| blob | 3bedea13a78895533e0c1756178cdbc47224e462 |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
10 any later version.
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 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. */
47 #include <setjmp.h>
58 HOST_WIDE_INT));
61 HOST_WIDE_INT *));
84 HOST_WIDE_INT *,
104 static tree fold_binary_op_with_conditional_arg
107 #ifndef BRANCH_COST
108 #define BRANCH_COST 1
109 #endif
111 #if defined(HOST_EBCDIC)
112 /* bit 8 is significant in EBCDIC */
113 #define CHARMASK 0xff
114 #else
115 #define CHARMASK 0x7f
116 #endif
118 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
119 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
120 and SUM1. Then this yields nonzero if overflow occurred during the
121 addition.
123 Overflow occurs if A and B have the same sign, but A and SUM differ in
124 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
125 sign. */
126 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
127 \f
128 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
129 We do that by representing the two-word integer in 4 words, with only
130 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
131 number. The value of the word is LOWPART + HIGHPART * BASE. */
133 #define LOWPART(x) \
134 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
135 #define HIGHPART(x) \
136 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
137 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
139 /* Unpack a two-word integer into 4 words.
140 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
141 WORDS points to the array of HOST_WIDE_INTs. */
143 static void
147 HOST_WIDE_INT hi;
148 {
153 }
155 /* Pack an array of 4 words into a two-word integer.
156 WORDS points to the array of words.
157 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
159 static void
164 {
167 }
168 \f
169 /* Make the integer constant T valid for its type by setting to 0 or 1 all
170 the bits in the constant that don't belong in the type.
172 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
173 nonzero, a signed overflow has already occurred in calculating T, so
174 propagate it.
176 Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
177 if it exists. */
179 int
181 tree t;
183 {
185 HOST_WIDE_INT high;
189 {
190 #ifdef CHECK_FLOAT_VALUE
192 overflow);
193 #endif
195 }
205 else
208 /* First clear all bits that are beyond the type's precision. */
211 ;
215 else
216 {
220 }
222 /* Unsigned types do not suffer sign extension or overflow unless they
223 are a sizetype. */
229 /* If the value's sign bit is set, extend the sign. */
237 {
238 /* Value is negative:
239 set to 1 all the bits that are outside this type's precision. */
243 else
244 {
248 }
249 }
251 /* Return nonzero if signed overflow occurred. */
252 return
255 }
256 \f
257 /* Add two doubleword integers with doubleword result.
258 Each argument is given as two `HOST_WIDE_INT' pieces.
259 One argument is L1 and H1; the other, L2 and H2.
260 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
262 int
268 {
270 HOST_WIDE_INT h;
278 }
280 /* Negate a doubleword integer with doubleword result.
281 Return nonzero if the operation overflows, assuming it's signed.
282 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
283 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
285 int
288 HOST_WIDE_INT h1;
291 {
293 {
297 }
298 else
299 {
303 }
304 }
305 \f
306 /* Multiply two doubleword integers with doubleword result.
307 Return nonzero if the operation overflows, assuming it's signed.
308 Each argument is given as two `HOST_WIDE_INT' pieces.
309 One argument is L1 and H1; the other, L2 and H2.
310 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
312 int
318 {
333 {
336 {
338 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
340 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
344 }
346 }
350 /* Check for overflow by calculating the top half of the answer in full;
351 it should agree with the low half's sign bit. */
354 {
357 }
359 {
362 }
364 }
365 \f
366 /* Shift the doubleword integer in L1, H1 left by COUNT places
367 keeping only PREC bits of result.
368 Shift right if COUNT is negative.
369 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
370 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
372 void
380 {
382 {
385 }
387 #ifdef SHIFT_COUNT_TRUNCATED
390 #endif
393 {
394 /* Shifting by the host word size is undefined according to the
395 ANSI standard, so we must handle this as a special case. */
398 }
400 {
403 }
404 else
405 {
409 }
410 }
412 /* Shift the doubleword integer in L1, H1 right by COUNT places
413 keeping only PREC bits of result. COUNT must be positive.
414 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
415 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
417 void
425 {
428 signmask = (arith
432 #ifdef SHIFT_COUNT_TRUNCATED
435 #endif
438 {
439 /* Shifting by the host word size is undefined according to the
440 ANSI standard, so we must handle this as a special case. */
443 }
445 {
449 }
450 else
451 {
456 }
457 }
458 \f
459 /* Rotate the doubleword integer in L1, H1 left by COUNT places
460 keeping only PREC bits of result.
461 Rotate right if COUNT is negative.
462 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
464 void
471 {
483 }
485 /* Rotate the doubleword integer in L1, H1 left by COUNT places
486 keeping only PREC bits of result. COUNT must be positive.
487 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
489 void
496 {
508 }
509 \f
510 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
511 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
512 CODE is a tree code for a kind of division, one of
513 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
514 or EXACT_DIV_EXPR
515 It controls how the quotient is rounded to a integer.
516 Return nonzero if the operation overflows.
517 UNS nonzero says do unsigned division. */
519 int
526 HOST_WIDE_INT hnum_orig;
528 HOST_WIDE_INT hden_orig;
531 {
547 /* calculate quotient sign and convert operands to unsigned. */
549 {
551 {
553 /* (minimum integer) / (-1) is the only overflow case. */
557 }
559 {
562 }
563 }
568 /* This unsigned division rounds toward zero. */
571 }
575 /* hden != 0 already checked. */
580 }
590 /* Special code for when the divisor < BASE. */
592 {
593 /* hnum != 0 already checked. */
595 {
599 }
600 }
601 else
602 {
603 /* Full double precision division,
604 with thanks to Don Knuth's "Seminumerical Algorithms". */
608 /* Find the highest non-zero divisor digit. */
611 {
614 }
616 /* Insure that the first digit of the divisor is at least BASE/2.
617 This is required by the quotient digit estimation algorithm. */
624 {
628 }
633 {
638 }
639 }
643 /* Main loop */
645 {
646 /* Guess the next quotient digit, quo_est, by dividing the first
647 two remaining dividend digits by the high order quotient digit.
648 quo_est is never low and is at most 2 high. */
655 else
658 /* Refine quo_est so it's usually correct, and at most one high. */
663 quo_est--;
665 /* Try QUO_EST as the quotient digit, by multiplying the
666 divisor by QUO_EST and subtracting from the remaining dividend.
667 Keep in mind that QUO_EST is the I - 1st digit. */
671 {
677 }
679 /* If quo_est was high by one, then num[i] went negative and
680 we need to correct things. */
682 {
683 quo_est--;
686 {
690 }
693 }
695 /* Store the quotient digit. */
697 }
698 }
702 finish_up:
703 /* if result is negative, make it so. */
707 /* compute trial remainder: rem = num - (quo * den) */
713 {
722 {
723 /* quo = quo - 1; */
726 }
727 else
734 {
737 }
738 else
744 {
750 /* Get absolute values */
756 /* If (2 * abs (lrem) >= abs (lden)) */
765 {
767 /* quo = quo - 1; */
770 else
771 /* quo = quo + 1; */
774 }
775 else
777 }
782 }
784 /* compute true remainder: rem = num - (quo * den) */
789 }
790 \f
791 #ifndef REAL_ARITHMETIC
792 /* Effectively truncate a real value to represent the nearest possible value
793 in a narrower mode. The result is actually represented in the same data
794 type as the argument, but its value is usually different.
796 A trap may occur during the FP operations and it is the responsibility
797 of the calling function to have a handler established. */
799 REAL_VALUE_TYPE
802 REAL_VALUE_TYPE arg;
803 {
805 }
807 #if TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
809 /* Check for infinity in an IEEE double precision number. */
811 int
813 REAL_VALUE_TYPE x;
814 {
815 /* The IEEE 64-bit double format. */
817 REAL_VALUE_TYPE d;
834 {
839 }
840 else
841 {
846 }
847 }
849 /* Check whether an IEEE double precision number is a NaN. */
851 int
853 REAL_VALUE_TYPE x;
854 {
855 /* The IEEE 64-bit double format. */
857 REAL_VALUE_TYPE d;
874 {
879 }
880 else
881 {
886 }
887 }
889 /* Check for a negative IEEE double precision number. */
891 int
893 REAL_VALUE_TYPE x;
894 {
895 /* The IEEE 64-bit double format. */
897 REAL_VALUE_TYPE d;
914 {
917 }
918 else
919 {
922 }
923 }
926 /* Let's assume other float formats don't have infinity.
927 (This can be overridden by redefining REAL_VALUE_ISINF.) */
929 int
931 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
932 {
934 }
936 /* Let's assume other float formats don't have NaNs.
937 (This can be overridden by redefining REAL_VALUE_ISNAN.) */
939 int
941 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
942 {
944 }
946 /* Let's assume other float formats don't have minus zero.
947 (This can be overridden by redefining REAL_VALUE_NEGATIVE.) */
949 int
951 REAL_VALUE_TYPE x;
952 {
954 }
957 /* Try to change R into its exact multiplicative inverse in machine mode
958 MODE. Return nonzero function value if successful. */
960 int
964 {
966 union
967 {
971 #ifdef CHECK_FLOAT_VALUE
973 #endif
975 /* Usually disable if bounds checks are not reliable. */
979 /* Set array index to the less significant bits in the unions, depending
980 on the endian-ness of the host doubles.
981 Disable if insufficient information on the data structure. */
982 #if HOST_FLOAT_FORMAT == UNKNOWN_FLOAT_FORMAT
984 #else
985 #if HOST_FLOAT_FORMAT == VAX_FLOAT_FORMAT
986 #define K 2
987 #else
988 #if HOST_FLOAT_FORMAT == IBM_FLOAT_FORMAT
989 #define K 2
990 #else
991 #define K (2 * HOST_FLOAT_WORDS_BIG_ENDIAN)
992 #endif
993 #endif
994 #endif
997 {
998 /* Don't do the optimization if there was an arithmetic error. */
999 fail:
1002 }
1005 /* Domain check the argument. */
1010 #ifdef REAL_INFINITY
1013 #endif
1015 /* Compute the reciprocal and check for numerical exactness.
1016 It is unnecessary to check all the significand bits to determine
1017 whether X is a power of 2. If X is not, then it is impossible for
1018 the bottom half significand of both X and 1/X to be all zero bits.
1019 Hence we ignore the data structure of the top half and examine only
1020 the low order bits of the two significands. */
1025 /* Truncate to the required mode and range-check the result. */
1027 #ifdef CHECK_FLOAT_VALUE
1031 #endif
1033 /* Fail if truncation changed the value. */
1037 #ifdef REAL_INFINITY
1040 #endif
1042 /* Output the reciprocal and return success flag. */
1046 }
1048 /* Convert C99 hexadecimal floating point string constant S. Return
1049 real value type in mode MODE. This function uses the host computer's
1050 floating point arithmetic when there is no REAL_ARITHMETIC. */
1052 REAL_VALUE_TYPE
1056 {
1057 REAL_VALUE_TYPE ip;
1076 /* Sign, if any, comes first. */
1079 {
1082 }
1084 /* The string is supposed to start with 0x or 0X . */
1086 {
1090 else
1092 }
1093 else
1103 {
1106 {
1112 else
1116 {
1122 }
1123 else
1124 {
1125 /* Record nonzero lost bits. */
1129 }
1131 }
1133 {
1136 }
1139 {
1142 /* Sign of exponent. */
1144 {
1147 }
1149 /* Value of exponent.
1150 The exponent field is a decimal integer. */
1152 {
1155 }
1158 /* F suffix is ambiguous in the significand part
1159 so it must appear after the decimal exponent field. */
1161 {
1165 }
1166 }
1169 {
1172 }
1173 else
1175 }
1177 /* Abort if last character read was not legitimate. */
1182 /* There must be either one decimal point or one p. */
1190 /* Normalize. */
1193 {
1197 }
1199 /* Leave a high guard bit for carry-out. */
1201 {
1206 }
1209 {
1213 }
1216 {
1220 }
1223 {
1224 /* Keep 24 bits precision, bits 0x7fffff80.
1225 Rounding bit is 0x40. */
1229 {
1232 }
1234 }
1235 else
1236 {
1237 /* We need real.c to do long double formats, so here default
1238 to double precision. */
1239 #if HOST_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
1240 /* IEEE double.
1241 Keep 53 bits precision, bits 0x7fffffff fffffc00.
1242 Rounding bit is low word 0x200. */
1245 {
1247 {
1251 }
1252 }
1254 #else
1255 /* Assume it's a VAX with 56-bit significand,
1256 bits 0x7fffffff ffffff80. */
1259 {
1261 {
1265 }
1266 }
1268 #endif
1269 }
1273 /* Apply shifts and exponent value as power of 2. */
1279 }
1282 \f
1283 /* Given T, an expression, return the negation of T. Allow for T to be
1284 null, in which case return null. */
1286 static tree
1288 tree t;
1289 {
1290 tree type;
1291 tree tem;
1300 {
1313 /* - (A - B) -> B - A */
1323 }
1326 }
1327 \f
1328 /* Split a tree IN into a constant, literal and variable parts that could be
1329 combined with CODE to make IN. "constant" means an expression with
1330 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1331 commutative arithmetic operation. Store the constant part into *CONP,
1332 the literal in &LITP and return the variable part. If a part isn't
1333 present, set it to null. If the tree does not decompose in this way,
1334 return the entire tree as the variable part and the other parts as null.
1336 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1337 case, we negate an operand that was subtracted. If NEGATE_P is true, we
1338 are negating all of IN.
1340 If IN is itself a literal or constant, return it as appropriate.
1342 Note that we do not guarantee that any of the three values will be the
1343 same type as IN, but they will have the same signedness and mode. */
1345 static tree
1347 tree in;
1351 {
1357 /* Strip any conversions that don't change the machine mode or signedness. */
1364 /* We can associate addition and subtraction together (even
1365 though the C standard doesn't say so) for integers because
1366 the value is not affected. For reals, the value might be
1367 affected, so we can't. */
1370 {
1376 /* First see if either of the operands is a literal, then a constant. */
1387 /* If we haven't dealt with either operand, this is not a case we can
1388 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1393 else
1396 /* Now do any needed negations. */
1400 }
1403 else
1407 {
1411 }
1414 }
1416 /* Re-associate trees split by the above function. T1 and T2 are either
1417 expressions to associate or null. Return the new expression, if any. If
1418 we build an operation, do it in TYPE and with CODE, except if CODE is a
1419 MINUS_EXPR, in which case we use PLUS_EXPR since split_tree will already
1420 have taken care of the negations. */
1422 static tree
1426 tree type;
1427 {
1436 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1437 try to fold this since we will have infinite recursion. But do
1438 deal with any NEGATE_EXPRs. */
1441 {
1448 else
1450 }
1453 }
1454 \f
1455 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1456 to produce a new constant.
1458 If NOTRUNC is nonzero, do not truncate the result to fit the data type.
1459 If FORSIZE is nonzero, compute overflow for unsigned types. */
1461 static tree
1466 {
1470 HOST_WIDE_INT hi;
1472 HOST_WIDE_INT garbageh;
1484 {
1504 /* It's unclear from the C standard whether shifts can overflow.
1505 The following code ignores overflow; perhaps a C standard
1506 interpretation ruling is needed. */
1536 /* This is a shortcut for a common special case. */
1541 {
1547 }
1549 /* ... fall through ... */
1553 {
1556 }
1559 {
1562 }
1570 /* This is a shortcut for a common special case. */
1575 {
1580 }
1582 /* ... fall through ... */
1598 else
1604 else
1610 }
1615 else
1616 {
1619 }
1627 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1628 So check if force_fit_type truncated the value. */
1639 }
1641 /* Define input and output argument for const_binop_1. */
1642 struct cb_args
1643 {
1648 };
1650 /* Do the real arithmetic for const_binop while protected by a
1651 float overflow handler. */
1653 static void
1655 PTR data;
1656 {
1658 REAL_VALUE_TYPE value;
1660 #ifdef REAL_ARITHMETIC
1662 #else
1664 {
1678 #ifndef REAL_INFINITY
1681 #endif
1696 }
1699 args->t
1702 }
1704 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1705 constant. We assume ARG1 and ARG2 have the same data type, or at least
1706 are the same kind of constant and the same machine mode.
1708 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1710 static tree
1715 {
1722 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
1724 {
1725 REAL_VALUE_TYPE d1;
1726 REAL_VALUE_TYPE d2;
1728 tree t;
1734 /* If either operand is a NaN, just return it. Otherwise, set up
1735 for floating-point trap; we return an overflow. */
1741 /* Setup input for const_binop_1() */
1748 /* Receive output from const_binop_1. */
1750 else
1751 {
1752 /* We got an exception from const_binop_1. */
1755 }
1765 }
1768 {
1777 {
1797 notrunc),
1803 notrunc));
1807 {
1808 register tree magsquared
1812 notrunc);
1815 const_binop
1820 notrunc),
1822 notrunc),
1823 notrunc),
1825 const_binop
1830 notrunc),
1832 notrunc),
1833 notrunc),
1835 }
1840 }
1842 }
1844 }
1845 \f
1846 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1847 bits are given by NUMBER and of the sizetype represented by KIND. */
1849 tree
1851 HOST_WIDE_INT number;
1853 {
1855 }
1857 /* Likewise, but the desired type is specified explicitly. */
1859 tree
1861 HOST_WIDE_INT number;
1862 tree type;
1863 {
1864 /* Type-size nodes already made for small sizes. */
1867 tree t;
1870 {
1874 }
1876 /* If this is a positive number that fits in the table we use to hold
1877 cached entries, see if it is already in the table and put it there
1878 if not. */
1880 {
1892 }
1898 }
1900 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1901 is a tree code. The type of the result is taken from the operands.
1902 Both must be the same type integer type and it must be a size type.
1903 If the operands are constant, so is the result. */
1905 tree
1909 {
1916 /* Handle the special case of two integer constants faster. */
1918 {
1919 /* And some specific cases even faster than that. */
1928 /* Handle general case of two integer constants. */
1930 }
1936 }
1938 /* Given two values, either both of sizetype or both of bitsizetype,
1939 compute the difference between the two values. Return the value
1940 in signed type corresponding to the type of the operands. */
1942 tree
1945 {
1947 tree ctype;
1953 /* If the type is already signed, just do the simple thing. */
1960 /* If either operand is not a constant, do the conversions to the signed
1961 type and subtract. The hardware will do the right thing with any
1962 overflow in the subtraction. */
1967 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1968 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1969 overflow) and negate (which can't either). Special-case a result
1970 of zero while we're here. */
1975 else
1978 }
1979 \f
1980 /* This structure is used to communicate arguments to fold_convert_1. */
1981 struct fc_args
1982 {
1986 };
1988 /* Function to convert floating-point constants, protected by floating
1989 point exception handler. */
1991 static void
1993 PTR data;
1994 {
2000 }
2002 /* Given T, a tree representing type conversion of ARG1, a constant,
2003 return a constant tree representing the result of conversion. */
2005 static tree
2009 {
2014 {
2016 {
2017 /* If we would build a constant wider than GCC supports,
2018 leave the conversion unfolded. */
2022 /* If we are trying to make a sizetype for a small integer, use
2023 size_int to pick up cached types to reduce duplicate nodes. */
2029 /* Given an integer constant, make new constant with new type,
2030 appropriately sign-extended or truncated. */
2034 /* Indicate an overflow if (1) ARG1 already overflowed,
2035 or (2) force_fit_type indicates an overflow.
2036 Tell force_fit_type that an overflow has already occurred
2037 if ARG1 is a too-large unsigned value and T is signed.
2038 But don't indicate an overflow if converting a pointer. */
2048 }
2049 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2051 {
2052 /* Don't initialize these, use assignments.
2053 Initialized local aggregates don't work on old compilers. */
2054 REAL_VALUE_TYPE x;
2055 REAL_VALUE_TYPE l;
2056 REAL_VALUE_TYPE u;
2067 /* See if X will be in range after truncation towards 0.
2068 To compensate for truncation, move the bounds away from 0,
2069 but reject if X exactly equals the adjusted bounds. */
2070 #ifdef REAL_ARITHMETIC
2074 #else
2075 l--;
2077 u++;
2078 #endif
2079 /* If X is a NaN, use zero instead and show we have an overflow.
2080 Otherwise, range check. */
2084 && !no_upper_bound
2088 #ifndef REAL_ARITHMETIC
2089 {
2091 HOST_WIDE_INT half_word
2100 {
2103 }
2104 else
2109 }
2110 #else
2111 {
2115 }
2116 #endif
2122 }
2125 }
2127 {
2128 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2133 {
2137 {
2141 }
2143 /* Setup input for fold_convert_1() */
2148 {
2149 /* Receive output from fold_convert_1() */
2151 }
2152 else
2153 {
2154 /* We got an exception from fold_convert_1() */
2157 }
2164 }
2165 }
2168 }
2169 \f
2170 /* Return an expr equal to X but certainly not valid as an lvalue. */
2172 tree
2174 tree x;
2175 {
2176 tree result;
2178 /* These things are certainly not lvalues. */
2189 }
2191 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2192 Zero means allow extended lvalues. */
2196 /* When pedantic, return an expr equal to X but certainly not valid as a
2197 pedantic lvalue. Otherwise, return X. */
2199 tree
2201 tree x;
2202 {
2205 else
2207 }
2208 \f
2209 /* Given a tree comparison code, return the code that is the logical inverse
2210 of the given code. It is not safe to do this for floating-point
2211 comparisons, except for NE_EXPR and EQ_EXPR. */
2213 static enum tree_code
2216 {
2218 {
2233 }
2234 }
2236 /* Similar, but return the comparison that results if the operands are
2237 swapped. This is safe for floating-point. */
2239 static enum tree_code
2242 {
2244 {
2258 }
2259 }
2261 /* Return nonzero if CODE is a tree code that represents a truth value. */
2263 static int
2266 {
2271 }
2272 \f
2273 /* Return nonzero if two operands are necessarily equal.
2274 If ONLY_CONST is non-zero, only return non-zero for constants.
2275 This function tests whether the operands are indistinguishable;
2276 it does not test whether they are equal using C's == operation.
2277 The distinction is important for IEEE floating point, because
2278 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2279 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
2281 int
2285 {
2286 /* If both types don't have the same signedness, then we can't consider
2287 them equal. We must check this before the STRIP_NOPS calls
2288 because they may change the signedness of the arguments. */
2296 /* This is needed for conversions and for COMPONENT_REF.
2297 Might as well play it safe and always test this. */
2303 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2304 We don't care about side effects in that case because the SAVE_EXPR
2305 takes care of that for us. In all other cases, two expressions are
2306 equal if they have no side effects. If we have two identical
2307 expressions with side effects that should be treated the same due
2308 to the only side effects being identical SAVE_EXPR's, that will
2309 be detected in the recursive calls below. */
2315 /* Next handle constant cases, those for which we can return 1 even
2316 if ONLY_CONST is set. */
2319 {
2333 only_const)
2335 only_const));
2348 }
2354 {
2356 /* Two conversions are equal only if signedness and modes match. */
2372 /* For commutative ops, allow the other order. */
2385 /* If either of the pointer (or reference) expressions we are dereferencing
2386 contain a side effect, these cannot be equal. */
2392 {
2413 }
2422 }
2423 }
2424 \f
2425 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2426 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2428 When in doubt, return 0. */
2430 static int
2433 tree other;
2434 {
2446 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2447 and see if the inner values are the same. This removes any
2448 signedness comparison, which doesn't matter here. */
2455 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2456 actual comparison operand, ARG0.
2458 First throw away any conversions to wider types
2459 already present in the operands. */
2468 {
2471 /* Make sure shorter operand is extended the right way
2472 to match the longer operand. */
2475 primarg1);
2479 }
2482 }
2483 \f
2484 /* See if ARG is an expression that is either a comparison or is performing
2485 arithmetic on comparisons. The comparisons must only be comparing
2486 two different values, which will be stored in *CVAL1 and *CVAL2; if
2487 they are non-zero it means that some operands have already been found.
2488 No variables may be used anywhere else in the expression except in the
2489 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2490 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2492 If this is true, return 1. Otherwise, return zero. */
2494 static int
2496 tree arg;
2499 {
2503 /* We can handle some of the 'e' cases here. */
2513 {
2514 /* If we've already found a CVAL1 or CVAL2, this expression is
2515 two complex to handle. */
2521 }
2524 {
2547 /* First see if we can handle the first operand, then the second. For
2548 the second operand, we know *CVAL1 can't be zero. It must be that
2549 one side of the comparison is each of the values; test for the
2550 case where this isn't true by failing if the two operands
2551 are the same. */
2560 ;
2564 ;
2565 else
2569 ;
2573 ;
2574 else
2581 }
2582 }
2583 \f
2584 /* ARG is a tree that is known to contain just arithmetic operations and
2585 comparisons. Evaluate the operations in the tree substituting NEW0 for
2586 any occurrence of OLD0 as an operand of a comparison and likewise for
2587 NEW1 and OLD1. */
2589 static tree
2591 tree arg;
2593 {
2598 /* We can handle some of the 'e' cases here. */
2606 {
2621 {
2638 }
2639 /* fall through - ??? */
2642 {
2646 /* We need to check both for exact equality and tree equality. The
2647 former will be true if the operand has a side-effect. In that
2648 case, we know the operand occurred exactly once. */
2661 }
2665 }
2666 }
2667 \f
2668 /* Return a tree for the case when the result of an expression is RESULT
2669 converted to TYPE and OMITTED was previously an operand of the expression
2670 but is now not needed (e.g., we folded OMITTED * 0).
2672 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2673 the conversion of RESULT to TYPE. */
2675 static tree
2678 {
2685 }
2687 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2689 static tree
2692 {
2699 }
2700 \f
2701 /* Return a simplified tree node for the truth-negation of ARG. This
2702 never alters ARG itself. We assume that ARG is an operation that
2703 returns a truth value (0 or 1). */
2705 tree
2707 tree arg;
2708 {
2715 /* If this is a comparison, we can simply invert it, except for
2716 floating-point non-equality comparisons, in which case we just
2717 enclose a TRUTH_NOT_EXPR around what we have. */
2720 {
2722 && !flag_unsafe_math_optimizations
2726 else
2729 }
2732 {
2747 /* Here we can invert either operand. We invert the first operand
2748 unless the second operand is a TRUTH_NOT_EXPR in which case our
2749 result is the XOR of the first operand with the inside of the
2750 negation of the second operand. */
2755 else
2810 }
2814 }
2816 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2817 operands are another bit-wise operation with a common input. If so,
2818 distribute the bit operations to save an operation and possibly two if
2819 constants are involved. For example, convert
2820 (A | B) & (A | C) into A | (B & C)
2821 Further simplification will occur if B and C are constants.
2823 If this optimization cannot be done, 0 will be returned. */
2825 static tree
2828 tree type;
2830 {
2831 tree common;
2841 {
2845 }
2847 {
2851 }
2853 {
2857 }
2859 {
2863 }
2864 else
2869 }
2870 \f
2871 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2872 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2874 static tree
2876 tree inner;
2877 tree type;
2880 {
2887 }
2889 /* Optimize a bit-field compare.
2891 There are two cases: First is a compare against a constant and the
2892 second is a comparison of two items where the fields are at the same
2893 bit position relative to the start of a chunk (byte, halfword, word)
2894 large enough to contain it. In these cases we can avoid the shift
2895 implicit in bitfield extractions.
2897 For constants, we emit a compare of the shifted constant with the
2898 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2899 compared. For two fields at the same position, we do the ANDs with the
2900 similar mask and compare the result of the ANDs.
2902 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2903 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2904 are the left and right operands of the comparison, respectively.
2906 If the optimization described above can be done, we return the resulting
2907 tree. Otherwise we return zero. */
2909 static tree
2912 tree compare_type;
2914 {
2924 tree mask;
2925 tree offset;
2927 /* Get all the information about the extractions being done. If the bit size
2928 if the same as the size of the underlying object, we aren't doing an
2929 extraction at all and so can do nothing. We also don't want to
2930 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2931 then will no longer be able to replace it. */
2939 {
2940 /* If this is not a constant, we can only do something if bit positions,
2941 sizes, and signedness are the same. */
2949 }
2951 /* See if we can find a mode to refer to this field. We should be able to,
2952 but fail if we can't. */
2961 /* Set signed and unsigned types of the precision of this mode for the
2962 shifts below. */
2966 /* Compute the bit position and size for the new reference and our offset
2967 within it. If the new reference is the same size as the original, we
2968 won't optimize anything, so return zero. */
2978 /* Make the mask to be used against the extracted field. */
2988 /* If not comparing with constant, just rework the comparison
2989 and return. */
2994 mask),
2998 mask));
3000 /* Otherwise, we are handling the constant case. See if the constant is too
3001 big for the field. Warn and return a tree of for 0 (false) if so. We do
3002 this not only for its own sake, but to avoid having to test for this
3003 error case below. If we didn't, we might generate wrong code.
3005 For unsigned fields, the constant shifted right by the field length should
3006 be all zero. For signed fields, the high-order bits should agree with
3007 the sign bit. */
3010 {
3014 {
3020 }
3021 }
3022 else
3023 {
3027 {
3033 }
3034 }
3036 /* Single-bit compares should always be against zero. */
3038 {
3041 }
3043 /* Make a new bitfield reference, shift the constant over the
3044 appropriate number of bits and mask it with the computed mask
3045 (in case this was a signed field). If we changed it, make a new one. */
3048 {
3051 }
3061 rhs);
3062 }
3063 \f
3064 /* Subroutine for fold_truthop: decode a field reference.
3066 If EXP is a comparison reference, we return the innermost reference.
3068 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3069 set to the starting bit number.
3071 If the innermost field can be completely contained in a mode-sized
3072 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3074 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3075 otherwise it is not changed.
3077 *PUNSIGNEDP is set to the signedness of the field.
3079 *PMASK is set to the mask used. This is either contained in a
3080 BIT_AND_EXPR or derived from the width of the field.
3082 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3084 Return 0 if this is not a component reference or is one that we can't
3085 do anything with. */
3087 static tree
3090 tree exp;
3096 {
3099 tree unsigned_type;
3103 /* All the optimizations using this function assume integer fields.
3104 There are problems with FP fields since the type_for_size call
3105 below can fail for, e.g., XFmode. */
3112 {
3118 }
3127 /* Compute the mask to access the bitfield. */
3137 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3145 }
3147 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
3148 bit positions. */
3150 static int
3152 tree mask;
3154 {
3157 tree tmask;
3162 return
3169 }
3171 /* Subroutine for fold_truthop: determine if an operand is simple enough
3172 to be evaluated unconditionally. */
3174 static int
3176 tree exp;
3177 {
3178 /* Strip any conversions that don't change the machine mode. */
3190 /* Don't regard global variables as simple. They may be
3191 allocated in ways unknown to the compiler (shared memory,
3192 #pragma weak, etc). */
3195 /* Loading a static variable is unduly expensive, but global
3196 registers aren't expensive. */
3198 }
3199 \f
3200 /* The following functions are subroutines to fold_range_test and allow it to
3201 try to change a logical combination of comparisons into a range test.
3203 For example, both
3204 X == 2 || X == 3 || X == 4 || X == 5
3205 and
3206 X >= 2 && X <= 5
3207 are converted to
3208 (unsigned) (X - 2) <= 3
3210 We describe each set of comparisons as being either inside or outside
3211 a range, using a variable named like IN_P, and then describe the
3212 range with a lower and upper bound. If one of the bounds is omitted,
3213 it represents either the highest or lowest value of the type.
3215 In the comments below, we represent a range by two numbers in brackets
3216 preceded by a "+" to designate being inside that range, or a "-" to
3217 designate being outside that range, so the condition can be inverted by
3218 flipping the prefix. An omitted bound is represented by a "-". For
3219 example, "- [-, 10]" means being outside the range starting at the lowest
3220 possible value and ending at 10, in other words, being greater than 10.
3221 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3222 always false.
3224 We set up things so that the missing bounds are handled in a consistent
3225 manner so neither a missing bound nor "true" and "false" need to be
3226 handled using a special case. */
3228 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3229 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3230 and UPPER1_P are nonzero if the respective argument is an upper bound
3231 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3232 must be specified for a comparison. ARG1 will be converted to ARG0's
3233 type if both are specified. */
3235 static tree
3238 tree type;
3241 {
3242 tree tem;
3246 /* If neither arg represents infinity, do the normal operation.
3247 Else, if not a comparison, return infinity. Else handle the special
3248 comparison rules. Note that most of the cases below won't occur, but
3249 are handled for consistency. */
3252 {
3257 }
3262 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3263 for neither. In real maths, we cannot assume open ended ranges are
3264 the same. But, this is computer arithmetic, where numbers are finite.
3265 We can therefore make the transformation of any unbounded range with
3266 the value Z, Z being greater than any representable number. This permits
3267 us to treat unbounded ranges as equal. */
3271 {
3292 }
3295 }
3296 \f
3297 /* Given EXP, a logical expression, set the range it is testing into
3298 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3299 actually being tested. *PLOW and *PHIGH will be made of the same type
3300 as the returned expression. If EXP is not a comparison, we will most
3301 likely not be returning a useful value and range. */
3303 static tree
3305 tree exp;
3308 {
3315 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3316 and see if we can refine the range. Some of the cases below may not
3317 happen, but it doesn't seem worth worrying about this. We "continue"
3318 the outer loop when we've changed something; otherwise we "break"
3319 the switch, which will "break" the while. */
3324 {
3328 {
3339 }
3341 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3342 lose a cast by accident. */
3347 {
3354 /* We can only do something if the range is testing for zero
3355 and if the second operand is an integer constant. Note that
3356 saying something is "in" the range we make is done by
3357 complementing IN_P since it will set in the initial case of
3358 being not equal to zero; "out" is leaving it alone. */
3365 {
3386 }
3390 /* If this is an unsigned comparison, we also know that EXP is
3391 greater than or equal to zero. We base the range tests we make
3392 on that fact, so we record it here so we can parse existing
3393 range tests. */
3395 {
3398 NULL_TREE))
3403 /* If the high bound is missing, but we
3404 have a low bound, reverse the range so
3405 it goes from zero to the low bound minus 1. */
3407 {
3412 }
3413 }
3417 /* (-x) IN [a,b] -> x in [-b, -a] */
3427 /* ~ X -> -X - 1 */
3436 /* If EXP is signed, any overflow in the computation is undefined,
3437 so we don't worry about it so long as our computations on
3438 the bounds don't overflow. For unsigned, overflow is defined
3439 and this is exactly the right thing. */
3448 /* Check for an unsigned range which has wrapped around the maximum
3449 value thus making n_high < n_low, and normalize it. */
3451 {
3457 /* If the range is of the form +/- [ x+1, x ], we won't
3458 be able to normalize it. But then, it represents the
3459 whole range or the empty set, so make it
3460 +/- [ -, - ]. */
3464 else
3466 }
3467 else
3490 /* If we're converting from an unsigned to a signed type,
3491 we will be doing the comparison as unsigned. The tests above
3492 have already verified that LOW and HIGH are both positive.
3494 So we have to make sure that the original unsigned value will
3495 be interpreted as positive. */
3497 {
3499 tree high_positive;
3501 /* A range without an upper bound is, naturally, unbounded.
3502 Since convert would have cropped a very large value, use
3503 the max value for the destination type. */
3504 high_positive
3512 /* If the low bound is specified, "and" the range with the
3513 range for which the original unsigned value will be
3514 positive. */
3516 {
3520 high_positive))
3524 }
3525 else
3526 {
3527 /* Otherwise, "or" the range with the range of the input
3528 that will be interpreted as negative. */
3532 high_positive))
3536 }
3537 }
3545 }
3548 }
3550 /* If EXP is a constant, we can evaluate whether this is true or false. */
3552 {
3559 }
3563 }
3564 \f
3565 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3566 type, TYPE, return an expression to test if EXP is in (or out of, depending
3567 on IN_P) the range. */
3569 static tree
3571 tree type;
3572 tree exp;
3575 {
3599 {
3603 }
3610 else
3612 }
3613 \f
3614 /* Given two ranges, see if we can merge them into one. Return 1 if we
3615 can, 0 if we can't. Set the output range into the specified parameters. */
3617 static int
3623 {
3627 tree tem;
3637 /* Make range 0 be the range that starts first, or ends last if they
3638 start at the same value. Swap them if it isn't. */
3641 || (lowequal
3644 {
3648 }
3650 /* Now flag two cases, whether the ranges are disjoint or whether the
3651 second range is totally subsumed in the first. Note that the tests
3652 below are simplified by the ones above. */
3658 /* We now have four cases, depending on whether we are including or
3659 excluding the two ranges. */
3661 {
3662 /* If they don't overlap, the result is false. If the second range
3663 is a subset it is the result. Otherwise, the range is from the start
3664 of the second to the end of the first. */
3669 else
3671 }
3674 {
3675 /* If they don't overlap, the result is the first range. If they are
3676 equal, the result is false. If the second range is a subset of the
3677 first, and the ranges begin at the same place, we go from just after
3678 the end of the first range to the end of the second. If the second
3679 range is not a subset of the first, or if it is a subset and both
3680 ranges end at the same place, the range starts at the start of the
3681 first range and ends just before the second range.
3682 Otherwise, we can't describe this as a single range. */
3688 {
3692 }
3694 {
3698 }
3699 else
3701 }
3704 {
3705 /* If they don't overlap, the result is the second range. If the second
3706 is a subset of the first, the result is false. Otherwise,
3707 the range starts just after the first range and ends at the
3708 end of the second. */
3713 else
3714 {
3718 }
3719 }
3721 else
3722 {
3723 /* The case where we are excluding both ranges. Here the complex case
3724 is if they don't overlap. In that case, the only time we have a
3725 range is if they are adjacent. If the second is a subset of the
3726 first, the result is the first. Otherwise, the range to exclude
3727 starts at the beginning of the first range and ends at the end of the
3728 second. */
3730 {
3737 else
3739 }
3742 else
3744 }
3748 }
3749 \f
3750 /* EXP is some logical combination of boolean tests. See if we can
3751 merge it into some range test. Return the new tree if so. */
3753 static tree
3755 tree exp;
3756 {
3763 tree tem;
3765 /* If this is an OR operation, invert both sides; we will invert
3766 again at the end. */
3770 /* If both expressions are the same, if we can merge the ranges, and we
3771 can build the range test, return it or it inverted. If one of the
3772 ranges is always true or always false, consider it to be the same
3773 expression as the other. */
3783 /* On machines where the branch cost is expensive, if this is a
3784 short-circuited branch and the underlying object on both sides
3785 is the same, make a non-short-circuit operation. */
3791 {
3792 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3793 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3794 which cases we can't do this. */
3803 {
3815 }
3816 }
3819 }
3820 \f
3821 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3822 bit value. Arrange things so the extra bits will be set to zero if and
3823 only if C is signed-extended to its full width. If MASK is nonzero,
3824 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3826 static tree
3828 tree c;
3831 tree mask;
3832 {
3835 tree temp;
3840 /* We work by getting just the sign bit into the low-order bit, then
3841 into the high-order bit, then sign-extend. We then XOR that value
3842 with C. */
3846 /* We must use a signed type in order to get an arithmetic right shift.
3847 However, we must also avoid introducing accidental overflows, so that
3848 a subsequent call to integer_zerop will work. Hence we must
3849 do the type conversion here. At this point, the constant is either
3850 zero or one, and the conversion to a signed type can never overflow.
3851 We could get an overflow if this conversion is done anywhere else. */
3859 /* If necessary, convert the type back to match the type of C. */
3864 }
3865 \f
3866 /* Find ways of folding logical expressions of LHS and RHS:
3867 Try to merge two comparisons to the same innermost item.
3868 Look for range tests like "ch >= '0' && ch <= '9'".
3869 Look for combinations of simple terms on machines with expensive branches
3870 and evaluate the RHS unconditionally.
3872 For example, if we have p->a == 2 && p->b == 4 and we can make an
3873 object large enough to span both A and B, we can do this with a comparison
3874 against the object ANDed with the a mask.
3876 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3877 operations to do this with one comparison.
3879 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3880 function and the one above.
3882 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3883 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3885 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3886 two operands.
3888 We return the simplified tree or 0 if no optimization is possible. */
3890 static tree
3894 {
3895 /* If this is the "or" of two comparisons, we can do something if
3896 the comparisons are NE_EXPR. If this is the "and", we can do something
3897 if the comparisons are EQ_EXPR. I.e.,
3898 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3900 WANTED_CODE is this operation code. For single bit fields, we can
3901 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3902 comparison for one-bit fields. */
3922 /* Start by getting the comparison codes. Fail if anything is volatile.
3923 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3924 it were surrounded with a NE_EXPR. */
3949 /* If the RHS can be evaluated unconditionally and its operands are
3950 simple, it wins to evaluate the RHS unconditionally on machines
3951 with expensive branches. In this case, this isn't a comparison
3952 that can be merged. Avoid doing this if the RHS is a floating-point
3953 comparison since those can trap. */
3961 /* See if the comparisons can be merged. Then get all the parameters for
3962 each side. */
3986 /* It must be true that the inner operation on the lhs of each
3987 comparison must be the same if we are to be able to do anything.
3988 Then see if we have constants. If not, the same must be true for
3989 the rhs's. */
4000 else
4003 /* If either comparison code is not correct for our logical operation,
4004 fail. However, we can convert a one-bit comparison against zero into
4005 the opposite comparison against that bit being set in the field. */
4009 {
4011 {
4012 /* Make the left operand unsigned, since we are only interested
4013 in the value of one bit. Otherwise we are doing the wrong
4014 thing below. */
4017 }
4018 else
4020 }
4022 /* This is analogous to the code for l_const above. */
4024 {
4026 {
4029 }
4030 else
4032 }
4034 /* See if we can find a mode that contains both fields being compared on
4035 the left. If we can't, fail. Otherwise, update all constants and masks
4036 to be relative to a field of that size. */
4041 volatilep);
4051 {
4054 }
4062 {
4070 {
4074 wanted_code == NE_EXPR
4076 }
4077 }
4079 {
4087 {
4091 wanted_code == NE_EXPR
4093 }
4094 }
4096 /* If the right sides are not constant, do the same for it. Also,
4097 disallow this optimization if a size or signedness mismatch occurs
4098 between the left and right sides. */
4100 {
4103 /* Make sure the two fields on the right
4104 correspond to the left without being swapped. */
4112 volatilep);
4122 {
4125 }
4132 /* Make a mask that corresponds to both fields being compared.
4133 Do this for both items being compared. If the operands are the
4134 same size and the bits being compared are in the same position
4135 then we can do this by masking both and comparing the masked
4136 results. */
4140 {
4152 }
4154 /* There is still another way we can do something: If both pairs of
4155 fields being compared are adjacent, we may be able to make a wider
4156 field containing them both.
4158 Note that we still must mask the lhs/rhs expressions. Furthermore,
4159 the mask must be shifted to account for the shift done by
4160 make_bit_field_ref. */
4165 {
4166 tree type;
4178 /* Convert to the smaller type before masking out unwanted bits. */
4181 {
4183 {
4187 }
4189 {
4193 }
4194 }
4203 }
4206 }
4208 /* Handle the case of comparisons with constants. If there is something in
4209 common between the masks, those bits of the constants must be the same.
4210 If not, the condition is always false. Test for this to avoid generating
4211 incorrect code below. */
4216 {
4218 {
4221 }
4222 else
4223 {
4226 }
4227 }
4229 /* Construct the expression we will return. First get the component
4230 reference we will make. Unless the mask is all ones the width of
4231 that field, perform the mask operation. Then compare with the
4232 merged constant. */
4242 }
4243 \f
4244 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4245 constant. */
4247 static tree
4249 tree t;
4250 {
4255 tree minmax_const;
4257 tree inner;
4267 /* If something does not permit us to optimize, return the original tree. */
4275 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4276 and GT_EXPR, doing the rest with recursive calls using logical
4277 simplifications. */
4279 {
4281 return
4285 return
4287 optimize_minmax_comparison
4289 optimize_minmax_comparison
4294 /* MAX (X, 0) == 0 -> X <= 0 */
4298 /* MAX (X, 0) == 5 -> X == 5 */
4302 /* MAX (X, 0) == -1 -> false */
4306 /* MIN (X, 0) == 0 -> X >= 0 */
4310 /* MIN (X, 0) == 5 -> false */
4313 else
4314 /* MIN (X, 0) == -1 -> X == -1 */
4319 /* MAX (X, 0) > 0 -> X > 0
4320 MAX (X, 0) > 5 -> X > 5 */
4324 /* MAX (X, 0) > -1 -> true */
4328 /* MIN (X, 0) > 0 -> false
4329 MIN (X, 0) > 5 -> false */
4332 else
4333 /* MIN (X, 0) > -1 -> X > -1 */
4338 }
4339 }
4340 \f
4341 /* T is an integer expression that is being multiplied, divided, or taken a
4342 modulus (CODE says which and what kind of divide or modulus) by a
4343 constant C. See if we can eliminate that operation by folding it with
4344 other operations already in T. WIDE_TYPE, if non-null, is a type that
4345 should be used for the computation if wider than our type.
4347 For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
4348 (X * 2) + (Y + 4). We must, however, be assured that either the original
4349 expression would not overflow or that overflow is undefined for the type
4350 in the language in question.
4352 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4353 the machine has a multiply-accumulate insn or that this is part of an
4354 addressing calculation.
4356 If we return a non-null expression, it is an equivalent form of the
4357 original computation, but need not be in the original type. */
4359 static tree
4361 tree t;
4362 tree c;
4364 tree wide_type;
4365 {
4375 /* Don't deal with constants of zero here; they confuse the code below. */
4385 /* Note that we need not handle conditional operations here since fold
4386 already handles those cases. So just do arithmetic here. */
4388 {
4390 /* For a constant, we can always simplify if we are a multiply
4391 or (for divide and modulus) if it is a multiple of our constant. */
4398 /* If op0 is an expression, and is unsigned, and the type is
4399 smaller than ctype, then we cannot widen the expression. */
4411 /* Pass the constant down and see if we can make a simplification. If
4412 we can, replace this expression with the inner simplification for
4413 possible later conversion to our or some other type. */
4425 /* If widening the type changes the signedness, then we can't perform
4426 this optimization as that changes the result. */
4430 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4433 {
4439 }
4449 /* If this has not been evaluated and the operand has no side effects,
4450 we can see if we can do something inside it and make a new one.
4451 Note that this test is overly conservative since we can do this
4452 if the only reason it had side effects is that it was another
4453 similar SAVE_EXPR, but that isn't worth bothering with. */
4456 wide_type)))
4457 {
4464 }
4468 /* If the second operand is constant, this is a multiplication
4469 or floor division, by a power of two, so we can treat it that
4470 way unless the multiplier or divisor overflows. */
4472 /* const_binop may not detect overflow correctly,
4473 so check for it explicitly here. */
4487 /* See if we can eliminate the operation on both sides. If we can, we
4488 can return a new PLUS or MINUS. If we can't, the only remaining
4489 cases where we can do anything are if the second operand is a
4490 constant. */
4495 /* If not multiplication, we can only do this if either operand
4496 is divisible by c. */
4502 /* If this was a subtraction, negate OP1 and set it to be an addition.
4503 This simplifies the logic below. */
4510 /* If either OP1 or C are negative, this optimization is not safe for
4511 some of the division and remainder types while for others we need
4512 to change the code. */
4514 {
4525 }
4527 /* If it's a multiply or a division/modulus operation of a multiple
4528 of our constant, do the operation and verify it doesn't overflow. */
4531 {
4535 }
4536 else
4539 /* If we have an unsigned type is not a sizetype, we cannot widen
4540 the operation since it will change the result if the original
4541 computation overflowed. */
4547 /* If we were able to eliminate our operation from the first side,
4548 apply our operation to the second side and reform the PLUS. */
4552 /* The last case is if we are a multiply. In that case, we can
4553 apply the distributive law to commute the multiply and addition
4554 if the multiplication of the constants doesn't overflow. */
4559 op1));
4564 /* We have a special case here if we are doing something like
4565 (C * 8) % 4 since we know that's zero. */
4572 /* ... fall through ... */
4576 /* If we can extract our operation from the LHS, do so and return a
4577 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4578 do something only if the second operand is a constant. */
4590 /* If these are the same operation types, we can associate them
4591 assuming no overflow. */
4598 /* If these operations "cancel" each other, we have the main
4599 optimizations of this pass, which occur when either constant is a
4600 multiple of the other, in which case we replace this with either an
4601 operation or CODE or TCODE.
4603 If we have an unsigned type that is not a sizetype, we canot do
4604 this since it will change the result if the original computation
4605 overflowed. */
4612 {
4623 }
4628 }
4631 }
4632 \f
4633 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4634 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4635 that we may sometimes modify the tree. */
4637 static tree
4639 tree t;
4640 tree s;
4641 {
4644 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4649 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4650 don't bother handling any other types. */
4652 {
4656 }
4661 {
4664 }
4667 }
4668 \f
4669 /* Return a node which has the indicated constant VALUE (either 0 or
4670 1), and is of the indicated TYPE. */
4672 static tree
4675 tree type;
4676 {
4681 integer_zero_node);
4682 else
4683 {
4688 }
4689 }
4691 /* Utility function for the following routine, to see how complex a nesting of
4692 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4693 we don't care (to avoid spending too much time on complex expressions.). */
4695 static int
4697 tree expr;
4699 {
4710 }
4712 /* Transform `a + (b ? x : y)' into `x ? (a + b) : (a + y)'.
4713 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4714 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4715 expression, and ARG to `a'. If COND_FIRST_P is non-zero, then the
4716 COND is the first argument to CODE; otherwise (as in the example
4717 given here), it is the second argument. TYPE is the type of the
4718 original expression. */
4720 static tree
4723 tree type;
4724 tree cond;
4725 tree arg;
4727 {
4731 /* In the end, we'll produce a COND_EXPR. Both arms of the
4732 conditional expression will be binary operations. The left-hand
4733 side of the expression to be executed if the condition is true
4734 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4735 of the expression to be executed if the condition is true will be
4736 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analagous --
4737 but apply to the expression to be executed if the conditional is
4738 false. */
4743 /* These are the codes to use for the left-hand side and right-hand
4744 side of the COND_EXPR. Normally, they are the same as CODE. */
4747 /* And these are the types of the expressions. */
4752 {
4756 }
4757 else
4758 {
4762 }
4765 {
4769 /* If this operand throws an expression, then it does not make
4770 sense to try to perform a logical or arithmetic operation
4771 involving it. Instead of building `a + throw 3' for example,
4772 we simply build `a, throw 3'. */
4774 {
4778 }
4780 {
4784 }
4785 }
4786 else
4787 {
4792 }
4794 /* If ARG is complex we want to make sure we only evaluate
4795 it once. Though this is only required if it is volatile, it
4796 might be more efficient even if it is not. However, if we
4797 succeed in folding one part to a constant, we do not need
4798 to make this SAVE_EXPR. Since we do this optimization
4799 primarily to see if we do end up with constant and this
4800 SAVE_EXPR interferes with later optimizations, suppressing
4801 it when we can is important.
4803 If we are not in a function, we can't make a SAVE_EXPR, so don't
4804 try to do so. Don't try to see if the result is a constant
4805 if an arm is a COND_EXPR since we get exponential behavior
4806 in that case. */
4813 {
4823 }
4836 else
4838 }
4840 \f
4841 /* Perform constant folding and related simplification of EXPR.
4842 The related simplifications include x*1 => x, x*0 => 0, etc.,
4843 and application of the associative law.
4844 NOP_EXPR conversions may be removed freely (as long as we
4845 are careful not to change the C type of the overall expression)
4846 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4847 but we can constant-fold them if they have constant operands. */
4849 tree
4851 tree expr;
4852 {
4855 tree tem;
4861 /* WINS will be nonzero when the switch is done
4862 if all operands are constant. */
4865 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4866 Likewise for a SAVE_EXPR that's already been evaluated. */
4870 /* Return right away if a constant. */
4874 #ifdef MAX_INTEGER_COMPUTATION_MODE
4876 #endif
4879 {
4880 tree subop;
4882 /* Special case for conversion ops that can have fixed point args. */
4885 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4891 else
4895 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4898 )
4899 /* Note that TREE_CONSTANT isn't enough:
4900 static var addresses are constant but we can't
4901 do arithmetic on them. */
4903 }
4905 {
4909 {
4911 tree subop;
4917 {
4918 /* Signedness matters here. Perhaps we can refine this
4919 later. */
4921 }
4922 else
4923 /* Strip any conversions that don't change the mode. */
4928 else
4932 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4935 )
4936 /* Note that TREE_CONSTANT isn't enough:
4937 static var addresses are constant but we can't
4938 do arithmetic on them. */
4945 }
4946 }
4948 /* If this is a commutative operation, and ARG0 is a constant, move it
4949 to ARG1 to reduce the number of tests below. */
4954 {
4959 }
4961 /* Now WINS is set as described above,
4962 ARG0 is the first operand of EXPR,
4963 and ARG1 is the second operand (if it has more than one operand).
4965 First check for cases where an arithmetic operation is applied to a
4966 compound, conditional, or comparison operation. Push the arithmetic
4967 operation inside the compound or conditional to see if any folding
4968 can then be done. Convert comparison to conditional for this purpose.
4969 The also optimizes non-constant cases that used to be done in
4970 expand_expr.
4972 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
4973 one of the operands is a comparison and the other is a comparison, a
4974 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4975 code below would make the expression more complex. Change it to a
4976 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
4977 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
4989 {
4999 }
5002 {
5007 {
5012 /* If this was a conversion, and all we did was to move into
5013 inside the COND_EXPR, bring it back out. But leave it if
5014 it is a conversion from integer to integer and the
5015 result precision is no wider than a word since such a
5016 conversion is cheap and may be optimized away by combine,
5017 while it couldn't if it were outside the COND_EXPR. Then return
5018 so we don't get into an infinite recursion loop taking the
5019 conversion out and then back in. */
5029 && (INTEGRAL_TYPE_P
5040 }
5045 }
5048 {
5061 return
5075 return
5078 }
5089 {
5104 /* Other kinds of FIX are not handled properly by fold_convert. */
5109 /* Handle cases of two conversions in a row. */
5112 {
5132 /* In addition to the cases of two conversions in a row
5133 handled below, if we are converting something to its own
5134 type via an object of identical or wider precision, neither
5135 conversion is needed. */
5141 /* Likewise, if the intermediate and final types are either both
5142 float or both integer, we don't need the middle conversion if
5143 it is wider than the final type and doesn't change the signedness
5144 (for integers). Avoid this if the final type is a pointer
5145 since then we sometimes need the inner conversion. Likewise if
5146 the outer has a precision not equal to the size of its mode. */
5156 /* If we have a sign-extension of a zero-extended value, we can
5157 replace that by a single zero-extension. */
5163 /* Two conversions in a row are not needed unless:
5164 - some conversion is floating-point (overstrict for now), or
5165 - the intermediate type is narrower than both initial and
5166 final, or
5167 - the intermediate type and innermost type differ in signedness,
5168 and the outermost type is wider than the intermediate, or
5169 - the initial type is a pointer type and the precisions of the
5170 intermediate and final types differ, or
5171 - the final type is a pointer type and the precisions of the
5172 initial and intermediate types differ. */
5186 }
5190 /* Detect assigning a bitfield. */
5193 {
5194 /* Don't leave an assignment inside a conversion
5195 unless assigning a bitfield. */
5198 /* First do the assignment, then return converted constant. */
5202 }
5204 {
5207 }
5212 {
5215 /* Fold an expression like: "foo"[2] */
5219 {
5223 }
5224 }
5230 {
5234 }
5243 {
5245 {
5247 HOST_WIDE_INT high;
5258 }
5261 }
5265 /* Convert - (a - b) to (b - a) for non-floating-point. */
5275 {
5277 {
5278 /* If the value is unsigned, then the absolute value is
5279 the same as the ordinary value. */
5282 /* Similarly, if the value is non-negative. */
5285 /* If the value is negative, then the absolute value is
5286 its negation. */
5287 else
5288 {
5290 HOST_WIDE_INT high;
5301 }
5302 }
5304 {
5308 }
5309 }
5336 {
5343 }
5349 /* A + (-B) -> A - B */
5352 /* (-A) + B -> B - A */
5356 {
5360 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5361 with a constant, and the two constants have no bits in common,
5362 we should treat this as a BIT_IOR_EXPR since this may produce more
5363 simplifications. */
5371 {
5374 }
5376 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5377 (plus (plus (mult) (mult)) (foo)) so that we can
5378 take advantage of the factoring cases below. */
5383 {
5388 else
5399 parg1));
5404 parg0));
5405 }
5408 {
5412 /* (A * C) + (B * C) -> (A+B) * C.
5413 We are most concerned about the case where C is a constant,
5414 but other combinations show up during loop reduction. Since
5415 it is not difficult, try all four possibilities. */
5432 /* No identical multiplicands; see if we can find a common
5433 power-of-two factor in non-power-of-two multiplies. This
5434 can help in multi-dimensional array access. */
5439 {
5444 /* Move min of absolute values to int11. */
5447 {
5451 }
5454 {
5459 }
5460 }
5465 same));
5466 }
5467 }
5468 /* In IEEE floating point, x+0 may not equal x. */
5473 /* x+(-0) equals x, even for IEEE. */
5478 bit_rotate:
5479 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5480 is a rotate of A by C1 bits. */
5481 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5482 is a rotate of A by B bits. */
5483 {
5492 {
5511 {
5519 TYPE_PRECISION
5524 ? LROTATE_EXPR
5527 }
5529 {
5537 TYPE_PRECISION
5542 ? LROTATE_EXPR
5545 }
5546 }
5547 }
5549 associate:
5550 /* In most languages, can't associate operations on floats through
5551 parentheses. Rather than remember where the parentheses were, we
5552 don't associate floats at all. It shouldn't matter much. However,
5553 associating multiplications is only very slightly inaccurate, so do
5554 that if -funsafe-math-optimizations is specified. */
5559 {
5562 /* Split both trees into variables, constants, and literals. Then
5563 associate each group together, the constants with literals,
5564 then the result with variables. This increases the chances of
5565 literals being recombined later and of generating relocatable
5566 expressions for the sum of a constant and literal. */
5570 /* Only do something if we found more than two objects. Otherwise,
5571 nothing has changed and we risk infinite recursion. */
5574 {
5580 }
5581 }
5583 binary:
5584 #if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
5591 {
5592 /* The return value should always have
5593 the same type as the original expression. */
5598 }
5602 /* A - (-B) -> A + B */
5605 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5607 return
5614 {
5620 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5621 about the case where C is a constant, just try one of the
5622 four possibilities. */
5632 }
5636 {
5637 /* Except with IEEE floating point, 0-x equals -x. */
5640 /* Except with IEEE floating point, x-0 equals x. */
5643 }
5645 /* Fold &x - &x. This can happen from &x.foo - &x.
5646 This is unsafe for certain floats even in non-IEEE formats.
5647 In IEEE, it is unsafe because it does wrong for NaNs.
5648 Also note that operand_equal_p is always false if an operand
5649 is volatile. */
5658 /* (-A) * (-B) -> A * B */
5664 {
5670 /* (a * (1 << b)) is (a << b) */
5685 }
5686 else
5687 {
5688 /* x*0 is 0, except for IEEE floating point. */
5693 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5694 However, ANSI says we can drop signals,
5695 so we can do this anyway. */
5698 /* x*2 is x+x */
5701 {
5704 }
5705 }
5709 bit_ior:
5718 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5720 This results in more efficient code for machines without a NAND
5721 instruction. Combine will canonicalize to the first form
5722 which will allow use of NAND instructions provided by the
5723 backend if they exist. */
5726 {
5731 }
5733 /* See if this can be simplified into a rotate first. If that
5734 is unsuccessful continue in the association code. */
5743 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5744 with a constant, and the two constants have no bits in common,
5745 we should treat this as a BIT_IOR_EXPR since this may produce more
5746 simplifications. */
5754 {
5757 }
5759 /* See if this can be simplified into a rotate first. If that
5760 is unsuccessful continue in the association code. */
5764 bit_and:
5772 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5775 {
5776 unsigned int prec
5783 }
5786 {
5787 unsigned int prec
5794 }
5796 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5798 This results in more efficient code for machines without a NOR
5799 instruction. Combine will canonicalize to the first form
5800 which will allow use of NOR instructions provided by the
5801 backend if they exist. */
5804 {
5809 }
5819 {
5823 }
5827 /* In most cases, do nothing with a divide by zero. */
5828 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
5829 #ifndef REAL_INFINITY
5832 #endif
5835 /* (-A) / (-B) -> A / B */
5840 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5841 However, ANSI says we can drop signals, so we can do this anyway. */
5845 /* If ARG1 is a constant, we can convert this to a multiply by the
5846 reciprocal. This does not have the same rounding properties,
5847 so only do this if -funsafe-math-optimizations. We can actually
5848 always safely do it if ARG1 is a power of two, but it's hard to
5849 tell if it is or not in a portable manner. */
5851 {
5856 /* Find the reciprocal if optimizing and the result is exact. */
5858 {
5859 REAL_VALUE_TYPE r;
5862 {
5865 }
5866 }
5867 }
5880 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5881 operation, EXACT_DIV_EXPR.
5883 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5884 At one time others generated faster code, it's not clear if they do
5885 after the last round to changes to the DIV code in expmed.c. */
5919 /* Since negative shift count is not well-defined,
5920 don't try to compute it in the compiler. */
5923 /* Rewrite an LROTATE_EXPR by a constant into an
5924 RROTATE_EXPR by a new constant. */
5926 {
5930 = const_binop
5937 }
5939 /* If we have a rotate of a bit operation with the rotate count and
5940 the second operand of the bit operation both constant,
5941 permute the two operations. */
5954 /* Two consecutive rotates adding up to the width of the mode can
5955 be ignored. */
5986 /* Note that the operand of this must be an int
5987 and its values must be 0 or 1.
5988 ("true" is a fixed value perhaps depending on the language,
5989 but we don't handle values other than 1 correctly yet.) */
5991 /* Avoid infinite recursion. */
5997 /* Note that the operands of this must be ints
5998 and their values must be 0 or 1.
5999 ("true" is a fixed value perhaps depending on the language.) */
6000 /* If first arg is constant zero, return it. */
6004 /* If either arg is constant true, drop it. */
6008 /* Preserve sequence points. */
6011 /* If second arg is constant zero, result is zero, but first arg
6012 must be evaluated. */
6015 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6016 case will be handled here. */
6020 truth_andor:
6021 /* We only do these simplifications if we are optimizing. */
6025 /* Check for things like (A || B) && (A || C). We can convert this
6026 to A || (B && C). Note that either operator can be any of the four
6027 truth and/or operations and the transformation will still be
6028 valid. Also note that we only care about order for the
6029 ANDIF and ORIF operators. If B contains side effects, this
6030 might change the truth-value of A. */
6037 {
6057 /* This case if tricky because we must either have commutative
6058 operators or else A10 must not have side-effects. */
6064 a01));
6065 }
6067 /* See if we can build a range comparison. */
6071 /* Check for the possibility of merging component references. If our
6072 lhs is another similar operation, try to merge its rhs with our
6073 rhs. Then try to merge our lhs and rhs. */
6085 /* Note that the operands of this must be ints
6086 and their values must be 0 or true.
6087 ("true" is a fixed value perhaps depending on the language.) */
6088 /* If first arg is constant true, return it. */
6092 /* If either arg is constant zero, drop it. */
6096 /* Preserve sequence points. */
6099 /* If second arg is constant true, result is true, but we must
6100 evaluate first arg. */
6103 /* Likewise for first arg, but note this only occurs here for
6104 TRUTH_OR_EXPR. */
6110 /* If either arg is constant zero, drop it. */
6115 /* If either arg is constant true, this is a logical inversion. */
6129 {
6130 /* (-a) CMP (-b) -> b CMP a */
6135 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6137 return
6143 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6144 /* a CMP (-0) -> a CMP 0 */
6149 }
6151 /* If one arg is a constant integer, put it last. */
6154 {
6161 }
6163 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6164 First, see if one arg is constant; find the constant arg
6165 and the other one. */
6166 {
6176 {
6177 /* This optimization is invalid for ordered comparisons
6178 if CONST+INCR overflows or if foo+incr might overflow.
6179 This optimization is invalid for floating point due to rounding.
6180 For pointer types we assume overflow doesn't happen. */
6184 {
6185 tree newconst
6189 /* Do not overwrite the current varop to be a preincrement,
6190 create a new node so that we won't confuse our caller who
6191 might create trees and throw them away, reusing the
6192 arguments that they passed to build. This shows up in
6193 the THEN or ELSE parts of ?: being postincrements. */
6198 /* If VAROP is a reference to a bitfield, we must mask
6199 the constant by the width of the field. */
6203 {
6204 int size
6206 (TREE_OPERAND
6210 tree folded_compare;
6212 /* First check whether the comparison would come out
6213 always the same. If we don't do that we would
6214 change the meaning with the masking. */
6218 else
6221 constop));
6236 mask)));
6237 }
6243 }
6244 }
6246 {
6250 {
6251 tree newconst
6255 /* Do not overwrite the current varop to be a predecrement,
6256 create a new node so that we won't confuse our caller who
6257 might create trees and throw them away, reusing the
6258 arguments that they passed to build. This shows up in
6259 the THEN or ELSE parts of ?: being postdecrements. */
6267 {
6268 int size
6270 (TREE_OPERAND
6274 tree folded_compare;
6279 else
6282 constop));
6297 mask)));
6298 }
6304 }
6305 }
6306 }
6308 /* Change X >= CST to X > (CST - 1) if CST is positive. */
6312 {
6314 {
6329 }
6330 }
6332 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6333 a MINUS_EXPR of a constant, we can convert it into a comparison with
6334 a revised constant as long as no overflow occurs. */
6346 /* Similarly for a NEGATE_EXPR. */
6355 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6356 for !=. Don't do this for ordered comparisons due to overflow. */
6362 /* If we are widening one operand of an integer comparison,
6363 see if the other operand is similarly being widened. Perhaps we
6364 can do the comparison in the narrower type. */
6374 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6375 constant, we can simplify it. */
6382 /* If we are comparing an ABS_EXPR with a constant, we can
6383 convert all the cases into explicit comparisons, but they may
6384 well not be faster than doing the ABS and one comparison.
6385 But ABS (X) <= C is a range comparison, which becomes a subtraction
6386 and a comparison, and is probably faster. */
6398 /* If this is an EQ or NE comparison with zero and ARG0 is
6399 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6400 two operations, but the latter can be done in one less insn
6401 on machines that have only two-operand insns or on which a
6402 constant cannot be the first operand. */
6405 {
6408 return
6416 integer_one_node)),
6417 arg1));
6420 return
6428 integer_one_node)),
6429 arg1));
6430 }
6432 /* If this is an NE or EQ comparison of zero against the result of a
6433 signed MOD operation whose second operand is a power of 2, make
6434 the MOD operation unsigned since it is simpler and equivalent. */
6443 {
6450 }
6452 /* If this is an NE comparison of zero with an AND of one, remove the
6453 comparison since the AND will give the correct value. */
6459 /* If we have (A & C) == C where C is a power of 2, convert this into
6460 (A & C) != 0. Similarly for NE_EXPR. */
6468 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6469 and similarly for >= into !=. */
6485 return
6492 /* Simplify comparison of something with itself. (For IEEE
6493 floating-point, we can only do some of these simplifications.) */
6495 {
6497 {
6508 /* For NE, we can only do this simplification if integer. */
6511 /* ... fall through ... */
6517 }
6518 }
6520 /* An unsigned comparison against 0 can be simplified. */
6525 {
6527 {
6539 arg0);
6543 arg0);
6546 }
6547 }
6549 /* Comparisons with the highest or lowest possible integer of
6550 the specified size will have known values and an unsigned
6551 <= 0x7fffffff can be simplified. */
6552 {
6560 {
6566 {
6570 arg0);
6578 arg0);
6585 }
6592 {
6596 arg0);
6604 arg0);
6611 }
6617 /* signed_type does not work on pointer types. */
6621 {
6625 arg0),
6627 integer_zero_node)));
6631 arg0),
6633 integer_zero_node)));
6637 }
6638 }
6639 }
6641 /* If we are comparing an expression that just has comparisons
6642 of two integer values, arithmetic expressions of those comparisons,
6643 and constants, we can simplify it. There are only three cases
6644 to check: the two values can either be equal, the first can be
6645 greater, or the second can be greater. Fold the expression for
6646 those three values. Since each value must be 0 or 1, we have
6647 eight possibilities, each of which corresponds to the constant 0
6648 or 1 or one of the six possible comparisons.
6650 This handles common cases like (a > b) == 0 but also handles
6651 expressions like ((x > y) - (y > x)) > 0, which supposedly
6652 occur in macroized code. */
6655 {
6660 /* Don't handle degenerate cases here; they should already
6661 have been handled anyway. */
6670 {
6674 /* We can't just pass T to eval_subst in case cval1 or cval2
6675 was the same as ARG1. */
6677 tree high_result
6680 arg1));
6681 tree equal_result
6684 arg1));
6685 tree low_result
6688 arg1));
6690 /* All three of these results should be 0 or 1. Confirm they
6691 are. Then use those values to select the proper code
6692 to use. */
6700 {
6701 /* Make a 3-bit mask with the high-order bit being the
6702 value for `>', the next for '=', and the low for '<'. */
6706 {
6708 /* Always false. */
6729 /* Always true. */
6731 }
6736 else
6738 }
6739 }
6740 }
6742 /* If this is a comparison of a field, we may be able to simplify it. */
6746 /* Handle the constant case even without -O
6747 to make sure the warnings are given. */
6749 {
6752 }
6754 /* If this is a comparison of complex values and either or both sides
6755 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6756 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6757 This may prevent needless evaluations. */
6764 {
6777 type,
6780 }
6782 /* From here on, the only cases we handle are when the result is
6783 known to be a constant.
6785 To compute GT, swap the arguments and do LT.
6786 To compute GE, do LT and invert the result.
6787 To compute LE, swap the arguments, do LT and invert the result.
6788 To compute NE, do EQ and invert the result.
6790 Therefore, the code below must handle only EQ and LT. */
6793 {
6796 }
6798 /* Note that it is safe to invert for real values here because we
6799 will check below in the one case that it matters. */
6804 {
6807 }
6809 /* Compute a result for LT or EQ if args permit;
6810 otherwise return T. */
6812 {
6815 else
6820 }
6823 /* Assume a nonexplicit constant cannot equal an explicit one,
6824 since such code would be undefined anyway.
6825 Exception: on sysvr4, using #pragma weak,
6826 a label can come out as 0. */
6833 #endif
6834 /* Two real constants can be compared explicitly. */
6836 {
6837 /* If either operand is a NaN, the result is false with two
6838 exceptions: First, an NE_EXPR is true on NaNs, but that case
6839 is already handled correctly since we will be inverting the
6840 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6841 or a GE_EXPR into a LT_EXPR, we must return true so that it
6842 will be inverted into false. */
6852 else
6856 }
6870 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6871 so all simple results must be passed through pedantic_non_lvalue. */
6873 return pedantic_non_lvalue
6878 /* If the second operand is zero, invert the comparison and swap
6879 the second and third operands. Likewise if the second operand
6880 is constant and the third is not or if the third operand is
6881 equivalent to the first operand of the comparison. */
6889 {
6890 /* See if this can be inverted. If it can't, possibly because
6891 it was a floating-point inequality comparison, don't do
6892 anything. */
6896 {
6900 /* arg1 should be the first argument of the new T. */
6903 }
6904 }
6906 /* If we have A op B ? A : C, we may be able to convert this to a
6907 simpler expression, depending on the operation and the values
6908 of B and C. IEEE floating point prevents this though,
6909 because A or B might be -0.0 or a NaN. */
6917 {
6923 /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
6924 depending on the comparison operation. */
6931 {
6933 return
6934 pedantic_non_lvalue
6936 negate_expr
6938 arg1))));
6946 return pedantic_non_lvalue
6953 return pedantic_non_lvalue
6957 arg1)))));
6960 }
6962 /* If this is A != 0 ? A : 0, this is simply A. For ==, it is
6963 always zero. */
6966 {
6971 }
6973 /* If this is A op B ? A : B, this is either A, B, min (A, B),
6974 or max (A, B), depending on the operation. */
6978 {
6983 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
6988 {
6995 /* In C++ a ?: expression can be an lvalue, so put the
6996 operand which will be used if they are equal first
6997 so that we can convert this back to the
6998 corresponding COND_EXPR. */
6999 return pedantic_non_lvalue
7008 return pedantic_non_lvalue
7017 }
7018 }
7020 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7021 we might still be able to simplify this. For example,
7022 if C1 is one less or one more than C2, this might have started
7023 out as a MIN or MAX and been transformed by this function.
7024 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7030 {
7032 /* We can replace A with C1 in this case. */
7039 /* If C1 is C2 + 1, this is min(A, C2). */
7044 return pedantic_non_lvalue
7049 /* If C1 is C2 - 1, this is min(A, C2). */
7054 return pedantic_non_lvalue
7059 /* If C1 is C2 - 1, this is max(A, C2). */
7064 return pedantic_non_lvalue
7069 /* If C1 is C2 + 1, this is max(A, C2). */
7074 return pedantic_non_lvalue
7081 }
7082 }
7084 /* If the second operand is simpler than the third, swap them
7085 since that produces better jump optimization results. */
7091 {
7092 /* See if this can be inverted. If it can't, possibly because
7093 it was a floating-point inequality comparison, don't do
7094 anything. */
7098 {
7102 /* arg1 should be the first argument of the new T. */
7105 }
7106 }
7108 /* Convert A ? 1 : 0 to simply A. */
7111 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7112 call to fold will try to move the conversion inside
7113 a COND, which will recurse. In that case, the COND_EXPR
7114 is probably the best choice, so leave it alone. */
7118 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7119 operation is simply A & 2. */
7133 /* When pedantic, a compound expression can be neither an lvalue
7134 nor an integer constant expression. */
7137 /* Don't let (0, 0) be null pointer constant. */
7179 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7180 appropriate. */
7185 {
7189 tree arg01;
7200 {
7214 arg01));
7215 }
7218 }
7221 /* Check for a built-in function. */
7226 {
7230 }
7236 }
7238 /* Determine if first argument is a multiple of second argument. Return 0 if
7239 it is not, or we cannot easily determined it to be.
7241 An example of the sort of thing we care about (at this point; this routine
7242 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7243 fold cases do now) is discovering that
7245 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7247 is a multiple of
7249 SAVE_EXPR (J * 8)
7251 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7253 This code also handles discovering that
7255 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7257 is a multiple of 8 so we don't have to worry about dealing with a
7258 possible remainder.
7260 Note that we *look* inside a SAVE_EXPR only to determine how it was
7261 calculated; it is not safe for fold to do much of anything else with the
7262 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7263 at run time. For example, the latter example above *cannot* be implemented
7264 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7265 evaluation time of the original SAVE_EXPR is not necessarily the same at
7266 the time the new expression is evaluated. The only optimization of this
7267 sort that would be valid is changing
7269 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7271 divided by 8 to
7273 SAVE_EXPR (I) * SAVE_EXPR (J)
7275 (where the same SAVE_EXPR (J) is used in the original and the
7276 transformed version). */
7278 static int
7280 tree type;
7281 tree top;
7282 tree bottom;
7283 {
7291 {
7303 {
7307 /* const_binop may not detect overflow correctly,
7308 so check for it explicitly here. */
7317 }
7321 /* Can't handle conversions from non-integral or wider integral type. */
7327 /* .. fall through ... */
7343 }
7344 }
7346 /* Return true if `t' is known to be non-negative. */
7348 int
7350 tree t;
7351 {
7353 {
7366 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7368 else
7369 /* We don't know sign of `t', so be conservative and return false. */
7371 }
7372 }
7374 /* Return true if `r' is known to be non-negative.
7375 Only handles constants at the moment. */
7377 int
7379 rtx r;
7380 {
7382 {
7393 /* These are always nonnegative. */
7398 }
7399 }