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fold-const.c (fold_binary_loc): Move X % -Y -> X % Y and X % C -> X & (C - 1) for C being a power-of two to ...

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2015-05-26  Richard Biener  <rguenther@suse.de>

	* fold-const.c (fold_binary_loc): Move X % -Y -> X % Y and
	X % C -> X & (C - 1) for C being a power-of two to ...
	* match.pd: ... patterns.

From-SVN: r223690
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Richard Biener 2015-05-26 12:00:48 +00:00 committed by Richard Biener
parent 534bd33b61
commit 8f0c696a7b
3 changed files with 30 additions and 37 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2015-05-26 Richard Biener <rguenther@suse.de>
* fold-const.c (fold_binary_loc): Move X % -Y -> X % Y and
X % C -> X & (C - 1) for C being a power-of two to ...
* match.pd: ... patterns.
2015-05-26 Marc Glisse <marc.glisse@inria.fr>
* match.pd (swapped_tcc_comparison): New operator list.

37
gcc/fold-const.c
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@ -11941,15 +11941,6 @@ fold_binary_loc (location_t loc,
case FLOOR_MOD_EXPR:
case ROUND_MOD_EXPR:
case TRUNC_MOD_EXPR:
/* X % -Y is the same as X % Y. */
if (code == TRUNC_MOD_EXPR
&& !TYPE_UNSIGNED (type)
&& TREE_CODE (arg1) == NEGATE_EXPR
&& !TYPE_OVERFLOW_TRAPS (type))
return fold_build2_loc (loc, code, type, fold_convert_loc (loc, type, arg0),
fold_convert_loc (loc, type,
TREE_OPERAND (arg1, 0)));
strict_overflow_p = false;
if (TREE_CODE (arg1) == INTEGER_CST
&& 0 != (tem = extract_muldiv (op0, arg1, code, NULL_TREE,
@ -11962,34 +11953,6 @@ fold_binary_loc (location_t loc,
return fold_convert_loc (loc, type, tem);
}
/* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
i.e. "X % C" into "X & (C - 1)", if X and C are positive. */
if ((code == TRUNC_MOD_EXPR || code == FLOOR_MOD_EXPR)
&& (TYPE_UNSIGNED (type)
|| tree_expr_nonnegative_warnv_p (op0, &strict_overflow_p)))
{
tree c = arg1;
/* Also optimize A % (C << N) where C is a power of 2,
to A & ((C << N) - 1). */
if (TREE_CODE (arg1) == LSHIFT_EXPR)
c = TREE_OPERAND (arg1, 0);
if (integer_pow2p (c) && tree_int_cst_sgn (c) > 0)
{
tree mask
= fold_build2_loc (loc, MINUS_EXPR, TREE_TYPE (arg1), arg1,
build_int_cst (TREE_TYPE (arg1), 1));
if (strict_overflow_p)
fold_overflow_warning (("assuming signed overflow does not "
"occur when simplifying "
"X % (power of two)"),
WARN_STRICT_OVERFLOW_MISC);
return fold_build2_loc (loc, BIT_AND_EXPR, type,
fold_convert_loc (loc, type, arg0),
fold_convert_loc (loc, type, mask));
}
}
return NULL_TREE;
case LROTATE_EXPR:

24
gcc/match.pd
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@ -230,6 +230,30 @@ along with GCC; see the file COPYING3. If not see
&& !sign_bit_p (@1, @1))
(trunc_mod @0 (negate @1))))
/* X % -Y is the same as X % Y. */
(simplify
(trunc_mod @0 (convert? (negate @1)))
(if (!TYPE_UNSIGNED (type)
&& !TYPE_OVERFLOW_TRAPS (type)
&& tree_nop_conversion_p (type, TREE_TYPE (@1)))
(trunc_mod @0 (convert @1))))
/* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
i.e. "X % C" into "X & (C - 1)", if X and C are positive.
Also optimize A % (C << N) where C is a power of 2,
to A & ((C << N) - 1). */
(match (power_of_two_cand @1)
INTEGER_CST@1)
(match (power_of_two_cand @1)
(lshift INTEGER_CST@1 @2))
(for mod (trunc_mod floor_mod)
(simplify
(mod @0 (power_of_two_cand@1 @2))
(if ((TYPE_UNSIGNED (type)
|| tree_expr_nonnegative_p (@0))
&& integer_pow2p (@2) && tree_int_cst_sgn (@2) > 0)
(bit_and @0 (minus @1 { build_int_cst (TREE_TYPE (@1), 1); })))))
/* X % Y is smaller than Y. */
(for cmp (lt ge)
(simplify