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[PATCH] Move X - (X / Y) * Y folding to match.pd
- From: Marek Polacek <polacek at redhat dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Biener <rguenther at suse dot de>
- Date: Fri, 26 Jun 2015 18:29:40 +0200
- Subject: [PATCH] Move X - (X / Y) * Y folding to match.pd
- Authentication-results: sourceware.org; auth=none
This is an attempt to move one pattern from fold-const.c to match.pd.
It ought to be 1:1, but is not, e.g. with this patch we won't fold e.g.
int
f (int a, int b)
{
return a - (unsigned) ((a / b) * b)
}
anymore, but we're able to fold
int
ff (int a, unsigned int b)
{
return a - ((a / b) * b);
}
and fold-const.c is not. I played around with converts, but didn't find
anything that would work well. Any suggestions how to make this pattern
better?
More to come...
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2015-06-26 Marek Polacek <polacek@redhat.com>
* fold-const.c (fold_binary_loc): Move X - (X / Y) * Y -> X % Y to ...
* match.pd: ... pattern here.
diff --git gcc/fold-const.c gcc/fold-const.c
index 6f12dd0..01e3983 100644
--- gcc/fold-const.c
+++ gcc/fold-const.c
@@ -10509,19 +10509,6 @@ fold_binary_loc (location_t loc,
fold_convert_loc (loc, type,
TREE_OPERAND (arg0, 0)));
- /* X - (X / Y) * Y is X % Y. */
- if ((INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
- && TREE_CODE (arg1) == MULT_EXPR
- && TREE_CODE (TREE_OPERAND (arg1, 0)) == TRUNC_DIV_EXPR
- && operand_equal_p (arg0,
- TREE_OPERAND (TREE_OPERAND (arg1, 0), 0), 0)
- && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg1, 0), 1),
- TREE_OPERAND (arg1, 1), 0))
- return
- fold_convert_loc (loc, type,
- fold_build2_loc (loc, TRUNC_MOD_EXPR, TREE_TYPE (arg0),
- arg0, TREE_OPERAND (arg1, 1)));
-
if (! FLOAT_TYPE_P (type))
{
/* Fold A - (A & B) into ~B & A. */
diff --git gcc/match.pd gcc/match.pd
index b2f8429..2bc158b 100644
--- gcc/match.pd
+++ gcc/match.pd
@@ -238,6 +238,12 @@ along with GCC; see the file COPYING3. If not see
&& tree_nop_conversion_p (type, TREE_TYPE (@1)))
(trunc_mod @0 (convert @1))))
+/* X - (X / Y) * Y is the same as X % Y. */
+(simplify
+ (minus @0 (mult (trunc_div @0 @1) @1))
+ (if (INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
+ (trunc_mod @0 @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,
Marek