| blob | e25b67fc76d72a9730a6865972e99aaaaa5ca3ce |
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 GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 02111-1307, USA. */
22 /*@@ This file should be rewritten to use an arbitrary precision
23 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
24 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
25 @@ The routines that translate from the ap rep should
26 @@ warn if precision et. al. is lost.
27 @@ This would also make life easier when this technology is used
28 @@ for cross-compilers. */
30 /* The entry points in this file are fold, size_int_wide, size_binop
31 and force_fit_type.
33 fold takes a tree as argument and returns a simplified tree.
35 size_binop takes a tree code for an arithmetic operation
36 and two operands that are trees, and produces a tree for the
37 result, assuming the type comes from `sizetype'.
39 size_int takes an integer value, and creates a tree constant
40 with type from `sizetype'.
42 force_fit_type takes a constant and prior overflow indicator, and
43 forces the value to fit the type. It returns an overflow indicator. */
58 HOST_WIDE_INT));
61 HOST_WIDE_INT *));
62 #ifndef REAL_ARITHMETIC
64 #endif
89 HOST_WIDE_INT *,
109 static tree fold_binary_op_with_conditional_arg
112 #ifndef BRANCH_COST
113 #define BRANCH_COST 1
114 #endif
116 #if defined(HOST_EBCDIC)
117 /* bit 8 is significant in EBCDIC */
118 #define CHARMASK 0xff
119 #else
120 #define CHARMASK 0x7f
121 #endif
123 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
124 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
125 and SUM1. Then this yields nonzero if overflow occurred during the
126 addition.
128 Overflow occurs if A and B have the same sign, but A and SUM differ in
129 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
130 sign. */
131 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
132 \f
133 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
134 We do that by representing the two-word integer in 4 words, with only
135 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
136 number. The value of the word is LOWPART + HIGHPART * BASE. */
138 #define LOWPART(x) \
139 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
140 #define HIGHPART(x) \
141 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
142 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
144 /* Unpack a two-word integer into 4 words.
145 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
146 WORDS points to the array of HOST_WIDE_INTs. */
148 static void
152 HOST_WIDE_INT hi;
153 {
158 }
160 /* Pack an array of 4 words into a two-word integer.
161 WORDS points to the array of words.
162 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
164 static void
169 {
172 }
173 \f
174 /* Make the integer constant T valid for its type by setting to 0 or 1 all
175 the bits in the constant that don't belong in the type.
177 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
178 nonzero, a signed overflow has already occurred in calculating T, so
179 propagate it.
181 Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
182 if it exists. */
184 int
186 tree t;
188 {
190 HOST_WIDE_INT high;
194 {
195 #ifdef CHECK_FLOAT_VALUE
197 overflow);
198 #endif
200 }
210 else
213 /* First clear all bits that are beyond the type's precision. */
216 ;
220 else
221 {
225 }
227 /* Unsigned types do not suffer sign extension or overflow unless they
228 are a sizetype. */
234 /* If the value's sign bit is set, extend the sign. */
242 {
243 /* Value is negative:
244 set to 1 all the bits that are outside this type's precision. */
248 else
249 {
253 }
254 }
256 /* Return nonzero if signed overflow occurred. */
257 return
260 }
261 \f
262 /* Add two doubleword integers with doubleword result.
263 Each argument is given as two `HOST_WIDE_INT' pieces.
264 One argument is L1 and H1; the other, L2 and H2.
265 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
267 int
273 {
275 HOST_WIDE_INT h;
283 }
285 /* Negate a doubleword integer with doubleword result.
286 Return nonzero if the operation overflows, assuming it's signed.
287 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
288 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
290 int
293 HOST_WIDE_INT h1;
296 {
298 {
302 }
303 else
304 {
308 }
309 }
310 \f
311 /* Multiply two doubleword integers with doubleword result.
312 Return nonzero if the operation overflows, assuming it's signed.
313 Each argument is given as two `HOST_WIDE_INT' pieces.
314 One argument is L1 and H1; the other, L2 and H2.
315 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
317 int
323 {
338 {
341 {
343 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
345 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
349 }
351 }
355 /* Check for overflow by calculating the top half of the answer in full;
356 it should agree with the low half's sign bit. */
359 {
362 }
364 {
367 }
369 }
370 \f
371 /* Shift the doubleword integer in L1, H1 left by COUNT places
372 keeping only PREC bits of result.
373 Shift right if COUNT is negative.
374 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
375 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
377 void
385 {
387 {
390 }
392 #ifdef SHIFT_COUNT_TRUNCATED
395 #endif
398 {
399 /* Shifting by the host word size is undefined according to the
400 ANSI standard, so we must handle this as a special case. */
403 }
405 {
408 }
409 else
410 {
414 }
415 }
417 /* Shift the doubleword integer in L1, H1 right by COUNT places
418 keeping only PREC bits of result. COUNT must be positive.
419 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
420 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
422 void
430 {
433 signmask = (arith
437 #ifdef SHIFT_COUNT_TRUNCATED
440 #endif
443 {
444 /* Shifting by the host word size is undefined according to the
445 ANSI standard, so we must handle this as a special case. */
448 }
450 {
454 }
455 else
456 {
461 }
462 }
463 \f
464 /* Rotate the doubleword integer in L1, H1 left by COUNT places
465 keeping only PREC bits of result.
466 Rotate right if COUNT is negative.
467 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
469 void
476 {
488 }
490 /* Rotate the doubleword integer in L1, H1 left by COUNT places
491 keeping only PREC bits of result. COUNT must be positive.
492 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
494 void
501 {
513 }
514 \f
515 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
516 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
517 CODE is a tree code for a kind of division, one of
518 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
519 or EXACT_DIV_EXPR
520 It controls how the quotient is rounded to an integer.
521 Return nonzero if the operation overflows.
522 UNS nonzero says do unsigned division. */
524 int
531 HOST_WIDE_INT hnum_orig;
533 HOST_WIDE_INT hden_orig;
536 {
552 /* calculate quotient sign and convert operands to unsigned. */
554 {
556 {
558 /* (minimum integer) / (-1) is the only overflow case. */
562 }
564 {
567 }
568 }
573 /* This unsigned division rounds toward zero. */
576 }
580 /* hden != 0 already checked. */
585 }
595 /* Special code for when the divisor < BASE. */
597 {
598 /* hnum != 0 already checked. */
600 {
604 }
605 }
606 else
607 {
608 /* Full double precision division,
609 with thanks to Don Knuth's "Seminumerical Algorithms". */
613 /* Find the highest non-zero divisor digit. */
616 {
619 }
621 /* Insure that the first digit of the divisor is at least BASE/2.
622 This is required by the quotient digit estimation algorithm. */
629 {
633 }
638 {
643 }
644 }
648 /* Main loop */
650 {
651 /* Guess the next quotient digit, quo_est, by dividing the first
652 two remaining dividend digits by the high order quotient digit.
653 quo_est is never low and is at most 2 high. */
660 else
663 /* Refine quo_est so it's usually correct, and at most one high. */
668 quo_est--;
670 /* Try QUO_EST as the quotient digit, by multiplying the
671 divisor by QUO_EST and subtracting from the remaining dividend.
672 Keep in mind that QUO_EST is the I - 1st digit. */
676 {
682 }
684 /* If quo_est was high by one, then num[i] went negative and
685 we need to correct things. */
687 {
688 quo_est--;
691 {
695 }
698 }
700 /* Store the quotient digit. */
702 }
703 }
707 finish_up:
708 /* if result is negative, make it so. */
712 /* compute trial remainder: rem = num - (quo * den) */
718 {
727 {
728 /* quo = quo - 1; */
731 }
732 else
739 {
742 }
743 else
749 {
755 /* Get absolute values */
761 /* If (2 * abs (lrem) >= abs (lden)) */
770 {
772 /* quo = quo - 1; */
775 else
776 /* quo = quo + 1; */
779 }
780 else
782 }
787 }
789 /* compute true remainder: rem = num - (quo * den) */
794 }
795 \f
796 #ifndef REAL_ARITHMETIC
797 /* Effectively truncate a real value to represent the nearest possible value
798 in a narrower mode. The result is actually represented in the same data
799 type as the argument, but its value is usually different.
801 A trap may occur during the FP operations and it is the responsibility
802 of the calling function to have a handler established. */
804 REAL_VALUE_TYPE
807 REAL_VALUE_TYPE arg;
808 {
810 }
812 #if TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
814 /* Check for infinity in an IEEE double precision number. */
816 int
818 REAL_VALUE_TYPE x;
819 {
820 /* The IEEE 64-bit double format. */
822 REAL_VALUE_TYPE d;
839 {
844 }
845 else
846 {
851 }
852 }
854 /* Check whether an IEEE double precision number is a NaN. */
856 int
858 REAL_VALUE_TYPE x;
859 {
860 /* The IEEE 64-bit double format. */
862 REAL_VALUE_TYPE d;
879 {
884 }
885 else
886 {
891 }
892 }
894 /* Check for a negative IEEE double precision number. */
896 int
898 REAL_VALUE_TYPE x;
899 {
900 /* The IEEE 64-bit double format. */
902 REAL_VALUE_TYPE d;
919 {
922 }
923 else
924 {
927 }
928 }
931 /* Let's assume other float formats don't have infinity.
932 (This can be overridden by redefining REAL_VALUE_ISINF.) */
934 int
936 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
937 {
939 }
941 /* Let's assume other float formats don't have NaNs.
942 (This can be overridden by redefining REAL_VALUE_ISNAN.) */
944 int
946 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
947 {
949 }
951 /* Let's assume other float formats don't have minus zero.
952 (This can be overridden by redefining REAL_VALUE_NEGATIVE.) */
954 int
956 REAL_VALUE_TYPE x;
957 {
959 }
962 /* Try to change R into its exact multiplicative inverse in machine mode
963 MODE. Return nonzero function value if successful. */
964 struct exact_real_inverse_args
965 {
969 };
971 static void
973 PTR p;
974 {
981 union
982 {
985 }
987 #ifdef CHECK_FLOAT_VALUE
989 #endif
991 /* Set array index to the less significant bits in the unions, depending
992 on the endian-ness of the host doubles. */
993 #if HOST_FLOAT_FORMAT == VAX_FLOAT_FORMAT \
994 || HOST_FLOAT_FORMAT == IBM_FLOAT_FORMAT
995 # define K 2
996 #else
997 # define K (2 * HOST_FLOAT_WORDS_BIG_ENDIAN)
998 #endif
1000 /* Domain check the argument. */
1005 #ifdef REAL_INFINITY
1008 #endif
1010 /* Compute the reciprocal and check for numerical exactness.
1011 It is unnecessary to check all the significand bits to determine
1012 whether X is a power of 2. If X is not, then it is impossible for
1013 the bottom half significand of both X and 1/X to be all zero bits.
1014 Hence we ignore the data structure of the top half and examine only
1015 the low order bits of the two significands. */
1020 /* Truncate to the required mode and range-check the result. */
1022 #ifdef CHECK_FLOAT_VALUE
1026 #endif
1028 /* Fail if truncation changed the value. */
1032 #ifdef REAL_INFINITY
1035 #endif
1037 /* Output the reciprocal and return success flag. */
1042 fail:
1046 #undef K
1047 }
1050 int
1054 {
1057 /* Disable if insufficient information on the data structure. */
1058 #if HOST_FLOAT_FORMAT == UNKNOWN_FLOAT_FORMAT
1060 #endif
1062 /* Usually disable if bounds checks are not reliable. */
1072 }
1074 /* Convert C99 hexadecimal floating point string constant S. Return
1075 real value type in mode MODE. This function uses the host computer's
1076 floating point arithmetic when there is no REAL_ARITHMETIC. */
1078 REAL_VALUE_TYPE
1082 {
1083 REAL_VALUE_TYPE ip;
1102 /* Sign, if any, comes first. */
1105 {
1108 }
1110 /* The string is supposed to start with 0x or 0X . */
1112 {
1116 else
1118 }
1119 else
1129 {
1132 {
1138 else
1142 {
1148 }
1149 else
1150 {
1151 /* Record nonzero lost bits. */
1155 }
1157 }
1159 {
1162 }
1165 {
1168 /* Sign of exponent. */
1170 {
1173 }
1175 /* Value of exponent.
1176 The exponent field is a decimal integer. */
1178 {
1181 }
1184 /* F suffix is ambiguous in the significand part
1185 so it must appear after the decimal exponent field. */
1187 {
1191 }
1192 }
1195 {
1198 }
1199 else
1201 }
1203 /* Abort if last character read was not legitimate. */
1208 /* There must be either one decimal point or one p. */
1216 /* Normalize. */
1219 {
1223 }
1225 /* Leave a high guard bit for carry-out. */
1227 {
1232 }
1235 {
1239 }
1242 {
1246 }
1249 {
1250 /* Keep 24 bits precision, bits 0x7fffff80.
1251 Rounding bit is 0x40. */
1255 {
1258 }
1260 }
1261 else
1262 {
1263 /* We need real.c to do long double formats, so here default
1264 to double precision. */
1265 #if HOST_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
1266 /* IEEE double.
1267 Keep 53 bits precision, bits 0x7fffffff fffffc00.
1268 Rounding bit is low word 0x200. */
1271 {
1273 {
1277 }
1278 }
1280 #else
1281 /* Assume it's a VAX with 56-bit significand,
1282 bits 0x7fffffff ffffff80. */
1285 {
1287 {
1291 }
1292 }
1294 #endif
1295 }
1299 /* Apply shifts and exponent value as power of 2. */
1305 }
1308 \f
1309 /* Given T, an expression, return the negation of T. Allow for T to be
1310 null, in which case return null. */
1312 static tree
1314 tree t;
1315 {
1316 tree type;
1317 tree tem;
1326 {
1339 /* - (A - B) -> B - A */
1349 }
1352 }
1353 \f
1354 /* Split a tree IN into a constant, literal and variable parts that could be
1355 combined with CODE to make IN. "constant" means an expression with
1356 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1357 commutative arithmetic operation. Store the constant part into *CONP,
1358 the literal in &LITP and return the variable part. If a part isn't
1359 present, set it to null. If the tree does not decompose in this way,
1360 return the entire tree as the variable part and the other parts as null.
1362 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1363 case, we negate an operand that was subtracted. If NEGATE_P is true, we
1364 are negating all of IN.
1366 If IN is itself a literal or constant, return it as appropriate.
1368 Note that we do not guarantee that any of the three values will be the
1369 same type as IN, but they will have the same signedness and mode. */
1371 static tree
1373 tree in;
1377 {
1383 /* Strip any conversions that don't change the machine mode or signedness. */
1390 /* We can associate addition and subtraction together (even
1391 though the C standard doesn't say so) for integers because
1392 the value is not affected. For reals, the value might be
1393 affected, so we can't. */
1396 {
1402 /* First see if either of the operands is a literal, then a constant. */
1413 /* If we haven't dealt with either operand, this is not a case we can
1414 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1419 else
1422 /* Now do any needed negations. */
1426 }
1429 else
1433 {
1437 }
1440 }
1442 /* Re-associate trees split by the above function. T1 and T2 are either
1443 expressions to associate or null. Return the new expression, if any. If
1444 we build an operation, do it in TYPE and with CODE, except if CODE is a
1445 MINUS_EXPR, in which case we use PLUS_EXPR since split_tree will already
1446 have taken care of the negations. */
1448 static tree
1452 tree type;
1453 {
1462 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1463 try to fold this since we will have infinite recursion. But do
1464 deal with any NEGATE_EXPRs. */
1467 {
1474 else
1476 }
1479 }
1480 \f
1481 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1482 to produce a new constant.
1484 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1486 static tree
1491 {
1495 HOST_WIDE_INT hi;
1497 HOST_WIDE_INT garbageh;
1498 tree t;
1501 int is_sizetype
1512 {
1532 /* It's unclear from the C standard whether shifts can overflow.
1533 The following code ignores overflow; perhaps a C standard
1534 interpretation ruling is needed. */
1564 /* This is a shortcut for a common special case. */
1569 {
1575 }
1577 /* ... fall through ... */
1581 {
1584 }
1587 {
1590 }
1597 /* This is a shortcut for a common special case. */
1602 {
1607 }
1609 /* ... fall through ... */
1625 else
1631 else
1637 }
1639 /* If this is for a sizetype, can be represented as one (signed)
1640 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1641 constants. */
1647 else
1648 {
1651 }
1654 = ((notrunc
1661 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1662 So check if force_fit_type truncated the value. */
1673 }
1675 /* Define input and output argument for const_binop_1. */
1676 struct cb_args
1677 {
1682 };
1684 /* Do the real arithmetic for const_binop while protected by a
1685 float overflow handler. */
1687 static void
1689 PTR data;
1690 {
1692 REAL_VALUE_TYPE value;
1694 #ifdef REAL_ARITHMETIC
1696 #else
1698 {
1712 #ifndef REAL_INFINITY
1715 #endif
1730 }
1733 args->t
1736 }
1738 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1739 constant. We assume ARG1 and ARG2 have the same data type, or at least
1740 are the same kind of constant and the same machine mode.
1742 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1744 static tree
1749 {
1756 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
1758 {
1759 REAL_VALUE_TYPE d1;
1760 REAL_VALUE_TYPE d2;
1762 tree t;
1768 /* If either operand is a NaN, just return it. Otherwise, set up
1769 for floating-point trap; we return an overflow. */
1775 /* Setup input for const_binop_1() */
1782 /* Receive output from const_binop_1. */
1784 else
1785 {
1786 /* We got an exception from const_binop_1. */
1789 }
1799 }
1802 {
1808 tree t;
1811 {
1831 notrunc),
1837 notrunc));
1841 {
1842 tree magsquared
1846 notrunc);
1849 const_binop
1854 notrunc),
1856 notrunc),
1857 notrunc),
1859 const_binop
1864 notrunc),
1866 notrunc),
1867 notrunc),
1869 }
1874 }
1876 }
1878 }
1880 /* These are the hash table functions for the hash table of INTEGER_CST
1881 nodes of a sizetype. */
1883 /* Return the hash code code X, an INTEGER_CST. */
1885 static hashval_t
1888 {
1894 }
1896 /* Return non-zero if the value represented by *X (an INTEGER_CST tree node)
1897 is the same as that given by *Y, which is the same. */
1899 static int
1903 {
1911 }
1912 \f
1913 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1914 bits are given by NUMBER and of the sizetype represented by KIND. */
1916 tree
1918 HOST_WIDE_INT number;
1920 {
1922 }
1924 /* Likewise, but the desired type is specified explicitly. */
1926 tree
1928 HOST_WIDE_INT number;
1929 tree type;
1930 {
1936 {
1941 }
1943 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1944 hash table, we return the value from the hash table. Otherwise, we
1945 place that in the hash table and make a new node for the next time. */
1954 {
1960 }
1961 else
1963 }
1965 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1966 is a tree code. The type of the result is taken from the operands.
1967 Both must be the same type integer type and it must be a size type.
1968 If the operands are constant, so is the result. */
1970 tree
1974 {
1981 /* Handle the special case of two integer constants faster. */
1983 {
1984 /* And some specific cases even faster than that. */
1993 /* Handle general case of two integer constants. */
1995 }
2001 }
2003 /* Given two values, either both of sizetype or both of bitsizetype,
2004 compute the difference between the two values. Return the value
2005 in signed type corresponding to the type of the operands. */
2007 tree
2010 {
2012 tree ctype;
2018 /* If the type is already signed, just do the simple thing. */
2025 /* If either operand is not a constant, do the conversions to the signed
2026 type and subtract. The hardware will do the right thing with any
2027 overflow in the subtraction. */
2032 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
2033 Otherwise, subtract the other way, convert to CTYPE (we know that can't
2034 overflow) and negate (which can't either). Special-case a result
2035 of zero while we're here. */
2040 else
2043 }
2044 \f
2045 /* This structure is used to communicate arguments to fold_convert_1. */
2046 struct fc_args
2047 {
2051 };
2053 /* Function to convert floating-point constants, protected by floating
2054 point exception handler. */
2056 static void
2058 PTR data;
2059 {
2065 }
2067 /* Given T, a tree representing type conversion of ARG1, a constant,
2068 return a constant tree representing the result of conversion. */
2070 static tree
2072 tree t;
2073 tree arg1;
2074 {
2079 {
2081 {
2082 /* If we would build a constant wider than GCC supports,
2083 leave the conversion unfolded. */
2087 /* If we are trying to make a sizetype for a small integer, use
2088 size_int to pick up cached types to reduce duplicate nodes. */
2094 /* Given an integer constant, make new constant with new type,
2095 appropriately sign-extended or truncated. */
2099 /* Indicate an overflow if (1) ARG1 already overflowed,
2100 or (2) force_fit_type indicates an overflow.
2101 Tell force_fit_type that an overflow has already occurred
2102 if ARG1 is a too-large unsigned value and T is signed.
2103 But don't indicate an overflow if converting a pointer. */
2113 }
2114 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2116 {
2117 /* Don't initialize these, use assignments.
2118 Initialized local aggregates don't work on old compilers. */
2119 REAL_VALUE_TYPE x;
2120 REAL_VALUE_TYPE l;
2121 REAL_VALUE_TYPE u;
2132 /* See if X will be in range after truncation towards 0.
2133 To compensate for truncation, move the bounds away from 0,
2134 but reject if X exactly equals the adjusted bounds. */
2135 #ifdef REAL_ARITHMETIC
2139 #else
2140 l--;
2142 u++;
2143 #endif
2144 /* If X is a NaN, use zero instead and show we have an overflow.
2145 Otherwise, range check. */
2149 && !no_upper_bound
2153 #ifndef REAL_ARITHMETIC
2154 {
2156 HOST_WIDE_INT half_word
2165 {
2168 }
2169 else
2174 }
2175 #else
2176 {
2180 }
2181 #endif
2187 }
2190 }
2192 {
2193 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2198 {
2202 {
2206 }
2208 /* Setup input for fold_convert_1() */
2213 {
2214 /* Receive output from fold_convert_1() */
2216 }
2217 else
2218 {
2219 /* We got an exception from fold_convert_1() */
2222 }
2229 }
2230 }
2233 }
2234 \f
2235 /* Return an expr equal to X but certainly not valid as an lvalue. */
2237 tree
2239 tree x;
2240 {
2241 tree result;
2243 /* These things are certainly not lvalues. */
2254 }
2256 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2257 Zero means allow extended lvalues. */
2261 /* When pedantic, return an expr equal to X but certainly not valid as a
2262 pedantic lvalue. Otherwise, return X. */
2264 tree
2266 tree x;
2267 {
2270 else
2272 }
2273 \f
2274 /* Given a tree comparison code, return the code that is the logical inverse
2275 of the given code. It is not safe to do this for floating-point
2276 comparisons, except for NE_EXPR and EQ_EXPR. */
2278 static enum tree_code
2281 {
2283 {
2298 }
2299 }
2301 /* Similar, but return the comparison that results if the operands are
2302 swapped. This is safe for floating-point. */
2304 static enum tree_code
2307 {
2309 {
2323 }
2324 }
2326 /* Return nonzero if CODE is a tree code that represents a truth value. */
2328 static int
2331 {
2336 }
2337 \f
2338 /* Return nonzero if two operands are necessarily equal.
2339 If ONLY_CONST is non-zero, only return non-zero for constants.
2340 This function tests whether the operands are indistinguishable;
2341 it does not test whether they are equal using C's == operation.
2342 The distinction is important for IEEE floating point, because
2343 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2344 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
2346 int
2350 {
2351 /* If both types don't have the same signedness, then we can't consider
2352 them equal. We must check this before the STRIP_NOPS calls
2353 because they may change the signedness of the arguments. */
2361 /* This is needed for conversions and for COMPONENT_REF.
2362 Might as well play it safe and always test this. */
2368 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2369 We don't care about side effects in that case because the SAVE_EXPR
2370 takes care of that for us. In all other cases, two expressions are
2371 equal if they have no side effects. If we have two identical
2372 expressions with side effects that should be treated the same due
2373 to the only side effects being identical SAVE_EXPR's, that will
2374 be detected in the recursive calls below. */
2380 /* Next handle constant cases, those for which we can return 1 even
2381 if ONLY_CONST is set. */
2384 {
2398 only_const)
2400 only_const));
2413 }
2419 {
2421 /* Two conversions are equal only if signedness and modes match. */
2437 /* For commutative ops, allow the other order. */
2450 /* If either of the pointer (or reference) expressions we are dereferencing
2451 contain a side effect, these cannot be equal. */
2457 {
2479 }
2488 }
2489 }
2490 \f
2491 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2492 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2494 When in doubt, return 0. */
2496 static int
2499 tree other;
2500 {
2512 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2513 and see if the inner values are the same. This removes any
2514 signedness comparison, which doesn't matter here. */
2521 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2522 actual comparison operand, ARG0.
2524 First throw away any conversions to wider types
2525 already present in the operands. */
2534 {
2537 /* Make sure shorter operand is extended the right way
2538 to match the longer operand. */
2541 primarg1);
2545 }
2548 }
2549 \f
2550 /* See if ARG is an expression that is either a comparison or is performing
2551 arithmetic on comparisons. The comparisons must only be comparing
2552 two different values, which will be stored in *CVAL1 and *CVAL2; if
2553 they are non-zero it means that some operands have already been found.
2554 No variables may be used anywhere else in the expression except in the
2555 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2556 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2558 If this is true, return 1. Otherwise, return zero. */
2560 static int
2562 tree arg;
2565 {
2569 /* We can handle some of the 'e' cases here. */
2579 {
2580 /* If we've already found a CVAL1 or CVAL2, this expression is
2581 two complex to handle. */
2587 }
2590 {
2613 /* First see if we can handle the first operand, then the second. For
2614 the second operand, we know *CVAL1 can't be zero. It must be that
2615 one side of the comparison is each of the values; test for the
2616 case where this isn't true by failing if the two operands
2617 are the same. */
2626 ;
2630 ;
2631 else
2635 ;
2639 ;
2640 else
2647 }
2648 }
2649 \f
2650 /* ARG is a tree that is known to contain just arithmetic operations and
2651 comparisons. Evaluate the operations in the tree substituting NEW0 for
2652 any occurrence of OLD0 as an operand of a comparison and likewise for
2653 NEW1 and OLD1. */
2655 static tree
2657 tree arg;
2659 {
2664 /* We can handle some of the 'e' cases here. */
2672 {
2687 {
2704 }
2705 /* fall through - ??? */
2708 {
2712 /* We need to check both for exact equality and tree equality. The
2713 former will be true if the operand has a side-effect. In that
2714 case, we know the operand occurred exactly once. */
2727 }
2731 }
2732 }
2733 \f
2734 /* Return a tree for the case when the result of an expression is RESULT
2735 converted to TYPE and OMITTED was previously an operand of the expression
2736 but is now not needed (e.g., we folded OMITTED * 0).
2738 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2739 the conversion of RESULT to TYPE. */
2741 static tree
2744 {
2751 }
2753 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2755 static tree
2758 {
2765 }
2766 \f
2767 /* Return a simplified tree node for the truth-negation of ARG. This
2768 never alters ARG itself. We assume that ARG is an operation that
2769 returns a truth value (0 or 1). */
2771 tree
2773 tree arg;
2774 {
2781 /* If this is a comparison, we can simply invert it, except for
2782 floating-point non-equality comparisons, in which case we just
2783 enclose a TRUTH_NOT_EXPR around what we have. */
2786 {
2788 && !flag_unsafe_math_optimizations
2792 else
2795 }
2798 {
2813 /* Here we can invert either operand. We invert the first operand
2814 unless the second operand is a TRUTH_NOT_EXPR in which case our
2815 result is the XOR of the first operand with the inside of the
2816 negation of the second operand. */
2821 else
2876 }
2880 }
2882 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2883 operands are another bit-wise operation with a common input. If so,
2884 distribute the bit operations to save an operation and possibly two if
2885 constants are involved. For example, convert
2886 (A | B) & (A | C) into A | (B & C)
2887 Further simplification will occur if B and C are constants.
2889 If this optimization cannot be done, 0 will be returned. */
2891 static tree
2894 tree type;
2896 {
2897 tree common;
2907 {
2911 }
2913 {
2917 }
2919 {
2923 }
2925 {
2929 }
2930 else
2935 }
2936 \f
2937 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2938 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2940 static tree
2942 tree inner;
2943 tree type;
2946 {
2953 }
2955 /* Optimize a bit-field compare.
2957 There are two cases: First is a compare against a constant and the
2958 second is a comparison of two items where the fields are at the same
2959 bit position relative to the start of a chunk (byte, halfword, word)
2960 large enough to contain it. In these cases we can avoid the shift
2961 implicit in bitfield extractions.
2963 For constants, we emit a compare of the shifted constant with the
2964 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2965 compared. For two fields at the same position, we do the ANDs with the
2966 similar mask and compare the result of the ANDs.
2968 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2969 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2970 are the left and right operands of the comparison, respectively.
2972 If the optimization described above can be done, we return the resulting
2973 tree. Otherwise we return zero. */
2975 static tree
2978 tree compare_type;
2980 {
2990 tree mask;
2991 tree offset;
2993 /* Get all the information about the extractions being done. If the bit size
2994 if the same as the size of the underlying object, we aren't doing an
2995 extraction at all and so can do nothing. We also don't want to
2996 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2997 then will no longer be able to replace it. */
3005 {
3006 /* If this is not a constant, we can only do something if bit positions,
3007 sizes, and signedness are the same. */
3015 }
3017 /* See if we can find a mode to refer to this field. We should be able to,
3018 but fail if we can't. */
3027 /* Set signed and unsigned types of the precision of this mode for the
3028 shifts below. */
3032 /* Compute the bit position and size for the new reference and our offset
3033 within it. If the new reference is the same size as the original, we
3034 won't optimize anything, so return zero. */
3044 /* Make the mask to be used against the extracted field. */
3054 /* If not comparing with constant, just rework the comparison
3055 and return. */
3060 mask),
3064 mask));
3066 /* Otherwise, we are handling the constant case. See if the constant is too
3067 big for the field. Warn and return a tree of for 0 (false) if so. We do
3068 this not only for its own sake, but to avoid having to test for this
3069 error case below. If we didn't, we might generate wrong code.
3071 For unsigned fields, the constant shifted right by the field length should
3072 be all zero. For signed fields, the high-order bits should agree with
3073 the sign bit. */
3076 {
3080 {
3086 }
3087 }
3088 else
3089 {
3093 {
3099 }
3100 }
3102 /* Single-bit compares should always be against zero. */
3104 {
3107 }
3109 /* Make a new bitfield reference, shift the constant over the
3110 appropriate number of bits and mask it with the computed mask
3111 (in case this was a signed field). If we changed it, make a new one. */
3114 {
3117 }
3127 rhs);
3128 }
3129 \f
3130 /* Subroutine for fold_truthop: decode a field reference.
3132 If EXP is a comparison reference, we return the innermost reference.
3134 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3135 set to the starting bit number.
3137 If the innermost field can be completely contained in a mode-sized
3138 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3140 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3141 otherwise it is not changed.
3143 *PUNSIGNEDP is set to the signedness of the field.
3145 *PMASK is set to the mask used. This is either contained in a
3146 BIT_AND_EXPR or derived from the width of the field.
3148 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3150 Return 0 if this is not a component reference or is one that we can't
3151 do anything with. */
3153 static tree
3156 tree exp;
3162 {
3165 tree unsigned_type;
3169 /* All the optimizations using this function assume integer fields.
3170 There are problems with FP fields since the type_for_size call
3171 below can fail for, e.g., XFmode. */
3178 {
3184 }
3193 /* Compute the mask to access the bitfield. */
3203 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3211 }
3213 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
3214 bit positions. */
3216 static int
3218 tree mask;
3220 {
3223 tree tmask;
3228 return
3235 }
3237 /* Subroutine for fold_truthop: determine if an operand is simple enough
3238 to be evaluated unconditionally. */
3240 static int
3242 tree exp;
3243 {
3244 /* Strip any conversions that don't change the machine mode. */
3256 /* Don't regard global variables as simple. They may be
3257 allocated in ways unknown to the compiler (shared memory,
3258 #pragma weak, etc). */
3261 /* Loading a static variable is unduly expensive, but global
3262 registers aren't expensive. */
3264 }
3265 \f
3266 /* The following functions are subroutines to fold_range_test and allow it to
3267 try to change a logical combination of comparisons into a range test.
3269 For example, both
3270 X == 2 || X == 3 || X == 4 || X == 5
3271 and
3272 X >= 2 && X <= 5
3273 are converted to
3274 (unsigned) (X - 2) <= 3
3276 We describe each set of comparisons as being either inside or outside
3277 a range, using a variable named like IN_P, and then describe the
3278 range with a lower and upper bound. If one of the bounds is omitted,
3279 it represents either the highest or lowest value of the type.
3281 In the comments below, we represent a range by two numbers in brackets
3282 preceded by a "+" to designate being inside that range, or a "-" to
3283 designate being outside that range, so the condition can be inverted by
3284 flipping the prefix. An omitted bound is represented by a "-". For
3285 example, "- [-, 10]" means being outside the range starting at the lowest
3286 possible value and ending at 10, in other words, being greater than 10.
3287 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3288 always false.
3290 We set up things so that the missing bounds are handled in a consistent
3291 manner so neither a missing bound nor "true" and "false" need to be
3292 handled using a special case. */
3294 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3295 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3296 and UPPER1_P are nonzero if the respective argument is an upper bound
3297 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3298 must be specified for a comparison. ARG1 will be converted to ARG0's
3299 type if both are specified. */
3301 static tree
3304 tree type;
3307 {
3308 tree tem;
3312 /* If neither arg represents infinity, do the normal operation.
3313 Else, if not a comparison, return infinity. Else handle the special
3314 comparison rules. Note that most of the cases below won't occur, but
3315 are handled for consistency. */
3318 {
3323 }
3328 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3329 for neither. In real maths, we cannot assume open ended ranges are
3330 the same. But, this is computer arithmetic, where numbers are finite.
3331 We can therefore make the transformation of any unbounded range with
3332 the value Z, Z being greater than any representable number. This permits
3333 us to treat unbounded ranges as equal. */
3337 {
3358 }
3361 }
3362 \f
3363 /* Given EXP, a logical expression, set the range it is testing into
3364 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3365 actually being tested. *PLOW and *PHIGH will be made of the same type
3366 as the returned expression. If EXP is not a comparison, we will most
3367 likely not be returning a useful value and range. */
3369 static tree
3371 tree exp;
3374 {
3381 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3382 and see if we can refine the range. Some of the cases below may not
3383 happen, but it doesn't seem worth worrying about this. We "continue"
3384 the outer loop when we've changed something; otherwise we "break"
3385 the switch, which will "break" the while. */
3390 {
3394 {
3405 }
3407 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3408 lose a cast by accident. */
3413 {
3420 /* We can only do something if the range is testing for zero
3421 and if the second operand is an integer constant. Note that
3422 saying something is "in" the range we make is done by
3423 complementing IN_P since it will set in the initial case of
3424 being not equal to zero; "out" is leaving it alone. */
3431 {
3452 }
3456 /* If this is an unsigned comparison, we also know that EXP is
3457 greater than or equal to zero. We base the range tests we make
3458 on that fact, so we record it here so we can parse existing
3459 range tests. */
3461 {
3464 NULL_TREE))
3469 /* If the high bound is missing, but we
3470 have a low bound, reverse the range so
3471 it goes from zero to the low bound minus 1. */
3473 {
3478 }
3479 }
3483 /* (-x) IN [a,b] -> x in [-b, -a] */
3493 /* ~ X -> -X - 1 */
3502 /* If EXP is signed, any overflow in the computation is undefined,
3503 so we don't worry about it so long as our computations on
3504 the bounds don't overflow. For unsigned, overflow is defined
3505 and this is exactly the right thing. */
3514 /* Check for an unsigned range which has wrapped around the maximum
3515 value thus making n_high < n_low, and normalize it. */
3517 {
3523 /* If the range is of the form +/- [ x+1, x ], we won't
3524 be able to normalize it. But then, it represents the
3525 whole range or the empty set, so make it
3526 +/- [ -, - ]. */
3530 else
3532 }
3533 else
3556 /* If we're converting from an unsigned to a signed type,
3557 we will be doing the comparison as unsigned. The tests above
3558 have already verified that LOW and HIGH are both positive.
3560 So we have to make sure that the original unsigned value will
3561 be interpreted as positive. */
3563 {
3565 tree high_positive;
3567 /* A range without an upper bound is, naturally, unbounded.
3568 Since convert would have cropped a very large value, use
3569 the max value for the destination type. */
3570 high_positive
3578 /* If the low bound is specified, "and" the range with the
3579 range for which the original unsigned value will be
3580 positive. */
3582 {
3586 high_positive))
3590 }
3591 else
3592 {
3593 /* Otherwise, "or" the range with the range of the input
3594 that will be interpreted as negative. */
3598 high_positive))
3602 }
3603 }
3611 }
3614 }
3616 /* If EXP is a constant, we can evaluate whether this is true or false. */
3618 {
3625 }
3629 }
3630 \f
3631 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3632 type, TYPE, return an expression to test if EXP is in (or out of, depending
3633 on IN_P) the range. */
3635 static tree
3637 tree type;
3638 tree exp;
3641 {
3665 {
3669 }
3676 else
3678 }
3679 \f
3680 /* Given two ranges, see if we can merge them into one. Return 1 if we
3681 can, 0 if we can't. Set the output range into the specified parameters. */
3683 static int
3689 {
3693 tree tem;
3703 /* Make range 0 be the range that starts first, or ends last if they
3704 start at the same value. Swap them if it isn't. */
3707 || (lowequal
3710 {
3714 }
3716 /* Now flag two cases, whether the ranges are disjoint or whether the
3717 second range is totally subsumed in the first. Note that the tests
3718 below are simplified by the ones above. */
3724 /* We now have four cases, depending on whether we are including or
3725 excluding the two ranges. */
3727 {
3728 /* If they don't overlap, the result is false. If the second range
3729 is a subset it is the result. Otherwise, the range is from the start
3730 of the second to the end of the first. */
3735 else
3737 }
3740 {
3741 /* If they don't overlap, the result is the first range. If they are
3742 equal, the result is false. If the second range is a subset of the
3743 first, and the ranges begin at the same place, we go from just after
3744 the end of the first range to the end of the second. If the second
3745 range is not a subset of the first, or if it is a subset and both
3746 ranges end at the same place, the range starts at the start of the
3747 first range and ends just before the second range.
3748 Otherwise, we can't describe this as a single range. */
3754 {
3758 }
3760 {
3764 }
3765 else
3767 }
3770 {
3771 /* If they don't overlap, the result is the second range. If the second
3772 is a subset of the first, the result is false. Otherwise,
3773 the range starts just after the first range and ends at the
3774 end of the second. */
3779 else
3780 {
3784 }
3785 }
3787 else
3788 {
3789 /* The case where we are excluding both ranges. Here the complex case
3790 is if they don't overlap. In that case, the only time we have a
3791 range is if they are adjacent. If the second is a subset of the
3792 first, the result is the first. Otherwise, the range to exclude
3793 starts at the beginning of the first range and ends at the end of the
3794 second. */
3796 {
3803 else
3805 }
3808 else
3810 }
3814 }
3815 \f
3816 /* EXP is some logical combination of boolean tests. See if we can
3817 merge it into some range test. Return the new tree if so. */
3819 static tree
3821 tree exp;
3822 {
3829 tree tem;
3831 /* If this is an OR operation, invert both sides; we will invert
3832 again at the end. */
3836 /* If both expressions are the same, if we can merge the ranges, and we
3837 can build the range test, return it or it inverted. If one of the
3838 ranges is always true or always false, consider it to be the same
3839 expression as the other. */
3849 /* On machines where the branch cost is expensive, if this is a
3850 short-circuited branch and the underlying object on both sides
3851 is the same, make a non-short-circuit operation. */
3857 {
3858 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3859 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3860 which cases we can't do this. */
3869 {
3881 }
3882 }
3885 }
3886 \f
3887 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3888 bit value. Arrange things so the extra bits will be set to zero if and
3889 only if C is signed-extended to its full width. If MASK is nonzero,
3890 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3892 static tree
3894 tree c;
3897 tree mask;
3898 {
3901 tree temp;
3906 /* We work by getting just the sign bit into the low-order bit, then
3907 into the high-order bit, then sign-extend. We then XOR that value
3908 with C. */
3912 /* We must use a signed type in order to get an arithmetic right shift.
3913 However, we must also avoid introducing accidental overflows, so that
3914 a subsequent call to integer_zerop will work. Hence we must
3915 do the type conversion here. At this point, the constant is either
3916 zero or one, and the conversion to a signed type can never overflow.
3917 We could get an overflow if this conversion is done anywhere else. */
3925 /* If necessary, convert the type back to match the type of C. */
3930 }
3931 \f
3932 /* Find ways of folding logical expressions of LHS and RHS:
3933 Try to merge two comparisons to the same innermost item.
3934 Look for range tests like "ch >= '0' && ch <= '9'".
3935 Look for combinations of simple terms on machines with expensive branches
3936 and evaluate the RHS unconditionally.
3938 For example, if we have p->a == 2 && p->b == 4 and we can make an
3939 object large enough to span both A and B, we can do this with a comparison
3940 against the object ANDed with the a mask.
3942 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3943 operations to do this with one comparison.
3945 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3946 function and the one above.
3948 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3949 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3951 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3952 two operands.
3954 We return the simplified tree or 0 if no optimization is possible. */
3956 static tree
3960 {
3961 /* If this is the "or" of two comparisons, we can do something if
3962 the comparisons are NE_EXPR. If this is the "and", we can do something
3963 if the comparisons are EQ_EXPR. I.e.,
3964 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3966 WANTED_CODE is this operation code. For single bit fields, we can
3967 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3968 comparison for one-bit fields. */
3988 /* Start by getting the comparison codes. Fail if anything is volatile.
3989 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3990 it were surrounded with a NE_EXPR. */
4015 /* If the RHS can be evaluated unconditionally and its operands are
4016 simple, it wins to evaluate the RHS unconditionally on machines
4017 with expensive branches. In this case, this isn't a comparison
4018 that can be merged. Avoid doing this if the RHS is a floating-point
4019 comparison since those can trap. */
4027 /* See if the comparisons can be merged. Then get all the parameters for
4028 each side. */
4052 /* It must be true that the inner operation on the lhs of each
4053 comparison must be the same if we are to be able to do anything.
4054 Then see if we have constants. If not, the same must be true for
4055 the rhs's. */
4066 else
4069 /* If either comparison code is not correct for our logical operation,
4070 fail. However, we can convert a one-bit comparison against zero into
4071 the opposite comparison against that bit being set in the field. */
4075 {
4077 {
4078 /* Make the left operand unsigned, since we are only interested
4079 in the value of one bit. Otherwise we are doing the wrong
4080 thing below. */
4083 }
4084 else
4086 }
4088 /* This is analogous to the code for l_const above. */
4090 {
4092 {
4095 }
4096 else
4098 }
4100 /* See if we can find a mode that contains both fields being compared on
4101 the left. If we can't, fail. Otherwise, update all constants and masks
4102 to be relative to a field of that size. */
4107 volatilep);
4117 {
4120 }
4128 {
4136 {
4140 wanted_code == NE_EXPR
4142 }
4143 }
4145 {
4153 {
4157 wanted_code == NE_EXPR
4159 }
4160 }
4162 /* If the right sides are not constant, do the same for it. Also,
4163 disallow this optimization if a size or signedness mismatch occurs
4164 between the left and right sides. */
4166 {
4169 /* Make sure the two fields on the right
4170 correspond to the left without being swapped. */
4178 volatilep);
4188 {
4191 }
4198 /* Make a mask that corresponds to both fields being compared.
4199 Do this for both items being compared. If the operands are the
4200 same size and the bits being compared are in the same position
4201 then we can do this by masking both and comparing the masked
4202 results. */
4206 {
4218 }
4220 /* There is still another way we can do something: If both pairs of
4221 fields being compared are adjacent, we may be able to make a wider
4222 field containing them both.
4224 Note that we still must mask the lhs/rhs expressions. Furthermore,
4225 the mask must be shifted to account for the shift done by
4226 make_bit_field_ref. */
4231 {
4232 tree type;
4244 /* Convert to the smaller type before masking out unwanted bits. */
4247 {
4249 {
4253 }
4255 {
4259 }
4260 }
4269 }
4272 }
4274 /* Handle the case of comparisons with constants. If there is something in
4275 common between the masks, those bits of the constants must be the same.
4276 If not, the condition is always false. Test for this to avoid generating
4277 incorrect code below. */
4282 {
4284 {
4287 }
4288 else
4289 {
4292 }
4293 }
4295 /* Construct the expression we will return. First get the component
4296 reference we will make. Unless the mask is all ones the width of
4297 that field, perform the mask operation. Then compare with the
4298 merged constant. */
4308 }
4309 \f
4310 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4311 constant. */
4313 static tree
4315 tree t;
4316 {
4321 tree minmax_const;
4323 tree inner;
4333 /* If something does not permit us to optimize, return the original tree. */
4341 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4342 and GT_EXPR, doing the rest with recursive calls using logical
4343 simplifications. */
4345 {
4347 return
4351 return
4353 optimize_minmax_comparison
4355 optimize_minmax_comparison
4360 /* MAX (X, 0) == 0 -> X <= 0 */
4364 /* MAX (X, 0) == 5 -> X == 5 */
4368 /* MAX (X, 0) == -1 -> false */
4372 /* MIN (X, 0) == 0 -> X >= 0 */
4376 /* MIN (X, 0) == 5 -> false */
4379 else
4380 /* MIN (X, 0) == -1 -> X == -1 */
4385 /* MAX (X, 0) > 0 -> X > 0
4386 MAX (X, 0) > 5 -> X > 5 */
4390 /* MAX (X, 0) > -1 -> true */
4394 /* MIN (X, 0) > 0 -> false
4395 MIN (X, 0) > 5 -> false */
4398 else
4399 /* MIN (X, 0) > -1 -> X > -1 */
4404 }
4405 }
4406 \f
4407 /* T is an integer expression that is being multiplied, divided, or taken a
4408 modulus (CODE says which and what kind of divide or modulus) by a
4409 constant C. See if we can eliminate that operation by folding it with
4410 other operations already in T. WIDE_TYPE, if non-null, is a type that
4411 should be used for the computation if wider than our type.
4413 For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
4414 (X * 2) + (Y + 4). We must, however, be assured that either the original
4415 expression would not overflow or that overflow is undefined for the type
4416 in the language in question.
4418 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4419 the machine has a multiply-accumulate insn or that this is part of an
4420 addressing calculation.
4422 If we return a non-null expression, it is an equivalent form of the
4423 original computation, but need not be in the original type. */
4425 static tree
4427 tree t;
4428 tree c;
4430 tree wide_type;
4431 {
4441 /* Don't deal with constants of zero here; they confuse the code below. */
4451 /* Note that we need not handle conditional operations here since fold
4452 already handles those cases. So just do arithmetic here. */
4454 {
4456 /* For a constant, we can always simplify if we are a multiply
4457 or (for divide and modulus) if it is a multiple of our constant. */
4464 /* If op0 is an expression, and is unsigned, and the type is
4465 smaller than ctype, then we cannot widen the expression. */
4477 /* Pass the constant down and see if we can make a simplification. If
4478 we can, replace this expression with the inner simplification for
4479 possible later conversion to our or some other type. */
4491 /* If widening the type changes the signedness, then we can't perform
4492 this optimization as that changes the result. */
4496 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4499 {
4505 }
4515 /* If this has not been evaluated and the operand has no side effects,
4516 we can see if we can do something inside it and make a new one.
4517 Note that this test is overly conservative since we can do this
4518 if the only reason it had side effects is that it was another
4519 similar SAVE_EXPR, but that isn't worth bothering with. */
4522 wide_type)))
4523 {
4530 }
4534 /* If the second operand is constant, this is a multiplication
4535 or floor division, by a power of two, so we can treat it that
4536 way unless the multiplier or divisor overflows. */
4538 /* const_binop may not detect overflow correctly,
4539 so check for it explicitly here. */
4553 /* See if we can eliminate the operation on both sides. If we can, we
4554 can return a new PLUS or MINUS. If we can't, the only remaining
4555 cases where we can do anything are if the second operand is a
4556 constant. */
4561 /* If not multiplication, we can only do this if either operand
4562 is divisible by c. */
4568 /* If this was a subtraction, negate OP1 and set it to be an addition.
4569 This simplifies the logic below. */
4576 /* If either OP1 or C are negative, this optimization is not safe for
4577 some of the division and remainder types while for others we need
4578 to change the code. */
4580 {
4588 }
4590 /* If it's a multiply or a division/modulus operation of a multiple
4591 of our constant, do the operation and verify it doesn't overflow. */
4594 {
4598 }
4599 else
4602 /* If we have an unsigned type is not a sizetype, we cannot widen
4603 the operation since it will change the result if the original
4604 computation overflowed. */
4610 /* If we were able to eliminate our operation from the first side,
4611 apply our operation to the second side and reform the PLUS. */
4615 /* The last case is if we are a multiply. In that case, we can
4616 apply the distributive law to commute the multiply and addition
4617 if the multiplication of the constants doesn't overflow. */
4622 op1));
4627 /* We have a special case here if we are doing something like
4628 (C * 8) % 4 since we know that's zero. */
4635 /* ... fall through ... */
4639 /* If we can extract our operation from the LHS, do so and return a
4640 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4641 do something only if the second operand is a constant. */
4653 /* If these are the same operation types, we can associate them
4654 assuming no overflow. */
4661 /* If these operations "cancel" each other, we have the main
4662 optimizations of this pass, which occur when either constant is a
4663 multiple of the other, in which case we replace this with either an
4664 operation or CODE or TCODE.
4666 If we have an unsigned type that is not a sizetype, we canot do
4667 this since it will change the result if the original computation
4668 overflowed. */
4675 {
4686 }
4691 }
4694 }
4695 \f
4696 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4697 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4698 that we may sometimes modify the tree. */
4700 static tree
4702 tree t;
4703 tree s;
4704 {
4707 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4712 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4713 don't bother handling any other types. */
4715 {
4719 }
4724 {
4727 }
4730 }
4731 \f
4732 /* Return a node which has the indicated constant VALUE (either 0 or
4733 1), and is of the indicated TYPE. */
4735 static tree
4738 tree type;
4739 {
4744 integer_zero_node);
4745 else
4746 {
4751 }
4752 }
4754 /* Utility function for the following routine, to see how complex a nesting of
4755 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4756 we don't care (to avoid spending too much time on complex expressions.). */
4758 static int
4760 tree expr;
4762 {
4773 }
4775 /* Transform `a + (b ? x : y)' into `x ? (a + b) : (a + y)'.
4776 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4777 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4778 expression, and ARG to `a'. If COND_FIRST_P is non-zero, then the
4779 COND is the first argument to CODE; otherwise (as in the example
4780 given here), it is the second argument. TYPE is the type of the
4781 original expression. */
4783 static tree
4786 tree type;
4787 tree cond;
4788 tree arg;
4790 {
4794 /* In the end, we'll produce a COND_EXPR. Both arms of the
4795 conditional expression will be binary operations. The left-hand
4796 side of the expression to be executed if the condition is true
4797 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4798 of the expression to be executed if the condition is true will be
4799 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analagous --
4800 but apply to the expression to be executed if the conditional is
4801 false. */
4806 /* These are the codes to use for the left-hand side and right-hand
4807 side of the COND_EXPR. Normally, they are the same as CODE. */
4810 /* And these are the types of the expressions. */
4815 {
4819 }
4820 else
4821 {
4825 }
4828 {
4832 /* If this operand throws an expression, then it does not make
4833 sense to try to perform a logical or arithmetic operation
4834 involving it. Instead of building `a + throw 3' for example,
4835 we simply build `a, throw 3'. */
4837 {
4841 }
4843 {
4847 }
4848 }
4849 else
4850 {
4855 }
4857 /* If ARG is complex we want to make sure we only evaluate
4858 it once. Though this is only required if it is volatile, it
4859 might be more efficient even if it is not. However, if we
4860 succeed in folding one part to a constant, we do not need
4861 to make this SAVE_EXPR. Since we do this optimization
4862 primarily to see if we do end up with constant and this
4863 SAVE_EXPR interferes with later optimizations, suppressing
4864 it when we can is important.
4866 If we are not in a function, we can't make a SAVE_EXPR, so don't
4867 try to do so. Don't try to see if the result is a constant
4868 if an arm is a COND_EXPR since we get exponential behavior
4869 in that case. */
4876 {
4886 }
4899 else
4901 }
4903 \f
4904 /* Perform constant folding and related simplification of EXPR.
4905 The related simplifications include x*1 => x, x*0 => 0, etc.,
4906 and application of the associative law.
4907 NOP_EXPR conversions may be removed freely (as long as we
4908 are careful not to change the C type of the overall expression)
4909 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4910 but we can constant-fold them if they have constant operands. */
4912 tree
4914 tree expr;
4915 {
4918 tree tem;
4924 /* WINS will be nonzero when the switch is done
4925 if all operands are constant. */
4928 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4929 Likewise for a SAVE_EXPR that's already been evaluated. */
4933 /* Return right away if a constant. */
4937 #ifdef MAX_INTEGER_COMPUTATION_MODE
4939 #endif
4942 {
4943 tree subop;
4945 /* Special case for conversion ops that can have fixed point args. */
4948 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4954 else
4958 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4961 )
4962 /* Note that TREE_CONSTANT isn't enough:
4963 static var addresses are constant but we can't
4964 do arithmetic on them. */
4966 }
4968 {
4972 {
4974 tree subop;
4980 {
4981 /* Signedness matters here. Perhaps we can refine this
4982 later. */
4984 }
4985 else
4986 /* Strip any conversions that don't change the mode. */
4991 else
4995 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4998 )
4999 /* Note that TREE_CONSTANT isn't enough:
5000 static var addresses are constant but we can't
5001 do arithmetic on them. */
5008 }
5009 }
5011 /* If this is a commutative operation, and ARG0 is a constant, move it
5012 to ARG1 to reduce the number of tests below. */
5017 {
5022 }
5024 /* Now WINS is set as described above,
5025 ARG0 is the first operand of EXPR,
5026 and ARG1 is the second operand (if it has more than one operand).
5028 First check for cases where an arithmetic operation is applied to a
5029 compound, conditional, or comparison operation. Push the arithmetic
5030 operation inside the compound or conditional to see if any folding
5031 can then be done. Convert comparison to conditional for this purpose.
5032 The also optimizes non-constant cases that used to be done in
5033 expand_expr.
5035 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
5036 one of the operands is a comparison and the other is a comparison, a
5037 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
5038 code below would make the expression more complex. Change it to a
5039 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5040 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5052 {
5062 }
5065 {
5070 {
5075 /* If this was a conversion, and all we did was to move into
5076 inside the COND_EXPR, bring it back out. But leave it if
5077 it is a conversion from integer to integer and the
5078 result precision is no wider than a word since such a
5079 conversion is cheap and may be optimized away by combine,
5080 while it couldn't if it were outside the COND_EXPR. Then return
5081 so we don't get into an infinite recursion loop taking the
5082 conversion out and then back in. */
5092 && (INTEGRAL_TYPE_P
5103 }
5108 }
5111 {
5124 return
5138 return
5141 }
5152 {
5167 /* Other kinds of FIX are not handled properly by fold_convert. */
5172 /* Handle cases of two conversions in a row. */
5175 {
5195 /* In addition to the cases of two conversions in a row
5196 handled below, if we are converting something to its own
5197 type via an object of identical or wider precision, neither
5198 conversion is needed. */
5204 /* Likewise, if the intermediate and final types are either both
5205 float or both integer, we don't need the middle conversion if
5206 it is wider than the final type and doesn't change the signedness
5207 (for integers). Avoid this if the final type is a pointer
5208 since then we sometimes need the inner conversion. Likewise if
5209 the outer has a precision not equal to the size of its mode. */
5219 /* If we have a sign-extension of a zero-extended value, we can
5220 replace that by a single zero-extension. */
5226 /* Two conversions in a row are not needed unless:
5227 - some conversion is floating-point (overstrict for now), or
5228 - the intermediate type is narrower than both initial and
5229 final, or
5230 - the intermediate type and innermost type differ in signedness,
5231 and the outermost type is wider than the intermediate, or
5232 - the initial type is a pointer type and the precisions of the
5233 intermediate and final types differ, or
5234 - the final type is a pointer type and the precisions of the
5235 initial and intermediate types differ. */
5249 }
5253 /* Detect assigning a bitfield. */
5256 {
5257 /* Don't leave an assignment inside a conversion
5258 unless assigning a bitfield. */
5261 /* First do the assignment, then return converted constant. */
5265 }
5267 {
5270 }
5275 {
5278 /* Fold an expression like: "foo"[2] */
5282 {
5286 }
5287 }
5293 {
5297 }
5306 {
5308 {
5310 HOST_WIDE_INT high;
5321 }
5324 }
5328 /* Convert - (a - b) to (b - a) for non-floating-point. */
5338 {
5340 {
5341 /* If the value is unsigned, then the absolute value is
5342 the same as the ordinary value. */
5345 /* Similarly, if the value is non-negative. */
5348 /* If the value is negative, then the absolute value is
5349 its negation. */
5350 else
5351 {
5353 HOST_WIDE_INT high;
5364 }
5365 }
5367 {
5371 }
5372 }
5399 {
5406 }
5412 /* A + (-B) -> A - B */
5415 /* (-A) + B -> B - A */
5419 {
5423 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5424 with a constant, and the two constants have no bits in common,
5425 we should treat this as a BIT_IOR_EXPR since this may produce more
5426 simplifications. */
5434 {
5437 }
5439 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5440 (plus (plus (mult) (mult)) (foo)) so that we can
5441 take advantage of the factoring cases below. */
5446 {
5451 else
5462 parg1));
5467 parg0));
5468 }
5471 {
5475 /* (A * C) + (B * C) -> (A+B) * C.
5476 We are most concerned about the case where C is a constant,
5477 but other combinations show up during loop reduction. Since
5478 it is not difficult, try all four possibilities. */
5495 /* No identical multiplicands; see if we can find a common
5496 power-of-two factor in non-power-of-two multiplies. This
5497 can help in multi-dimensional array access. */
5502 {
5507 /* Move min of absolute values to int11. */
5510 {
5514 }
5517 {
5522 }
5523 }
5528 same));
5529 }
5530 }
5531 /* In IEEE floating point, x+0 may not equal x. */
5536 /* x+(-0) equals x, even for IEEE. */
5541 bit_rotate:
5542 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5543 is a rotate of A by C1 bits. */
5544 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5545 is a rotate of A by B bits. */
5546 {
5555 {
5574 {
5582 TYPE_PRECISION
5587 ? LROTATE_EXPR
5590 }
5592 {
5600 TYPE_PRECISION
5605 ? LROTATE_EXPR
5608 }
5609 }
5610 }
5612 associate:
5613 /* In most languages, can't associate operations on floats through
5614 parentheses. Rather than remember where the parentheses were, we
5615 don't associate floats at all. It shouldn't matter much. However,
5616 associating multiplications is only very slightly inaccurate, so do
5617 that if -funsafe-math-optimizations is specified. */
5622 {
5625 /* Split both trees into variables, constants, and literals. Then
5626 associate each group together, the constants with literals,
5627 then the result with variables. This increases the chances of
5628 literals being recombined later and of generating relocatable
5629 expressions for the sum of a constant and literal. */
5633 /* Only do something if we found more than two objects. Otherwise,
5634 nothing has changed and we risk infinite recursion. */
5637 {
5643 }
5644 }
5646 binary:
5647 #if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
5654 {
5655 /* The return value should always have
5656 the same type as the original expression. */
5661 }
5665 /* A - (-B) -> A + B */
5668 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5670 return
5677 {
5683 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5684 about the case where C is a constant, just try one of the
5685 four possibilities. */
5695 }
5699 {
5700 /* Except with IEEE floating point, 0-x equals -x. */
5703 /* Except with IEEE floating point, x-0 equals x. */
5706 }
5708 /* Fold &x - &x. This can happen from &x.foo - &x.
5709 This is unsafe for certain floats even in non-IEEE formats.
5710 In IEEE, it is unsafe because it does wrong for NaNs.
5711 Also note that operand_equal_p is always false if an operand
5712 is volatile. */
5721 /* (-A) * (-B) -> A * B */
5727 {
5733 /* (a * (1 << b)) is (a << b) */
5748 }
5749 else
5750 {
5751 /* x*0 is 0, except for IEEE floating point. */
5756 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5757 However, ANSI says we can drop signals,
5758 so we can do this anyway. */
5761 /* x*2 is x+x */
5764 {
5767 }
5768 }
5772 bit_ior:
5781 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5783 This results in more efficient code for machines without a NAND
5784 instruction. Combine will canonicalize to the first form
5785 which will allow use of NAND instructions provided by the
5786 backend if they exist. */
5789 {
5794 }
5796 /* See if this can be simplified into a rotate first. If that
5797 is unsuccessful continue in the association code. */
5806 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5807 with a constant, and the two constants have no bits in common,
5808 we should treat this as a BIT_IOR_EXPR since this may produce more
5809 simplifications. */
5817 {
5820 }
5822 /* See if this can be simplified into a rotate first. If that
5823 is unsuccessful continue in the association code. */
5827 bit_and:
5835 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5838 {
5839 unsigned int prec
5846 }
5849 {
5850 unsigned int prec
5857 }
5859 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5861 This results in more efficient code for machines without a NOR
5862 instruction. Combine will canonicalize to the first form
5863 which will allow use of NOR instructions provided by the
5864 backend if they exist. */
5867 {
5872 }
5882 {
5886 }
5890 /* In most cases, do nothing with a divide by zero. */
5891 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
5892 #ifndef REAL_INFINITY
5895 #endif
5898 /* (-A) / (-B) -> A / B */
5903 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5904 However, ANSI says we can drop signals, so we can do this anyway. */
5908 /* If ARG1 is a constant, we can convert this to a multiply by the
5909 reciprocal. This does not have the same rounding properties,
5910 so only do this if -funsafe-math-optimizations. We can actually
5911 always safely do it if ARG1 is a power of two, but it's hard to
5912 tell if it is or not in a portable manner. */
5914 {
5919 /* Find the reciprocal if optimizing and the result is exact. */
5921 {
5922 REAL_VALUE_TYPE r;
5925 {
5928 }
5929 }
5930 }
5931 /* Convert A/B/C to A/(B*C). */
5934 {
5937 arg1)));
5938 }
5939 /* Convert A/(B/C) to (A/B)*C. */
5942 {
5947 }
5960 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5961 operation, EXACT_DIV_EXPR.
5963 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5964 At one time others generated faster code, it's not clear if they do
5965 after the last round to changes to the DIV code in expmed.c. */
5999 /* Since negative shift count is not well-defined,
6000 don't try to compute it in the compiler. */
6003 /* Rewrite an LROTATE_EXPR by a constant into an
6004 RROTATE_EXPR by a new constant. */
6006 {
6010 = const_binop
6017 }
6019 /* If we have a rotate of a bit operation with the rotate count and
6020 the second operand of the bit operation both constant,
6021 permute the two operations. */
6034 /* Two consecutive rotates adding up to the width of the mode can
6035 be ignored. */
6066 /* Note that the operand of this must be an int
6067 and its values must be 0 or 1.
6068 ("true" is a fixed value perhaps depending on the language,
6069 but we don't handle values other than 1 correctly yet.) */
6071 /* Avoid infinite recursion. */
6077 /* Note that the operands of this must be ints
6078 and their values must be 0 or 1.
6079 ("true" is a fixed value perhaps depending on the language.) */
6080 /* If first arg is constant zero, return it. */
6084 /* If either arg is constant true, drop it. */
6088 /* Preserve sequence points. */
6091 /* If second arg is constant zero, result is zero, but first arg
6092 must be evaluated. */
6095 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6096 case will be handled here. */
6100 truth_andor:
6101 /* We only do these simplifications if we are optimizing. */
6105 /* Check for things like (A || B) && (A || C). We can convert this
6106 to A || (B && C). Note that either operator can be any of the four
6107 truth and/or operations and the transformation will still be
6108 valid. Also note that we only care about order for the
6109 ANDIF and ORIF operators. If B contains side effects, this
6110 might change the truth-value of A. */
6117 {
6137 /* This case if tricky because we must either have commutative
6138 operators or else A10 must not have side-effects. */
6144 a01));
6145 }
6147 /* See if we can build a range comparison. */
6151 /* Check for the possibility of merging component references. If our
6152 lhs is another similar operation, try to merge its rhs with our
6153 rhs. Then try to merge our lhs and rhs. */
6165 /* Note that the operands of this must be ints
6166 and their values must be 0 or true.
6167 ("true" is a fixed value perhaps depending on the language.) */
6168 /* If first arg is constant true, return it. */
6172 /* If either arg is constant zero, drop it. */
6176 /* Preserve sequence points. */
6179 /* If second arg is constant true, result is true, but we must
6180 evaluate first arg. */
6183 /* Likewise for first arg, but note this only occurs here for
6184 TRUTH_OR_EXPR. */
6190 /* If either arg is constant zero, drop it. */
6195 /* If either arg is constant true, this is a logical inversion. */
6209 {
6210 /* (-a) CMP (-b) -> b CMP a */
6215 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6217 return
6223 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6224 /* a CMP (-0) -> a CMP 0 */
6229 }
6231 /* If one arg is a constant integer, put it last. */
6234 {
6241 }
6243 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6244 First, see if one arg is constant; find the constant arg
6245 and the other one. */
6246 {
6256 {
6257 /* This optimization is invalid for ordered comparisons
6258 if CONST+INCR overflows or if foo+incr might overflow.
6259 This optimization is invalid for floating point due to rounding.
6260 For pointer types we assume overflow doesn't happen. */
6264 {
6265 tree newconst
6269 /* Do not overwrite the current varop to be a preincrement,
6270 create a new node so that we won't confuse our caller who
6271 might create trees and throw them away, reusing the
6272 arguments that they passed to build. This shows up in
6273 the THEN or ELSE parts of ?: being postincrements. */
6278 /* If VAROP is a reference to a bitfield, we must mask
6279 the constant by the width of the field. */
6283 {
6284 int size
6286 (TREE_OPERAND
6290 tree folded_compare;
6292 /* First check whether the comparison would come out
6293 always the same. If we don't do that we would
6294 change the meaning with the masking. */
6298 else
6301 constop));
6316 mask)));
6317 }
6323 }
6324 }
6326 {
6330 {
6331 tree newconst
6335 /* Do not overwrite the current varop to be a predecrement,
6336 create a new node so that we won't confuse our caller who
6337 might create trees and throw them away, reusing the
6338 arguments that they passed to build. This shows up in
6339 the THEN or ELSE parts of ?: being postdecrements. */
6347 {
6348 int size
6350 (TREE_OPERAND
6354 tree folded_compare;
6359 else
6362 constop));
6377 mask)));
6378 }
6384 }
6385 }
6386 }
6388 /* Change X >= CST to X > (CST - 1) if CST is positive. */
6392 {
6394 {
6409 }
6410 }
6412 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6413 a MINUS_EXPR of a constant, we can convert it into a comparison with
6414 a revised constant as long as no overflow occurs. */
6426 /* Similarly for a NEGATE_EXPR. */
6435 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6436 for !=. Don't do this for ordered comparisons due to overflow. */
6442 /* If we are widening one operand of an integer comparison,
6443 see if the other operand is similarly being widened. Perhaps we
6444 can do the comparison in the narrower type. */
6454 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6455 constant, we can simplify it. */
6462 /* If we are comparing an ABS_EXPR with a constant, we can
6463 convert all the cases into explicit comparisons, but they may
6464 well not be faster than doing the ABS and one comparison.
6465 But ABS (X) <= C is a range comparison, which becomes a subtraction
6466 and a comparison, and is probably faster. */
6478 /* If this is an EQ or NE comparison with zero and ARG0 is
6479 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6480 two operations, but the latter can be done in one less insn
6481 on machines that have only two-operand insns or on which a
6482 constant cannot be the first operand. */
6485 {
6488 return
6496 integer_one_node)),
6497 arg1));
6500 return
6508 integer_one_node)),
6509 arg1));
6510 }
6512 /* If this is an NE or EQ comparison of zero against the result of a
6513 signed MOD operation whose second operand is a power of 2, make
6514 the MOD operation unsigned since it is simpler and equivalent. */
6523 {
6530 }
6532 /* If this is an NE comparison of zero with an AND of one, remove the
6533 comparison since the AND will give the correct value. */
6539 /* If we have (A & C) == C where C is a power of 2, convert this into
6540 (A & C) != 0. Similarly for NE_EXPR. */
6548 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6549 and similarly for >= into !=. */
6565 return
6572 /* Simplify comparison of something with itself. (For IEEE
6573 floating-point, we can only do some of these simplifications.) */
6575 {
6577 {
6588 /* For NE, we can only do this simplification if integer. */
6591 /* ... fall through ... */
6597 }
6598 }
6600 /* An unsigned comparison against 0 can be simplified. */
6605 {
6607 {
6619 arg0);
6623 arg0);
6626 }
6627 }
6629 /* Comparisons with the highest or lowest possible integer of
6630 the specified size will have known values and an unsigned
6631 <= 0x7fffffff can be simplified. */
6632 {
6640 {
6646 {
6650 arg0);
6658 arg0);
6665 }
6672 {
6676 arg0);
6684 arg0);
6691 }
6697 /* signed_type does not work on pointer types. */
6701 {
6705 arg0),
6707 integer_zero_node)));
6711 arg0),
6713 integer_zero_node)));
6717 }
6718 }
6719 }
6721 /* If we are comparing an expression that just has comparisons
6722 of two integer values, arithmetic expressions of those comparisons,
6723 and constants, we can simplify it. There are only three cases
6724 to check: the two values can either be equal, the first can be
6725 greater, or the second can be greater. Fold the expression for
6726 those three values. Since each value must be 0 or 1, we have
6727 eight possibilities, each of which corresponds to the constant 0
6728 or 1 or one of the six possible comparisons.
6730 This handles common cases like (a > b) == 0 but also handles
6731 expressions like ((x > y) - (y > x)) > 0, which supposedly
6732 occur in macroized code. */
6735 {
6740 /* Don't handle degenerate cases here; they should already
6741 have been handled anyway. */
6750 {
6754 /* We can't just pass T to eval_subst in case cval1 or cval2
6755 was the same as ARG1. */
6757 tree high_result
6760 arg1));
6761 tree equal_result
6764 arg1));
6765 tree low_result
6768 arg1));
6770 /* All three of these results should be 0 or 1. Confirm they
6771 are. Then use those values to select the proper code
6772 to use. */
6780 {
6781 /* Make a 3-bit mask with the high-order bit being the
6782 value for `>', the next for '=', and the low for '<'. */
6786 {
6788 /* Always false. */
6809 /* Always true. */
6811 }
6816 else
6818 }
6819 }
6820 }
6822 /* If this is a comparison of a field, we may be able to simplify it. */
6826 /* Handle the constant case even without -O
6827 to make sure the warnings are given. */
6829 {
6832 }
6834 /* If this is a comparison of complex values and either or both sides
6835 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6836 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6837 This may prevent needless evaluations. */
6844 {
6857 type,
6860 }
6862 /* From here on, the only cases we handle are when the result is
6863 known to be a constant.
6865 To compute GT, swap the arguments and do LT.
6866 To compute GE, do LT and invert the result.
6867 To compute LE, swap the arguments, do LT and invert the result.
6868 To compute NE, do EQ and invert the result.
6870 Therefore, the code below must handle only EQ and LT. */
6873 {
6876 }
6878 /* Note that it is safe to invert for real values here because we
6879 will check below in the one case that it matters. */
6884 {
6887 }
6889 /* Compute a result for LT or EQ if args permit;
6890 otherwise return T. */
6892 {
6895 else
6900 }
6903 /* Assume a nonexplicit constant cannot equal an explicit one,
6904 since such code would be undefined anyway.
6905 Exception: on sysvr4, using #pragma weak,
6906 a label can come out as 0. */
6913 #endif
6914 /* Two real constants can be compared explicitly. */
6916 {
6917 /* If either operand is a NaN, the result is false with two
6918 exceptions: First, an NE_EXPR is true on NaNs, but that case
6919 is already handled correctly since we will be inverting the
6920 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6921 or a GE_EXPR into a LT_EXPR, we must return true so that it
6922 will be inverted into false. */
6932 else
6936 }
6950 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6951 so all simple results must be passed through pedantic_non_lvalue. */
6953 return pedantic_non_lvalue
6958 /* If the second operand is zero, invert the comparison and swap
6959 the second and third operands. Likewise if the second operand
6960 is constant and the third is not or if the third operand is
6961 equivalent to the first operand of the comparison. */
6969 {
6970 /* See if this can be inverted. If it can't, possibly because
6971 it was a floating-point inequality comparison, don't do
6972 anything. */
6976 {
6980 /* arg1 should be the first argument of the new T. */
6983 }
6984 }
6986 /* If we have A op B ? A : C, we may be able to convert this to a
6987 simpler expression, depending on the operation and the values
6988 of B and C. IEEE floating point prevents this though,
6989 because A or B might be -0.0 or a NaN. */
6997 {
7003 /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
7004 depending on the comparison operation. */
7011 {
7013 return
7014 pedantic_non_lvalue
7016 negate_expr
7018 arg1))));
7026 return pedantic_non_lvalue
7033 return pedantic_non_lvalue
7037 arg1)))));
7040 }
7042 /* If this is A != 0 ? A : 0, this is simply A. For ==, it is
7043 always zero. */
7046 {
7051 }
7053 /* If this is A op B ? A : B, this is either A, B, min (A, B),
7054 or max (A, B), depending on the operation. */
7058 {
7063 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
7068 {
7075 /* In C++ a ?: expression can be an lvalue, so put the
7076 operand which will be used if they are equal first
7077 so that we can convert this back to the
7078 corresponding COND_EXPR. */
7079 return pedantic_non_lvalue
7088 return pedantic_non_lvalue
7097 }
7098 }
7100 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7101 we might still be able to simplify this. For example,
7102 if C1 is one less or one more than C2, this might have started
7103 out as a MIN or MAX and been transformed by this function.
7104 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7110 {
7112 /* We can replace A with C1 in this case. */
7119 /* If C1 is C2 + 1, this is min(A, C2). */
7124 return pedantic_non_lvalue
7129 /* If C1 is C2 - 1, this is min(A, C2). */
7134 return pedantic_non_lvalue
7139 /* If C1 is C2 - 1, this is max(A, C2). */
7144 return pedantic_non_lvalue
7149 /* If C1 is C2 + 1, this is max(A, C2). */
7154 return pedantic_non_lvalue
7161 }
7162 }
7164 /* If the second operand is simpler than the third, swap them
7165 since that produces better jump optimization results. */
7171 {
7172 /* See if this can be inverted. If it can't, possibly because
7173 it was a floating-point inequality comparison, don't do
7174 anything. */
7178 {
7182 /* arg1 should be the first argument of the new T. */
7185 }
7186 }
7188 /* Convert A ? 1 : 0 to simply A. */
7191 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7192 call to fold will try to move the conversion inside
7193 a COND, which will recurse. In that case, the COND_EXPR
7194 is probably the best choice, so leave it alone. */
7198 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7199 operation is simply A & 2. */
7213 /* When pedantic, a compound expression can be neither an lvalue
7214 nor an integer constant expression. */
7217 /* Don't let (0, 0) be null pointer constant. */
7259 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7260 appropriate. */
7265 {
7269 tree arg01;
7280 {
7294 arg01));
7295 }
7298 }
7301 /* Check for a built-in function. */
7306 {
7310 }
7316 }
7318 /* Determine if first argument is a multiple of second argument. Return 0 if
7319 it is not, or we cannot easily determined it to be.
7321 An example of the sort of thing we care about (at this point; this routine
7322 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7323 fold cases do now) is discovering that
7325 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7327 is a multiple of
7329 SAVE_EXPR (J * 8)
7331 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7333 This code also handles discovering that
7335 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7337 is a multiple of 8 so we don't have to worry about dealing with a
7338 possible remainder.
7340 Note that we *look* inside a SAVE_EXPR only to determine how it was
7341 calculated; it is not safe for fold to do much of anything else with the
7342 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7343 at run time. For example, the latter example above *cannot* be implemented
7344 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7345 evaluation time of the original SAVE_EXPR is not necessarily the same at
7346 the time the new expression is evaluated. The only optimization of this
7347 sort that would be valid is changing
7349 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7351 divided by 8 to
7353 SAVE_EXPR (I) * SAVE_EXPR (J)
7355 (where the same SAVE_EXPR (J) is used in the original and the
7356 transformed version). */
7358 static int
7360 tree type;
7361 tree top;
7362 tree bottom;
7363 {
7371 {
7383 {
7387 /* const_binop may not detect overflow correctly,
7388 so check for it explicitly here. */
7397 }
7401 /* Can't handle conversions from non-integral or wider integral type. */
7407 /* .. fall through ... */
7423 }
7424 }
7426 /* Return true if `t' is known to be non-negative. */
7428 int
7430 tree t;
7431 {
7433 {
7474 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7476 else
7477 /* We don't know sign of `t', so be conservative and return false. */
7479 }
7480 }
7482 /* Return true if `r' is known to be non-negative.
7483 Only handles constants at the moment. */
7485 int
7487 rtx r;
7488 {
7490 {
7501 /* These are always nonnegative. */
7506 }
7507 }