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[PATCH v2 2/2] combine successive multiplications by constants
- From: Alexander Monakov <amonakov at ispras dot ru>
- To: gcc-patches at gcc dot gnu dot org
- Date: Fri, 21 Jul 2017 18:55:50 +0300
- Subject: [PATCH v2 2/2] combine successive multiplications by constants
- Authentication-results: sourceware.org; auth=none
- References: <20170721155550.5846-1-amonakov@ispras.ru>
Previous revision here: https://gcc.gnu.org/ml/gcc-patches/2017-07/msg01090.html
Reassociate X * CST1 * CST2 to X * (CST1 * CST2).
Changed in this revision:
- remove the check for @2 being 0 or -1
* match.pd ((X * CST1) * CST2): Simplify to X * (CST1 * CST2).
testsuite:
* gcc.dg/tree-ssa/assoc-2.c: Enhance.
* gcc.dg/tree-ssa/slsr-4.c: Adjust.
---
gcc/match.pd | 13 +++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c | 13 ++++++++++++-
gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c | 8 ++------
3 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/gcc/match.pd b/gcc/match.pd
index 39e1e5c..732b80c 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -284,6 +284,19 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
|| mul != wi::min_value (TYPE_PRECISION (type), SIGNED))
{ build_zero_cst (type); })))))
+/* Combine successive multiplications. Similar to above, but handling
+ overflow is different. */
+(simplify
+ (mult (mult @0 INTEGER_CST@1) INTEGER_CST@2)
+ (with {
+ bool overflow_p;
+ wide_int mul = wi::mul (@1, @2, TYPE_SIGN (type), &overflow_p);
+ }
+ /* Skip folding on overflow: the only special case is @1 * @2 == -INT_MIN,
+ otherwise undefined overflow implies that @0 must be zero. */
+ (if (!overflow_p || TYPE_OVERFLOW_WRAPS (type))
+ (mult @0 { wide_int_to_tree (type, mul); }))))
+
/* Optimize A / A to 1.0 if we don't care about
NaNs or Infinities. */
(simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c b/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c
index a92c882..cc0e9d4 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c
@@ -5,4 +5,15 @@ int f0(int a, int b){
return a * 33 * b * 55;
}
-/* { dg-final { scan-tree-dump-times "mult_expr" 2 "gimple" } } */
+int f1(int a){
+ a *= 33;
+ return a * 55;
+}
+
+int f2(int a, int b){
+ a *= 33;
+ return a * b * 55;
+}
+
+/* { dg-final { scan-tree-dump-times "mult_expr" 7 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "mult_expr" 5 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c b/gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c
index 17d7b4c..1e943b7 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c
@@ -23,13 +23,9 @@ f (int i)
foo (y);
}
-/* { dg-final { scan-tree-dump-times "\\* 4" 1 "slsr" } } */
-/* { dg-final { scan-tree-dump-times "\\* 10" 1 "slsr" } } */
-/* { dg-final { scan-tree-dump-times "\\+ 20;" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\* 40" 1 "slsr" } } */
/* { dg-final { scan-tree-dump-times "\\+ 200" 1 "slsr" } } */
-/* { dg-final { scan-tree-dump-times "\\- 16;" 1 "slsr" } } */
/* { dg-final { scan-tree-dump-times "\\- 160" 1 "slsr" } } */
-/* { dg-final { scan-tree-dump-times "\\* 4" 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-times "\\* 10" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\* 40" 1 "optimized" } } */
/* { dg-final { scan-tree-dump-times "\\+ 200" 1 "optimized" } } */
/* { dg-final { scan-tree-dump-times "\\+ 40" 1 "optimized" } } */
--
1.8.3.1