| blob | 1f1d63f5db20f96d0a99a551ebd87ca4bec8488e |
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 {
2724 else
2727 }
2730 {
2745 /* Here we can invert either operand. We invert the first operand
2746 unless the second operand is a TRUTH_NOT_EXPR in which case our
2747 result is the XOR of the first operand with the inside of the
2748 negation of the second operand. */
2753 else
2808 }
2812 }
2814 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2815 operands are another bit-wise operation with a common input. If so,
2816 distribute the bit operations to save an operation and possibly two if
2817 constants are involved. For example, convert
2818 (A | B) & (A | C) into A | (B & C)
2819 Further simplification will occur if B and C are constants.
2821 If this optimization cannot be done, 0 will be returned. */
2823 static tree
2826 tree type;
2828 {
2829 tree common;
2839 {
2843 }
2845 {
2849 }
2851 {
2855 }
2857 {
2861 }
2862 else
2867 }
2868 \f
2869 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2870 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2872 static tree
2874 tree inner;
2875 tree type;
2878 {
2885 }
2887 /* Optimize a bit-field compare.
2889 There are two cases: First is a compare against a constant and the
2890 second is a comparison of two items where the fields are at the same
2891 bit position relative to the start of a chunk (byte, halfword, word)
2892 large enough to contain it. In these cases we can avoid the shift
2893 implicit in bitfield extractions.
2895 For constants, we emit a compare of the shifted constant with the
2896 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2897 compared. For two fields at the same position, we do the ANDs with the
2898 similar mask and compare the result of the ANDs.
2900 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2901 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2902 are the left and right operands of the comparison, respectively.
2904 If the optimization described above can be done, we return the resulting
2905 tree. Otherwise we return zero. */
2907 static tree
2910 tree compare_type;
2912 {
2922 tree mask;
2923 tree offset;
2925 /* Get all the information about the extractions being done. If the bit size
2926 if the same as the size of the underlying object, we aren't doing an
2927 extraction at all and so can do nothing. We also don't want to
2928 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2929 then will no longer be able to replace it. */
2937 {
2938 /* If this is not a constant, we can only do something if bit positions,
2939 sizes, and signedness are the same. */
2947 }
2949 /* See if we can find a mode to refer to this field. We should be able to,
2950 but fail if we can't. */
2959 /* Set signed and unsigned types of the precision of this mode for the
2960 shifts below. */
2964 /* Compute the bit position and size for the new reference and our offset
2965 within it. If the new reference is the same size as the original, we
2966 won't optimize anything, so return zero. */
2976 /* Make the mask to be used against the extracted field. */
2986 /* If not comparing with constant, just rework the comparison
2987 and return. */
2992 mask),
2996 mask));
2998 /* Otherwise, we are handling the constant case. See if the constant is too
2999 big for the field. Warn and return a tree of for 0 (false) if so. We do
3000 this not only for its own sake, but to avoid having to test for this
3001 error case below. If we didn't, we might generate wrong code.
3003 For unsigned fields, the constant shifted right by the field length should
3004 be all zero. For signed fields, the high-order bits should agree with
3005 the sign bit. */
3008 {
3012 {
3018 }
3019 }
3020 else
3021 {
3025 {
3031 }
3032 }
3034 /* Single-bit compares should always be against zero. */
3036 {
3039 }
3041 /* Make a new bitfield reference, shift the constant over the
3042 appropriate number of bits and mask it with the computed mask
3043 (in case this was a signed field). If we changed it, make a new one. */
3046 {
3049 }
3059 rhs);
3060 }
3061 \f
3062 /* Subroutine for fold_truthop: decode a field reference.
3064 If EXP is a comparison reference, we return the innermost reference.
3066 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3067 set to the starting bit number.
3069 If the innermost field can be completely contained in a mode-sized
3070 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3072 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3073 otherwise it is not changed.
3075 *PUNSIGNEDP is set to the signedness of the field.
3077 *PMASK is set to the mask used. This is either contained in a
3078 BIT_AND_EXPR or derived from the width of the field.
3080 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3082 Return 0 if this is not a component reference or is one that we can't
3083 do anything with. */
3085 static tree
3088 tree exp;
3094 {
3097 tree unsigned_type;
3101 /* All the optimizations using this function assume integer fields.
3102 There are problems with FP fields since the type_for_size call
3103 below can fail for, e.g., XFmode. */
3110 {
3116 }
3125 /* Compute the mask to access the bitfield. */
3135 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3143 }
3145 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
3146 bit positions. */
3148 static int
3150 tree mask;
3152 {
3155 tree tmask;
3160 return
3167 }
3169 /* Subroutine for fold_truthop: determine if an operand is simple enough
3170 to be evaluated unconditionally. */
3172 static int
3174 tree exp;
3175 {
3176 /* Strip any conversions that don't change the machine mode. */
3188 /* Don't regard global variables as simple. They may be
3189 allocated in ways unknown to the compiler (shared memory,
3190 #pragma weak, etc). */
3193 /* Loading a static variable is unduly expensive, but global
3194 registers aren't expensive. */
3196 }
3197 \f
3198 /* The following functions are subroutines to fold_range_test and allow it to
3199 try to change a logical combination of comparisons into a range test.
3201 For example, both
3202 X == 2 || X == 3 || X == 4 || X == 5
3203 and
3204 X >= 2 && X <= 5
3205 are converted to
3206 (unsigned) (X - 2) <= 3
3208 We describe each set of comparisons as being either inside or outside
3209 a range, using a variable named like IN_P, and then describe the
3210 range with a lower and upper bound. If one of the bounds is omitted,
3211 it represents either the highest or lowest value of the type.
3213 In the comments below, we represent a range by two numbers in brackets
3214 preceded by a "+" to designate being inside that range, or a "-" to
3215 designate being outside that range, so the condition can be inverted by
3216 flipping the prefix. An omitted bound is represented by a "-". For
3217 example, "- [-, 10]" means being outside the range starting at the lowest
3218 possible value and ending at 10, in other words, being greater than 10.
3219 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3220 always false.
3222 We set up things so that the missing bounds are handled in a consistent
3223 manner so neither a missing bound nor "true" and "false" need to be
3224 handled using a special case. */
3226 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3227 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3228 and UPPER1_P are nonzero if the respective argument is an upper bound
3229 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3230 must be specified for a comparison. ARG1 will be converted to ARG0's
3231 type if both are specified. */
3233 static tree
3236 tree type;
3239 {
3240 tree tem;
3244 /* If neither arg represents infinity, do the normal operation.
3245 Else, if not a comparison, return infinity. Else handle the special
3246 comparison rules. Note that most of the cases below won't occur, but
3247 are handled for consistency. */
3250 {
3255 }
3260 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3261 for neither. In real maths, we cannot assume open ended ranges are
3262 the same. But, this is computer arithmetic, where numbers are finite.
3263 We can therefore make the transformation of any unbounded range with
3264 the value Z, Z being greater than any representable number. This permits
3265 us to treat unbounded ranges as equal. */
3269 {
3290 }
3293 }
3294 \f
3295 /* Given EXP, a logical expression, set the range it is testing into
3296 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3297 actually being tested. *PLOW and *PHIGH will be made of the same type
3298 as the returned expression. If EXP is not a comparison, we will most
3299 likely not be returning a useful value and range. */
3301 static tree
3303 tree exp;
3306 {
3313 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3314 and see if we can refine the range. Some of the cases below may not
3315 happen, but it doesn't seem worth worrying about this. We "continue"
3316 the outer loop when we've changed something; otherwise we "break"
3317 the switch, which will "break" the while. */
3322 {
3326 {
3337 }
3339 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3340 lose a cast by accident. */
3345 {
3352 /* We can only do something if the range is testing for zero
3353 and if the second operand is an integer constant. Note that
3354 saying something is "in" the range we make is done by
3355 complementing IN_P since it will set in the initial case of
3356 being not equal to zero; "out" is leaving it alone. */
3363 {
3384 }
3388 /* If this is an unsigned comparison, we also know that EXP is
3389 greater than or equal to zero. We base the range tests we make
3390 on that fact, so we record it here so we can parse existing
3391 range tests. */
3393 {
3396 NULL_TREE))
3401 /* If the high bound is missing, but we
3402 have a low bound, reverse the range so
3403 it goes from zero to the low bound minus 1. */
3405 {
3410 }
3411 }
3415 /* (-x) IN [a,b] -> x in [-b, -a] */
3425 /* ~ X -> -X - 1 */
3434 /* If EXP is signed, any overflow in the computation is undefined,
3435 so we don't worry about it so long as our computations on
3436 the bounds don't overflow. For unsigned, overflow is defined
3437 and this is exactly the right thing. */
3446 /* Check for an unsigned range which has wrapped around the maximum
3447 value thus making n_high < n_low, and normalize it. */
3449 {
3455 /* If the range is of the form +/- [ x+1, x ], we won't
3456 be able to normalize it. But then, it represents the
3457 whole range or the empty set, so make it
3458 +/- [ -, - ]. */
3462 else
3464 }
3465 else
3488 /* If we're converting from an unsigned to a signed type,
3489 we will be doing the comparison as unsigned. The tests above
3490 have already verified that LOW and HIGH are both positive.
3492 So we have to make sure that the original unsigned value will
3493 be interpreted as positive. */
3495 {
3497 tree high_positive;
3499 /* A range without an upper bound is, naturally, unbounded.
3500 Since convert would have cropped a very large value, use
3501 the max value for the destination type. */
3502 high_positive
3510 /* If the low bound is specified, "and" the range with the
3511 range for which the original unsigned value will be
3512 positive. */
3514 {
3518 high_positive))
3522 }
3523 else
3524 {
3525 /* Otherwise, "or" the range with the range of the input
3526 that will be interpreted as negative. */
3530 high_positive))
3534 }
3535 }
3543 }
3546 }
3548 /* If EXP is a constant, we can evaluate whether this is true or false. */
3550 {
3557 }
3561 }
3562 \f
3563 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3564 type, TYPE, return an expression to test if EXP is in (or out of, depending
3565 on IN_P) the range. */
3567 static tree
3569 tree type;
3570 tree exp;
3573 {
3597 {
3601 }
3608 else
3610 }
3611 \f
3612 /* Given two ranges, see if we can merge them into one. Return 1 if we
3613 can, 0 if we can't. Set the output range into the specified parameters. */
3615 static int
3621 {
3625 tree tem;
3635 /* Make range 0 be the range that starts first, or ends last if they
3636 start at the same value. Swap them if it isn't. */
3639 || (lowequal
3642 {
3646 }
3648 /* Now flag two cases, whether the ranges are disjoint or whether the
3649 second range is totally subsumed in the first. Note that the tests
3650 below are simplified by the ones above. */
3656 /* We now have four cases, depending on whether we are including or
3657 excluding the two ranges. */
3659 {
3660 /* If they don't overlap, the result is false. If the second range
3661 is a subset it is the result. Otherwise, the range is from the start
3662 of the second to the end of the first. */
3667 else
3669 }
3672 {
3673 /* If they don't overlap, the result is the first range. If they are
3674 equal, the result is false. If the second range is a subset of the
3675 first, and the ranges begin at the same place, we go from just after
3676 the end of the first range to the end of the second. If the second
3677 range is not a subset of the first, or if it is a subset and both
3678 ranges end at the same place, the range starts at the start of the
3679 first range and ends just before the second range.
3680 Otherwise, we can't describe this as a single range. */
3686 {
3690 }
3692 {
3696 }
3697 else
3699 }
3702 {
3703 /* If they don't overlap, the result is the second range. If the second
3704 is a subset of the first, the result is false. Otherwise,
3705 the range starts just after the first range and ends at the
3706 end of the second. */
3711 else
3712 {
3716 }
3717 }
3719 else
3720 {
3721 /* The case where we are excluding both ranges. Here the complex case
3722 is if they don't overlap. In that case, the only time we have a
3723 range is if they are adjacent. If the second is a subset of the
3724 first, the result is the first. Otherwise, the range to exclude
3725 starts at the beginning of the first range and ends at the end of the
3726 second. */
3728 {
3735 else
3737 }
3740 else
3742 }
3746 }
3747 \f
3748 /* EXP is some logical combination of boolean tests. See if we can
3749 merge it into some range test. Return the new tree if so. */
3751 static tree
3753 tree exp;
3754 {
3761 tree tem;
3763 /* If this is an OR operation, invert both sides; we will invert
3764 again at the end. */
3768 /* If both expressions are the same, if we can merge the ranges, and we
3769 can build the range test, return it or it inverted. If one of the
3770 ranges is always true or always false, consider it to be the same
3771 expression as the other. */
3781 /* On machines where the branch cost is expensive, if this is a
3782 short-circuited branch and the underlying object on both sides
3783 is the same, make a non-short-circuit operation. */
3789 {
3790 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3791 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3792 which cases we can't do this. */
3801 {
3813 }
3814 }
3817 }
3818 \f
3819 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3820 bit value. Arrange things so the extra bits will be set to zero if and
3821 only if C is signed-extended to its full width. If MASK is nonzero,
3822 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3824 static tree
3826 tree c;
3829 tree mask;
3830 {
3833 tree temp;
3838 /* We work by getting just the sign bit into the low-order bit, then
3839 into the high-order bit, then sign-extend. We then XOR that value
3840 with C. */
3844 /* We must use a signed type in order to get an arithmetic right shift.
3845 However, we must also avoid introducing accidental overflows, so that
3846 a subsequent call to integer_zerop will work. Hence we must
3847 do the type conversion here. At this point, the constant is either
3848 zero or one, and the conversion to a signed type can never overflow.
3849 We could get an overflow if this conversion is done anywhere else. */
3857 /* If necessary, convert the type back to match the type of C. */
3862 }
3863 \f
3864 /* Find ways of folding logical expressions of LHS and RHS:
3865 Try to merge two comparisons to the same innermost item.
3866 Look for range tests like "ch >= '0' && ch <= '9'".
3867 Look for combinations of simple terms on machines with expensive branches
3868 and evaluate the RHS unconditionally.
3870 For example, if we have p->a == 2 && p->b == 4 and we can make an
3871 object large enough to span both A and B, we can do this with a comparison
3872 against the object ANDed with the a mask.
3874 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3875 operations to do this with one comparison.
3877 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3878 function and the one above.
3880 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3881 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3883 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3884 two operands.
3886 We return the simplified tree or 0 if no optimization is possible. */
3888 static tree
3892 {
3893 /* If this is the "or" of two comparisons, we can do something if
3894 the comparisons are NE_EXPR. If this is the "and", we can do something
3895 if the comparisons are EQ_EXPR. I.e.,
3896 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3898 WANTED_CODE is this operation code. For single bit fields, we can
3899 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3900 comparison for one-bit fields. */
3920 /* Start by getting the comparison codes. Fail if anything is volatile.
3921 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3922 it were surrounded with a NE_EXPR. */
3947 /* If the RHS can be evaluated unconditionally and its operands are
3948 simple, it wins to evaluate the RHS unconditionally on machines
3949 with expensive branches. In this case, this isn't a comparison
3950 that can be merged. Avoid doing this if the RHS is a floating-point
3951 comparison since those can trap. */
3959 /* See if the comparisons can be merged. Then get all the parameters for
3960 each side. */
3984 /* It must be true that the inner operation on the lhs of each
3985 comparison must be the same if we are to be able to do anything.
3986 Then see if we have constants. If not, the same must be true for
3987 the rhs's. */
3998 else
4001 /* If either comparison code is not correct for our logical operation,
4002 fail. However, we can convert a one-bit comparison against zero into
4003 the opposite comparison against that bit being set in the field. */
4007 {
4009 {
4010 /* Make the left operand unsigned, since we are only interested
4011 in the value of one bit. Otherwise we are doing the wrong
4012 thing below. */
4015 }
4016 else
4018 }
4020 /* This is analogous to the code for l_const above. */
4022 {
4024 {
4027 }
4028 else
4030 }
4032 /* See if we can find a mode that contains both fields being compared on
4033 the left. If we can't, fail. Otherwise, update all constants and masks
4034 to be relative to a field of that size. */
4039 volatilep);
4049 {
4052 }
4060 {
4068 {
4072 wanted_code == NE_EXPR
4074 }
4075 }
4077 {
4085 {
4089 wanted_code == NE_EXPR
4091 }
4092 }
4094 /* If the right sides are not constant, do the same for it. Also,
4095 disallow this optimization if a size or signedness mismatch occurs
4096 between the left and right sides. */
4098 {
4101 /* Make sure the two fields on the right
4102 correspond to the left without being swapped. */
4110 volatilep);
4120 {
4123 }
4130 /* Make a mask that corresponds to both fields being compared.
4131 Do this for both items being compared. If the operands are the
4132 same size and the bits being compared are in the same position
4133 then we can do this by masking both and comparing the masked
4134 results. */
4138 {
4150 }
4152 /* There is still another way we can do something: If both pairs of
4153 fields being compared are adjacent, we may be able to make a wider
4154 field containing them both.
4156 Note that we still must mask the lhs/rhs expressions. Furthermore,
4157 the mask must be shifted to account for the shift done by
4158 make_bit_field_ref. */
4163 {
4164 tree type;
4176 /* Convert to the smaller type before masking out unwanted bits. */
4179 {
4181 {
4185 }
4187 {
4191 }
4192 }
4201 }
4204 }
4206 /* Handle the case of comparisons with constants. If there is something in
4207 common between the masks, those bits of the constants must be the same.
4208 If not, the condition is always false. Test for this to avoid generating
4209 incorrect code below. */
4214 {
4216 {
4219 }
4220 else
4221 {
4224 }
4225 }
4227 /* Construct the expression we will return. First get the component
4228 reference we will make. Unless the mask is all ones the width of
4229 that field, perform the mask operation. Then compare with the
4230 merged constant. */
4240 }
4241 \f
4242 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4243 constant. */
4245 static tree
4247 tree t;
4248 {
4253 tree minmax_const;
4255 tree inner;
4265 /* If something does not permit us to optimize, return the original tree. */
4273 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4274 and GT_EXPR, doing the rest with recursive calls using logical
4275 simplifications. */
4277 {
4279 return
4283 return
4285 optimize_minmax_comparison
4287 optimize_minmax_comparison
4292 /* MAX (X, 0) == 0 -> X <= 0 */
4296 /* MAX (X, 0) == 5 -> X == 5 */
4300 /* MAX (X, 0) == -1 -> false */
4304 /* MIN (X, 0) == 0 -> X >= 0 */
4308 /* MIN (X, 0) == 5 -> false */
4311 else
4312 /* MIN (X, 0) == -1 -> X == -1 */
4317 /* MAX (X, 0) > 0 -> X > 0
4318 MAX (X, 0) > 5 -> X > 5 */
4322 /* MAX (X, 0) > -1 -> true */
4326 /* MIN (X, 0) > 0 -> false
4327 MIN (X, 0) > 5 -> false */
4330 else
4331 /* MIN (X, 0) > -1 -> X > -1 */
4336 }
4337 }
4338 \f
4339 /* T is an integer expression that is being multiplied, divided, or taken a
4340 modulus (CODE says which and what kind of divide or modulus) by a
4341 constant C. See if we can eliminate that operation by folding it with
4342 other operations already in T. WIDE_TYPE, if non-null, is a type that
4343 should be used for the computation if wider than our type.
4345 For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
4346 (X * 2) + (Y + 4). We must, however, be assured that either the original
4347 expression would not overflow or that overflow is undefined for the type
4348 in the language in question.
4350 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4351 the machine has a multiply-accumulate insn or that this is part of an
4352 addressing calculation.
4354 If we return a non-null expression, it is an equivalent form of the
4355 original computation, but need not be in the original type. */
4357 static tree
4359 tree t;
4360 tree c;
4362 tree wide_type;
4363 {
4373 /* Don't deal with constants of zero here; they confuse the code below. */
4383 /* Note that we need not handle conditional operations here since fold
4384 already handles those cases. So just do arithmetic here. */
4386 {
4388 /* For a constant, we can always simplify if we are a multiply
4389 or (for divide and modulus) if it is a multiple of our constant. */
4396 /* If op0 is an expression, and is unsigned, and the type is
4397 smaller than ctype, then we cannot widen the expression. */
4409 /* Pass the constant down and see if we can make a simplification. If
4410 we can, replace this expression with the inner simplification for
4411 possible later conversion to our or some other type. */
4423 /* If widening the type changes the signedness, then we can't perform
4424 this optimization as that changes the result. */
4428 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4431 {
4437 }
4447 /* If this has not been evaluated and the operand has no side effects,
4448 we can see if we can do something inside it and make a new one.
4449 Note that this test is overly conservative since we can do this
4450 if the only reason it had side effects is that it was another
4451 similar SAVE_EXPR, but that isn't worth bothering with. */
4454 wide_type)))
4459 /* If the second operand is constant, this is a multiplication
4460 or floor division, by a power of two, so we can treat it that
4461 way unless the multiplier or divisor overflows. */
4463 /* const_binop may not detect overflow correctly,
4464 so check for it explicitly here. */
4478 /* See if we can eliminate the operation on both sides. If we can, we
4479 can return a new PLUS or MINUS. If we can't, the only remaining
4480 cases where we can do anything are if the second operand is a
4481 constant. */
4486 /* If not multiplication, we can only do this if either operand
4487 is divisible by c. */
4493 /* If this was a subtraction, negate OP1 and set it to be an addition.
4494 This simplifies the logic below. */
4501 /* If either OP1 or C are negative, this optimization is not safe for
4502 some of the division and remainder types while for others we need
4503 to change the code. */
4505 {
4516 }
4518 /* If it's a multiply or a division/modulus operation of a multiple
4519 of our constant, do the operation and verify it doesn't overflow. */
4522 {
4526 }
4527 else
4530 /* If we have an unsigned type is not a sizetype, we cannot widen
4531 the operation since it will change the result if the original
4532 computation overflowed. */
4538 /* If we were able to eliminate our operation from the first side,
4539 apply our operation to the second side and reform the PLUS. */
4543 /* The last case is if we are a multiply. In that case, we can
4544 apply the distributive law to commute the multiply and addition
4545 if the multiplication of the constants doesn't overflow. */
4550 op1));
4555 /* We have a special case here if we are doing something like
4556 (C * 8) % 4 since we know that's zero. */
4563 /* ... fall through ... */
4567 /* If we can extract our operation from the LHS, do so and return a
4568 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4569 do something only if the second operand is a constant. */
4581 /* If these are the same operation types, we can associate them
4582 assuming no overflow. */
4589 /* If these operations "cancel" each other, we have the main
4590 optimizations of this pass, which occur when either constant is a
4591 multiple of the other, in which case we replace this with either an
4592 operation or CODE or TCODE.
4594 If we have an unsigned type that is not a sizetype, we canot do
4595 this since it will change the result if the original computation
4596 overflowed. */
4603 {
4614 }
4619 }
4622 }
4623 \f
4624 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4625 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4626 that we may sometimes modify the tree. */
4628 static tree
4630 tree t;
4631 tree s;
4632 {
4635 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4640 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4641 don't bother handling any other types. */
4643 {
4647 }
4652 {
4655 }
4658 }
4659 \f
4660 /* Return a node which has the indicated constant VALUE (either 0 or
4661 1), and is of the indicated TYPE. */
4663 static tree
4666 tree type;
4667 {
4672 integer_zero_node);
4673 else
4674 {
4679 }
4680 }
4682 /* Utility function for the following routine, to see how complex a nesting of
4683 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4684 we don't care (to avoid spending too much time on complex expressions.). */
4686 static int
4688 tree expr;
4690 {
4701 }
4703 /* Transform `a + (b ? x : y)' into `x ? (a + b) : (a + y)'.
4704 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4705 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4706 expression, and ARG to `a'. If COND_FIRST_P is non-zero, then the
4707 COND is the first argument to CODE; otherwise (as in the example
4708 given here), it is the second argument. TYPE is the type of the
4709 original expression. */
4711 static tree
4714 tree type;
4715 tree cond;
4716 tree arg;
4718 {
4722 /* In the end, we'll produce a COND_EXPR. Both arms of the
4723 conditional expression will be binary operations. The left-hand
4724 side of the expression to be executed if the condition is true
4725 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4726 of the expression to be executed if the condition is true will be
4727 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analagous --
4728 but apply to the expression to be executed if the conditional is
4729 false. */
4734 /* These are the codes to use for the left-hand side and right-hand
4735 side of the COND_EXPR. Normally, they are the same as CODE. */
4738 /* And these are the types of the expressions. */
4743 {
4747 }
4748 else
4749 {
4753 }
4756 {
4760 /* If this operand throws an expression, then it does not make
4761 sense to try to perform a logical or arithmetic operation
4762 involving it. Instead of building `a + throw 3' for example,
4763 we simply build `a, throw 3'. */
4765 {
4769 }
4771 {
4775 }
4776 }
4777 else
4778 {
4783 }
4785 /* If ARG is complex we want to make sure we only evaluate
4786 it once. Though this is only required if it is volatile, it
4787 might be more efficient even if it is not. However, if we
4788 succeed in folding one part to a constant, we do not need
4789 to make this SAVE_EXPR. Since we do this optimization
4790 primarily to see if we do end up with constant and this
4791 SAVE_EXPR interferes with later optimizations, suppressing
4792 it when we can is important.
4794 If we are not in a function, we can't make a SAVE_EXPR, so don't
4795 try to do so. Don't try to see if the result is a constant
4796 if an arm is a COND_EXPR since we get exponential behavior
4797 in that case. */
4804 {
4814 }
4827 else
4829 }
4831 \f
4832 /* Perform constant folding and related simplification of EXPR.
4833 The related simplifications include x*1 => x, x*0 => 0, etc.,
4834 and application of the associative law.
4835 NOP_EXPR conversions may be removed freely (as long as we
4836 are careful not to change the C type of the overall expression)
4837 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4838 but we can constant-fold them if they have constant operands. */
4840 tree
4842 tree expr;
4843 {
4846 tree tem;
4852 /* WINS will be nonzero when the switch is done
4853 if all operands are constant. */
4856 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4857 Likewise for a SAVE_EXPR that's already been evaluated. */
4861 /* Return right away if a constant. */
4865 #ifdef MAX_INTEGER_COMPUTATION_MODE
4867 #endif
4870 {
4871 tree subop;
4873 /* Special case for conversion ops that can have fixed point args. */
4876 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4882 else
4886 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4889 )
4890 /* Note that TREE_CONSTANT isn't enough:
4891 static var addresses are constant but we can't
4892 do arithmetic on them. */
4894 }
4896 {
4900 {
4902 tree subop;
4908 {
4909 /* Signedness matters here. Perhaps we can refine this
4910 later. */
4912 }
4913 else
4914 /* Strip any conversions that don't change the mode. */
4919 else
4923 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4926 )
4927 /* Note that TREE_CONSTANT isn't enough:
4928 static var addresses are constant but we can't
4929 do arithmetic on them. */
4936 }
4937 }
4939 /* If this is a commutative operation, and ARG0 is a constant, move it
4940 to ARG1 to reduce the number of tests below. */
4945 {
4950 }
4952 /* Now WINS is set as described above,
4953 ARG0 is the first operand of EXPR,
4954 and ARG1 is the second operand (if it has more than one operand).
4956 First check for cases where an arithmetic operation is applied to a
4957 compound, conditional, or comparison operation. Push the arithmetic
4958 operation inside the compound or conditional to see if any folding
4959 can then be done. Convert comparison to conditional for this purpose.
4960 The also optimizes non-constant cases that used to be done in
4961 expand_expr.
4963 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
4964 one of the operands is a comparison and the other is a comparison, a
4965 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4966 code below would make the expression more complex. Change it to a
4967 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
4968 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
4980 {
4990 }
4993 {
4998 {
5003 /* If this was a conversion, and all we did was to move into
5004 inside the COND_EXPR, bring it back out. But leave it if
5005 it is a conversion from integer to integer and the
5006 result precision is no wider than a word since such a
5007 conversion is cheap and may be optimized away by combine,
5008 while it couldn't if it were outside the COND_EXPR. Then return
5009 so we don't get into an infinite recursion loop taking the
5010 conversion out and then back in. */
5020 && (INTEGRAL_TYPE_P
5031 }
5036 }
5039 {
5052 return
5066 return
5069 }
5080 {
5095 /* Other kinds of FIX are not handled properly by fold_convert. */
5100 /* Handle cases of two conversions in a row. */
5103 {
5123 /* In addition to the cases of two conversions in a row
5124 handled below, if we are converting something to its own
5125 type via an object of identical or wider precision, neither
5126 conversion is needed. */
5132 /* Likewise, if the intermediate and final types are either both
5133 float or both integer, we don't need the middle conversion if
5134 it is wider than the final type and doesn't change the signedness
5135 (for integers). Avoid this if the final type is a pointer
5136 since then we sometimes need the inner conversion. Likewise if
5137 the outer has a precision not equal to the size of its mode. */
5147 /* If we have a sign-extension of a zero-extended value, we can
5148 replace that by a single zero-extension. */
5154 /* Two conversions in a row are not needed unless:
5155 - some conversion is floating-point (overstrict for now), or
5156 - the intermediate type is narrower than both initial and
5157 final, or
5158 - the intermediate type and innermost type differ in signedness,
5159 and the outermost type is wider than the intermediate, or
5160 - the initial type is a pointer type and the precisions of the
5161 intermediate and final types differ, or
5162 - the final type is a pointer type and the precisions of the
5163 initial and intermediate types differ. */
5177 }
5181 /* Detect assigning a bitfield. */
5184 {
5185 /* Don't leave an assignment inside a conversion
5186 unless assigning a bitfield. */
5189 /* First do the assignment, then return converted constant. */
5193 }
5195 {
5198 }
5203 {
5206 /* Fold an expression like: "foo"[2] */
5210 {
5214 }
5215 }
5221 {
5225 }
5234 {
5236 {
5238 HOST_WIDE_INT high;
5249 }
5252 }
5256 /* Convert - (a - b) to (b - a) for non-floating-point. */
5266 {
5268 {
5269 /* If the value is unsigned, then the absolute value is
5270 the same as the ordinary value. */
5273 /* Similarly, if the value is non-negative. */
5276 /* If the value is negative, then the absolute value is
5277 its negation. */
5278 else
5279 {
5281 HOST_WIDE_INT high;
5292 }
5293 }
5295 {
5299 }
5300 }
5327 {
5334 }
5340 /* A + (-B) -> A - B */
5343 /* (-A) + B -> B - A */
5347 {
5351 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5352 with a constant, and the two constants have no bits in common,
5353 we should treat this as a BIT_IOR_EXPR since this may produce more
5354 simplifications. */
5362 {
5365 }
5367 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5368 (plus (plus (mult) (mult)) (foo)) so that we can
5369 take advantage of the factoring cases below. */
5374 {
5379 else
5390 parg1));
5395 parg0));
5396 }
5399 {
5403 /* (A * C) + (B * C) -> (A+B) * C.
5404 We are most concerned about the case where C is a constant,
5405 but other combinations show up during loop reduction. Since
5406 it is not difficult, try all four possibilities. */
5423 /* No identical multiplicands; see if we can find a common
5424 power-of-two factor in non-power-of-two multiplies. This
5425 can help in multi-dimensional array access. */
5430 {
5435 /* Move min of absolute values to int11. */
5438 {
5442 }
5445 {
5450 }
5451 }
5456 same));
5457 }
5458 }
5459 /* In IEEE floating point, x+0 may not equal x. */
5464 /* x+(-0) equals x, even for IEEE. */
5469 bit_rotate:
5470 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5471 is a rotate of A by C1 bits. */
5472 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5473 is a rotate of A by B bits. */
5474 {
5483 {
5502 {
5510 TYPE_PRECISION
5515 ? LROTATE_EXPR
5518 }
5520 {
5528 TYPE_PRECISION
5533 ? LROTATE_EXPR
5536 }
5537 }
5538 }
5540 associate:
5541 /* In most languages, can't associate operations on floats through
5542 parentheses. Rather than remember where the parentheses were, we
5543 don't associate floats at all. It shouldn't matter much. However,
5544 associating multiplications is only very slightly inaccurate, so do
5545 that if -ffast-math is specified. */
5550 {
5553 /* Split both trees into variables, constants, and literals. Then
5554 associate each group together, the constants with literals,
5555 then the result with variables. This increases the chances of
5556 literals being recombined later and of generating relocatable
5557 expressions for the sum of a constant and literal. */
5561 /* Only do something if we found more than two objects. Otherwise,
5562 nothing has changed and we risk infinite recursion. */
5565 {
5571 }
5572 }
5574 binary:
5575 #if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
5582 {
5583 /* The return value should always have
5584 the same type as the original expression. */
5589 }
5593 /* A - (-B) -> A + B */
5596 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5598 return
5605 {
5611 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5612 about the case where C is a constant, just try one of the
5613 four possibilities. */
5623 }
5627 {
5628 /* Except with IEEE floating point, 0-x equals -x. */
5631 /* Except with IEEE floating point, x-0 equals x. */
5634 }
5636 /* Fold &x - &x. This can happen from &x.foo - &x.
5637 This is unsafe for certain floats even in non-IEEE formats.
5638 In IEEE, it is unsafe because it does wrong for NaNs.
5639 Also note that operand_equal_p is always false if an operand
5640 is volatile. */
5649 /* (-A) * (-B) -> A * B */
5655 {
5661 /* (a * (1 << b)) is (a << b) */
5676 }
5677 else
5678 {
5679 /* x*0 is 0, except for IEEE floating point. */
5684 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5685 However, ANSI says we can drop signals,
5686 so we can do this anyway. */
5689 /* x*2 is x+x */
5692 {
5695 }
5696 }
5700 bit_ior:
5709 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5711 This results in more efficient code for machines without a NAND
5712 instruction. Combine will canonicalize to the first form
5713 which will allow use of NAND instructions provided by the
5714 backend if they exist. */
5717 {
5722 }
5724 /* See if this can be simplified into a rotate first. If that
5725 is unsuccessful continue in the association code. */
5734 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5735 with a constant, and the two constants have no bits in common,
5736 we should treat this as a BIT_IOR_EXPR since this may produce more
5737 simplifications. */
5745 {
5748 }
5750 /* See if this can be simplified into a rotate first. If that
5751 is unsuccessful continue in the association code. */
5755 bit_and:
5763 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5766 {
5767 unsigned int prec
5774 }
5777 {
5778 unsigned int prec
5785 }
5787 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5789 This results in more efficient code for machines without a NOR
5790 instruction. Combine will canonicalize to the first form
5791 which will allow use of NOR instructions provided by the
5792 backend if they exist. */
5795 {
5800 }
5810 {
5814 }
5818 /* In most cases, do nothing with a divide by zero. */
5819 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
5820 #ifndef REAL_INFINITY
5823 #endif
5826 /* (-A) / (-B) -> A / B */
5831 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5832 However, ANSI says we can drop signals, so we can do this anyway. */
5836 /* If ARG1 is a constant, we can convert this to a multiply by the
5837 reciprocal. This does not have the same rounding properties,
5838 so only do this if -ffast-math. We can actually always safely
5839 do it if ARG1 is a power of two, but it's hard to tell if it is
5840 or not in a portable manner. */
5842 {
5847 /* Find the reciprocal if optimizing and the result is exact. */
5849 {
5850 REAL_VALUE_TYPE r;
5853 {
5856 }
5857 }
5858 }
5871 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5872 operation, EXACT_DIV_EXPR.
5874 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5875 At one time others generated faster code, it's not clear if they do
5876 after the last round to changes to the DIV code in expmed.c. */
5910 /* Since negative shift count is not well-defined,
5911 don't try to compute it in the compiler. */
5914 /* Rewrite an LROTATE_EXPR by a constant into an
5915 RROTATE_EXPR by a new constant. */
5917 {
5921 = const_binop
5928 }
5930 /* If we have a rotate of a bit operation with the rotate count and
5931 the second operand of the bit operation both constant,
5932 permute the two operations. */
5945 /* Two consecutive rotates adding up to the width of the mode can
5946 be ignored. */
5977 /* Note that the operand of this must be an int
5978 and its values must be 0 or 1.
5979 ("true" is a fixed value perhaps depending on the language,
5980 but we don't handle values other than 1 correctly yet.) */
5982 /* Avoid infinite recursion. */
5988 /* Note that the operands of this must be ints
5989 and their values must be 0 or 1.
5990 ("true" is a fixed value perhaps depending on the language.) */
5991 /* If first arg is constant zero, return it. */
5995 /* If either arg is constant true, drop it. */
5999 /* Preserve sequence points. */
6002 /* If second arg is constant zero, result is zero, but first arg
6003 must be evaluated. */
6006 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6007 case will be handled here. */
6011 truth_andor:
6012 /* We only do these simplifications if we are optimizing. */
6016 /* Check for things like (A || B) && (A || C). We can convert this
6017 to A || (B && C). Note that either operator can be any of the four
6018 truth and/or operations and the transformation will still be
6019 valid. Also note that we only care about order for the
6020 ANDIF and ORIF operators. If B contains side effects, this
6021 might change the truth-value of A. */
6028 {
6048 /* This case if tricky because we must either have commutative
6049 operators or else A10 must not have side-effects. */
6055 a01));
6056 }
6058 /* See if we can build a range comparison. */
6062 /* Check for the possibility of merging component references. If our
6063 lhs is another similar operation, try to merge its rhs with our
6064 rhs. Then try to merge our lhs and rhs. */
6076 /* Note that the operands of this must be ints
6077 and their values must be 0 or true.
6078 ("true" is a fixed value perhaps depending on the language.) */
6079 /* If first arg is constant true, return it. */
6083 /* If either arg is constant zero, drop it. */
6087 /* Preserve sequence points. */
6090 /* If second arg is constant true, result is true, but we must
6091 evaluate first arg. */
6094 /* Likewise for first arg, but note this only occurs here for
6095 TRUTH_OR_EXPR. */
6101 /* If either arg is constant zero, drop it. */
6106 /* If either arg is constant true, this is a logical inversion. */
6120 {
6121 /* (-a) CMP (-b) -> b CMP a */
6126 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6128 return
6134 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6135 /* a CMP (-0) -> a CMP 0 */
6140 }
6142 /* If one arg is a constant integer, put it last. */
6145 {
6152 }
6154 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6155 First, see if one arg is constant; find the constant arg
6156 and the other one. */
6157 {
6167 {
6168 /* This optimization is invalid for ordered comparisons
6169 if CONST+INCR overflows or if foo+incr might overflow.
6170 This optimization is invalid for floating point due to rounding.
6171 For pointer types we assume overflow doesn't happen. */
6175 {
6176 tree newconst
6180 /* Do not overwrite the current varop to be a preincrement,
6181 create a new node so that we won't confuse our caller who
6182 might create trees and throw them away, reusing the
6183 arguments that they passed to build. This shows up in
6184 the THEN or ELSE parts of ?: being postincrements. */
6189 /* If VAROP is a reference to a bitfield, we must mask
6190 the constant by the width of the field. */
6194 {
6195 int size
6197 (TREE_OPERAND
6201 tree folded_compare;
6203 /* First check whether the comparison would come out
6204 always the same. If we don't do that we would
6205 change the meaning with the masking. */
6209 else
6212 constop));
6227 mask)));
6228 }
6234 }
6235 }
6237 {
6241 {
6242 tree newconst
6246 /* Do not overwrite the current varop to be a predecrement,
6247 create a new node so that we won't confuse our caller who
6248 might create trees and throw them away, reusing the
6249 arguments that they passed to build. This shows up in
6250 the THEN or ELSE parts of ?: being postdecrements. */
6258 {
6259 int size
6261 (TREE_OPERAND
6265 tree folded_compare;
6270 else
6273 constop));
6288 mask)));
6289 }
6295 }
6296 }
6297 }
6299 /* Change X >= CST to X > (CST - 1) if CST is positive. */
6303 {
6305 {
6320 }
6321 }
6323 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6324 a MINUS_EXPR of a constant, we can convert it into a comparison with
6325 a revised constant as long as no overflow occurs. */
6337 /* Similarly for a NEGATE_EXPR. */
6346 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6347 for !=. Don't do this for ordered comparisons due to overflow. */
6353 /* If we are widening one operand of an integer comparison,
6354 see if the other operand is similarly being widened. Perhaps we
6355 can do the comparison in the narrower type. */
6365 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6366 constant, we can simplify it. */
6373 /* If we are comparing an ABS_EXPR with a constant, we can
6374 convert all the cases into explicit comparisons, but they may
6375 well not be faster than doing the ABS and one comparison.
6376 But ABS (X) <= C is a range comparison, which becomes a subtraction
6377 and a comparison, and is probably faster. */
6389 /* If this is an EQ or NE comparison with zero and ARG0 is
6390 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6391 two operations, but the latter can be done in one less insn
6392 on machines that have only two-operand insns or on which a
6393 constant cannot be the first operand. */
6396 {
6399 return
6407 integer_one_node)),
6408 arg1));
6411 return
6419 integer_one_node)),
6420 arg1));
6421 }
6423 /* If this is an NE or EQ comparison of zero against the result of a
6424 signed MOD operation whose second operand is a power of 2, make
6425 the MOD operation unsigned since it is simpler and equivalent. */
6434 {
6441 }
6443 /* If this is an NE comparison of zero with an AND of one, remove the
6444 comparison since the AND will give the correct value. */
6450 /* If we have (A & C) == C where C is a power of 2, convert this into
6451 (A & C) != 0. Similarly for NE_EXPR. */
6459 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6460 and similarly for >= into !=. */
6476 return
6483 /* Simplify comparison of something with itself. (For IEEE
6484 floating-point, we can only do some of these simplifications.) */
6486 {
6488 {
6499 /* For NE, we can only do this simplification if integer. */
6502 /* ... fall through ... */
6508 }
6509 }
6511 /* An unsigned comparison against 0 can be simplified. */
6516 {
6518 {
6530 arg0);
6534 arg0);
6537 }
6538 }
6540 /* Comparisons with the highest or lowest possible integer of
6541 the specified size will have known values and an unsigned
6542 <= 0x7fffffff can be simplified. */
6543 {
6551 {
6557 {
6561 arg0);
6569 arg0);
6576 }
6583 {
6587 arg0);
6595 arg0);
6602 }
6608 /* signed_type does not work on pointer types. */
6612 {
6616 arg0),
6618 integer_zero_node)));
6622 arg0),
6624 integer_zero_node)));
6628 }
6629 }
6630 }
6632 /* If we are comparing an expression that just has comparisons
6633 of two integer values, arithmetic expressions of those comparisons,
6634 and constants, we can simplify it. There are only three cases
6635 to check: the two values can either be equal, the first can be
6636 greater, or the second can be greater. Fold the expression for
6637 those three values. Since each value must be 0 or 1, we have
6638 eight possibilities, each of which corresponds to the constant 0
6639 or 1 or one of the six possible comparisons.
6641 This handles common cases like (a > b) == 0 but also handles
6642 expressions like ((x > y) - (y > x)) > 0, which supposedly
6643 occur in macroized code. */
6646 {
6651 /* Don't handle degenerate cases here; they should already
6652 have been handled anyway. */
6661 {
6665 /* We can't just pass T to eval_subst in case cval1 or cval2
6666 was the same as ARG1. */
6668 tree high_result
6671 arg1));
6672 tree equal_result
6675 arg1));
6676 tree low_result
6679 arg1));
6681 /* All three of these results should be 0 or 1. Confirm they
6682 are. Then use those values to select the proper code
6683 to use. */
6691 {
6692 /* Make a 3-bit mask with the high-order bit being the
6693 value for `>', the next for '=', and the low for '<'. */
6697 {
6699 /* Always false. */
6720 /* Always true. */
6722 }
6727 else
6729 }
6730 }
6731 }
6733 /* If this is a comparison of a field, we may be able to simplify it. */
6737 /* Handle the constant case even without -O
6738 to make sure the warnings are given. */
6740 {
6743 }
6745 /* If this is a comparison of complex values and either or both sides
6746 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6747 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6748 This may prevent needless evaluations. */
6755 {
6768 type,
6771 }
6773 /* From here on, the only cases we handle are when the result is
6774 known to be a constant.
6776 To compute GT, swap the arguments and do LT.
6777 To compute GE, do LT and invert the result.
6778 To compute LE, swap the arguments, do LT and invert the result.
6779 To compute NE, do EQ and invert the result.
6781 Therefore, the code below must handle only EQ and LT. */
6784 {
6787 }
6789 /* Note that it is safe to invert for real values here because we
6790 will check below in the one case that it matters. */
6795 {
6798 }
6800 /* Compute a result for LT or EQ if args permit;
6801 otherwise return T. */
6803 {
6806 else
6811 }
6814 /* Assume a nonexplicit constant cannot equal an explicit one,
6815 since such code would be undefined anyway.
6816 Exception: on sysvr4, using #pragma weak,
6817 a label can come out as 0. */
6824 #endif
6825 /* Two real constants can be compared explicitly. */
6827 {
6828 /* If either operand is a NaN, the result is false with two
6829 exceptions: First, an NE_EXPR is true on NaNs, but that case
6830 is already handled correctly since we will be inverting the
6831 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6832 or a GE_EXPR into a LT_EXPR, we must return true so that it
6833 will be inverted into false. */
6843 else
6847 }
6861 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6862 so all simple results must be passed through pedantic_non_lvalue. */
6864 return pedantic_non_lvalue
6869 /* If the second operand is zero, invert the comparison and swap
6870 the second and third operands. Likewise if the second operand
6871 is constant and the third is not or if the third operand is
6872 equivalent to the first operand of the comparison. */
6880 {
6881 /* See if this can be inverted. If it can't, possibly because
6882 it was a floating-point inequality comparison, don't do
6883 anything. */
6887 {
6891 /* arg1 should be the first argument of the new T. */
6894 }
6895 }
6897 /* If we have A op B ? A : C, we may be able to convert this to a
6898 simpler expression, depending on the operation and the values
6899 of B and C. IEEE floating point prevents this though,
6900 because A or B might be -0.0 or a NaN. */
6908 {
6914 /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
6915 depending on the comparison operation. */
6922 {
6924 return
6925 pedantic_non_lvalue
6927 negate_expr
6929 arg1))));
6937 return pedantic_non_lvalue
6944 return pedantic_non_lvalue
6948 arg1)))));
6951 }
6953 /* If this is A != 0 ? A : 0, this is simply A. For ==, it is
6954 always zero. */
6957 {
6962 }
6964 /* If this is A op B ? A : B, this is either A, B, min (A, B),
6965 or max (A, B), depending on the operation. */
6969 {
6974 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
6979 {
6986 /* In C++ a ?: expression can be an lvalue, so put the
6987 operand which will be used if they are equal first
6988 so that we can convert this back to the
6989 corresponding COND_EXPR. */
6990 return pedantic_non_lvalue
6999 return pedantic_non_lvalue
7008 }
7009 }
7011 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7012 we might still be able to simplify this. For example,
7013 if C1 is one less or one more than C2, this might have started
7014 out as a MIN or MAX and been transformed by this function.
7015 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7021 {
7023 /* We can replace A with C1 in this case. */
7030 /* If C1 is C2 + 1, this is min(A, C2). */
7035 return pedantic_non_lvalue
7040 /* If C1 is C2 - 1, this is min(A, C2). */
7045 return pedantic_non_lvalue
7050 /* If C1 is C2 - 1, this is max(A, C2). */
7055 return pedantic_non_lvalue
7060 /* If C1 is C2 + 1, this is max(A, C2). */
7065 return pedantic_non_lvalue
7072 }
7073 }
7075 /* If the second operand is simpler than the third, swap them
7076 since that produces better jump optimization results. */
7082 {
7083 /* See if this can be inverted. If it can't, possibly because
7084 it was a floating-point inequality comparison, don't do
7085 anything. */
7089 {
7093 /* arg1 should be the first argument of the new T. */
7096 }
7097 }
7099 /* Convert A ? 1 : 0 to simply A. */
7102 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7103 call to fold will try to move the conversion inside
7104 a COND, which will recurse. In that case, the COND_EXPR
7105 is probably the best choice, so leave it alone. */
7109 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7110 operation is simply A & 2. */
7124 /* When pedantic, a compound expression can be neither an lvalue
7125 nor an integer constant expression. */
7128 /* Don't let (0, 0) be null pointer constant. */
7170 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7171 appropriate. */
7176 {
7180 tree arg01;
7191 {
7205 arg01));
7206 }
7209 }
7212 /* Check for a built-in function. */
7217 {
7221 }
7227 }
7229 /* Determine if first argument is a multiple of second argument. Return 0 if
7230 it is not, or we cannot easily determined it to be.
7232 An example of the sort of thing we care about (at this point; this routine
7233 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7234 fold cases do now) is discovering that
7236 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7238 is a multiple of
7240 SAVE_EXPR (J * 8)
7242 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7244 This code also handles discovering that
7246 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7248 is a multiple of 8 so we don't have to worry about dealing with a
7249 possible remainder.
7251 Note that we *look* inside a SAVE_EXPR only to determine how it was
7252 calculated; it is not safe for fold to do much of anything else with the
7253 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7254 at run time. For example, the latter example above *cannot* be implemented
7255 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7256 evaluation time of the original SAVE_EXPR is not necessarily the same at
7257 the time the new expression is evaluated. The only optimization of this
7258 sort that would be valid is changing
7260 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7262 divided by 8 to
7264 SAVE_EXPR (I) * SAVE_EXPR (J)
7266 (where the same SAVE_EXPR (J) is used in the original and the
7267 transformed version). */
7269 static int
7271 tree type;
7272 tree top;
7273 tree bottom;
7274 {
7282 {
7294 {
7298 /* const_binop may not detect overflow correctly,
7299 so check for it explicitly here. */
7308 }
7312 /* Can't handle conversions from non-integral or wider integral type. */
7318 /* .. fall through ... */
7334 }
7335 }
7337 /* Return true if `t' is known to be non-negative. */
7339 int
7341 tree t;
7342 {
7344 {
7357 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7359 else
7360 /* We don't know sign of `t', so be conservative and return false. */
7362 }
7363 }
7365 /* Return true if `r' is known to be non-negative.
7366 Only handles constants at the moment. */
7368 int
7370 rtx r;
7371 {
7373 {
7384 /* These are always nonnegative. */
7389 }
7390 }