
260 int
264 {
266 HOST_WIDE_INT h;
274 }
276 /* Negate a doubleword integer with doubleword result.
277 Return nonzero if the operation overflows, assuming it's signed.
278 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
279 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
281 int
284 {
286 {
290 }
291 else
292 {
296 }
297 }
298 \f
299 /* Multiply two doubleword integers with doubleword result.
300 Return nonzero if the operation overflows, assuming it's signed.
301 Each argument is given as two `HOST_WIDE_INT' pieces.
302 One argument is L1 and H1; the other, L2 and H2.
303 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
305 int
309 {
324 {
327 {
329 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
331 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
335 }
337 }
341 /* Check for overflow by calculating the top half of the answer in full;
342 it should agree with the low half's sign bit. */
345 {
348 }
350 {
353 }
355 }
356 \f
357 /* Shift the doubleword integer in L1, H1 left by COUNT places
358 keeping only PREC bits of result.
359 Shift right if COUNT is negative.
360 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
361 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
363 void
367 {
371 {
374 }
376 #ifdef SHIFT_COUNT_TRUNCATED
379 #endif
382 {
383 /* Shifting by the host word size is undefined according to the
384 ANSI standard, so we must handle this as a special case. */
387 }
389 {
392 }
393 else
394 {
398 }
400 /* Sign extend all bits that are beyond the precision. */
408 ;
410 {
413 }
414 else
415 {
419 }
420 }
422 /* Shift the doubleword integer in L1, H1 right by COUNT places
423 keeping only PREC bits of result. COUNT must be positive.
424 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
425 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
427 void
432 {
435 signmask = (arith
439 #ifdef SHIFT_COUNT_TRUNCATED
442 #endif
445 {
446 /* Shifting by the host word size is undefined according to the
447 ANSI standard, so we must handle this as a special case. */
450 }
452 {
455 }
456 else
457 {
461 }
463 /* Zero / sign extend all bits that are beyond the precision. */
466 {
469 }
471 ;
473 {
476 }
477 else
478 {
482 }
483 }
484 \f
485 /* Rotate the doubleword integer in L1, H1 left by COUNT places
486 keeping only PREC bits of result.
487 Rotate right if COUNT is negative.
488 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
490 void
494 {
506 }
508 /* Rotate the doubleword integer in L1, H1 left by COUNT places
509 keeping only PREC bits of result. COUNT must be positive.
510 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
512 void
516 {
528 }
529 \f
530 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
531 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
532 CODE is a tree code for a kind of division, one of
533 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
534 or EXACT_DIV_EXPR
535 It controls how the quotient is rounded to an integer.
536 Return nonzero if the operation overflows.
537 UNS nonzero says do unsigned division. */
539 int
542 HOST_WIDE_INT hnum_orig,
544 HOST_WIDE_INT hden_orig,
548 {
564 /* Calculate quotient sign and convert operands to unsigned. */
566 {
568 {
570 /* (minimum integer) / (-1) is the only overflow case. */
574 }
576 {
579 }
580 }
585 /* This unsigned division rounds toward zero. */
588 }
592 /* hden != 0 already checked. */
597 }
607 /* Special code for when the divisor < BASE. */
609 {
610 /* hnum != 0 already checked. */
612 {
616 }
617 }
618 else
619 {
620 /* Full double precision division,
621 with thanks to Don Knuth's "Seminumerical Algorithms". */
625 /* Find the highest nonzero divisor digit. */
628 {
631 }
633 /* Insure that the first digit of the divisor is at least BASE/2.
634 This is required by the quotient digit estimation algorithm. */
641 {
645 }
650 {
655 }
656 }
660 /* Main loop */
662 {
663 /* Guess the next quotient digit, quo_est, by dividing the first
664 two remaining dividend digits by the high order quotient digit.
665 quo_est is never low and is at most 2 high. */
672 else
675 /* Refine quo_est so it's usually correct, and at most one high. */
680 quo_est--;
682 /* Try QUO_EST as the quotient digit, by multiplying the
683 divisor by QUO_EST and subtracting from the remaining dividend.
684 Keep in mind that QUO_EST is the I - 1st digit. */
688 {
694 }
696 /* If quo_est was high by one, then num[i] went negative and
697 we need to correct things. */
699 {
700 quo_est--;
703 {
707 }
710 }
712 /* Store the quotient digit. */
714 }
715 }
719 finish_up:
720 /* If result is negative, make it so. */
724 /* compute trial remainder: rem = num - (quo * den) */
730 {
739 {
740 /* quo = quo - 1; */
743 }
744 else
751 {
754 }
755 else
761 {
767 /* Get absolute values. */
773 /* If (2 * abs (lrem) >= abs (lden)) */
782 {
784 /* quo = quo - 1; */
787 else
788 /* quo = quo + 1; */
791 }
792 else
794 }
799 }
801 /* compute true remainder: rem = num - (quo * den) */
806 }
807 \f
808 /* Return true if built-in mathematical function specified by CODE
809 preserves the sign of it argument, i.e. -f(x) == f(-x). */
811 static bool
813 {
815 {
832 }
834 }
837 /* Determine whether an expression T can be cheaply negated using
838 the function negate_expr. */
840 static bool
842 {
845 tree type;
854 {
859 /* Check that -CST will not overflow type. */
862 {
867 }
868 else
883 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
892 /* Fall through. */
901 /* Negate -((double)float) as (double)(-float). */
903 {
907 }
911 /* Negate -f(x) as f(-x). */
918 }
920 }
922 /* Given T, an expression, return the negation of T. Allow for T to be
923 null, in which case return null. */
925 static tree
927 {
928 tree type;
929 tree tem;
938 {
940 {
942 HOST_WIDE_INT high;
953 }
962 /* Two's complement FP formats, such as c4x, may overflow. */
968 {
977 }
984 /* - (A - B) -> B - A */
997 /* Fall through. */
1001 {
1014 }
1018 /* Convert -((double)float) into (double)(-float). */
1020 {
1024 }
1028 /* Negate -f(x) as f(-x). */
1031 {
1038 }
1043 }
1046 }
1047 \f
1048 /* Split a tree IN into a constant, literal and variable parts that could be
1049 combined with CODE to make IN. "constant" means an expression with
1050 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1051 commutative arithmetic operation. Store the constant part into *CONP,
1052 the literal in *LITP and return the variable part. If a part isn't
1053 present, set it to null. If the tree does not decompose in this way,
1054 return the entire tree as the variable part and the other parts as null.
1056 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1057 case, we negate an operand that was subtracted. Except if it is a
1058 literal for which we use *MINUS_LITP instead.
1060 If NEGATE_P is true, we are negating all of IN, again except a literal
1061 for which we use *MINUS_LITP instead.
1063 If IN is itself a literal or constant, return it as appropriate.
1065 Note that we do not guarantee that any of the three values will be the
1066 same type as IN, but they will have the same signedness and mode. */
1068 static tree
1071 {
1078 /* Strip any conversions that don't change the machine mode or signedness. */
1085 /* We can associate addition and subtraction together (even
1086 though the C standard doesn't say so) for integers because
1087 the value is not affected. For reals, the value might be
1088 affected, so we can't. */
1091 {
1097 /* First see if either of the operands is a literal, then a constant. */
1108 /* If we haven't dealt with either operand, this is not a case we can
1109 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1114 else
1117 /* Now do any needed negations. */
1124 }
1127 else
1131 {
1138 }
1141 }
1143 /* Re-associate trees split by the above function. T1 and T2 are either
1144 expressions to associate or null. Return the new expression, if any. If
1145 we build an operation, do it in TYPE and with CODE. */
1147 static tree
1149 {
1155 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1156 try to fold this since we will have infinite recursion. But do
1157 deal with any NEGATE_EXPRs. */
1160 {
1162 {
1169 }
1171 }
1174 }
1175 \f
1176 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1177 to produce a new constant.
1179 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1181 static tree
1183 {
1187 HOST_WIDE_INT hi;
1189 HOST_WIDE_INT garbageh;
1190 tree t;
1193 int is_sizetype
1204 {
1220 /* It's unclear from the C standard whether shifts can overflow.
1221 The following code ignores overflow; perhaps a C standard
1222 interpretation ruling is needed. */
1252 /* This is a shortcut for a common special case. */
1257 {
1263 }
1265 /* ... fall through ... */
1269 {
1272 }
1275 {
1278 }
1285 /* This is a shortcut for a common special case. */
1290 {
1295 }
1297 /* ... fall through ... */
1313 else
1319 else
1325 }
1327 /* If this is for a sizetype, can be represented as one (signed)
1328 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1329 constants. */
1335 else
1336 {
1339 }
1342 = ((notrunc
1349 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1350 So check if force_fit_type truncated the value. */
1361 }
1363 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1364 constant. We assume ARG1 and ARG2 have the same data type, or at least
1365 are the same kind of constant and the same machine mode.
1367 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1369 static tree
1371 {
1379 {
1381 REAL_VALUE_TYPE d1;
1382 REAL_VALUE_TYPE d2;
1383 REAL_VALUE_TYPE value;
1392 /* Don't perform operation if we honor signaling NaNs and
1393 either operand is a NaN. */
1398 /* Don't perform operation if it would raise a division
1399 by zero exception. */
1405 /* If either operand is a NaN, just return it. Otherwise, set up
1406 for floating-point trap; we return an overflow. */
1424 }
1426 {
1432 tree t;
1435 {
1455 notrunc),
1461 notrunc));
1465 {
1466 tree magsquared
1470 notrunc);
1473 const_binop
1478 notrunc),
1480 notrunc),
1481 notrunc),
1483 const_binop
1488 notrunc),
1490 notrunc),
1491 notrunc),
1493 }
1498 }
1500 }
1502 }
1504 /* These are the hash table functions for the hash table of INTEGER_CST
1505 nodes of a sizetype. */
1507 /* Return the hash code code X, an INTEGER_CST. */
1509 static hashval_t
1511 {
1517 }
1519 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1520 is the same as that given by *Y, which is the same. */
1522 static int
1524 {
1532 }
1533 \f
1534 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1535 bits are given by NUMBER and of the sizetype represented by KIND. */
1537 tree
1539 {
1541 }
1543 /* Likewise, but the desired type is specified explicitly. */
1547 htab_t size_htab;
1549 tree
1551 {
1555 {
1558 }
1560 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1561 hash table, we return the value from the hash table. Otherwise, we
1562 place that in the hash table and make a new node for the next time. */
1571 {
1577 }
1578 else
1580 }
1582 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1583 is a tree code. The type of the result is taken from the operands.
1584 Both must be the same type integer type and it must be a size type.
1585 If the operands are constant, so is the result. */
1587 tree
1589 {
1596 /* Handle the special case of two integer constants faster. */
1598 {
1599 /* And some specific cases even faster than that. */
1608 /* Handle general case of two integer constants. */
1610 }
1616 }
1618 /* Given two values, either both of sizetype or both of bitsizetype,
1619 compute the difference between the two values. Return the value
1620 in signed type corresponding to the type of the operands. */
1622 tree
1624 {
1626 tree ctype;
1632 /* If the type is already signed, just do the simple thing. */
1639 /* If either operand is not a constant, do the conversions to the signed
1640 type and subtract. The hardware will do the right thing with any
1641 overflow in the subtraction. */
1646 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1647 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1648 overflow) and negate (which can't either). Special-case a result
1649 of zero while we're here. */
1654 else
1657 }
1658 \f
1660 /* Given T, a tree representing type conversion of ARG1, a constant,
1661 return a constant tree representing the result of conversion. */
1663 static tree
1665 {
1670 {
1672 {
1673 /* If we would build a constant wider than GCC supports,
1674 leave the conversion unfolded. */
1678 /* If we are trying to make a sizetype for a small integer, use
1679 size_int to pick up cached types to reduce duplicate nodes. */
1685 /* Given an integer constant, make new constant with new type,
1686 appropriately sign-extended or truncated. */
1690 /* Indicate an overflow if (1) ARG1 already overflowed,
1691 or (2) force_fit_type indicates an overflow.
1692 Tell force_fit_type that an overflow has already occurred
1693 if ARG1 is a too-large unsigned value and T is signed.
1694 But don't indicate an overflow if converting a pointer. */
1704 }
1706 {
1707 /* The following code implements the floating point to integer
1708 conversion rules required by the Java Language Specification,
1709 that IEEE NaNs are mapped to zero and values that overflow
1710 the target precision saturate, i.e. values greater than
1711 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1712 are mapped to INT_MIN. These semantics are allowed by the
1713 C and C++ standards that simply state that the behavior of
1714 FP-to-integer conversion is unspecified upon overflow. */
1719 /* If x is NaN, return zero and show we have an overflow. */
1721 {
1725 }
1727 /* See if X will be in range after truncation towards 0.
1728 To compensate for truncation, move the bounds away from 0,
1729 but reject if X exactly equals the adjusted bounds. */
1732 {
1737 {
1741 }
1742 }
1745 {
1748 {
1752 {
1756 }
1757 }
1758 }
1769 }
1771 }
1773 {
1777 {
1779 {
1780 /* We make a copy of ARG1 so that we don't modify an
1781 existing constant tree. */
1785 }
1796 }
1797 }
1800 }
1801 \f
1802 /* Return an expr equal to X but certainly not valid as an lvalue. */
1804 tree
1806 {
1807 tree result;
1809 /* These things are certainly not lvalues. */
1820 }
1822 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
1823 Zero means allow extended lvalues. */
1827 /* When pedantic, return an expr equal to X but certainly not valid as a
1828 pedantic lvalue. Otherwise, return X. */
1830 tree
1832 {
1835 else
1837 }
1838 \f
1839 /* Given a tree comparison code, return the code that is the logical inverse
1840 of the given code. It is not safe to do this for floating-point
1841 comparisons, except for NE_EXPR and EQ_EXPR. */
1843 static enum tree_code
1845 {
1847 {
1862 }
1863 }
1865 /* Similar, but return the comparison that results if the operands are
1866 swapped. This is safe for floating-point. */
1868 static enum tree_code
1870 {
1872 {
1886 }
1887 }
1890 /* Convert a comparison tree code from an enum tree_code representation
1891 into a compcode bit-based encoding. This function is the inverse of
1892 compcode_to_comparison. */
1894 static int
1896 {
1898 {
1913 }
1914 }
1916 /* Convert a compcode bit-based encoding of a comparison operator back
1917 to GCC's enum tree_code representation. This function is the
1918 inverse of comparison_to_compcode. */
1920 static enum tree_code
1922 {
1924 {
1939 }
1940 }
1942 /* Return nonzero if CODE is a tree code that represents a truth value. */
1944 static int
1946 {
1951 }
1952 \f
1953 /* Return nonzero if two operands (typically of the same tree node)
1954 are necessarily equal. If either argument has side-effects this
1955 function returns zero.
1957 If ONLY_CONST is nonzero, only return nonzero for constants.
1958 This function tests whether the operands are indistinguishable;
1959 it does not test whether they are equal using C's == operation.
1960 The distinction is important for IEEE floating point, because
1961 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
1962 (2) two NaNs may be indistinguishable, but NaN!=NaN.
1964 If ONLY_CONST is zero, a VAR_DECL is considered equal to itself
1965 even though it may hold multiple values during a function.
1966 This is because a GCC tree node guarantees that nothing else is
1967 executed between the evaluation of its "operands" (which may often
1968 be evaluated in arbitrary order). Hence if the operands themselves
1969 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
1970 same value in each operand/subexpression. Hence a zero value for
1971 ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
1972 If comparing arbitrary expression trees, such as from different
1973 statements, ONLY_CONST must usually be nonzero. */
1975 int
1977 {
1978 tree fndecl;
1980 /* If both types don't have the same signedness, then we can't consider
1981 them equal. We must check this before the STRIP_NOPS calls
1982 because they may change the signedness of the arguments. */
1990 /* This is needed for conversions and for COMPONENT_REF.
1991 Might as well play it safe and always test this. */
1997 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
1998 We don't care about side effects in that case because the SAVE_EXPR
1999 takes care of that for us. In all other cases, two expressions are
2000 equal if they have no side effects. If we have two identical
2001 expressions with side effects that should be treated the same due
2002 to the only side effects being identical SAVE_EXPR's, that will
2003 be detected in the recursive calls below. */
2009 /* Next handle constant cases, those for which we can return 1 even
2010 if ONLY_CONST is set. */
2013 {
2026 {
2036 {
2041 }
2044 }
2048 only_const)
2050 only_const));
2063 }
2069 {
2071 /* Two conversions are equal only if signedness and modes match. */
2087 /* For commutative ops, allow the other order. */
2100 /* If either of the pointer (or reference) expressions we are
2101 dereferencing contain a side effect, these cannot be equal. */
2107 {
2129 }
2133 {
2143 /* If the CALL_EXPRs call different functions, then they
2144 clearly can not be equal. */
2149 /* Only consider const functions equivalent. */
2155 /* Now see if all the arguments are the same. operand_equal_p
2156 does not handle TREE_LIST, so we walk the operands here
2157 feeding them to operand_equal_p. */
2161 {
2167 }
2169 /* If we get here and both argument lists are exhausted
2170 then the CALL_EXPRs are equal. */
2175 }
2178 /* Consider __builtin_sqrt equal to sqrt. */
2186 }
2187 }
2188 \f
2189 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2190 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2192 When in doubt, return 0. */
2194 static int
2196 {
2208 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2209 and see if the inner values are the same. This removes any
2210 signedness comparison, which doesn't matter here. */
2217 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2218 actual comparison operand, ARG0.
2220 First throw away any conversions to wider types
2221 already present in the operands. */
2230 {
2233 /* Make sure shorter operand is extended the right way
2234 to match the longer operand. */
2240 }
2243 }
2244 \f
2245 /* See if ARG is an expression that is either a comparison or is performing
2246 arithmetic on comparisons. The comparisons must only be comparing
2247 two different values, which will be stored in *CVAL1 and *CVAL2; if
2248 they are nonzero it means that some operands have already been found.
2249 No variables may be used anywhere else in the expression except in the
2250 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2251 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2253 If this is true, return 1. Otherwise, return zero. */
2255 static int
2257 {
2261 /* We can handle some of the 'e' cases here. */
2271 {
2272 /* If we've already found a CVAL1 or CVAL2, this expression is
2273 two complex to handle. */
2279 }
2282 {
2305 /* First see if we can handle the first operand, then the second. For
2306 the second operand, we know *CVAL1 can't be zero. It must be that
2307 one side of the comparison is each of the values; test for the
2308 case where this isn't true by failing if the two operands
2309 are the same. */
2318 ;
2322 ;
2323 else
2327 ;
2331 ;
2332 else
2339 }
2340 }
2341 \f
2342 /* ARG is a tree that is known to contain just arithmetic operations and
2343 comparisons. Evaluate the operations in the tree substituting NEW0 for
2344 any occurrence of OLD0 as an operand of a comparison and likewise for
2345 NEW1 and OLD1. */
2347 static tree
2349 {
2354 /* We can handle some of the 'e' cases here. */
2362 {
2377 {
2394 }
2395 /* Fall through - ??? */
2398 {
2402 /* We need to check both for exact equality and tree equality. The
2403 former will be true if the operand has a side-effect. In that
2404 case, we know the operand occurred exactly once. */
2417 }
2421 }
2422 }
2423 \f
2424 /* Return a tree for the case when the result of an expression is RESULT
2425 converted to TYPE and OMITTED was previously an operand of the expression
2426 but is now not needed (e.g., we folded OMITTED * 0).
2428 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2429 the conversion of RESULT to TYPE. */
2431 tree
2433 {
2440 }
2442 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2444 static tree
2446 {
2453 }
2454 \f
2455 /* Return a simplified tree node for the truth-negation of ARG. This
2456 never alters ARG itself. We assume that ARG is an operation that
2457 returns a truth value (0 or 1). */
2459 tree
2461 {
2468 /* If this is a comparison, we can simply invert it, except for
2469 floating-point non-equality comparisons, in which case we just
2470 enclose a TRUTH_NOT_EXPR around what we have. */
2473 {
2475 && !flag_unsafe_math_optimizations
2479 else
2482 }
2485 {
2500 /* Here we can invert either operand. We invert the first operand
2501 unless the second operand is a TRUTH_NOT_EXPR in which case our
2502 result is the XOR of the first operand with the inside of the
2503 negation of the second operand. */
2508 else
2563 }
2567 }
2569 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2570 operands are another bit-wise operation with a common input. If so,
2571 distribute the bit operations to save an operation and possibly two if
2572 constants are involved. For example, convert
2573 (A | B) & (A | C) into A | (B & C)
2574 Further simplification will occur if B and C are constants.
2576 If this optimization cannot be done, 0 will be returned. */
2578 static tree
2580 {
2581 tree common;
2591 {
2595 }
2597 {
2601 }
2603 {
2607 }
2609 {
2613 }
2614 else
2619 }
2620 \f
2621 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2622 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2624 static tree
2627 {
2634 }
2636 /* Optimize a bit-field compare.
2638 There are two cases: First is a compare against a constant and the
2639 second is a comparison of two items where the fields are at the same
2640 bit position relative to the start of a chunk (byte, halfword, word)
2641 large enough to contain it. In these cases we can avoid the shift
2642 implicit in bitfield extractions.
2644 For constants, we emit a compare of the shifted constant with the
2645 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2646 compared. For two fields at the same position, we do the ANDs with the
2647 similar mask and compare the result of the ANDs.
2649 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2650 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2651 are the left and right operands of the comparison, respectively.
2653 If the optimization described above can be done, we return the resulting
2654 tree. Otherwise we return zero. */
2656 static tree
2659 {
2668 tree mask;
2669 tree offset;
2671 /* Get all the information about the extractions being done. If the bit size
2672 if the same as the size of the underlying object, we aren't doing an
2673 extraction at all and so can do nothing. We also don't want to
2674 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2675 then will no longer be able to replace it. */
2683 {
2684 /* If this is not a constant, we can only do something if bit positions,
2685 sizes, and signedness are the same. */
2693 }
2695 /* See if we can find a mode to refer to this field. We should be able to,
2696 but fail if we can't. */
2705 /* Set signed and unsigned types of the precision of this mode for the
2706 shifts below. */
2710 /* Compute the bit position and size for the new reference and our offset
2711 within it. If the new reference is the same size as the original, we
2712 won't optimize anything, so return zero. */
2722 /* Make the mask to be used against the extracted field. */
2732 /* If not comparing with constant, just rework the comparison
2733 and return. */
2738 mask),
2742 mask));
2744 /* Otherwise, we are handling the constant case. See if the constant is too
2745 big for the field. Warn and return a tree of for 0 (false) if so. We do
2746 this not only for its own sake, but to avoid having to test for this
2747 error case below. If we didn't, we might generate wrong code.
2749 For unsigned fields, the constant shifted right by the field length should
2750 be all zero. For signed fields, the high-order bits should agree with
2751 the sign bit. */
2754 {
2758 {
2764 }
2765 }
2766 else
2767 {
2771 {
2777 }
2778 }
2780 /* Single-bit compares should always be against zero. */
2782 {
2785 }
2787 /* Make a new bitfield reference, shift the constant over the
2788 appropriate number of bits and mask it with the computed mask
2789 (in case this was a signed field). If we changed it, make a new one. */
2792 {
2795 }
2805 rhs);
2806 }
2807 \f
2808 /* Subroutine for fold_truthop: decode a field reference.
2810 If EXP is a comparison reference, we return the innermost reference.
2812 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
2813 set to the starting bit number.
2815 If the innermost field can be completely contained in a mode-sized
2816 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
2818 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
2819 otherwise it is not changed.
2821 *PUNSIGNEDP is set to the signedness of the field.
2823 *PMASK is set to the mask used. This is either contained in a
2824 BIT_AND_EXPR or derived from the width of the field.
2826 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
2828 Return 0 if this is not a component reference or is one that we can't
2829 do anything with. */
2831 static tree
2836 {
2840 tree unsigned_type;
2843 /* All the optimizations using this function assume integer fields.
2844 There are problems with FP fields since the type_for_size call
2845 below can fail for, e.g., XFmode. */
2849 /* We are interested in the bare arrangement of bits, so strip everything
2850 that doesn't affect the machine mode. However, record the type of the
2851 outermost expression if it may matter below. */
2859 {
2865 }
2874 /* If the number of bits in the reference is the same as the bitsize of
2875 the outer type, then the outer type gives the signedness. Otherwise
2876 (in case of a small bitfield) the signedness is unchanged. */
2880 /* Compute the mask to access the bitfield. */
2890 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
2898 }
2900 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
2901 bit positions. */
2903 static int
2905 {
2908 tree tmask;
2913 return
2920 }
2922 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
2923 represents the sign bit of EXP's type. If EXP represents a sign
2924 or zero extension, also test VAL against the unextended type.
2925 The return value is the (sub)expression whose sign bit is VAL,
2926 or NULL_TREE otherwise. */
2928 static tree
2930 {
2934 tree t;
2936 /* Tree EXP must have an integral type. */
2941 /* Tree VAL must be an integer constant. */
2948 {
2955 }
2956 else
2957 {
2964 }
2966 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
2967 treat VAL as if it were unsigned. */
2972 /* Handle extension from a narrower type. */
2978 }
2980 /* Subroutine for fold_truthop: determine if an operand is simple enough
2981 to be evaluated unconditionally. */
2983 static int
2985 {
2986 /* Strip any conversions that don't change the machine mode. */
2998 /* Don't regard global variables as simple. They may be
2999 allocated in ways unknown to the compiler (shared memory,
3000 #pragma weak, etc). */
3003 /* Loading a static variable is unduly expensive, but global
3004 registers aren't expensive. */
3006 }
3007 \f
3008 /* The following functions are subroutines to fold_range_test and allow it to
3009 try to change a logical combination of comparisons into a range test.
3011 For example, both
3012 X == 2 || X == 3 || X == 4 || X == 5
3013 and
3014 X >= 2 && X <= 5
3015 are converted to
3016 (unsigned) (X - 2) <= 3
3018 We describe each set of comparisons as being either inside or outside
3019 a range, using a variable named like IN_P, and then describe the
3020 range with a lower and upper bound. If one of the bounds is omitted,
3021 it represents either the highest or lowest value of the type.
3023 In the comments below, we represent a range by two numbers in brackets
3024 preceded by a "+" to designate being inside that range, or a "-" to
3025 designate being outside that range, so the condition can be inverted by
3026 flipping the prefix. An omitted bound is represented by a "-". For
3027 example, "- [-, 10]" means being outside the range starting at the lowest
3028 possible value and ending at 10, in other words, being greater than 10.
3029 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3030 always false.
3032 We set up things so that the missing bounds are handled in a consistent
3033 manner so neither a missing bound nor "true" and "false" need to be
3034 handled using a special case. */
3036 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3037 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3038 and UPPER1_P are nonzero if the respective argument is an upper bound
3039 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3040 must be specified for a comparison. ARG1 will be converted to ARG0's
3041 type if both are specified. */
3043 static tree
3046 {
3047 tree tem;
3051 /* If neither arg represents infinity, do the normal operation.
3052 Else, if not a comparison, return infinity. Else handle the special
3053 comparison rules. Note that most of the cases below won't occur, but
3054 are handled for consistency. */
3057 {
3062 }
3067 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3068 for neither. In real maths, we cannot assume open ended ranges are
3069 the same. But, this is computer arithmetic, where numbers are finite.
3070 We can therefore make the transformation of any unbounded range with
3071 the value Z, Z being greater than any representable number. This permits
3072 us to treat unbounded ranges as equal. */
3076 {
3097 }
3100 }
3101 \f
3102 /* Given EXP, a logical expression, set the range it is testing into
3103 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3104 actually being tested. *PLOW and *PHIGH will be made of the same type
3105 as the returned expression. If EXP is not a comparison, we will most
3106 likely not be returning a useful value and range. */
3108 static tree
3110 {
3117 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3118 and see if we can refine the range. Some of the cases below may not
3119 happen, but it doesn't seem worth worrying about this. We "continue"
3120 the outer loop when we've changed something; otherwise we "break"
3121 the switch, which will "break" the while. */
3126 {
3130 {
3142 }
3144 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3145 lose a cast by accident. */
3150 {
3157 /* We can only do something if the range is testing for zero
3158 and if the second operand is an integer constant. Note that
3159 saying something is "in" the range we make is done by
3160 complementing IN_P since it will set in the initial case of
3161 being not equal to zero; "out" is leaving it alone. */
3168 {
3189 }
3193 /* If this is an unsigned comparison, we also know that EXP is
3194 greater than or equal to zero. We base the range tests we make
3195 on that fact, so we record it here so we can parse existing
3196 range tests. */
3198 {
3201 NULL_TREE))
3206 /* If the high bound is missing, but we have a nonzero low
3207 bound, reverse the range so it goes from zero to the low bound
3208 minus 1. */
3210 {
3215 }
3216 }
3220 /* (-x) IN [a,b] -> x in [-b, -a] */
3230 /* ~ X -> -X - 1 */
3239 /* If EXP is signed, any overflow in the computation is undefined,
3240 so we don't worry about it so long as our computations on
3241 the bounds don't overflow. For unsigned, overflow is defined
3242 and this is exactly the right thing. */
3251 /* Check for an unsigned range which has wrapped around the maximum
3252 value thus making n_high < n_low, and normalize it. */
3254 {
3260 /* If the range is of the form +/- [ x+1, x ], we won't
3261 be able to normalize it. But then, it represents the
3262 whole range or the empty set, so make it
3263 +/- [ -, - ]. */
3267 else
3269 }
3270 else
3293 /* If we're converting from an unsigned to a signed type,
3294 we will be doing the comparison as unsigned. The tests above
3295 have already verified that LOW and HIGH are both positive.
3297 So we have to make sure that the original unsigned value will
3298 be interpreted as positive. */
3300 {
3303 tree high_positive;
3305 /* A range without an upper bound is, naturally, unbounded.
3306 Since convert would have cropped a very large value, use
3307 the max value for the destination type. */
3308 high_positive
3317 /* If the low bound is specified, "and" the range with the
3318 range for which the original unsigned value will be
3319 positive. */
3321 {
3325 high_positive))
3329 }
3330 else
3331 {
3332 /* Otherwise, "or" the range with the range of the input
3333 that will be interpreted as negative. */
3337 high_positive))
3341 }
3342 }
3350 }
3353 }
3355 /* If EXP is a constant, we can evaluate whether this is true or false. */
3357 {
3364 }
3368 }
3369 \f
3370 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3371 type, TYPE, return an expression to test if EXP is in (or out of, depending
3372 on IN_P) the range. */
3374 static tree
3376 {
3378 tree value;
3397 {
3399 {
3403 }
3405 }
3407 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3409 {
3411 HOST_WIDE_INT hi;
3416 {
3419 }
3420 else
3421 {
3424 }
3427 {
3429 {
3432 }
3435 }
3436 }
3445 }
3446 \f
3447 /* Given two ranges, see if we can merge them into one. Return 1 if we
3448 can, 0 if we can't. Set the output range into the specified parameters. */
3450 static int
3453 {
3457 tree tem;
3467 /* Make range 0 be the range that starts first, or ends last if they
3468 start at the same value. Swap them if it isn't. */
3471 || (lowequal
3474 {
3478 }
3480 /* Now flag two cases, whether the ranges are disjoint or whether the
3481 second range is totally subsumed in the first. Note that the tests
3482 below are simplified by the ones above. */
3488 /* We now have four cases, depending on whether we are including or
3489 excluding the two ranges. */
3491 {
3492 /* If they don't overlap, the result is false. If the second range
3493 is a subset it is the result. Otherwise, the range is from the start
3494 of the second to the end of the first. */
3499 else
3501 }
3504 {
3505 /* If they don't overlap, the result is the first range. If they are
3506 equal, the result is false. If the second range is a subset of the
3507 first, and the ranges begin at the same place, we go from just after
3508 the end of the first range to the end of the second. If the second
3509 range is not a subset of the first, or if it is a subset and both
3510 ranges end at the same place, the range starts at the start of the
3511 first range and ends just before the second range.
3512 Otherwise, we can't describe this as a single range. */
3518 {
3522 }
3524 {
3528 }
3529 else
3531 }
3534 {
3535 /* If they don't overlap, the result is the second range. If the second
3536 is a subset of the first, the result is false. Otherwise,
3537 the range starts just after the first range and ends at the
3538 end of the second. */
3543 else
3544 {
3548 }
3549 }
3551 else
3552 {
3553 /* The case where we are excluding both ranges. Here the complex case
3554 is if they don't overlap. In that case, the only time we have a
3555 range is if they are adjacent. If the second is a subset of the
3556 first, the result is the first. Otherwise, the range to exclude
3557 starts at the beginning of the first range and ends at the end of the
3558 second. */
3560 {
3567 else
3569 }
3572 else
3574 }
3578 }
3579 \f
3580 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3581 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3582 #endif
3584 /* EXP is some logical combination of boolean tests. See if we can
3585 merge it into some range test. Return the new tree if so. */
3587 static tree
3589 {
3596 tree tem;
3598 /* If this is an OR operation, invert both sides; we will invert
3599 again at the end. */
3603 /* If both expressions are the same, if we can merge the ranges, and we
3604 can build the range test, return it or it inverted. If one of the
3605 ranges is always true or always false, consider it to be the same
3606 expression as the other. */
3616 /* On machines where the branch cost is expensive, if this is a
3617 short-circuited branch and the underlying object on both sides
3618 is the same, make a non-short-circuit operation. */
3624 {
3625 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3626 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3627 which cases we can't do this. */
3636 {
3648 }
3649 }
3652 }
3653 \f
3654 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3655 bit value. Arrange things so the extra bits will be set to zero if and
3656 only if C is signed-extended to its full width. If MASK is nonzero,
3657 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3659 static tree
3661 {
3664 tree temp;
3669 /* We work by getting just the sign bit into the low-order bit, then
3670 into the high-order bit, then sign-extend. We then XOR that value
3671 with C. */
3675 /* We must use a signed type in order to get an arithmetic right shift.
3676 However, we must also avoid introducing accidental overflows, so that
3677 a subsequent call to integer_zerop will work. Hence we must
3678 do the type conversion here. At this point, the constant is either
3679 zero or one, and the conversion to a signed type can never overflow.
3680 We could get an overflow if this conversion is done anywhere else. */
3688 /* If necessary, convert the type back to match the type of C. */
3693 }
3694 \f
3695 /* Find ways of folding logical expressions of LHS and RHS:
3696 Try to merge two comparisons to the same innermost item.
3697 Look for range tests like "ch >= '0' && ch <= '9'".
3698 Look for combinations of simple terms on machines with expensive branches
3699 and evaluate the RHS unconditionally.
3701 For example, if we have p->a == 2 && p->b == 4 and we can make an
3702 object large enough to span both A and B, we can do this with a comparison
3703 against the object ANDed with the a mask.
3705 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3706 operations to do this with one comparison.
3708 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3709 function and the one above.
3711 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3712 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3714 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3715 two operands.
3717 We return the simplified tree or 0 if no optimization is possible. */
3719 static tree
3721 {
3722 /* If this is the "or" of two comparisons, we can do something if
3723 the comparisons are NE_EXPR. If this is the "and", we can do something
3724 if the comparisons are EQ_EXPR. I.e.,
3725 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3727 WANTED_CODE is this operation code. For single bit fields, we can
3728 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3729 comparison for one-bit fields. */
3749 /* Start by getting the comparison codes. Fail if anything is volatile.
3750 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3751 it were surrounded with a NE_EXPR. */
3776 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3780 {
3785 {
3793 }
3796 {
3805 }
3806 else
3816 }
3818 /* If the RHS can be evaluated unconditionally and its operands are
3819 simple, it wins to evaluate the RHS unconditionally on machines
3820 with expensive branches. In this case, this isn't a comparison
3821 that can be merged. Avoid doing this if the RHS is a floating-point
3822 comparison since those can trap. */
3828 {
3829 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
3837 integer_zero_node);
3839 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
3847 integer_zero_node);
3850 }
3852 /* See if the comparisons can be merged. Then get all the parameters for
3853 each side. */
3877 /* It must be true that the inner operation on the lhs of each
3878 comparison must be the same if we are to be able to do anything.
3879 Then see if we have constants. If not, the same must be true for
3880 the rhs's. */
3891 else
3894 /* If either comparison code is not correct for our logical operation,
3895 fail. However, we can convert a one-bit comparison against zero into
3896 the opposite comparison against that bit being set in the field. */
3900 {
3902 {
3903 /* Make the left operand unsigned, since we are only interested
3904 in the value of one bit. Otherwise we are doing the wrong
3905 thing below. */
3908 }
3909 else
3911 }
3913 /* This is analogous to the code for l_const above. */
3915 {
3917 {
3920 }
3921 else
3923 }
3925 /* After this point all optimizations will generate bit-field
3926 references, which we might not want. */
3930 /* See if we can find a mode that contains both fields being compared on
3931 the left. If we can't, fail. Otherwise, update all constants and masks
3932 to be relative to a field of that size. */
3937 volatilep);
3947 {
3950 }
3958 {
3966 {
3970 wanted_code == NE_EXPR
3972 }
3973 }
3975 {
3983 {
3987 wanted_code == NE_EXPR
3989 }
3990 }
3992 /* If the right sides are not constant, do the same for it. Also,
3993 disallow this optimization if a size or signedness mismatch occurs
3994 between the left and right sides. */
3996 {
3999 /* Make sure the two fields on the right
4000 correspond to the left without being swapped. */
4008 volatilep);
4018 {
4021 }
4028 /* Make a mask that corresponds to both fields being compared.
4029 Do this for both items being compared. If the operands are the
4030 same size and the bits being compared are in the same position
4031 then we can do this by masking both and comparing the masked
4032 results. */
4036 {
4048 }
4050 /* There is still another way we can do something: If both pairs of
4051 fields being compared are adjacent, we may be able to make a wider
4052 field containing them both.
4054 Note that we still must mask the lhs/rhs expressions. Furthermore,
4055 the mask must be shifted to account for the shift done by
4056 make_bit_field_ref. */
4061 {
4062 tree type;
4074 /* Convert to the smaller type before masking out unwanted bits. */
4077 {
4079 {
4083 }
4085 {
4089 }
4090 }
4099 }
4102 }
4104 /* Handle the case of comparisons with constants. If there is something in
4105 common between the masks, those bits of the constants must be the same.
4106 If not, the condition is always false. Test for this to avoid generating
4107 incorrect code below. */
4112 {
4114 {
4117 }
4118 else
4119 {
4122 }
4123 }
4125 /* Construct the expression we will return. First get the component
4126 reference we will make. Unless the mask is all ones the width of
4127 that field, perform the mask operation. Then compare with the
4128 merged constant. */
4138 }
4139 \f
4140 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4141 constant. */
4143 static tree
4145 {
4150 tree minmax_const;
4152 tree inner;
4162 /* If something does not permit us to optimize, return the original tree. */
4170 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4171 and GT_EXPR, doing the rest with recursive calls using logical
4172 simplifications. */
4174 {
4176 return
4180 return
4182 optimize_minmax_comparison
4184 optimize_minmax_comparison
4189 /* MAX (X, 0) == 0 -> X <= 0 */
4193 /* MAX (X, 0) == 5 -> X == 5 */
4197 /* MAX (X, 0) == -1 -> false */
4201 /* MIN (X, 0) == 0 -> X >= 0 */
4205 /* MIN (X, 0) == 5 -> false */
4208 else
4209 /* MIN (X, 0) == -1 -> X == -1 */
4214 /* MAX (X, 0) > 0 -> X > 0
4215 MAX (X, 0) > 5 -> X > 5 */
4219 /* MAX (X, 0) > -1 -> true */
4223 /* MIN (X, 0) > 0 -> false
4224 MIN (X, 0) > 5 -> false */
4227 else
4228 /* MIN (X, 0) > -1 -> X > -1 */
4233 }
4234 }
4235 \f
4236 /* T is an integer expression that is being multiplied, divided, or taken a
4237 modulus (CODE says which and what kind of divide or modulus) by a
4238 constant C. See if we can eliminate that operation by folding it with
4239 other operations already in T. WIDE_TYPE, if non-null, is a type that
4240 should be used for the computation if wider than our type.
4242 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4243 (X * 2) + (Y * 4). We must, however, be assured that either the original
4244 expression would not overflow or that overflow is undefined for the type
4245 in the language in question.
4247 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4248 the machine has a multiply-accumulate insn or that this is part of an
4249 addressing calculation.
4251 If we return a non-null expression, it is an equivalent form of the
4252 original computation, but need not be in the original type. */
4254 static tree
4256 {
4257 /* To avoid exponential search depth, refuse to allow recursion past
4258 three levels. Beyond that (1) it's highly unlikely that we'll find
4259 something interesting and (2) we've probably processed it before
4260 when we built the inner expression. */
4263 tree ret;
4268 depth++;
4270 depth--;
4273 }
4275 static tree
4277 {
4287 /* Don't deal with constants of zero here; they confuse the code below. */
4297 /* Note that we need not handle conditional operations here since fold
4298 already handles those cases. So just do arithmetic here. */
4300 {
4302 /* For a constant, we can always simplify if we are a multiply
4303 or (for divide and modulus) if it is a multiple of our constant. */
4310 /* If op0 is an expression ... */
4315 /* ... and is unsigned, and its type is smaller than ctype,
4316 then we cannot pass through as widening. */
4322 /* ... or its type is larger than ctype,
4323 then we cannot pass through this truncation. */
4326 /* ... or signedness changes for division or modulus,
4327 then we cannot pass through this conversion. */
4333 /* Pass the constant down and see if we can make a simplification. If
4334 we can, replace this expression with the inner simplification for
4335 possible later conversion to our or some other type. */
4340 code == MULT_EXPR
4351 /* If widening the type changes the signedness, then we can't perform
4352 this optimization as that changes the result. */
4356 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4359 {
4365 }
4375 /* If the second operand is constant, this is a multiplication
4376 or floor division, by a power of two, so we can treat it that
4377 way unless the multiplier or divisor overflows. */
4379 /* const_binop may not detect overflow correctly,
4380 so check for it explicitly here. */
4394 /* See if we can eliminate the operation on both sides. If we can, we
4395 can return a new PLUS or MINUS. If we can't, the only remaining
4396 cases where we can do anything are if the second operand is a
4397 constant. */
4402 /* If not multiplication, we can only do this if both operands
4403 are divisible by c. */
4409 /* If this was a subtraction, negate OP1 and set it to be an addition.
4410 This simplifies the logic below. */
4417 /* If either OP1 or C are negative, this optimization is not safe for
4418 some of the division and remainder types while for others we need
4419 to change the code. */
4421 {
4429 }
4431 /* If it's a multiply or a division/modulus operation of a multiple
4432 of our constant, do the operation and verify it doesn't overflow. */
4435 {
4438 /* We allow the constant to overflow with wrapping semantics. */
4442 }
4443 else
4446 /* If we have an unsigned type is not a sizetype, we cannot widen
4447 the operation since it will change the result if the original
4448 computation overflowed. */
4454 /* If we were able to eliminate our operation from the first side,
4455 apply our operation to the second side and reform the PLUS. */
4459 /* The last case is if we are a multiply. In that case, we can
4460 apply the distributive law to commute the multiply and addition
4461 if the multiplication of the constants doesn't overflow. */
4466 op1));
4471 /* We have a special case here if we are doing something like
4472 (C * 8) % 4 since we know that's zero. */
4479 /* ... fall through ... */
4483 /* If we can extract our operation from the LHS, do so and return a
4484 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4485 do something only if the second operand is a constant. */
4497 /* If these are the same operation types, we can associate them
4498 assuming no overflow. */
4505 /* If these operations "cancel" each other, we have the main
4506 optimizations of this pass, which occur when either constant is a
4507 multiple of the other, in which case we replace this with either an
4508 operation or CODE or TCODE.
4510 If we have an unsigned type that is not a sizetype, we cannot do
4511 this since it will change the result if the original computation
4512 overflowed. */
4515 && ! flag_wrapv
4520 {
4531 }
4536 }
4539 }
4540 \f
4541 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4542 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4543 that we may sometimes modify the tree. */
4545 static tree
4547 {
4550 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4555 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4556 don't bother handling any other types. */
4558 {
4562 }
4567 {
4570 }
4573 }
4574 \f
4575 /* Return a node which has the indicated constant VALUE (either 0 or
4576 1), and is of the indicated TYPE. */
4578 static tree
4580 {
4585 integer_zero_node);
4586 else
4587 {
4592 }
4593 }
4595 /* Utility function for the following routine, to see how complex a nesting of
4596 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4597 we don't care (to avoid spending too much time on complex expressions.). */
4599 static int
4601 {
4612 }
4614 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4615 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4616 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4617 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4618 COND is the first argument to CODE; otherwise (as in the example
4619 given here), it is the second argument. TYPE is the type of the
4620 original expression. */
4622 static tree
4625 {
4629 /* In the end, we'll produce a COND_EXPR. Both arms of the
4630 conditional expression will be binary operations. The left-hand
4631 side of the expression to be executed if the condition is true
4632 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4633 of the expression to be executed if the condition is true will be
4634 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4635 but apply to the expression to be executed if the conditional is
4636 false. */
4641 /* These are the codes to use for the left-hand side and right-hand
4642 side of the COND_EXPR. Normally, they are the same as CODE. */
4645 /* And these are the types of the expressions. */
4651 {
4655 }
4656 else
4657 {
4661 }
4664 {
4668 /* If this operand throws an expression, then it does not make
4669 sense to try to perform a logical or arithmetic operation
4670 involving it. Instead of building `a + throw 3' for example,
4671 we simply build `a, throw 3'. */
4673 {
4675 {
4678 }
4679 else
4681 }
4683 {
4685 {
4688 }
4689 else
4691 }
4692 }
4693 else
4694 {
4699 }
4701 /* If ARG is complex we want to make sure we only evaluate it once. Though
4702 this is only required if it is volatile, it might be more efficient even
4703 if it is not. However, if we succeed in folding one part to a constant,
4704 we do not need to make this SAVE_EXPR. Since we do this optimization
4705 primarily to see if we do end up with constant and this SAVE_EXPR
4706 interferes with later optimizations, suppressing it when we can is
4707 important.
4709 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4710 do so. Don't try to see if the result is a constant if an arm is a
4711 COND_EXPR since we get exponential behavior in that case. */
4720 {
4729 {
4733 }
4734 }
4747 else
4749 }
4751 \f
4752 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4754 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4755 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4756 ADDEND is the same as X.
4758 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4759 and finite. The problematic cases are when X is zero, and its mode
4760 has signed zeros. In the case of rounding towards -infinity,
4761 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4762 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4764 static bool
4766 {
4770 /* Don't allow the fold with -fsignaling-nans. */
4774 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4778 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4783 /* The mode has signed zeros, and we have to honor their sign.
4784 In this situation, there is only one case we can return true for.
4785 X - 0 is the same as X unless rounding towards -infinity is
4786 supported. */
4788 }
4790 /* Subroutine of fold() that checks comparisons of built-in math
4791 functions against real constants.
4793 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
4794 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
4795 is the type of the result and ARG0 and ARG1 are the operands of the
4796 comparison. ARG1 must be a TREE_REAL_CST.
4798 The function returns the constant folded tree if a simplification
4799 can be made, and NULL_TREE otherwise. */
4801 static tree
4804 {
4805 REAL_VALUE_TYPE c;
4810 {
4816 {
4817 /* sqrt(x) < y is always false, if y is negative. */
4821 arg);
4823 /* sqrt(x) > y is always true, if y is negative and we
4824 don't care about NaNs, i.e. negative values of x. */
4828 arg);
4830 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
4833 }
4835 {
4836 REAL_VALUE_TYPE c2;
4842 {
4843 /* sqrt(x) > y is x == +Inf, when y is very large. */
4848 /* sqrt(x) > y is always false, when y is very large
4849 and we don't care about infinities. */
4852 arg);
4853 }
4855 /* sqrt(x) > c is the same as x > c*c. */
4858 }
4860 {
4861 REAL_VALUE_TYPE c2;
4867 {
4868 /* sqrt(x) < y is always true, when y is a very large
4869 value and we don't care about NaNs or Infinities. */
4873 arg);
4875 /* sqrt(x) < y is x != +Inf when y is very large and we
4876 don't care about NaNs. */
4881 /* sqrt(x) < y is x >= 0 when y is very large and we
4882 don't care about Infinities. */
4887 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
4896 dconst0))),
4899 c2)))));
4900 }
4902 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
4907 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
4910 {
4915 dconst0))),
4918 c2)))));
4919 }
4920 }
4921 }
4924 }
4926 /* Subroutine of fold() that optimizes comparisons against Infinities,
4927 either +Inf or -Inf.
4929 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
4930 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
4931 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
4933 The function returns the constant folded tree if a simplification
4934 can be made, and NULL_TREE otherwise. */
4936 static tree
4938 {
4940 REAL_VALUE_TYPE max;
4941 tree temp;
4946 /* For negative infinity swap the sense of the comparison. */
4952 {
4954 /* x > +Inf is always false, if with ignore sNANs. */
4959 arg0);
4962 /* x <= +Inf is always true, if we don't case about NaNs. */
4966 arg0);
4968 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
4971 {
4974 }
4979 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
4985 /* x < +Inf is always equal to x <= DBL_MAX. */
4991 /* x != +Inf is always equal to !(x > DBL_MAX). */
5002 }
5005 }
5007 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5008 equality/inequality test, then return a simplified form of
5009 the test using shifts and logical operations. Otherwise return
5010 NULL. TYPE is the desired result type. */
5012 tree
5014 tree result_type)
5015 {
5016 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5017 operand 0. */
5019 {
5024 /* Extract the arguments of the EQ/NE. */
5028 /* This requires us to invert the code. */
5030 }
5032 /* If this is testing a single bit, we can optimize the test. */
5036 {
5043 tree arg00;
5045 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5046 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5049 {
5054 }
5056 /* At this point, we know that arg0 is not testing the sign bit. */
5060 /* Otherwise we have (A & C) != 0 where C is a single bit,
5061 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5062 Similarly for (A & C) == 0. */
5064 /* If INNER is a right shift of a constant and it plus BITNUM does
5065 not overflow, adjust BITNUM and INNER. */
5072 {
5075 }
5077 /* If we are going to be able to omit the AND below, we must do our
5078 operations as unsigned. If we must use the AND, we have a choice.
5079 Normally unsigned is faster, but for some machines signed is. */
5080 #ifdef LOAD_EXTEND_OP
5082 #else
5084 #endif
5099 /* Put the AND last so it can combine with more things. */
5103 /* Make sure to return the proper type. */
5107 }
5109 }
5111 /* Check whether we are allowed to reorder operands arg0 and arg1,
5112 such that the evaluation of arg1 occurs before arg0. */
5114 static bool
5116 {
5123 }
5125 /* Test whether it is preferable two swap two operands, ARG0 and
5126 ARG1, for example because ARG0 is an integer constant and ARG1
5127 isn't. If REORDER is true, only recommend swapping if we can
5128 evaluate the operands in reverse order. */
5130 static bool
5132 {
5169 }
5171 /* Perform constant folding and related simplification of EXPR.
5172 The related simplifications include x*1 => x, x*0 => 0, etc.,
5173 and application of the associative law.
5174 NOP_EXPR conversions may be removed freely (as long as we
5175 are careful not to change the C type of the overall expression)
5176 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5177 but we can constant-fold them if they have constant operands. */
5179 #ifdef ENABLE_FOLD_CHECKING
5180 # define fold(x) fold_1 (x)
5182 static
5183 #endif
5184 tree
5186 {
5189 tree tem;
5195 /* WINS will be nonzero when the switch is done
5196 if all operands are constant. */
5199 /* Don't try to process an RTL_EXPR since its operands aren't trees.
5200 Likewise for a SAVE_EXPR that's already been evaluated. */
5204 /* Return right away if a constant. */
5211 {
5212 tree subop;
5214 /* Special case for conversion ops that can have fixed point args. */
5217 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
5223 else
5228 /* Note that TREE_CONSTANT isn't enough:
5229 static var addresses are constant but we can't
5230 do arithmetic on them. */
5232 }
5234 {
5238 {
5240 tree subop;
5246 {
5247 /* Signedness matters here. Perhaps we can refine this
5248 later. */
5250 }
5251 else
5252 /* Strip any conversions that don't change the mode. */
5257 else
5262 /* Note that TREE_CONSTANT isn't enough:
5263 static var addresses are constant but we can't
5264 do arithmetic on them. */
5271 }
5272 }
5274 /* If this is a commutative operation, and ARG0 is a constant, move it
5275 to ARG1 to reduce the number of tests below. */
5282 /* Now WINS is set as described above,
5283 ARG0 is the first operand of EXPR,
5284 and ARG1 is the second operand (if it has more than one operand).
5286 First check for cases where an arithmetic operation is applied to a
5287 compound, conditional, or comparison operation. Push the arithmetic
5288 operation inside the compound or conditional to see if any folding
5289 can then be done. Convert comparison to conditional for this purpose.
5290 The also optimizes non-constant cases that used to be done in
5291 expand_expr.
5293 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5294 one of the operands is a comparison and the other is a comparison, a
5295 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5296 code below would make the expression more complex. Change it to a
5297 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5298 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5310 {
5320 }
5323 {
5328 {
5338 /* If this was a conversion, and all we did was to move into
5339 inside the COND_EXPR, bring it back out. But leave it if
5340 it is a conversion from integer to integer and the
5341 result precision is no wider than a word since such a
5342 conversion is cheap and may be optimized away by combine,
5343 while it couldn't if it were outside the COND_EXPR. Then return
5344 so we don't get into an infinite recursion loop taking the
5345 conversion out and then back in. */
5357 && (INTEGRAL_TYPE_P
5368 }
5373 }
5384 {
5399 return
5413 return
5416 }
5419 {
5435 /* Other kinds of FIX are not handled properly by fold_convert. */
5440 /* Handle cases of two conversions in a row. */
5443 {
5463 /* In addition to the cases of two conversions in a row
5464 handled below, if we are converting something to its own
5465 type via an object of identical or wider precision, neither
5466 conversion is needed. */
5472 /* Likewise, if the intermediate and final types are either both
5473 float or both integer, we don't need the middle conversion if
5474 it is wider than the final type and doesn't change the signedness
5475 (for integers). Avoid this if the final type is a pointer
5476 since then we sometimes need the inner conversion. Likewise if
5477 the outer has a precision not equal to the size of its mode. */
5487 /* If we have a sign-extension of a zero-extended value, we can
5488 replace that by a single zero-extension. */
5494 /* Two conversions in a row are not needed unless:
5495 - some conversion is floating-point (overstrict for now), or
5496 - the intermediate type is narrower than both initial and
5497 final, or
5498 - the intermediate type and innermost type differ in signedness,
5499 and the outermost type is wider than the intermediate, or
5500 - the initial type is a pointer type and the precisions of the
5501 intermediate and final types differ, or
5502 - the final type is a pointer type and the precisions of the
5503 initial and intermediate types differ. */
5517 }
5521 /* Detect assigning a bitfield. */
5524 {
5525 /* Don't leave an assignment inside a conversion
5526 unless assigning a bitfield. */
5531 /* First do the assignment, then return converted constant. */
5535 }
5537 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5538 constants (if x has signed type, the sign bit cannot be set
5539 in c). This folds extension into the BIT_AND_EXPR. */
5544 {
5554 <= HOST_BITS_PER_WIDE_INT
5556 {
5563 #ifdef LOAD_EXTEND_OP
5567 {
5571 }
5572 #endif
5573 }
5578 }
5581 {
5583 {
5587 }
5589 }
5601 {
5605 }
5610 {
5614 }
5624 {
5626 {
5627 /* If the value is unsigned, then the absolute value is
5628 the same as the ordinary value. */
5631 /* Similarly, if the value is non-negative. */
5634 /* If the value is negative, then the absolute value is
5635 its negation. */
5636 else
5637 {
5639 HOST_WIDE_INT high;
5650 }
5651 }
5653 {
5657 }
5658 }
5661 /* Convert fabs((double)float) into (double)fabsf(float). */
5664 {
5668 targ0)));
5669 }
5696 {
5703 }
5709 /* A + (-B) -> A - B */
5712 /* (-A) + B -> B - A */
5716 {
5720 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5721 with a constant, and the two constants have no bits in common,
5722 we should treat this as a BIT_IOR_EXPR since this may produce more
5723 simplifications. */
5731 {
5734 }
5736 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5737 (plus (plus (mult) (mult)) (foo)) so that we can
5738 take advantage of the factoring cases below. */
5743 {
5748 else
5769 }
5772 {
5776 /* (A * C) + (B * C) -> (A+B) * C.
5777 We are most concerned about the case where C is a constant,
5778 but other combinations show up during loop reduction. Since
5779 it is not difficult, try all four possibilities. */
5796 /* No identical multiplicands; see if we can find a common
5797 power-of-two factor in non-power-of-two multiplies. This
5798 can help in multi-dimensional array access. */
5803 {
5808 /* Move min of absolute values to int11. */
5811 {
5815 }
5818 {
5823 }
5824 }
5829 same));
5830 }
5831 }
5832 else
5833 {
5834 /* See if ARG1 is zero and X + ARG1 reduces to X. */
5838 /* Likewise if the operands are reversed. */
5842 /* Convert x+x into x*2.0. */
5848 /* Convert x*c+x into x*(c+1). */
5854 {
5855 REAL_VALUE_TYPE c;
5861 }
5863 /* Convert x+x*c into x*(c+1). */
5869 {
5870 REAL_VALUE_TYPE c;
5876 }
5878 /* Convert x*c1+x*c2 into x*(c1+c2). */
5888 {
5897 }
5898 }
5900 bit_rotate:
5901 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5902 is a rotate of A by C1 bits. */
5903 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5904 is a rotate of A by B bits. */
5905 {
5914 {
5933 {
5941 TYPE_PRECISION
5946 ? LROTATE_EXPR
5949 }
5951 {
5959 TYPE_PRECISION
5964 ? LROTATE_EXPR
5967 }
5968 }
5969 }
5971 associate:
5972 /* In most languages, can't associate operations on floats through
5973 parentheses. Rather than remember where the parentheses were, we
5974 don't associate floats at all, unless the user has specified
5975 -funsafe-math-optimizations. */
5979 {
5983 /* Split both trees into variables, constants, and literals. Then
5984 associate each group together, the constants with literals,
5985 then the result with variables. This increases the chances of
5986 literals being recombined later and of generating relocatable
5987 expressions for the sum of a constant and literal. */
5992 /* Only do something if we found more than two objects. Otherwise,
5993 nothing has changed and we risk infinite recursion. */
5998 {
5999 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6008 /* Preserve the MINUS_EXPR if the negative part of the literal is
6009 greater than the positive part. Otherwise, the multiplicative
6010 folding code (i.e extract_muldiv) may be fooled in case
6011 unsigned constants are subtracted, like in the following
6012 example: ((X*2 + 4) - 8U)/2. */
6014 {
6018 {
6022 }
6023 else
6024 {
6028 }
6029 }
6031 {
6035 else
6036 {
6041 }
6042 }
6046 }
6047 }
6049 binary:
6053 {
6054 /* The return value should always have
6055 the same type as the original expression. */
6060 }
6064 /* A - (-B) -> A + B */
6067 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6077 {
6083 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
6084 about the case where C is a constant, just try one of the
6085 four possibilities. */
6096 /* Fold A - (A & B) into ~B & A. */
6099 {
6104 arg0));
6109 arg0));
6110 }
6112 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6113 any power of 2 minus 1. */
6118 {
6124 {
6128 }
6129 }
6130 }
6132 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6136 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6137 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6138 (-ARG1 + ARG0) reduces to -ARG1. */
6142 /* Fold &x - &x. This can happen from &x.foo - &x.
6143 This is unsafe for certain floats even in non-IEEE formats.
6144 In IEEE, it is unsafe because it does wrong for NaNs.
6145 Also note that operand_equal_p is always false if an operand
6146 is volatile. */
6155 /* (-A) * (-B) -> A * B */
6166 {
6172 /* (a * (1 << b)) is (a << b) */
6188 }
6189 else
6190 {
6191 /* Maybe fold x * 0 to 0. The expressions aren't the same
6192 when x is NaN, since x * 0 is also NaN. Nor are they the
6193 same in modes with signed zeros, since multiplying a
6194 negative value by 0 gives -0, not +0. */
6199 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
6204 /* Transform x * -1.0 into -x. */
6209 /* Convert (C1/X)*C2 into (C1*C2)/X. */
6214 {
6220 }
6223 {
6227 /* Optimizations of sqrt(...)*sqrt(...). */
6231 {
6236 /* Optimize sqrt(x)*sqrt(x) as x. */
6241 /* Optimize sqrt(x)*sqrt(y) as sqrt(x*y). */
6246 }
6248 /* Optimize expN(x)*expN(y) as expN(x+y). */
6262 {
6269 }
6271 /* Optimizations of pow(...)*pow(...). */
6275 {
6283 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
6285 {
6290 arg01));
6292 }
6294 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
6296 {
6301 arg));
6303 }
6304 }
6306 /* Optimize tan(x)*cos(x) as sin(x). */
6315 {
6316 tree sinfn;
6319 {
6334 }
6339 }
6341 /* Optimize x*pow(x,c) as pow(x,c+1). */
6345 {
6352 {
6354 REAL_VALUE_TYPE c;
6363 }
6364 }
6366 /* Optimize pow(x,c)*x as pow(x,c+1). */
6370 {
6377 {
6379 REAL_VALUE_TYPE c;
6388 }
6389 }
6391 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
6394 {
6395 tree powfn;
6403 else
6407 {
6412 }
6413 }
6414 }
6415 }
6419 bit_ior:
6428 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6430 This results in more efficient code for machines without a NAND
6431 instruction. Combine will canonicalize to the first form
6432 which will allow use of NAND instructions provided by the
6433 backend if they exist. */
6436 {
6441 }
6443 /* See if this can be simplified into a rotate first. If that
6444 is unsuccessful continue in the association code. */
6453 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6454 with a constant, and the two constants have no bits in common,
6455 we should treat this as a BIT_IOR_EXPR since this may produce more
6456 simplifications. */
6464 {
6467 }
6469 /* See if this can be simplified into a rotate first. If that
6470 is unsuccessful continue in the association code. */
6481 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6484 {
6485 unsigned int prec
6492 }
6494 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6496 This results in more efficient code for machines without a NOR
6497 instruction. Combine will canonicalize to the first form
6498 which will allow use of NOR instructions provided by the
6499 backend if they exist. */
6502 {
6507 }
6512 /* Don't touch a floating-point divide by zero unless the mode
6513 of the constant can represent infinity. */
6519 /* (-A) / (-B) -> A / B */
6529 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6534 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
6539 /* If ARG1 is a constant, we can convert this to a multiply by the
6540 reciprocal. This does not have the same rounding properties,
6541 so only do this if -funsafe-math-optimizations. We can actually
6542 always safely do it if ARG1 is a power of two, but it's hard to
6543 tell if it is or not in a portable manner. */
6545 {
6550 /* Find the reciprocal if optimizing and the result is exact. */
6552 {
6553 REAL_VALUE_TYPE r;
6556 {
6559 }
6560 }
6561 }
6562 /* Convert A/B/C to A/(B*C). */
6569 /* Convert A/(B/C) to (A/B)*C. */
6577 /* Convert C1/(X*C2) into (C1/C2)/X. */
6582 {
6588 }
6591 {
6593 /* Optimize x/expN(y) into x*expN(-y). */
6606 {
6613 }
6615 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6619 {
6628 }
6629 }
6632 {
6636 /* Optimize sin(x)/cos(x) as tan(x). */
6642 {
6643 tree tanfn;
6651 else
6657 }
6659 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
6665 {
6666 tree tanfn;
6674 else
6678 {
6683 tmp));
6684 }
6685 }
6687 /* Optimize pow(x,c)/x as pow(x,c-1). */
6691 {
6697 {
6699 REAL_VALUE_TYPE c;
6708 }
6709 }
6710 }
6723 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
6724 operation, EXACT_DIV_EXPR.
6726 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
6727 At one time others generated faster code, it's not clear if they do
6728 after the last round to changes to the DIV code in expmed.c. */
6763 /* Optimize -1 >> x for arithmetic right shifts. */
6766 /* ... fall through ... */
6769 shift:
6775 /* Since negative shift count is not well-defined,
6776 don't try to compute it in the compiler. */
6779 /* Rewrite an LROTATE_EXPR by a constant into an
6780 RROTATE_EXPR by a new constant. */
6782 {
6787 }
6789 /* If we have a rotate of a bit operation with the rotate count and
6790 the second operand of the bit operation both constant,
6791 permute the two operations. */
6803 /* Two consecutive rotates adding up to the width of the mode can
6804 be ignored. */
6835 /* Note that the operand of this must be an int
6836 and its values must be 0 or 1.
6837 ("true" is a fixed value perhaps depending on the language,
6838 but we don't handle values other than 1 correctly yet.) */
6840 /* Avoid infinite recursion. */
6842 {
6847 }
6851 /* Note that the operands of this must be ints
6852 and their values must be 0 or 1.
6853 ("true" is a fixed value perhaps depending on the language.) */
6854 /* If first arg is constant zero, return it. */
6858 /* If either arg is constant true, drop it. */
6862 /* Preserve sequence points. */
6865 /* If second arg is constant zero, result is zero, but first arg
6866 must be evaluated. */
6869 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6870 case will be handled here. */
6874 truth_andor:
6875 /* We only do these simplifications if we are optimizing. */
6879 /* Check for things like (A || B) && (A || C). We can convert this
6880 to A || (B && C). Note that either operator can be any of the four
6881 truth and/or operations and the transformation will still be
6882 valid. Also note that we only care about order for the
6883 ANDIF and ORIF operators. If B contains side effects, this
6884 might change the truth-value of A. */
6891 {
6911 /* This case if tricky because we must either have commutative
6912 operators or else A10 must not have side-effects. */
6918 a01));
6919 }
6921 /* See if we can build a range comparison. */
6925 /* Check for the possibility of merging component references. If our
6926 lhs is another similar operation, try to merge its rhs with our
6927 rhs. Then try to merge our lhs and rhs. */
6939 /* Note that the operands of this must be ints
6940 and their values must be 0 or true.
6941 ("true" is a fixed value perhaps depending on the language.) */
6942 /* If first arg is constant true, return it. */
6946 /* If either arg is constant zero, drop it. */
6950 /* Preserve sequence points. */
6953 /* If second arg is constant true, result is true, but we must
6954 evaluate first arg. */
6957 /* Likewise for first arg, but note this only occurs here for
6958 TRUTH_OR_EXPR. */
6964 /* If either arg is constant zero, drop it. */
6969 /* If either arg is constant true, this is a logical inversion. */
6982 /* If one arg is a real or integer constant, put it last. */
6987 {
6995 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7000 /* (-a) CMP (-b) -> b CMP a */
7007 {
7008 REAL_VALUE_TYPE cst;
7011 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7013 return
7019 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7020 /* a CMP (-0) -> a CMP 0 */
7025 /* x != NaN is always true, other ops are always false. */
7028 {
7031 }
7033 /* Fold comparisons against infinity. */
7035 {
7039 }
7040 }
7042 /* If this is a comparison of a real constant with a PLUS_EXPR
7043 or a MINUS_EXPR of a real constant, we can convert it into a
7044 comparison with a revised real constant as long as no overflow
7045 occurs when unsafe_math_optimizations are enabled. */
7057 /* Likewise, we can simplify a comparison of a real constant with
7058 a MINUS_EXPR whose first operand is also a real constant, i.e.
7059 (c1 - x) < c2 becomes x > c1-c2. */
7070 /* Fold comparisons against built-in math functions. */
7072 && flag_unsafe_math_optimizations
7074 {
7078 {
7082 }
7083 }
7084 }
7086 /* Convert foo++ == CONST into ++foo == CONST + INCR.
7087 First, see if one arg is constant; find the constant arg
7088 and the other one. */
7089 {
7099 {
7100 /* This optimization is invalid for ordered comparisons
7101 if CONST+INCR overflows or if foo+incr might overflow.
7102 This optimization is invalid for floating point due to rounding.
7103 For pointer types we assume overflow doesn't happen. */
7107 {
7108 tree newconst
7112 /* Do not overwrite the current varop to be a preincrement,
7113 create a new node so that we won't confuse our caller who
7114 might create trees and throw them away, reusing the
7115 arguments that they passed to build. This shows up in
7116 the THEN or ELSE parts of ?: being postincrements. */
7121 /* If VAROP is a reference to a bitfield, we must mask
7122 the constant by the width of the field. */
7126 {
7127 int size
7129 (TREE_OPERAND
7133 tree folded_compare;
7135 /* First check whether the comparison would come out
7136 always the same. If we don't do that we would
7137 change the meaning with the masking. */
7141 else
7144 constop));
7159 mask)));
7160 }
7166 }
7167 }
7169 {
7173 {
7174 tree newconst
7178 /* Do not overwrite the current varop to be a predecrement,
7179 create a new node so that we won't confuse our caller who
7180 might create trees and throw them away, reusing the
7181 arguments that they passed to build. This shows up in
7182 the THEN or ELSE parts of ?: being postdecrements. */
7190 {
7191 int size
7193 (TREE_OPERAND
7197 tree folded_compare;
7202 else
7205 constop));
7220 mask)));
7221 }
7227 }
7228 }
7229 }
7231 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
7232 This transformation affects the cases which are handled in later
7233 optimizations involving comparisons with non-negative constants. */
7237 {
7239 {
7250 }
7251 }
7253 /* Comparisons with the highest or lowest possible integer of
7254 the specified size will have known values. */
7255 {
7263 {
7270 {
7273 }
7274 else
7275 {
7278 }
7283 {
7287 arg0);
7294 arg0);
7298 /* The GE_EXPR and LT_EXPR cases above are not normally
7299 reached because of previous transformations. */
7303 }
7307 {
7316 }
7320 {
7324 arg0);
7331 arg0);
7337 }
7341 {
7350 }
7355 /* signed_type does not work on pointer types. */
7357 {
7358 /* The following case also applies to X < signed_max+1
7359 and X >= signed_max+1 because previous transformations. */
7361 {
7365 return fold
7369 }
7370 }
7371 }
7372 }
7374 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
7375 a MINUS_EXPR of a constant, we can convert it into a comparison with
7376 a revised constant as long as no overflow occurs. */
7388 /* Similarly for a NEGATE_EXPR. */
7397 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7398 for !=. Don't do this for ordered comparisons due to overflow. */
7404 /* If we are widening one operand of an integer comparison,
7405 see if the other operand is similarly being widened. Perhaps we
7406 can do the comparison in the narrower type. */
7416 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7417 constant, we can simplify it. */
7424 /* If we are comparing an ABS_EXPR with a constant, we can
7425 convert all the cases into explicit comparisons, but they may
7426 well not be faster than doing the ABS and one comparison.
7427 But ABS (X) <= C is a range comparison, which becomes a subtraction
7428 and a comparison, and is probably faster. */
7440 /* If this is an EQ or NE comparison with zero and ARG0 is
7441 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7442 two operations, but the latter can be done in one less insn
7443 on machines that have only two-operand insns or on which a
7444 constant cannot be the first operand. */
7447 {
7450 return
7458 integer_one_node)),
7459 arg1));
7462 return
7470 integer_one_node)),
7471 arg1));
7472 }
7474 /* If this is an NE or EQ comparison of zero against the result of a
7475 signed MOD operation whose second operand is a power of 2, make
7476 the MOD operation unsigned since it is simpler and equivalent. */
7485 {
7492 }
7494 /* If this is an NE comparison of zero with an AND of one, remove the
7495 comparison since the AND will give the correct value. */
7501 /* If we have (A & C) == C where C is a power of 2, convert this into
7502 (A & C) != 0. Similarly for NE_EXPR. */
7510 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7511 2, then fold the expression into shifts and logical operations. */
7516 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
7517 Similarly for NE_EXPR. */
7522 {
7523 tree dandnotc
7531 }
7533 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
7534 Similarly for NE_EXPR. */
7539 {
7540 tree candnotd
7547 }
7549 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7550 and similarly for >= into !=. */
7566 return
7573 /* Simplify comparison of something with itself. (For IEEE
7574 floating-point, we can only do some of these simplifications.) */
7576 {
7578 {
7593 /* For NE, we can only do this simplification if integer
7594 or we don't honor IEEE floating point NaNs. */
7598 /* ... fall through ... */
7604 }
7605 }
7607 /* If we are comparing an expression that just has comparisons
7608 of two integer values, arithmetic expressions of those comparisons,
7609 and constants, we can simplify it. There are only three cases
7610 to check: the two values can either be equal, the first can be
7611 greater, or the second can be greater. Fold the expression for
7612 those three values. Since each value must be 0 or 1, we have
7613 eight possibilities, each of which corresponds to the constant 0
7614 or 1 or one of the six possible comparisons.
7616 This handles common cases like (a > b) == 0 but also handles
7617 expressions like ((x > y) - (y > x)) > 0, which supposedly
7618 occur in macroized code. */
7621 {
7626 /* Don't handle degenerate cases here; they should already
7627 have been handled anyway. */
7636 {
7640 /* We can't just pass T to eval_subst in case cval1 or cval2
7641 was the same as ARG1. */
7643 tree high_result
7646 arg1));
7647 tree equal_result
7650 arg1));
7651 tree low_result
7654 arg1));
7656 /* All three of these results should be 0 or 1. Confirm they
7657 are. Then use those values to select the proper code
7658 to use. */
7666 {
7667 /* Make a 3-bit mask with the high-order bit being the
7668 value for `>', the next for '=', and the low for '<'. */
7672 {
7674 /* Always false. */
7695 /* Always true. */
7697 }
7702 else
7704 }
7705 }
7706 }
7708 /* If this is a comparison of a field, we may be able to simplify it. */
7713 /* Handle the constant case even without -O
7714 to make sure the warnings are given. */
7716 {
7720 }
7722 /* If this is a comparison of complex values and either or both sides
7723 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
7724 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
7725 This may prevent needless evaluations. */
7732 {
7745 type,
7748 }
7750 /* Optimize comparisons of strlen vs zero to a compare of the
7751 first character of the string vs zero. To wit,
7752 strlen(ptr) == 0 => *ptr == 0
7753 strlen(ptr) != 0 => *ptr != 0
7754 Other cases should reduce to one of these two (or a constant)
7755 due to the return value of strlen being unsigned. */
7759 {
7761 tree arglist;
7773 integer_zero_node));
7774 }
7776 /* From here on, the only cases we handle are when the result is
7777 known to be a constant.
7779 To compute GT, swap the arguments and do LT.
7780 To compute GE, do LT and invert the result.
7781 To compute LE, swap the arguments, do LT and invert the result.
7782 To compute NE, do EQ and invert the result.
7784 Therefore, the code below must handle only EQ and LT. */
7787 {
7790 }
7792 /* Note that it is safe to invert for real values here because we
7793 will check below in the one case that it matters. */
7798 {
7801 }
7803 /* Compute a result for LT or EQ if args permit;
7804 otherwise return T. */
7806 {
7809 else
7814 }
7817 /* Assume a nonexplicit constant cannot equal an explicit one,
7818 since such code would be undefined anyway.
7819 Exception: on sysvr4, using #pragma weak,
7820 a label can come out as 0. */
7827 #endif
7828 /* Two real constants can be compared explicitly. */
7830 {
7831 /* If either operand is a NaN, the result is false with two
7832 exceptions: First, an NE_EXPR is true on NaNs, but that case
7833 is already handled correctly since we will be inverting the
7834 result for NE_EXPR. Second, if we had inverted a LE_EXPR
7835 or a GE_EXPR into a LT_EXPR, we must return true so that it
7836 will be inverted into false. */
7846 else
7850 }
7864 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
7865 so all simple results must be passed through pedantic_non_lvalue. */
7867 return pedantic_non_lvalue
7872 /* If we have A op B ? A : C, we may be able to convert this to a
7873 simpler expression, depending on the operation and the values
7874 of B and C. Signed zeros prevent all of these transformations,
7875 for reasons given above each one. */
7881 {
7887 /* If we have A op 0 ? A : -A, consider applying the following
7888 transformations:
7890 A == 0? A : -A same as -A
7891 A != 0? A : -A same as A
7892 A >= 0? A : -A same as abs (A)
7893 A > 0? A : -A same as abs (A)
7894 A <= 0? A : -A same as -abs (A)
7895 A < 0? A : -A same as -abs (A)
7897 None of these transformations work for modes with signed
7898 zeros. If A is +/-0, the first two transformations will
7899 change the sign of the result (from +0 to -0, or vice
7900 versa). The last four will fix the sign of the result,
7901 even though the original expressions could be positive or
7902 negative, depending on the sign of A.
7904 Note that all these transformations are correct if A is
7905 NaN, since the two alternatives (A and -A) are also NaNs. */
7912 {
7914 return
7915 pedantic_non_lvalue
7917 negate_expr
7919 arg1))));
7927 return pedantic_non_lvalue
7935 return pedantic_non_lvalue
7939 arg1)))));
7942 }
7944 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
7945 A == 0 ? A : 0 is always 0 unless A is -0. Note that
7946 both transformations are correct when A is NaN: A != 0
7947 is then true, and A == 0 is false. */
7950 {
7955 }
7957 /* Try some transformations of A op B ? A : B.
7959 A == B? A : B same as B
7960 A != B? A : B same as A
7961 A >= B? A : B same as max (A, B)
7962 A > B? A : B same as max (B, A)
7963 A <= B? A : B same as min (A, B)
7964 A < B? A : B same as min (B, A)
7966 As above, these transformations don't work in the presence
7967 of signed zeros. For example, if A and B are zeros of
7968 opposite sign, the first two transformations will change
7969 the sign of the result. In the last four, the original
7970 expressions give different results for (A=+0, B=-0) and
7971 (A=-0, B=+0), but the transformed expressions do not.
7973 The first two transformations are correct if either A or B
7974 is a NaN. In the first transformation, the condition will
7975 be false, and B will indeed be chosen. In the case of the
7976 second transformation, the condition A != B will be true,
7977 and A will be chosen.
7979 The conversions to max() and min() are not correct if B is
7980 a number and A is not. The conditions in the original
7981 expressions will be false, so all four give B. The min()
7982 and max() versions would give a NaN instead. */
7985 {
7990 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
7992 {
7996 }
7999 {
8006 /* In C++ a ?: expression can be an lvalue, so put the
8007 operand which will be used if they are equal first
8008 so that we can convert this back to the
8009 corresponding COND_EXPR. */
8011 return pedantic_non_lvalue
8021 return pedantic_non_lvalue
8030 }
8031 }
8033 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
8034 we might still be able to simplify this. For example,
8035 if C1 is one less or one more than C2, this might have started
8036 out as a MIN or MAX and been transformed by this function.
8037 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
8043 {
8045 /* We can replace A with C1 in this case. */
8051 /* If C1 is C2 + 1, this is min(A, C2). */
8056 return pedantic_non_lvalue
8061 /* If C1 is C2 - 1, this is min(A, C2). */
8066 return pedantic_non_lvalue
8071 /* If C1 is C2 - 1, this is max(A, C2). */
8076 return pedantic_non_lvalue
8081 /* If C1 is C2 + 1, this is max(A, C2). */
8086 return pedantic_non_lvalue
8093 }
8094 }
8096 /* If the second operand is simpler than the third, swap them
8097 since that produces better jump optimization results. */
8100 {
8101 /* See if this can be inverted. If it can't, possibly because
8102 it was a floating-point inequality comparison, don't do
8103 anything. */
8109 }
8111 /* Convert A ? 1 : 0 to simply A. */
8114 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8115 call to fold will try to move the conversion inside
8116 a COND, which will recurse. In that case, the COND_EXPR
8117 is probably the best choice, so leave it alone. */
8121 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8122 over COND_EXPR in cases such as floating point comparisons. */
8129 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
8130 operation is simply A & 2. */
8141 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8148 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8152 {
8153 /* Only perform transformation if ARG0 is easily inverted. */
8158 }
8163 /* When pedantic, a compound expression can be neither an lvalue
8164 nor an integer constant expression. */
8167 /* Don't let (0, 0) be null pointer constant. */
8209 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8210 appropriate. */
8215 {
8219 tree arg01;
8230 {
8244 arg01));
8245 }
8248 }
8251 /* Check for a built-in function. */
8256 {
8260 }
8266 }
8268 #ifdef ENABLE_FOLD_CHECKING
8269 #undef fold
8275 /* When --enable-checking=fold, compute a digest of expr before
8276 and after actual fold call to see if fold did not accidentally
8277 change original expr. */
8279 tree
8281 {
8282 tree ret;
8285 htab_t ht;
8304 }
8306 void
8308 {
8311 htab_t ht;
8321 }
8323 static void
8325 {
8327 }
8329 static void
8331 {
8349 {
8350 /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified. */
8354 }
8356 {
8357 /* Allow DECL_ASSEMBLER_NAME to be modified. */
8361 }
8364 {
8365 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
8370 }
8377 {
8380 {
8394 }
8398 {
8409 }
8413 {
8419 }
8420 /* FALLTHROUGH */
8456 }
8457 }
8459 #endif
8461 /* Perform constant folding and related simplification of initializer
8462 expression EXPR. This behaves identically to "fold" but ignores
8463 potential run-time traps and exceptions that fold must preserve. */
8465 tree
8467 {
8471 tree result;
8484 }
8486 /* Determine if first argument is a multiple of second argument. Return 0 if
8487 it is not, or we cannot easily determined it to be.
8489 An example of the sort of thing we care about (at this point; this routine
8490 could surely be made more general, and expanded to do what the *_DIV_EXPR's
8491 fold cases do now) is discovering that
8493 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8495 is a multiple of
8497 SAVE_EXPR (J * 8)
8499 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
8501 This code also handles discovering that
8503 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8505 is a multiple of 8 so we don't have to worry about dealing with a
8506 possible remainder.
8508 Note that we *look* inside a SAVE_EXPR only to determine how it was
8509 calculated; it is not safe for fold to do much of anything else with the
8510 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
8511 at run time. For example, the latter example above *cannot* be implemented
8512 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
8513 evaluation time of the original SAVE_EXPR is not necessarily the same at
8514 the time the new expression is evaluated. The only optimization of this
8515 sort that would be valid is changing
8517 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
8519 divided by 8 to
8521 SAVE_EXPR (I) * SAVE_EXPR (J)
8523 (where the same SAVE_EXPR (J) is used in the original and the
8524 transformed version). */
8526 static int
8528 {
8536 {
8548 {
8552 /* const_binop may not detect overflow correctly,
8553 so check for it explicitly here. */
8562 }
8566 /* Can't handle conversions from non-integral or wider integral type. */
8572 /* .. fall through ... */
8588 }
8589 }
8591 /* Return true if `t' is known to be non-negative. */
8593 int
8595 {
8597 {
8612 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8613 both unsigned and at least 2 bits shorter than the result. */
8617 {
8622 {
8626 }
8627 }
8632 {
8633 /* x * x for floating point x is always non-negative. */
8638 }
8640 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8641 both unsigned and their total bits is shorter than the result. */
8645 {
8652 }
8673 {
8678 {
8682 {
8686 }
8687 }
8689 {
8695 }
8696 }
8724 {
8731 {
8791 }
8792 }
8794 /* ... fall through ... */
8798 /* Truth values evaluate to 0 or 1, which is nonnegative. */
8800 }
8802 /* We don't know sign of `t', so be conservative and return false. */
8804 }
8806 /* Return true if `r' is known to be non-negative.
8807 Only handles constants at the moment. */
8809 int
8811 {
8813 {
8823 {
8825 rtx elt;
8830 {
8834 }
8837 }
8841 /* These are always nonnegative. */
8846 }
8847 }