| blob | 5b39098d0db8cc5486043b840bd4e8cbe27311d2 |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 02111-1307, USA. */
22 /*@@ This file should be rewritten to use an arbitrary precision
23 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
24 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
25 @@ The routines that translate from the ap rep should
26 @@ warn if precision et. al. is lost.
27 @@ This would also make life easier when this technology is used
28 @@ for cross-compilers. */
30 /* The entry points in this file are fold, size_int_wide, size_binop
31 and force_fit_type.
33 fold takes a tree as argument and returns a simplified tree.
35 size_binop takes a tree code for an arithmetic operation
36 and two operands that are trees, and produces a tree for the
37 result, assuming the type comes from `sizetype'.
39 size_int takes an integer value, and creates a tree constant
40 with type from `sizetype'.
42 force_fit_type takes a constant and prior overflow indicator, and
43 forces the value to fit the type. It returns an overflow indicator. */
96 tree);
116 /* The following constants represent a bit based encoding of GCC's
117 comparison operators. This encoding simplifies transformations
118 on relational comparison operators, such as AND and OR. */
119 #define COMPCODE_FALSE 0
120 #define COMPCODE_LT 1
121 #define COMPCODE_EQ 2
122 #define COMPCODE_LE 3
123 #define COMPCODE_GT 4
124 #define COMPCODE_NE 5
125 #define COMPCODE_GE 6
126 #define COMPCODE_TRUE 7
128 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
129 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
130 and SUM1. Then this yields nonzero if overflow occurred during the
131 addition.
133 Overflow occurs if A and B have the same sign, but A and SUM differ in
134 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
135 sign. */
136 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
137 \f
138 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
139 We do that by representing the two-word integer in 4 words, with only
140 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
141 number. The value of the word is LOWPART + HIGHPART * BASE. */
143 #define LOWPART(x) \
144 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
145 #define HIGHPART(x) \
146 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
147 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
149 /* Unpack a two-word integer into 4 words.
150 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
151 WORDS points to the array of HOST_WIDE_INTs. */
153 static void
155 {
160 }
162 /* Pack an array of 4 words into a two-word integer.
163 WORDS points to the array of words.
164 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
166 static void
169 {
172 }
173 \f
174 /* Make the integer constant T valid for its type by setting to 0 or 1 all
175 the bits in the constant that don't belong in the type.
177 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
178 nonzero, a signed overflow has already occurred in calculating T, so
179 propagate it. */
181 int
183 {
185 HOST_WIDE_INT high;
189 {
190 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
191 Consider doing it via real_convert now. */
193 }
204 else
207 /* First clear all bits that are beyond the type's precision. */
210 ;
214 else
215 {
219 }
221 /* Unsigned types do not suffer sign extension or overflow unless they
222 are a sizetype. */
228 /* If the value's sign bit is set, extend the sign. */
236 {
237 /* Value is negative:
238 set to 1 all the bits that are outside this type's precision. */
242 else
243 {
247 }
248 }
250 /* Return nonzero if signed overflow occurred. */
251 return
254 }
255 \f
256 /* Add two doubleword integers with doubleword result.
257 Each argument is given as two `HOST_WIDE_INT' pieces.
258 One argument is L1 and H1; the other, L2 and H2.
259 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
261 int
265 {
267 HOST_WIDE_INT h;
275 }
277 /* Negate a doubleword integer with doubleword result.
278 Return nonzero if the operation overflows, assuming it's signed.
279 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
280 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
282 int
285 {
287 {
291 }
292 else
293 {
297 }
298 }
299 \f
300 /* Multiply two doubleword integers with doubleword result.
301 Return nonzero if the operation overflows, assuming it's signed.
302 Each argument is given as two `HOST_WIDE_INT' pieces.
303 One argument is L1 and H1; the other, L2 and H2.
304 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
306 int
310 {
325 {
328 {
330 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
332 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
336 }
338 }
342 /* Check for overflow by calculating the top half of the answer in full;
343 it should agree with the low half's sign bit. */
346 {
349 }
351 {
354 }
356 }
357 \f
358 /* Shift the doubleword integer in L1, H1 left by COUNT places
359 keeping only PREC bits of result.
360 Shift right if COUNT is negative.
361 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
362 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
364 void
368 {
372 {
375 }
377 #ifdef SHIFT_COUNT_TRUNCATED
380 #endif
383 {
384 /* Shifting by the host word size is undefined according to the
385 ANSI standard, so we must handle this as a special case. */
388 }
390 {
393 }
394 else
395 {
399 }
401 /* Sign extend all bits that are beyond the precision. */
409 ;
411 {
414 }
415 else
416 {
420 }
421 }
423 /* Shift the doubleword integer in L1, H1 right by COUNT places
424 keeping only PREC bits of result. COUNT must be positive.
425 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
426 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
428 void
433 {
436 signmask = (arith
440 #ifdef SHIFT_COUNT_TRUNCATED
443 #endif
446 {
447 /* Shifting by the host word size is undefined according to the
448 ANSI standard, so we must handle this as a special case. */
451 }
453 {
456 }
457 else
458 {
462 }
464 /* Zero / sign extend all bits that are beyond the precision. */
467 {
470 }
472 ;
474 {
477 }
478 else
479 {
483 }
484 }
485 \f
486 /* Rotate the doubleword integer in L1, H1 left by COUNT places
487 keeping only PREC bits of result.
488 Rotate right if COUNT is negative.
489 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
491 void
495 {
507 }
509 /* Rotate the doubleword integer in L1, H1 left by COUNT places
510 keeping only PREC bits of result. COUNT must be positive.
511 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
513 void
517 {
529 }
530 \f
531 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
532 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
533 CODE is a tree code for a kind of division, one of
534 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
535 or EXACT_DIV_EXPR
536 It controls how the quotient is rounded to an integer.
537 Return nonzero if the operation overflows.
538 UNS nonzero says do unsigned division. */
540 int
543 HOST_WIDE_INT hnum_orig,
545 HOST_WIDE_INT hden_orig,
549 {
565 /* Calculate quotient sign and convert operands to unsigned. */
567 {
569 {
571 /* (minimum integer) / (-1) is the only overflow case. */
575 }
577 {
580 }
581 }
586 /* This unsigned division rounds toward zero. */
589 }
593 /* hden != 0 already checked. */
598 }
608 /* Special code for when the divisor < BASE. */
610 {
611 /* hnum != 0 already checked. */
613 {
617 }
618 }
619 else
620 {
621 /* Full double precision division,
622 with thanks to Don Knuth's "Seminumerical Algorithms". */
626 /* Find the highest nonzero divisor digit. */
629 {
632 }
634 /* Insure that the first digit of the divisor is at least BASE/2.
635 This is required by the quotient digit estimation algorithm. */
642 {
646 }
651 {
656 }
657 }
661 /* Main loop */
663 {
664 /* Guess the next quotient digit, quo_est, by dividing the first
665 two remaining dividend digits by the high order quotient digit.
666 quo_est is never low and is at most 2 high. */
673 else
676 /* Refine quo_est so it's usually correct, and at most one high. */
681 quo_est--;
683 /* Try QUO_EST as the quotient digit, by multiplying the
684 divisor by QUO_EST and subtracting from the remaining dividend.
685 Keep in mind that QUO_EST is the I - 1st digit. */
689 {
695 }
697 /* If quo_est was high by one, then num[i] went negative and
698 we need to correct things. */
700 {
701 quo_est--;
704 {
708 }
711 }
713 /* Store the quotient digit. */
715 }
716 }
720 finish_up:
721 /* If result is negative, make it so. */
725 /* compute trial remainder: rem = num - (quo * den) */
731 {
740 {
741 /* quo = quo - 1; */
744 }
745 else
752 {
755 }
756 else
762 {
768 /* Get absolute values. */
774 /* If (2 * abs (lrem) >= abs (lden)) */
783 {
785 /* quo = quo - 1; */
788 else
789 /* quo = quo + 1; */
792 }
793 else
795 }
800 }
802 /* Compute true remainder: rem = num - (quo * den) */
807 }
808 \f
809 /* Return true if built-in mathematical function specified by CODE
810 preserves the sign of it argument, i.e. -f(x) == f(-x). */
812 static bool
814 {
816 {
833 }
835 }
837 /* Determine whether an expression T can be cheaply negated using
838 the function negate_expr. */
840 static bool
842 {
845 tree type;
854 {
859 /* Check that -CST will not overflow type. */
862 {
867 }
868 else
885 /* -(A + B) -> (-B) - A. */
890 /* -(A + B) -> (-A) - B. */
894 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
903 /* Fall through. */
912 /* Negate -((double)float) as (double)(-float). */
914 {
918 }
922 /* Negate -f(x) as f(-x). */
929 }
931 }
933 /* Given T, an expression, return the negation of T. Allow for T to be
934 null, in which case return null. */
936 static tree
938 {
939 tree type;
940 tree tem;
949 {
951 {
953 HOST_WIDE_INT high;
964 }
973 /* Two's complement FP formats, such as c4x, may overflow. */
979 {
988 }
996 {
997 /* -(A + B) -> (-B) - A. */
1005 /* -(A + B) -> (-A) - B. */
1011 }
1015 /* - (A - B) -> B - A */
1028 /* Fall through. */
1032 {
1045 }
1049 /* Convert -((double)float) into (double)(-float). */
1051 {
1055 }
1059 /* Negate -f(x) as f(-x). */
1062 {
1069 }
1074 }
1078 }
1079 \f
1080 /* Split a tree IN into a constant, literal and variable parts that could be
1081 combined with CODE to make IN. "constant" means an expression with
1082 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1083 commutative arithmetic operation. Store the constant part into *CONP,
1084 the literal in *LITP and return the variable part. If a part isn't
1085 present, set it to null. If the tree does not decompose in this way,
1086 return the entire tree as the variable part and the other parts as null.
1088 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1089 case, we negate an operand that was subtracted. Except if it is a
1090 literal for which we use *MINUS_LITP instead.
1092 If NEGATE_P is true, we are negating all of IN, again except a literal
1093 for which we use *MINUS_LITP instead.
1095 If IN is itself a literal or constant, return it as appropriate.
1097 Note that we do not guarantee that any of the three values will be the
1098 same type as IN, but they will have the same signedness and mode. */
1100 static tree
1103 {
1110 /* Strip any conversions that don't change the machine mode or signedness. */
1117 /* We can associate addition and subtraction together (even
1118 though the C standard doesn't say so) for integers because
1119 the value is not affected. For reals, the value might be
1120 affected, so we can't. */
1123 {
1129 /* First see if either of the operands is a literal, then a constant. */
1140 /* If we haven't dealt with either operand, this is not a case we can
1141 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1146 else
1149 /* Now do any needed negations. */
1156 }
1159 else
1163 {
1170 }
1173 }
1175 /* Re-associate trees split by the above function. T1 and T2 are either
1176 expressions to associate or null. Return the new expression, if any. If
1177 we build an operation, do it in TYPE and with CODE. */
1179 static tree
1181 {
1187 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1188 try to fold this since we will have infinite recursion. But do
1189 deal with any NEGATE_EXPRs. */
1192 {
1194 {
1201 }
1204 }
1208 }
1209 \f
1210 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1211 to produce a new constant.
1213 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1215 static tree
1217 {
1221 HOST_WIDE_INT hi;
1223 HOST_WIDE_INT garbageh;
1224 tree t;
1227 int is_sizetype
1238 {
1254 /* It's unclear from the C standard whether shifts can overflow.
1255 The following code ignores overflow; perhaps a C standard
1256 interpretation ruling is needed. */
1286 /* This is a shortcut for a common special case. */
1291 {
1297 }
1299 /* ... fall through ... */
1303 {
1306 }
1309 {
1312 }
1319 /* This is a shortcut for a common special case. */
1324 {
1329 }
1331 /* ... fall through ... */
1347 else
1353 else
1359 }
1361 /* If this is for a sizetype, can be represented as one (signed)
1362 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1363 constants. */
1369 else
1370 {
1373 }
1376 = ((notrunc
1383 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1384 So check if force_fit_type truncated the value. */
1395 }
1397 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1398 constant. We assume ARG1 and ARG2 have the same data type, or at least
1399 are the same kind of constant and the same machine mode.
1401 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1403 static tree
1405 {
1413 {
1415 REAL_VALUE_TYPE d1;
1416 REAL_VALUE_TYPE d2;
1417 REAL_VALUE_TYPE value;
1426 /* Don't perform operation if we honor signaling NaNs and
1427 either operand is a NaN. */
1432 /* Don't perform operation if it would raise a division
1433 by zero exception. */
1439 /* If either operand is a NaN, just return it. Otherwise, set up
1440 for floating-point trap; we return an overflow. */
1458 }
1460 {
1466 tree t;
1469 {
1489 notrunc),
1495 notrunc));
1499 {
1500 tree magsquared
1504 notrunc);
1507 const_binop
1512 notrunc),
1514 notrunc),
1515 notrunc),
1517 const_binop
1522 notrunc),
1524 notrunc),
1525 notrunc),
1527 }
1532 }
1534 }
1536 }
1538 /* These are the hash table functions for the hash table of INTEGER_CST
1539 nodes of a sizetype. */
1541 /* Return the hash code code X, an INTEGER_CST. */
1543 static hashval_t
1545 {
1551 }
1553 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1554 is the same as that given by *Y, which is the same. */
1556 static int
1558 {
1566 }
1567 \f
1568 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1569 bits are given by NUMBER and of the sizetype represented by KIND. */
1571 tree
1573 {
1575 }
1577 /* Likewise, but the desired type is specified explicitly. */
1581 htab_t size_htab;
1583 tree
1585 {
1589 {
1592 }
1594 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1595 hash table, we return the value from the hash table. Otherwise, we
1596 place that in the hash table and make a new node for the next time. */
1605 {
1611 }
1612 else
1614 }
1616 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1617 is a tree code. The type of the result is taken from the operands.
1618 Both must be the same type integer type and it must be a size type.
1619 If the operands are constant, so is the result. */
1621 tree
1623 {
1630 /* Handle the special case of two integer constants faster. */
1632 {
1633 /* And some specific cases even faster than that. */
1642 /* Handle general case of two integer constants. */
1644 }
1650 }
1652 /* Given two values, either both of sizetype or both of bitsizetype,
1653 compute the difference between the two values. Return the value
1654 in signed type corresponding to the type of the operands. */
1656 tree
1658 {
1660 tree ctype;
1666 /* If the type is already signed, just do the simple thing. */
1673 /* If either operand is not a constant, do the conversions to the signed
1674 type and subtract. The hardware will do the right thing with any
1675 overflow in the subtraction. */
1680 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1681 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1682 overflow) and negate (which can't either). Special-case a result
1683 of zero while we're here. */
1688 else
1692 }
1693 \f
1695 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1696 type TYPE. If no simplification can be done return NULL_TREE. */
1698 static tree
1700 {
1702 tree t;
1708 {
1710 {
1711 /* If we would build a constant wider than GCC supports,
1712 leave the conversion unfolded. */
1716 /* If we are trying to make a sizetype for a small integer, use
1717 size_int to pick up cached types to reduce duplicate nodes. */
1723 /* Given an integer constant, make new constant with new type,
1724 appropriately sign-extended or truncated. */
1728 /* Indicate an overflow if (1) ARG1 already overflowed,
1729 or (2) force_fit_type indicates an overflow.
1730 Tell force_fit_type that an overflow has already occurred
1731 if ARG1 is a too-large unsigned value and T is signed.
1732 But don't indicate an overflow if converting a pointer. */
1743 }
1745 {
1746 /* The following code implements the floating point to integer
1747 conversion rules required by the Java Language Specification,
1748 that IEEE NaNs are mapped to zero and values that overflow
1749 the target precision saturate, i.e. values greater than
1750 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1751 are mapped to INT_MIN. These semantics are allowed by the
1752 C and C++ standards that simply state that the behavior of
1753 FP-to-integer conversion is unspecified upon overflow. */
1757 REAL_VALUE_TYPE r;
1761 {
1776 }
1778 /* If R is NaN, return zero and show we have an overflow. */
1780 {
1784 }
1786 /* See if R is less than the lower bound or greater than the
1787 upper bound. */
1790 {
1794 {
1798 }
1799 }
1802 {
1805 {
1808 {
1812 }
1813 }
1814 }
1826 }
1827 }
1829 {
1833 {
1835 {
1836 /* We make a copy of ARG1 so that we don't modify an
1837 existing constant tree. */
1841 }
1852 }
1853 }
1855 }
1857 /* Convert expression ARG to type TYPE. Used by the middle-end for
1858 simple conversions in preference to calling the front-end's convert. */
1860 static tree
1862 {
1864 tree tem;
1878 {
1880 {
1884 }
1888 {
1891 }
1896 }
1898 {
1900 {
1904 }
1906 {
1910 }
1918 {
1921 }
1922 }
1924 {
1932 {
1936 {
1940 }
1948 }
1949 }
1951 {
1960 }
1964 }
1965 \f
1966 /* Return an expr equal to X but certainly not valid as an lvalue. */
1968 tree
1970 {
1971 tree result;
1973 /* These things are certainly not lvalues. */
1984 }
1986 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
1987 Zero means allow extended lvalues. */
1991 /* When pedantic, return an expr equal to X but certainly not valid as a
1992 pedantic lvalue. Otherwise, return X. */
1994 tree
1996 {
1999 else
2001 }
2002 \f
2003 /* Given a tree comparison code, return the code that is the logical inverse
2004 of the given code. It is not safe to do this for floating-point
2005 comparisons, except for NE_EXPR and EQ_EXPR. */
2007 static enum tree_code
2009 {
2011 {
2026 }
2027 }
2029 /* Similar, but return the comparison that results if the operands are
2030 swapped. This is safe for floating-point. */
2032 static enum tree_code
2034 {
2036 {
2050 }
2051 }
2054 /* Convert a comparison tree code from an enum tree_code representation
2055 into a compcode bit-based encoding. This function is the inverse of
2056 compcode_to_comparison. */
2058 static int
2060 {
2062 {
2077 }
2078 }
2080 /* Convert a compcode bit-based encoding of a comparison operator back
2081 to GCC's enum tree_code representation. This function is the
2082 inverse of comparison_to_compcode. */
2084 static enum tree_code
2086 {
2088 {
2103 }
2104 }
2106 /* Return nonzero if CODE is a tree code that represents a truth value. */
2108 static int
2110 {
2115 }
2116 \f
2117 /* Return nonzero if two operands (typically of the same tree node)
2118 are necessarily equal. If either argument has side-effects this
2119 function returns zero.
2121 If ONLY_CONST is nonzero, only return nonzero for constants.
2122 This function tests whether the operands are indistinguishable;
2123 it does not test whether they are equal using C's == operation.
2124 The distinction is important for IEEE floating point, because
2125 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2126 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2128 If ONLY_CONST is zero, a VAR_DECL is considered equal to itself
2129 even though it may hold multiple values during a function.
2130 This is because a GCC tree node guarantees that nothing else is
2131 executed between the evaluation of its "operands" (which may often
2132 be evaluated in arbitrary order). Hence if the operands themselves
2133 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2134 same value in each operand/subexpression. Hence a zero value for
2135 ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
2136 If comparing arbitrary expression trees, such as from different
2137 statements, ONLY_CONST must usually be nonzero. */
2139 int
2141 {
2142 tree fndecl;
2144 /* If both types don't have the same signedness, then we can't consider
2145 them equal. We must check this before the STRIP_NOPS calls
2146 because they may change the signedness of the arguments. */
2154 /* This is needed for conversions and for COMPONENT_REF.
2155 Might as well play it safe and always test this. */
2161 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2162 We don't care about side effects in that case because the SAVE_EXPR
2163 takes care of that for us. In all other cases, two expressions are
2164 equal if they have no side effects. If we have two identical
2165 expressions with side effects that should be treated the same due
2166 to the only side effects being identical SAVE_EXPR's, that will
2167 be detected in the recursive calls below. */
2173 /* Next handle constant cases, those for which we can return 1 even
2174 if ONLY_CONST is set. */
2177 {
2190 {
2200 {
2202 only_const))
2206 }
2209 }
2213 only_const)
2215 only_const));
2228 }
2234 {
2236 /* Two conversions are equal only if signedness and modes match. */
2252 /* For commutative ops, allow the other order. */
2260 /* If either of the pointer (or reference) expressions we are
2261 dereferencing contain a side effect, these cannot be equal. */
2267 {
2289 }
2293 {
2303 /* If the CALL_EXPRs call different functions, then they
2304 clearly can not be equal. */
2309 /* Only consider const functions equivalent. */
2315 /* Now see if all the arguments are the same. operand_equal_p
2316 does not handle TREE_LIST, so we walk the operands here
2317 feeding them to operand_equal_p. */
2321 {
2327 }
2329 /* If we get here and both argument lists are exhausted
2330 then the CALL_EXPRs are equal. */
2335 }
2338 /* Consider __builtin_sqrt equal to sqrt. */
2346 }
2347 }
2348 \f
2349 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2350 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2352 When in doubt, return 0. */
2354 static int
2356 {
2368 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2369 and see if the inner values are the same. This removes any
2370 signedness comparison, which doesn't matter here. */
2377 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2378 actual comparison operand, ARG0.
2380 First throw away any conversions to wider types
2381 already present in the operands. */
2390 {
2393 /* Make sure shorter operand is extended the right way
2394 to match the longer operand. */
2400 }
2403 }
2404 \f
2405 /* See if ARG is an expression that is either a comparison or is performing
2406 arithmetic on comparisons. The comparisons must only be comparing
2407 two different values, which will be stored in *CVAL1 and *CVAL2; if
2408 they are nonzero it means that some operands have already been found.
2409 No variables may be used anywhere else in the expression except in the
2410 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2411 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2413 If this is true, return 1. Otherwise, return zero. */
2415 static int
2417 {
2421 /* We can handle some of the 'e' cases here. */
2431 {
2432 /* If we've already found a CVAL1 or CVAL2, this expression is
2433 two complex to handle. */
2439 }
2442 {
2465 /* First see if we can handle the first operand, then the second. For
2466 the second operand, we know *CVAL1 can't be zero. It must be that
2467 one side of the comparison is each of the values; test for the
2468 case where this isn't true by failing if the two operands
2469 are the same. */
2478 ;
2482 ;
2483 else
2487 ;
2491 ;
2492 else
2499 }
2500 }
2501 \f
2502 /* ARG is a tree that is known to contain just arithmetic operations and
2503 comparisons. Evaluate the operations in the tree substituting NEW0 for
2504 any occurrence of OLD0 as an operand of a comparison and likewise for
2505 NEW1 and OLD1. */
2507 static tree
2509 {
2514 /* We can handle some of the 'e' cases here. */
2522 {
2537 {
2554 }
2555 /* Fall through - ??? */
2558 {
2562 /* We need to check both for exact equality and tree equality. The
2563 former will be true if the operand has a side-effect. In that
2564 case, we know the operand occurred exactly once. */
2577 }
2581 }
2582 }
2583 \f
2584 /* Return a tree for the case when the result of an expression is RESULT
2585 converted to TYPE and OMITTED was previously an operand of the expression
2586 but is now not needed (e.g., we folded OMITTED * 0).
2588 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2589 the conversion of RESULT to TYPE. */
2591 tree
2593 {
2600 }
2602 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2604 static tree
2606 {
2613 }
2614 \f
2615 /* Return a simplified tree node for the truth-negation of ARG. This
2616 never alters ARG itself. We assume that ARG is an operation that
2617 returns a truth value (0 or 1). */
2619 tree
2621 {
2628 /* If this is a comparison, we can simply invert it, except for
2629 floating-point non-equality comparisons, in which case we just
2630 enclose a TRUTH_NOT_EXPR around what we have. */
2633 {
2635 && !flag_unsafe_math_optimizations
2647 else
2650 }
2653 {
2668 /* Here we can invert either operand. We invert the first operand
2669 unless the second operand is a TRUTH_NOT_EXPR in which case our
2670 result is the XOR of the first operand with the inside of the
2671 negation of the second operand. */
2676 else
2732 }
2736 }
2738 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2739 operands are another bit-wise operation with a common input. If so,
2740 distribute the bit operations to save an operation and possibly two if
2741 constants are involved. For example, convert
2742 (A | B) & (A | C) into A | (B & C)
2743 Further simplification will occur if B and C are constants.
2745 If this optimization cannot be done, 0 will be returned. */
2747 static tree
2749 {
2750 tree common;
2760 {
2764 }
2766 {
2770 }
2772 {
2776 }
2778 {
2782 }
2783 else
2788 }
2789 \f
2790 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2791 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2793 static tree
2796 {
2803 }
2805 /* Optimize a bit-field compare.
2807 There are two cases: First is a compare against a constant and the
2808 second is a comparison of two items where the fields are at the same
2809 bit position relative to the start of a chunk (byte, halfword, word)
2810 large enough to contain it. In these cases we can avoid the shift
2811 implicit in bitfield extractions.
2813 For constants, we emit a compare of the shifted constant with the
2814 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2815 compared. For two fields at the same position, we do the ANDs with the
2816 similar mask and compare the result of the ANDs.
2818 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2819 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2820 are the left and right operands of the comparison, respectively.
2822 If the optimization described above can be done, we return the resulting
2823 tree. Otherwise we return zero. */
2825 static tree
2828 {
2837 tree mask;
2838 tree offset;
2840 /* Get all the information about the extractions being done. If the bit size
2841 if the same as the size of the underlying object, we aren't doing an
2842 extraction at all and so can do nothing. We also don't want to
2843 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2844 then will no longer be able to replace it. */
2852 {
2853 /* If this is not a constant, we can only do something if bit positions,
2854 sizes, and signedness are the same. */
2862 }
2864 /* See if we can find a mode to refer to this field. We should be able to,
2865 but fail if we can't. */
2874 /* Set signed and unsigned types of the precision of this mode for the
2875 shifts below. */
2879 /* Compute the bit position and size for the new reference and our offset
2880 within it. If the new reference is the same size as the original, we
2881 won't optimize anything, so return zero. */
2891 /* Make the mask to be used against the extracted field. */
2901 /* If not comparing with constant, just rework the comparison
2902 and return. */
2907 mask),
2911 mask));
2913 /* Otherwise, we are handling the constant case. See if the constant is too
2914 big for the field. Warn and return a tree of for 0 (false) if so. We do
2915 this not only for its own sake, but to avoid having to test for this
2916 error case below. If we didn't, we might generate wrong code.
2918 For unsigned fields, the constant shifted right by the field length should
2919 be all zero. For signed fields, the high-order bits should agree with
2920 the sign bit. */
2923 {
2927 {
2933 }
2934 }
2935 else
2936 {
2940 {
2946 }
2947 }
2949 /* Single-bit compares should always be against zero. */
2951 {
2954 }
2956 /* Make a new bitfield reference, shift the constant over the
2957 appropriate number of bits and mask it with the computed mask
2958 (in case this was a signed field). If we changed it, make a new one. */
2961 {
2964 }
2974 rhs);
2975 }
2976 \f
2977 /* Subroutine for fold_truthop: decode a field reference.
2979 If EXP is a comparison reference, we return the innermost reference.
2981 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
2982 set to the starting bit number.
2984 If the innermost field can be completely contained in a mode-sized
2985 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
2987 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
2988 otherwise it is not changed.
2990 *PUNSIGNEDP is set to the signedness of the field.
2992 *PMASK is set to the mask used. This is either contained in a
2993 BIT_AND_EXPR or derived from the width of the field.
2995 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
2997 Return 0 if this is not a component reference or is one that we can't
2998 do anything with. */
3000 static tree
3005 {
3009 tree unsigned_type;
3012 /* All the optimizations using this function assume integer fields.
3013 There are problems with FP fields since the type_for_size call
3014 below can fail for, e.g., XFmode. */
3018 /* We are interested in the bare arrangement of bits, so strip everything
3019 that doesn't affect the machine mode. However, record the type of the
3020 outermost expression if it may matter below. */
3028 {
3034 }
3043 /* If the number of bits in the reference is the same as the bitsize of
3044 the outer type, then the outer type gives the signedness. Otherwise
3045 (in case of a small bitfield) the signedness is unchanged. */
3049 /* Compute the mask to access the bitfield. */
3059 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3067 }
3069 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3070 bit positions. */
3072 static int
3074 {
3077 tree tmask;
3082 return
3089 }
3091 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3092 represents the sign bit of EXP's type. If EXP represents a sign
3093 or zero extension, also test VAL against the unextended type.
3094 The return value is the (sub)expression whose sign bit is VAL,
3095 or NULL_TREE otherwise. */
3097 static tree
3099 {
3103 tree t;
3105 /* Tree EXP must have an integral type. */
3110 /* Tree VAL must be an integer constant. */
3117 {
3124 }
3125 else
3126 {
3133 }
3135 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3136 treat VAL as if it were unsigned. */
3141 /* Handle extension from a narrower type. */
3147 }
3149 /* Subroutine for fold_truthop: determine if an operand is simple enough
3150 to be evaluated unconditionally. */
3152 static int
3154 {
3155 /* Strip any conversions that don't change the machine mode. */
3167 /* Don't regard global variables as simple. They may be
3168 allocated in ways unknown to the compiler (shared memory,
3169 #pragma weak, etc). */
3172 /* Loading a static variable is unduly expensive, but global
3173 registers aren't expensive. */
3175 }
3176 \f
3177 /* The following functions are subroutines to fold_range_test and allow it to
3178 try to change a logical combination of comparisons into a range test.
3180 For example, both
3181 X == 2 || X == 3 || X == 4 || X == 5
3182 and
3183 X >= 2 && X <= 5
3184 are converted to
3185 (unsigned) (X - 2) <= 3
3187 We describe each set of comparisons as being either inside or outside
3188 a range, using a variable named like IN_P, and then describe the
3189 range with a lower and upper bound. If one of the bounds is omitted,
3190 it represents either the highest or lowest value of the type.
3192 In the comments below, we represent a range by two numbers in brackets
3193 preceded by a "+" to designate being inside that range, or a "-" to
3194 designate being outside that range, so the condition can be inverted by
3195 flipping the prefix. An omitted bound is represented by a "-". For
3196 example, "- [-, 10]" means being outside the range starting at the lowest
3197 possible value and ending at 10, in other words, being greater than 10.
3198 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3199 always false.
3201 We set up things so that the missing bounds are handled in a consistent
3202 manner so neither a missing bound nor "true" and "false" need to be
3203 handled using a special case. */
3205 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3206 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3207 and UPPER1_P are nonzero if the respective argument is an upper bound
3208 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3209 must be specified for a comparison. ARG1 will be converted to ARG0's
3210 type if both are specified. */
3212 static tree
3215 {
3216 tree tem;
3220 /* If neither arg represents infinity, do the normal operation.
3221 Else, if not a comparison, return infinity. Else handle the special
3222 comparison rules. Note that most of the cases below won't occur, but
3223 are handled for consistency. */
3226 {
3231 }
3236 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3237 for neither. In real maths, we cannot assume open ended ranges are
3238 the same. But, this is computer arithmetic, where numbers are finite.
3239 We can therefore make the transformation of any unbounded range with
3240 the value Z, Z being greater than any representable number. This permits
3241 us to treat unbounded ranges as equal. */
3245 {
3266 }
3269 }
3270 \f
3271 /* Given EXP, a logical expression, set the range it is testing into
3272 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3273 actually being tested. *PLOW and *PHIGH will be made of the same type
3274 as the returned expression. If EXP is not a comparison, we will most
3275 likely not be returning a useful value and range. */
3277 static tree
3279 {
3286 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3287 and see if we can refine the range. Some of the cases below may not
3288 happen, but it doesn't seem worth worrying about this. We "continue"
3289 the outer loop when we've changed something; otherwise we "break"
3290 the switch, which will "break" the while. */
3296 {
3300 {
3312 }
3314 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3315 lose a cast by accident. */
3320 {
3327 /* We can only do something if the range is testing for zero
3328 and if the second operand is an integer constant. Note that
3329 saying something is "in" the range we make is done by
3330 complementing IN_P since it will set in the initial case of
3331 being not equal to zero; "out" is leaving it alone. */
3338 {
3359 }
3363 /* If this is an unsigned comparison, we also know that EXP is
3364 greater than or equal to zero. We base the range tests we make
3365 on that fact, so we record it here so we can parse existing
3366 range tests. */
3368 {
3371 NULL_TREE))
3376 /* If the high bound is missing, but we have a nonzero low
3377 bound, reverse the range so it goes from zero to the low bound
3378 minus 1. */
3380 {
3385 }
3386 }
3390 /* (-x) IN [a,b] -> x in [-b, -a] */
3402 /* ~ X -> -X - 1 */
3411 /* If EXP is signed, any overflow in the computation is undefined,
3412 so we don't worry about it so long as our computations on
3413 the bounds don't overflow. For unsigned, overflow is defined
3414 and this is exactly the right thing. */
3423 /* Check for an unsigned range which has wrapped around the maximum
3424 value thus making n_high < n_low, and normalize it. */
3426 {
3432 /* If the range is of the form +/- [ x+1, x ], we won't
3433 be able to normalize it. But then, it represents the
3434 whole range or the empty set, so make it
3435 +/- [ -, - ]. */
3439 else
3441 }
3442 else
3465 /* If we're converting from an unsigned to a signed type,
3466 we will be doing the comparison as unsigned. The tests above
3467 have already verified that LOW and HIGH are both positive.
3469 So we have to make sure that the original unsigned value will
3470 be interpreted as positive. */
3472 {
3475 tree high_positive;
3477 /* A range without an upper bound is, naturally, unbounded.
3478 Since convert would have cropped a very large value, use
3479 the max value for the destination type. */
3480 high_positive
3487 high_positive),
3489 integer_one_node)));
3491 /* If the low bound is specified, "and" the range with the
3492 range for which the original unsigned value will be
3493 positive. */
3495 {
3499 high_positive))
3503 }
3504 else
3505 {
3506 /* Otherwise, "or" the range with the range of the input
3507 that will be interpreted as negative. */
3511 high_positive))
3515 }
3516 }
3524 }
3527 }
3529 /* If EXP is a constant, we can evaluate whether this is true or false. */
3531 {
3538 }
3542 }
3543 \f
3544 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3545 type, TYPE, return an expression to test if EXP is in (or out of, depending
3546 on IN_P) the range. */
3548 static tree
3550 {
3552 tree value;
3571 {
3573 {
3577 }
3579 }
3581 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3583 {
3585 HOST_WIDE_INT hi;
3590 {
3593 }
3594 else
3595 {
3598 }
3601 {
3603 {
3606 }
3609 }
3610 }
3617 value);
3620 }
3621 \f
3622 /* Given two ranges, see if we can merge them into one. Return 1 if we
3623 can, 0 if we can't. Set the output range into the specified parameters. */
3625 static int
3628 {
3632 tree tem;
3642 /* Make range 0 be the range that starts first, or ends last if they
3643 start at the same value. Swap them if it isn't. */
3646 || (lowequal
3649 {
3653 }
3655 /* Now flag two cases, whether the ranges are disjoint or whether the
3656 second range is totally subsumed in the first. Note that the tests
3657 below are simplified by the ones above. */
3663 /* We now have four cases, depending on whether we are including or
3664 excluding the two ranges. */
3666 {
3667 /* If they don't overlap, the result is false. If the second range
3668 is a subset it is the result. Otherwise, the range is from the start
3669 of the second to the end of the first. */
3674 else
3676 }
3679 {
3680 /* If they don't overlap, the result is the first range. If they are
3681 equal, the result is false. If the second range is a subset of the
3682 first, and the ranges begin at the same place, we go from just after
3683 the end of the first range to the end of the second. If the second
3684 range is not a subset of the first, or if it is a subset and both
3685 ranges end at the same place, the range starts at the start of the
3686 first range and ends just before the second range.
3687 Otherwise, we can't describe this as a single range. */
3693 {
3697 }
3699 {
3703 }
3704 else
3706 }
3709 {
3710 /* If they don't overlap, the result is the second range. If the second
3711 is a subset of the first, the result is false. Otherwise,
3712 the range starts just after the first range and ends at the
3713 end of the second. */
3718 else
3719 {
3723 }
3724 }
3726 else
3727 {
3728 /* The case where we are excluding both ranges. Here the complex case
3729 is if they don't overlap. In that case, the only time we have a
3730 range is if they are adjacent. If the second is a subset of the
3731 first, the result is the first. Otherwise, the range to exclude
3732 starts at the beginning of the first range and ends at the end of the
3733 second. */
3735 {
3742 else
3744 }
3747 else
3749 }
3753 }
3754 \f
3755 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3756 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3757 #endif
3759 /* EXP is some logical combination of boolean tests. See if we can
3760 merge it into some range test. Return the new tree if so. */
3762 static tree
3764 {
3771 tree tem;
3773 /* If this is an OR operation, invert both sides; we will invert
3774 again at the end. */
3778 /* If both expressions are the same, if we can merge the ranges, and we
3779 can build the range test, return it or it inverted. If one of the
3780 ranges is always true or always false, consider it to be the same
3781 expression as the other. */
3791 /* On machines where the branch cost is expensive, if this is a
3792 short-circuited branch and the underlying object on both sides
3793 is the same, make a non-short-circuit operation. */
3799 {
3800 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3801 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3802 which cases we can't do this. */
3811 {
3823 }
3824 }
3827 }
3828 \f
3829 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3830 bit value. Arrange things so the extra bits will be set to zero if and
3831 only if C is signed-extended to its full width. If MASK is nonzero,
3832 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3834 static tree
3836 {
3839 tree temp;
3844 /* We work by getting just the sign bit into the low-order bit, then
3845 into the high-order bit, then sign-extend. We then XOR that value
3846 with C. */
3850 /* We must use a signed type in order to get an arithmetic right shift.
3851 However, we must also avoid introducing accidental overflows, so that
3852 a subsequent call to integer_zerop will work. Hence we must
3853 do the type conversion here. At this point, the constant is either
3854 zero or one, and the conversion to a signed type can never overflow.
3855 We could get an overflow if this conversion is done anywhere else. */
3864 /* If necessary, convert the type back to match the type of C. */
3869 }
3870 \f
3871 /* Find ways of folding logical expressions of LHS and RHS:
3872 Try to merge two comparisons to the same innermost item.
3873 Look for range tests like "ch >= '0' && ch <= '9'".
3874 Look for combinations of simple terms on machines with expensive branches
3875 and evaluate the RHS unconditionally.
3877 For example, if we have p->a == 2 && p->b == 4 and we can make an
3878 object large enough to span both A and B, we can do this with a comparison
3879 against the object ANDed with the a mask.
3881 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3882 operations to do this with one comparison.
3884 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3885 function and the one above.
3887 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3888 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3890 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3891 two operands.
3893 We return the simplified tree or 0 if no optimization is possible. */
3895 static tree
3897 {
3898 /* If this is the "or" of two comparisons, we can do something if
3899 the comparisons are NE_EXPR. If this is the "and", we can do something
3900 if the comparisons are EQ_EXPR. I.e.,
3901 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3903 WANTED_CODE is this operation code. For single bit fields, we can
3904 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3905 comparison for one-bit fields. */
3925 /* Start by getting the comparison codes. Fail if anything is volatile.
3926 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3927 it were surrounded with a NE_EXPR. */
3952 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3956 {
3961 {
3969 }
3972 {
3981 }
3982 else
3992 }
3994 /* If the RHS can be evaluated unconditionally and its operands are
3995 simple, it wins to evaluate the RHS unconditionally on machines
3996 with expensive branches. In this case, this isn't a comparison
3997 that can be merged. Avoid doing this if the RHS is a floating-point
3998 comparison since those can trap. */
4004 {
4005 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4013 integer_zero_node);
4015 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4023 integer_zero_node);
4026 }
4028 /* See if the comparisons can be merged. Then get all the parameters for
4029 each side. */
4053 /* It must be true that the inner operation on the lhs of each
4054 comparison must be the same if we are to be able to do anything.
4055 Then see if we have constants. If not, the same must be true for
4056 the rhs's. */
4067 else
4070 /* If either comparison code is not correct for our logical operation,
4071 fail. However, we can convert a one-bit comparison against zero into
4072 the opposite comparison against that bit being set in the field. */
4076 {
4078 {
4079 /* Make the left operand unsigned, since we are only interested
4080 in the value of one bit. Otherwise we are doing the wrong
4081 thing below. */
4084 }
4085 else
4087 }
4089 /* This is analogous to the code for l_const above. */
4091 {
4093 {
4096 }
4097 else
4099 }
4101 /* After this point all optimizations will generate bit-field
4102 references, which we might not want. */
4106 /* See if we can find a mode that contains both fields being compared on
4107 the left. If we can't, fail. Otherwise, update all constants and masks
4108 to be relative to a field of that size. */
4113 volatilep);
4123 {
4126 }
4134 {
4142 {
4146 wanted_code == NE_EXPR
4148 }
4149 }
4151 {
4159 {
4163 wanted_code == NE_EXPR
4165 }
4166 }
4168 /* If the right sides are not constant, do the same for it. Also,
4169 disallow this optimization if a size or signedness mismatch occurs
4170 between the left and right sides. */
4172 {
4175 /* Make sure the two fields on the right
4176 correspond to the left without being swapped. */
4184 volatilep);
4194 {
4197 }
4204 /* Make a mask that corresponds to both fields being compared.
4205 Do this for both items being compared. If the operands are the
4206 same size and the bits being compared are in the same position
4207 then we can do this by masking both and comparing the masked
4208 results. */
4212 {
4224 }
4226 /* There is still another way we can do something: If both pairs of
4227 fields being compared are adjacent, we may be able to make a wider
4228 field containing them both.
4230 Note that we still must mask the lhs/rhs expressions. Furthermore,
4231 the mask must be shifted to account for the shift done by
4232 make_bit_field_ref. */
4237 {
4238 tree type;
4250 /* Convert to the smaller type before masking out unwanted bits. */
4253 {
4255 {
4259 }
4261 {
4265 }
4266 }
4275 }
4278 }
4280 /* Handle the case of comparisons with constants. If there is something in
4281 common between the masks, those bits of the constants must be the same.
4282 If not, the condition is always false. Test for this to avoid generating
4283 incorrect code below. */
4288 {
4290 {
4293 }
4294 else
4295 {
4298 }
4299 }
4301 /* Construct the expression we will return. First get the component
4302 reference we will make. Unless the mask is all ones the width of
4303 that field, perform the mask operation. Then compare with the
4304 merged constant. */
4314 }
4315 \f
4316 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4317 constant. */
4319 static tree
4321 {
4326 tree minmax_const;
4328 tree inner;
4338 /* If something does not permit us to optimize, return the original tree. */
4346 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4347 and GT_EXPR, doing the rest with recursive calls using logical
4348 simplifications. */
4350 {
4352 return
4356 return
4358 optimize_minmax_comparison
4360 optimize_minmax_comparison
4365 /* MAX (X, 0) == 0 -> X <= 0 */
4369 /* MAX (X, 0) == 5 -> X == 5 */
4373 /* MAX (X, 0) == -1 -> false */
4377 /* MIN (X, 0) == 0 -> X >= 0 */
4381 /* MIN (X, 0) == 5 -> false */
4384 else
4385 /* MIN (X, 0) == -1 -> X == -1 */
4390 /* MAX (X, 0) > 0 -> X > 0
4391 MAX (X, 0) > 5 -> X > 5 */
4395 /* MAX (X, 0) > -1 -> true */
4399 /* MIN (X, 0) > 0 -> false
4400 MIN (X, 0) > 5 -> false */
4403 else
4404 /* MIN (X, 0) > -1 -> X > -1 */
4409 }
4410 }
4411 \f
4412 /* T is an integer expression that is being multiplied, divided, or taken a
4413 modulus (CODE says which and what kind of divide or modulus) by a
4414 constant C. See if we can eliminate that operation by folding it with
4415 other operations already in T. WIDE_TYPE, if non-null, is a type that
4416 should be used for the computation if wider than our type.
4418 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4419 (X * 2) + (Y * 4). We must, however, be assured that either the original
4420 expression would not overflow or that overflow is undefined for the type
4421 in the language in question.
4423 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4424 the machine has a multiply-accumulate insn or that this is part of an
4425 addressing calculation.
4427 If we return a non-null expression, it is an equivalent form of the
4428 original computation, but need not be in the original type. */
4430 static tree
4432 {
4433 /* To avoid exponential search depth, refuse to allow recursion past
4434 three levels. Beyond that (1) it's highly unlikely that we'll find
4435 something interesting and (2) we've probably processed it before
4436 when we built the inner expression. */
4439 tree ret;
4444 depth++;
4446 depth--;
4449 }
4451 static tree
4453 {
4463 /* Don't deal with constants of zero here; they confuse the code below. */
4473 /* Note that we need not handle conditional operations here since fold
4474 already handles those cases. So just do arithmetic here. */
4476 {
4478 /* For a constant, we can always simplify if we are a multiply
4479 or (for divide and modulus) if it is a multiple of our constant. */
4487 /* If op0 is an expression ... */
4492 /* ... and is unsigned, and its type is smaller than ctype,
4493 then we cannot pass through as widening. */
4499 /* ... or its type is larger than ctype,
4500 then we cannot pass through this truncation. */
4503 /* ... or signedness changes for division or modulus,
4504 then we cannot pass through this conversion. */
4510 /* Pass the constant down and see if we can make a simplification. If
4511 we can, replace this expression with the inner simplification for
4512 possible later conversion to our or some other type. */
4517 code == MULT_EXPR
4528 /* If widening the type changes the signedness, then we can't perform
4529 this optimization as that changes the result. */
4533 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4536 {
4542 }
4552 /* If the second operand is constant, this is a multiplication
4553 or floor division, by a power of two, so we can treat it that
4554 way unless the multiplier or divisor overflows. */
4556 /* const_binop may not detect overflow correctly,
4557 so check for it explicitly here. */
4562 size_one_node,
4572 /* See if we can eliminate the operation on both sides. If we can, we
4573 can return a new PLUS or MINUS. If we can't, the only remaining
4574 cases where we can do anything are if the second operand is a
4575 constant. */
4580 /* If not multiplication, we can only do this if both operands
4581 are divisible by c. */
4587 /* If this was a subtraction, negate OP1 and set it to be an addition.
4588 This simplifies the logic below. */
4595 /* If either OP1 or C are negative, this optimization is not safe for
4596 some of the division and remainder types while for others we need
4597 to change the code. */
4599 {
4607 }
4609 /* If it's a multiply or a division/modulus operation of a multiple
4610 of our constant, do the operation and verify it doesn't overflow. */
4613 {
4616 /* We allow the constant to overflow with wrapping semantics. */
4620 }
4621 else
4624 /* If we have an unsigned type is not a sizetype, we cannot widen
4625 the operation since it will change the result if the original
4626 computation overflowed. */
4632 /* If we were able to eliminate our operation from the first side,
4633 apply our operation to the second side and reform the PLUS. */
4637 /* The last case is if we are a multiply. In that case, we can
4638 apply the distributive law to commute the multiply and addition
4639 if the multiplication of the constants doesn't overflow. */
4645 op1));
4650 /* We have a special case here if we are doing something like
4651 (C * 8) % 4 since we know that's zero. */
4658 /* ... fall through ... */
4662 /* If we can extract our operation from the LHS, do so and return a
4663 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4664 do something only if the second operand is a constant. */
4676 /* If these are the same operation types, we can associate them
4677 assuming no overflow. */
4684 /* If these operations "cancel" each other, we have the main
4685 optimizations of this pass, which occur when either constant is a
4686 multiple of the other, in which case we replace this with either an
4687 operation or CODE or TCODE.
4689 If we have an unsigned type that is not a sizetype, we cannot do
4690 this since it will change the result if the original computation
4691 overflowed. */
4694 && ! flag_wrapv
4699 {
4710 }
4715 }
4718 }
4719 \f
4720 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4721 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4722 that we may sometimes modify the tree. */
4724 static tree
4726 {
4729 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4734 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4735 don't bother handling any other types. */
4737 {
4741 }
4746 {
4749 }
4752 }
4753 \f
4754 /* Return a node which has the indicated constant VALUE (either 0 or
4755 1), and is of the indicated TYPE. */
4757 static tree
4759 {
4764 integer_zero_node);
4765 else
4766 {
4771 }
4772 }
4774 /* Utility function for the following routine, to see how complex a nesting of
4775 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4776 we don't care (to avoid spending too much time on complex expressions.). */
4778 static int
4780 {
4791 }
4793 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4794 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4795 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4796 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4797 COND is the first argument to CODE; otherwise (as in the example
4798 given here), it is the second argument. TYPE is the type of the
4799 original expression. */
4801 static tree
4804 {
4808 /* In the end, we'll produce a COND_EXPR. Both arms of the
4809 conditional expression will be binary operations. The left-hand
4810 side of the expression to be executed if the condition is true
4811 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4812 of the expression to be executed if the condition is true will be
4813 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4814 but apply to the expression to be executed if the conditional is
4815 false. */
4820 /* These are the codes to use for the left-hand side and right-hand
4821 side of the COND_EXPR. Normally, they are the same as CODE. */
4824 /* And these are the types of the expressions. */
4830 {
4834 }
4835 else
4836 {
4840 }
4843 {
4847 /* If this operand throws an expression, then it does not make
4848 sense to try to perform a logical or arithmetic operation
4849 involving it. Instead of building `a + throw 3' for example,
4850 we simply build `a, throw 3'. */
4852 {
4854 {
4857 }
4858 else
4860 }
4862 {
4864 {
4867 }
4868 else
4870 }
4871 }
4872 else
4873 {
4878 }
4880 /* If ARG is complex we want to make sure we only evaluate it once. Though
4881 this is only required if it is volatile, it might be more efficient even
4882 if it is not. However, if we succeed in folding one part to a constant,
4883 we do not need to make this SAVE_EXPR. Since we do this optimization
4884 primarily to see if we do end up with constant and this SAVE_EXPR
4885 interferes with later optimizations, suppressing it when we can is
4886 important.
4888 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4889 do so. Don't try to see if the result is a constant if an arm is a
4890 COND_EXPR since we get exponential behavior in that case. */
4899 {
4908 {
4912 }
4913 }
4922 /* If ARG involves a SAVE_EXPR, we need to ensure it is evaluated
4923 ahead of the COND_EXPR we made. Otherwise we would have it only
4924 evaluated in one branch, with the other branch using the result
4925 but missing the evaluation code. Beware that the save_expr call
4926 above might not return a SAVE_EXPR, so testing the TREE_CODE
4927 of ARG is not enough to decide here. Â */
4932 else
4934 }
4936 \f
4937 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4939 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4940 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4941 ADDEND is the same as X.
4943 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4944 and finite. The problematic cases are when X is zero, and its mode
4945 has signed zeros. In the case of rounding towards -infinity,
4946 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4947 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4949 static bool
4951 {
4955 /* Don't allow the fold with -fsignaling-nans. */
4959 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4963 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4968 /* The mode has signed zeros, and we have to honor their sign.
4969 In this situation, there is only one case we can return true for.
4970 X - 0 is the same as X unless rounding towards -infinity is
4971 supported. */
4973 }
4975 /* Subroutine of fold() that checks comparisons of built-in math
4976 functions against real constants.
4978 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
4979 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
4980 is the type of the result and ARG0 and ARG1 are the operands of the
4981 comparison. ARG1 must be a TREE_REAL_CST.
4983 The function returns the constant folded tree if a simplification
4984 can be made, and NULL_TREE otherwise. */
4986 static tree
4989 {
4990 REAL_VALUE_TYPE c;
4995 {
5001 {
5002 /* sqrt(x) < y is always false, if y is negative. */
5006 arg);
5008 /* sqrt(x) > y is always true, if y is negative and we
5009 don't care about NaNs, i.e. negative values of x. */
5013 arg);
5015 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5018 }
5020 {
5021 REAL_VALUE_TYPE c2;
5027 {
5028 /* sqrt(x) > y is x == +Inf, when y is very large. */
5033 /* sqrt(x) > y is always false, when y is very large
5034 and we don't care about infinities. */
5037 arg);
5038 }
5040 /* sqrt(x) > c is the same as x > c*c. */
5043 }
5045 {
5046 REAL_VALUE_TYPE c2;
5052 {
5053 /* sqrt(x) < y is always true, when y is a very large
5054 value and we don't care about NaNs or Infinities. */
5058 arg);
5060 /* sqrt(x) < y is x != +Inf when y is very large and we
5061 don't care about NaNs. */
5066 /* sqrt(x) < y is x >= 0 when y is very large and we
5067 don't care about Infinities. */
5072 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5081 dconst0))),
5084 c2)))));
5085 }
5087 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5092 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5095 {
5100 dconst0))),
5103 c2)))));
5104 }
5105 }
5106 }
5109 }
5111 /* Subroutine of fold() that optimizes comparisons against Infinities,
5112 either +Inf or -Inf.
5114 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5115 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5116 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5118 The function returns the constant folded tree if a simplification
5119 can be made, and NULL_TREE otherwise. */
5121 static tree
5123 {
5125 REAL_VALUE_TYPE max;
5126 tree temp;
5131 /* For negative infinity swap the sense of the comparison. */
5137 {
5139 /* x > +Inf is always false, if with ignore sNANs. */
5144 arg0);
5147 /* x <= +Inf is always true, if we don't case about NaNs. */
5151 arg0);
5153 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5156 {
5159 }
5164 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5170 /* x < +Inf is always equal to x <= DBL_MAX. */
5176 /* x != +Inf is always equal to !(x > DBL_MAX). */
5187 }
5190 }
5192 /* If CODE with arguments ARG0 and ARG1 represents a single bit
5193 equality/inequality test, then return a simplified form of
5194 the test using shifts and logical operations. Otherwise return
5195 NULL. TYPE is the desired result type. */
5197 tree
5199 tree result_type)
5200 {
5201 /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
5202 operand 0. */
5204 {
5209 /* Extract the arguments of the EQ/NE. */
5213 /* This requires us to invert the code. */
5215 }
5217 /* If this is testing a single bit, we can optimize the test. */
5221 {
5228 tree arg00;
5230 /* If we have (A & C) != 0 where C is the sign bit of A, convert
5231 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
5234 {
5239 }
5241 /* At this point, we know that arg0 is not testing the sign bit. */
5245 /* Otherwise we have (A & C) != 0 where C is a single bit,
5246 convert that into ((A >> C2) & 1). Where C2 = log2(C).
5247 Similarly for (A & C) == 0. */
5249 /* If INNER is a right shift of a constant and it plus BITNUM does
5250 not overflow, adjust BITNUM and INNER. */
5257 {
5260 }
5262 /* If we are going to be able to omit the AND below, we must do our
5263 operations as unsigned. If we must use the AND, we have a choice.
5264 Normally unsigned is faster, but for some machines signed is. */
5265 #ifdef LOAD_EXTEND_OP
5267 #else
5269 #endif
5284 /* Put the AND last so it can combine with more things. */
5288 /* Make sure to return the proper type. */
5292 }
5294 }
5296 /* Check whether we are allowed to reorder operands arg0 and arg1,
5297 such that the evaluation of arg1 occurs before arg0. */
5299 static bool
5301 {
5308 }
5310 /* Test whether it is preferable two swap two operands, ARG0 and
5311 ARG1, for example because ARG0 is an integer constant and ARG1
5312 isn't. If REORDER is true, only recommend swapping if we can
5313 evaluate the operands in reverse order. */
5315 static bool
5317 {
5354 }
5356 /* Perform constant folding and related simplification of EXPR.
5357 The related simplifications include x*1 => x, x*0 => 0, etc.,
5358 and application of the associative law.
5359 NOP_EXPR conversions may be removed freely (as long as we
5360 are careful not to change the C type of the overall expression)
5361 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
5362 but we can constant-fold them if they have constant operands. */
5364 #ifdef ENABLE_FOLD_CHECKING
5365 # define fold(x) fold_1 (x)
5367 static
5368 #endif
5369 tree
5371 {
5374 tree tem;
5380 /* WINS will be nonzero when the switch is done
5381 if all operands are constant. */
5384 /* Don't try to process an RTL_EXPR since its operands aren't trees.
5385 Likewise for a SAVE_EXPR that's already been evaluated. */
5389 /* Return right away if a constant. */
5396 {
5397 tree subop;
5399 /* Special case for conversion ops that can have fixed point args. */
5402 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
5408 else
5413 /* Note that TREE_CONSTANT isn't enough:
5414 static var addresses are constant but we can't
5415 do arithmetic on them. */
5417 }
5419 {
5423 {
5425 tree subop;
5431 {
5432 /* Signedness matters here. Perhaps we can refine this
5433 later. */
5435 }
5436 else
5437 /* Strip any conversions that don't change the mode. */
5442 else
5447 /* Note that TREE_CONSTANT isn't enough:
5448 static var addresses are constant but we can't
5449 do arithmetic on them. */
5456 }
5457 }
5459 /* If this is a commutative operation, and ARG0 is a constant, move it
5460 to ARG1 to reduce the number of tests below. */
5465 /* Now WINS is set as described above,
5466 ARG0 is the first operand of EXPR,
5467 and ARG1 is the second operand (if it has more than one operand).
5469 First check for cases where an arithmetic operation is applied to a
5470 compound, conditional, or comparison operation. Push the arithmetic
5471 operation inside the compound or conditional to see if any folding
5472 can then be done. Convert comparison to conditional for this purpose.
5473 The also optimizes non-constant cases that used to be done in
5474 expand_expr.
5476 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5477 one of the operands is a comparison and the other is a comparison, a
5478 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5479 code below would make the expression more complex. Change it to a
5480 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5481 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5493 {
5503 }
5506 {
5511 {
5521 /* If this was a conversion, and all we did was to move into
5522 inside the COND_EXPR, bring it back out. But leave it if
5523 it is a conversion from integer to integer and the
5524 result precision is no wider than a word since such a
5525 conversion is cheap and may be optimized away by combine,
5526 while it couldn't if it were outside the COND_EXPR. Then return
5527 so we don't get into an infinite recursion loop taking the
5528 conversion out and then back in. */
5540 && (INTEGRAL_TYPE_P
5551 }
5556 }
5567 {
5582 return
5596 return
5599 }
5602 {
5623 /* Handle cases of two conversions in a row. */
5626 {
5646 /* In addition to the cases of two conversions in a row
5647 handled below, if we are converting something to its own
5648 type via an object of identical or wider precision, neither
5649 conversion is needed. */
5656 /* Likewise, if the intermediate and final types are either both
5657 float or both integer, we don't need the middle conversion if
5658 it is wider than the final type and doesn't change the signedness
5659 (for integers). Avoid this if the final type is a pointer
5660 since then we sometimes need the inner conversion. Likewise if
5661 the outer has a precision not equal to the size of its mode. */
5672 /* If we have a sign-extension of a zero-extended value, we can
5673 replace that by a single zero-extension. */
5680 /* Two conversions in a row are not needed unless:
5681 - some conversion is floating-point (overstrict for now), or
5682 - the intermediate type is narrower than both initial and
5683 final, or
5684 - the intermediate type and innermost type differ in signedness,
5685 and the outermost type is wider than the intermediate, or
5686 - the initial type is a pointer type and the precisions of the
5687 intermediate and final types differ, or
5688 - the final type is a pointer type and the precisions of the
5689 initial and intermediate types differ. */
5704 }
5708 /* Detect assigning a bitfield. */
5711 {
5712 /* Don't leave an assignment inside a conversion
5713 unless assigning a bitfield. */
5718 /* First do the assignment, then return converted constant. */
5722 }
5724 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5725 constants (if x has signed type, the sign bit cannot be set
5726 in c). This folds extension into the BIT_AND_EXPR. */
5731 {
5741 <= HOST_BITS_PER_WIDE_INT
5743 {
5750 #ifdef LOAD_EXTEND_OP
5754 {
5758 }
5759 #endif
5760 }
5765 }
5779 {
5783 }
5788 {
5792 }
5802 {
5804 {
5805 /* If the value is unsigned, then the absolute value is
5806 the same as the ordinary value. */
5809 /* Similarly, if the value is non-negative. */
5812 /* If the value is negative, then the absolute value is
5813 its negation. */
5814 else
5815 {
5817 HOST_WIDE_INT high;
5828 }
5829 }
5831 {
5835 }
5836 }
5839 /* Convert fabs((double)float) into (double)fabsf(float). */
5842 {
5847 targ0)));
5848 }
5875 {
5882 }
5888 /* A + (-B) -> A - B */
5891 /* (-A) + B -> B - A */
5895 {
5899 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5900 with a constant, and the two constants have no bits in common,
5901 we should treat this as a BIT_IOR_EXPR since this may produce more
5902 simplifications. */
5910 {
5913 }
5915 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5916 (plus (plus (mult) (mult)) (foo)) so that we can
5917 take advantage of the factoring cases below. */
5922 {
5927 else
5948 }
5951 {
5955 /* (A * C) + (B * C) -> (A+B) * C.
5956 We are most concerned about the case where C is a constant,
5957 but other combinations show up during loop reduction. Since
5958 it is not difficult, try all four possibilities. */
5975 /* No identical multiplicands; see if we can find a common
5976 power-of-two factor in non-power-of-two multiplies. This
5977 can help in multi-dimensional array access. */
5982 {
5987 /* Move min of absolute values to int11. */
5990 {
5994 }
5997 {
6002 }
6003 }
6008 same));
6009 }
6010 }
6011 else
6012 {
6013 /* See if ARG1 is zero and X + ARG1 reduces to X. */
6017 /* Likewise if the operands are reversed. */
6021 /* Convert x+x into x*2.0. */
6027 /* Convert x*c+x into x*(c+1). */
6033 {
6034 REAL_VALUE_TYPE c;
6040 }
6042 /* Convert x+x*c into x*(c+1). */
6048 {
6049 REAL_VALUE_TYPE c;
6055 }
6057 /* Convert x*c1+x*c2 into x*(c1+c2). */
6067 {
6076 }
6077 }
6079 bit_rotate:
6080 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
6081 is a rotate of A by C1 bits. */
6082 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
6083 is a rotate of A by B bits. */
6084 {
6093 {
6112 {
6120 TYPE_PRECISION
6125 ? LROTATE_EXPR
6128 }
6130 {
6138 TYPE_PRECISION
6143 ? LROTATE_EXPR
6146 }
6147 }
6148 }
6150 associate:
6151 /* In most languages, can't associate operations on floats through
6152 parentheses. Rather than remember where the parentheses were, we
6153 don't associate floats at all, unless the user has specified
6154 -funsafe-math-optimizations. */
6158 {
6162 /* Split both trees into variables, constants, and literals. Then
6163 associate each group together, the constants with literals,
6164 then the result with variables. This increases the chances of
6165 literals being recombined later and of generating relocatable
6166 expressions for the sum of a constant and literal. */
6171 /* Only do something if we found more than two objects. Otherwise,
6172 nothing has changed and we risk infinite recursion. */
6177 {
6178 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
6187 /* Preserve the MINUS_EXPR if the negative part of the literal is
6188 greater than the positive part. Otherwise, the multiplicative
6189 folding code (i.e extract_muldiv) may be fooled in case
6190 unsigned constants are subtracted, like in the following
6191 example: ((X*2 + 4) - 8U)/2. */
6193 {
6197 {
6201 }
6202 else
6203 {
6207 }
6208 }
6210 {
6215 else
6216 {
6222 }
6223 }
6228 }
6229 }
6231 binary:
6235 {
6236 /* The return value should always have
6237 the same type as the original expression. */
6242 }
6246 /* A - (-B) -> A + B */
6249 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
6259 {
6265 /* Fold A - (A & B) into ~B & A. */
6268 {
6273 arg0));
6278 arg0));
6279 }
6281 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
6282 any power of 2 minus 1. */
6287 {
6293 {
6297 }
6298 }
6299 }
6301 /* See if ARG1 is zero and X - ARG1 reduces to X. */
6305 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
6306 ARG0 is zero and X + ARG0 reduces to X, since that would mean
6307 (-ARG1 + ARG0) reduces to -ARG1. */
6311 /* Fold &x - &x. This can happen from &x.foo - &x.
6312 This is unsafe for certain floats even in non-IEEE formats.
6313 In IEEE, it is unsafe because it does wrong for NaNs.
6314 Also note that operand_equal_p is always false if an operand
6315 is volatile. */
6321 /* A - B -> A + (-B) if B is easily negatable. */
6330 {
6331 /* (A * C) - (B * C) -> (A-B) * C. */
6339 /* (A * C1) - (A * C2) -> A * (C1-C2). */
6347 }
6352 /* (-A) * (-B) -> A * B */
6363 {
6369 /* (a * (1 << b)) is (a << b) */
6385 }
6386 else
6387 {
6388 /* Maybe fold x * 0 to 0. The expressions aren't the same
6389 when x is NaN, since x * 0 is also NaN. Nor are they the
6390 same in modes with signed zeros, since multiplying a
6391 negative value by 0 gives -0, not +0. */
6396 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
6401 /* Transform x * -1.0 into -x. */
6406 /* Convert (C1/X)*C2 into (C1*C2)/X. */
6411 {
6417 }
6420 {
6424 /* Optimizations of sqrt(...)*sqrt(...). */
6428 {
6433 /* Optimize sqrt(x)*sqrt(x) as x. */
6438 /* Optimize sqrt(x)*sqrt(y) as sqrt(x*y). */
6443 }
6445 /* Optimize expN(x)*expN(y) as expN(x+y). */
6459 {
6466 }
6468 /* Optimizations of pow(...)*pow(...). */
6472 {
6480 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
6482 {
6487 arg01));
6489 }
6491 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
6493 {
6498 arg));
6500 }
6501 }
6503 /* Optimize tan(x)*cos(x) as sin(x). */
6512 {
6513 tree sinfn;
6516 {
6531 }
6536 }
6538 /* Optimize x*pow(x,c) as pow(x,c+1). */
6542 {
6549 {
6551 REAL_VALUE_TYPE c;
6560 }
6561 }
6563 /* Optimize pow(x,c)*x as pow(x,c+1). */
6567 {
6574 {
6576 REAL_VALUE_TYPE c;
6585 }
6586 }
6588 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
6591 {
6592 tree powfn;
6600 else
6604 {
6609 }
6610 }
6611 }
6612 }
6616 bit_ior:
6625 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
6627 This results in more efficient code for machines without a NAND
6628 instruction. Combine will canonicalize to the first form
6629 which will allow use of NAND instructions provided by the
6630 backend if they exist. */
6633 {
6638 }
6640 /* See if this can be simplified into a rotate first. If that
6641 is unsuccessful continue in the association code. */
6650 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
6651 with a constant, and the two constants have no bits in common,
6652 we should treat this as a BIT_IOR_EXPR since this may produce more
6653 simplifications. */
6661 {
6664 }
6666 /* See if this can be simplified into a rotate first. If that
6667 is unsuccessful continue in the association code. */
6678 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
6681 {
6682 unsigned int prec
6689 }
6691 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6693 This results in more efficient code for machines without a NOR
6694 instruction. Combine will canonicalize to the first form
6695 which will allow use of NOR instructions provided by the
6696 backend if they exist. */
6699 {
6704 }
6709 /* Don't touch a floating-point divide by zero unless the mode
6710 of the constant can represent infinity. */
6716 /* (-A) / (-B) -> A / B */
6726 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6731 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
6736 /* If ARG1 is a constant, we can convert this to a multiply by the
6737 reciprocal. This does not have the same rounding properties,
6738 so only do this if -funsafe-math-optimizations. We can actually
6739 always safely do it if ARG1 is a power of two, but it's hard to
6740 tell if it is or not in a portable manner. */
6742 {
6747 /* Find the reciprocal if optimizing and the result is exact. */
6749 {
6750 REAL_VALUE_TYPE r;
6753 {
6756 }
6757 }
6758 }
6759 /* Convert A/B/C to A/(B*C). */
6766 /* Convert A/(B/C) to (A/B)*C. */
6774 /* Convert C1/(X*C2) into (C1/C2)/X. */
6779 {
6785 }
6788 {
6790 /* Optimize x/expN(y) into x*expN(-y). */
6803 {
6810 }
6812 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6816 {
6825 }
6826 }
6829 {
6833 /* Optimize sin(x)/cos(x) as tan(x). */
6839 {
6840 tree tanfn;
6848 else
6854 }
6856 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
6862 {
6863 tree tanfn;
6871 else
6875 {
6880 tmp));
6881 }
6882 }
6884 /* Optimize pow(x,c)/x as pow(x,c-1). */
6888 {
6894 {
6896 REAL_VALUE_TYPE c;
6905 }
6906 }
6907 }
6920 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
6921 operation, EXACT_DIV_EXPR.
6923 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
6924 At one time others generated faster code, it's not clear if they do
6925 after the last round to changes to the DIV code in expmed.c. */
6960 /* Optimize -1 >> x for arithmetic right shifts. */
6963 /* ... fall through ... */
6966 shift:
6972 /* Since negative shift count is not well-defined,
6973 don't try to compute it in the compiler. */
6976 /* Rewrite an LROTATE_EXPR by a constant into an
6977 RROTATE_EXPR by a new constant. */
6979 {
6984 }
6986 /* If we have a rotate of a bit operation with the rotate count and
6987 the second operand of the bit operation both constant,
6988 permute the two operations. */
7000 /* Two consecutive rotates adding up to the width of the mode can
7001 be ignored. */
7032 /* Note that the operand of this must be an int
7033 and its values must be 0 or 1.
7034 ("true" is a fixed value perhaps depending on the language,
7035 but we don't handle values other than 1 correctly yet.) */
7037 /* Avoid infinite recursion. */
7039 {
7044 }
7048 /* Note that the operands of this must be ints
7049 and their values must be 0 or 1.
7050 ("true" is a fixed value perhaps depending on the language.) */
7051 /* If first arg is constant zero, return it. */
7055 /* If either arg is constant true, drop it. */
7059 /* Preserve sequence points. */
7062 /* If second arg is constant zero, result is zero, but first arg
7063 must be evaluated. */
7066 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
7067 case will be handled here. */
7071 truth_andor:
7072 /* We only do these simplifications if we are optimizing. */
7076 /* Check for things like (A || B) && (A || C). We can convert this
7077 to A || (B && C). Note that either operator can be any of the four
7078 truth and/or operations and the transformation will still be
7079 valid. Also note that we only care about order for the
7080 ANDIF and ORIF operators. If B contains side effects, this
7081 might change the truth-value of A. */
7088 {
7108 /* This case if tricky because we must either have commutative
7109 operators or else A10 must not have side-effects. */
7115 a01));
7116 }
7118 /* See if we can build a range comparison. */
7122 /* Check for the possibility of merging component references. If our
7123 lhs is another similar operation, try to merge its rhs with our
7124 rhs. Then try to merge our lhs and rhs. */
7136 /* Note that the operands of this must be ints
7137 and their values must be 0 or true.
7138 ("true" is a fixed value perhaps depending on the language.) */
7139 /* If first arg is constant true, return it. */
7143 /* If either arg is constant zero, drop it. */
7147 /* Preserve sequence points. */
7150 /* If second arg is constant true, result is true, but we must
7151 evaluate first arg. */
7154 /* Likewise for first arg, but note this only occurs here for
7155 TRUTH_OR_EXPR. */
7161 /* If either arg is constant zero, drop it. */
7166 /* If either arg is constant true, this is a logical inversion. */
7179 /* If one arg is a real or integer constant, put it last. */
7184 {
7192 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
7197 /* (-a) CMP (-b) -> b CMP a */
7204 {
7205 REAL_VALUE_TYPE cst;
7208 /* (-a) CMP CST -> a swap(CMP) (-CST) */
7210 return
7216 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
7217 /* a CMP (-0) -> a CMP 0 */
7222 /* x != NaN is always true, other ops are always false. */
7225 {
7228 }
7230 /* Fold comparisons against infinity. */
7232 {
7236 }
7237 }
7239 /* If this is a comparison of a real constant with a PLUS_EXPR
7240 or a MINUS_EXPR of a real constant, we can convert it into a
7241 comparison with a revised real constant as long as no overflow
7242 occurs when unsafe_math_optimizations are enabled. */
7254 /* Likewise, we can simplify a comparison of a real constant with
7255 a MINUS_EXPR whose first operand is also a real constant, i.e.
7256 (c1 - x) < c2 becomes x > c1-c2. */
7267 /* Fold comparisons against built-in math functions. */
7269 && flag_unsafe_math_optimizations
7271 {
7275 {
7279 }
7280 }
7281 }
7283 /* Convert foo++ == CONST into ++foo == CONST + INCR.
7284 First, see if one arg is constant; find the constant arg
7285 and the other one. */
7286 {
7296 {
7297 /* This optimization is invalid for ordered comparisons
7298 if CONST+INCR overflows or if foo+incr might overflow.
7299 This optimization is invalid for floating point due to rounding.
7300 For pointer types we assume overflow doesn't happen. */
7304 {
7305 tree newconst
7309 /* Do not overwrite the current varop to be a preincrement,
7310 create a new node so that we won't confuse our caller who
7311 might create trees and throw them away, reusing the
7312 arguments that they passed to build. This shows up in
7313 the THEN or ELSE parts of ?: being postincrements. */
7318 /* If VAROP is a reference to a bitfield, we must mask
7319 the constant by the width of the field. */
7323 {
7324 int size
7326 (TREE_OPERAND
7330 tree folded_compare;
7332 /* First check whether the comparison would come out
7333 always the same. If we don't do that we would
7334 change the meaning with the masking. */
7338 else
7341 constop));
7356 mask)));
7357 }
7363 }
7364 }
7366 {
7370 {
7371 tree newconst
7375 /* Do not overwrite the current varop to be a predecrement,
7376 create a new node so that we won't confuse our caller who
7377 might create trees and throw them away, reusing the
7378 arguments that they passed to build. This shows up in
7379 the THEN or ELSE parts of ?: being postdecrements. */
7387 {
7388 int size
7390 (TREE_OPERAND
7394 tree folded_compare;
7399 else
7402 constop));
7417 mask)));
7418 }
7424 }
7425 }
7426 }
7428 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
7429 This transformation affects the cases which are handled in later
7430 optimizations involving comparisons with non-negative constants. */
7434 {
7436 {
7447 }
7448 }
7450 /* Comparisons with the highest or lowest possible integer of
7451 the specified size will have known values. */
7452 {
7460 {
7467 {
7470 }
7471 else
7472 {
7475 }
7480 {
7484 integer_zero_node),
7485 arg0);
7492 integer_one_node),
7493 arg0);
7497 /* The GE_EXPR and LT_EXPR cases above are not normally
7498 reached because of previous transformations. */
7502 }
7506 {
7515 }
7519 {
7523 integer_zero_node),
7524 arg0);
7531 integer_one_node),
7532 arg0);
7538 }
7542 {
7551 }
7556 /* signed_type does not work on pointer types. */
7558 {
7559 /* The following case also applies to X < signed_max+1
7560 and X >= signed_max+1 because previous transformations. */
7562 {
7566 return fold
7570 }
7571 }
7572 }
7573 }
7575 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
7576 a MINUS_EXPR of a constant, we can convert it into a comparison with
7577 a revised constant as long as no overflow occurs. */
7589 /* Similarly for a NEGATE_EXPR. */
7598 /* If we have X - Y == 0, we can convert that to X == Y and similarly
7599 for !=. Don't do this for ordered comparisons due to overflow. */
7605 /* If we are widening one operand of an integer comparison,
7606 see if the other operand is similarly being widened. Perhaps we
7607 can do the comparison in the narrower type. */
7618 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
7619 constant, we can simplify it. */
7626 /* If we are comparing an ABS_EXPR with a constant, we can
7627 convert all the cases into explicit comparisons, but they may
7628 well not be faster than doing the ABS and one comparison.
7629 But ABS (X) <= C is a range comparison, which becomes a subtraction
7630 and a comparison, and is probably faster. */
7642 /* If this is an EQ or NE comparison with zero and ARG0 is
7643 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
7644 two operations, but the latter can be done in one less insn
7645 on machines that have only two-operand insns or on which a
7646 constant cannot be the first operand. */
7649 {
7652 return
7660 integer_one_node)),
7661 arg1));
7664 return
7672 integer_one_node)),
7673 arg1));
7674 }
7676 /* If this is an NE or EQ comparison of zero against the result of a
7677 signed MOD operation whose second operand is a power of 2, make
7678 the MOD operation unsigned since it is simpler and equivalent. */
7687 {
7696 }
7698 /* If this is an NE comparison of zero with an AND of one, remove the
7699 comparison since the AND will give the correct value. */
7705 /* If we have (A & C) == C where C is a power of 2, convert this into
7706 (A & C) != 0. Similarly for NE_EXPR. */
7714 /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
7715 2, then fold the expression into shifts and logical operations. */
7720 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
7721 Similarly for NE_EXPR. */
7726 {
7727 tree dandnotc
7735 }
7737 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
7738 Similarly for NE_EXPR. */
7743 {
7744 tree candnotd
7751 }
7753 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
7754 and similarly for >= into !=. */
7770 return
7778 /* Simplify comparison of something with itself. (For IEEE
7779 floating-point, we can only do some of these simplifications.) */
7781 {
7783 {
7798 /* For NE, we can only do this simplification if integer
7799 or we don't honor IEEE floating point NaNs. */
7803 /* ... fall through ... */
7809 }
7810 }
7812 /* If we are comparing an expression that just has comparisons
7813 of two integer values, arithmetic expressions of those comparisons,
7814 and constants, we can simplify it. There are only three cases
7815 to check: the two values can either be equal, the first can be
7816 greater, or the second can be greater. Fold the expression for
7817 those three values. Since each value must be 0 or 1, we have
7818 eight possibilities, each of which corresponds to the constant 0
7819 or 1 or one of the six possible comparisons.
7821 This handles common cases like (a > b) == 0 but also handles
7822 expressions like ((x > y) - (y > x)) > 0, which supposedly
7823 occur in macroized code. */
7826 {
7831 /* Don't handle degenerate cases here; they should already
7832 have been handled anyway. */
7841 {
7845 /* We can't just pass T to eval_subst in case cval1 or cval2
7846 was the same as ARG1. */
7848 tree high_result
7851 arg1));
7852 tree equal_result
7855 arg1));
7856 tree low_result
7859 arg1));
7861 /* All three of these results should be 0 or 1. Confirm they
7862 are. Then use those values to select the proper code
7863 to use. */
7871 {
7872 /* Make a 3-bit mask with the high-order bit being the
7873 value for `>', the next for '=', and the low for '<'. */
7877 {
7879 /* Always false. */
7900 /* Always true. */
7902 }
7907 else
7909 }
7910 }
7911 }
7913 /* If this is a comparison of a field, we may be able to simplify it. */
7918 /* Handle the constant case even without -O
7919 to make sure the warnings are given. */
7921 {
7925 }
7927 /* If this is a comparison of complex values and either or both sides
7928 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
7929 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
7930 This may prevent needless evaluations. */
7937 {
7950 type,
7953 }
7955 /* Optimize comparisons of strlen vs zero to a compare of the
7956 first character of the string vs zero. To wit,
7957 strlen(ptr) == 0 => *ptr == 0
7958 strlen(ptr) != 0 => *ptr != 0
7959 Other cases should reduce to one of these two (or a constant)
7960 due to the return value of strlen being unsigned. */
7964 {
7966 tree arglist;
7978 integer_zero_node));
7979 }
7981 /* From here on, the only cases we handle are when the result is
7982 known to be a constant.
7984 To compute GT, swap the arguments and do LT.
7985 To compute GE, do LT and invert the result.
7986 To compute LE, swap the arguments, do LT and invert the result.
7987 To compute NE, do EQ and invert the result.
7989 Therefore, the code below must handle only EQ and LT. */
7992 {
7995 }
7997 /* Note that it is safe to invert for real values here because we
7998 will check below in the one case that it matters. */
8003 {
8006 }
8008 /* Compute a result for LT or EQ if args permit;
8009 otherwise return T. */
8011 {
8014 else
8019 }
8022 /* Assume a nonexplicit constant cannot equal an explicit one,
8023 since such code would be undefined anyway.
8024 Exception: on sysvr4, using #pragma weak,
8025 a label can come out as 0. */
8032 #endif
8033 /* Two real constants can be compared explicitly. */
8035 {
8036 /* If either operand is a NaN, the result is false with two
8037 exceptions: First, an NE_EXPR is true on NaNs, but that case
8038 is already handled correctly since we will be inverting the
8039 result for NE_EXPR. Second, if we had inverted a LE_EXPR
8040 or a GE_EXPR into a LT_EXPR, we must return true so that it
8041 will be inverted into false. */
8051 else
8055 }
8069 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
8070 so all simple results must be passed through pedantic_non_lvalue. */
8072 {
8074 /* Only optimize constant conditions when the selected branch
8075 has the same type as the COND_EXPR. This avoids optimizing
8076 away "c ? x : throw", where the throw has a void type. */
8081 }
8085 /* If we have A op B ? A : C, we may be able to convert this to a
8086 simpler expression, depending on the operation and the values
8087 of B and C. Signed zeros prevent all of these transformations,
8088 for reasons given above each one. */
8094 {
8100 /* If we have A op 0 ? A : -A, consider applying the following
8101 transformations:
8103 A == 0? A : -A same as -A
8104 A != 0? A : -A same as A
8105 A >= 0? A : -A same as abs (A)
8106 A > 0? A : -A same as abs (A)
8107 A <= 0? A : -A same as -abs (A)
8108 A < 0? A : -A same as -abs (A)
8110 None of these transformations work for modes with signed
8111 zeros. If A is +/-0, the first two transformations will
8112 change the sign of the result (from +0 to -0, or vice
8113 versa). The last four will fix the sign of the result,
8114 even though the original expressions could be positive or
8115 negative, depending on the sign of A.
8117 Note that all these transformations are correct if A is
8118 NaN, since the two alternatives (A and -A) are also NaNs. */
8125 {
8149 }
8151 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
8152 A == 0 ? A : 0 is always 0 unless A is -0. Note that
8153 both transformations are correct when A is NaN: A != 0
8154 is then true, and A == 0 is false. */
8157 {
8162 }
8164 /* Try some transformations of A op B ? A : B.
8166 A == B? A : B same as B
8167 A != B? A : B same as A
8168 A >= B? A : B same as max (A, B)
8169 A > B? A : B same as max (B, A)
8170 A <= B? A : B same as min (A, B)
8171 A < B? A : B same as min (B, A)
8173 As above, these transformations don't work in the presence
8174 of signed zeros. For example, if A and B are zeros of
8175 opposite sign, the first two transformations will change
8176 the sign of the result. In the last four, the original
8177 expressions give different results for (A=+0, B=-0) and
8178 (A=-0, B=+0), but the transformed expressions do not.
8180 The first two transformations are correct if either A or B
8181 is a NaN. In the first transformation, the condition will
8182 be false, and B will indeed be chosen. In the case of the
8183 second transformation, the condition A != B will be true,
8184 and A will be chosen.
8186 The conversions to max() and min() are not correct if B is
8187 a number and A is not. The conditions in the original
8188 expressions will be false, so all four give B. The min()
8189 and max() versions would give a NaN instead. */
8192 {
8197 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
8199 {
8203 }
8206 {
8213 /* In C++ a ?: expression can be an lvalue, so put the
8214 operand which will be used if they are equal first
8215 so that we can convert this back to the
8216 corresponding COND_EXPR. */
8237 }
8238 }
8240 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
8241 we might still be able to simplify this. For example,
8242 if C1 is one less or one more than C2, this might have started
8243 out as a MIN or MAX and been transformed by this function.
8244 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
8250 {
8252 /* We can replace A with C1 in this case. */
8258 /* If C1 is C2 + 1, this is min(A, C2). */
8263 return pedantic_non_lvalue
8268 /* If C1 is C2 - 1, this is min(A, C2). */
8273 return pedantic_non_lvalue
8278 /* If C1 is C2 - 1, this is max(A, C2). */
8283 return pedantic_non_lvalue
8288 /* If C1 is C2 + 1, this is max(A, C2). */
8293 return pedantic_non_lvalue
8300 }
8301 }
8303 /* If the second operand is simpler than the third, swap them
8304 since that produces better jump optimization results. */
8307 {
8308 /* See if this can be inverted. If it can't, possibly because
8309 it was a floating-point inequality comparison, don't do
8310 anything. */
8316 }
8318 /* Convert A ? 1 : 0 to simply A. */
8321 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
8322 call to fold will try to move the conversion inside
8323 a COND, which will recurse. In that case, the COND_EXPR
8324 is probably the best choice, so leave it alone. */
8328 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
8329 over COND_EXPR in cases such as floating point comparisons. */
8336 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
8337 operation is simply A & 2. */
8349 /* Convert A ? B : 0 into A && B if A and B are truth values. */
8356 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
8360 {
8361 /* Only perform transformation if ARG0 is easily inverted. */
8366 }
8371 /* When pedantic, a compound expression can be neither an lvalue
8372 nor an integer constant expression. */
8375 /* Don't let (0, 0) be null pointer constant. */
8417 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
8418 appropriate. */
8423 {
8427 tree arg01;
8438 {
8452 arg01));
8453 }
8456 }
8459 /* Check for a built-in function. */
8464 {
8468 }
8474 }
8476 #ifdef ENABLE_FOLD_CHECKING
8477 #undef fold
8483 /* When --enable-checking=fold, compute a digest of expr before
8484 and after actual fold call to see if fold did not accidentally
8485 change original expr. */
8487 tree
8489 {
8490 tree ret;
8493 htab_t ht;
8512 }
8514 void
8516 {
8519 htab_t ht;
8529 }
8531 static void
8533 {
8535 }
8537 static void
8539 {
8557 {
8558 /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified. */
8562 }
8564 {
8565 /* Allow DECL_ASSEMBLER_NAME to be modified. */
8569 }
8572 {
8573 /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified. */
8578 }
8585 {
8588 {
8602 }
8606 {
8617 }
8621 {
8627 }
8628 /* Fall through. */
8664 }
8665 }
8667 #endif
8669 /* Perform constant folding and related simplification of initializer
8670 expression EXPR. This behaves identically to "fold" but ignores
8671 potential run-time traps and exceptions that fold must preserve. */
8673 tree
8675 {
8679 tree result;
8692 }
8694 /* Determine if first argument is a multiple of second argument. Return 0 if
8695 it is not, or we cannot easily determined it to be.
8697 An example of the sort of thing we care about (at this point; this routine
8698 could surely be made more general, and expanded to do what the *_DIV_EXPR's
8699 fold cases do now) is discovering that
8701 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8703 is a multiple of
8705 SAVE_EXPR (J * 8)
8707 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
8709 This code also handles discovering that
8711 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
8713 is a multiple of 8 so we don't have to worry about dealing with a
8714 possible remainder.
8716 Note that we *look* inside a SAVE_EXPR only to determine how it was
8717 calculated; it is not safe for fold to do much of anything else with the
8718 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
8719 at run time. For example, the latter example above *cannot* be implemented
8720 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
8721 evaluation time of the original SAVE_EXPR is not necessarily the same at
8722 the time the new expression is evaluated. The only optimization of this
8723 sort that would be valid is changing
8725 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
8727 divided by 8 to
8729 SAVE_EXPR (I) * SAVE_EXPR (J)
8731 (where the same SAVE_EXPR (J) is used in the original and the
8732 transformed version). */
8734 static int
8736 {
8744 {
8756 {
8760 /* const_binop may not detect overflow correctly,
8761 so check for it explicitly here. */
8767 size_one_node,
8771 }
8775 /* Can't handle conversions from non-integral or wider integral type. */
8781 /* .. fall through ... */
8797 }
8798 }
8800 /* Return true if `t' is known to be non-negative. */
8802 int
8804 {
8806 {
8821 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
8822 both unsigned and at least 2 bits shorter than the result. */
8826 {
8831 {
8835 }
8836 }
8841 {
8842 /* x * x for floating point x is always non-negative. */
8847 }
8849 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
8850 both unsigned and their total bits is shorter than the result. */
8854 {
8861 }
8882 {
8887 {
8891 {
8895 }
8896 }
8898 {
8904 }
8905 }
8933 {
8940 {
9000 }
9001 }
9003 /* ... fall through ... */
9007 /* Truth values evaluate to 0 or 1, which is nonnegative. */
9009 }
9011 /* We don't know sign of `t', so be conservative and return false. */
9013 }
9015 /* Return true if `r' is known to be non-negative.
9016 Only handles constants at the moment. */
9018 int
9020 {
9022 {
9032 {
9034 rtx elt;
9039 {
9043 }
9046 }
9050 /* These are always nonnegative. */
9055 }
9056 }