This patch fixes a missed optimization in match.pd. It takes the pattern, x / y
* y == x, and optimizes it to x % y == 0. This produces fewer instructions.
There are also tests for the optimizations to be added to the test suite.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR tree-optimization/104992
gcc/ChangeLog:
* match.pd x / y * y == x: New simplification.
gcc/testsuite/ChangeLog:
* gcc.dg/pr104992-1.c: New test.
* gcc.dg/pr104992.c: New test.
---
gcc/match.pd | 5 +++++
gcc/testsuite/gcc.dg/pr104992-1.c | 30 ++++++++++++++++++++++++++
gcc/testsuite/gcc.dg/pr104992.c | 35 +++++++++++++++++++++++++++++++
3 files changed, 70 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/pr104992-1.c
create mode 100644 gcc/testsuite/gcc.dg/pr104992.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 9736393061a..f7ab2174b8a 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -8054,3 +8054,8 @@ and,
(if (TYPE_UNSIGNED (TREE_TYPE (@0)))
(bit_and @0 @1)
(cond (le @0 @1) @0 (bit_and @0 @1))))))
+
+/* x / y * y == x -> x % y == 0. */
+(simplify
+ (eq (mult (trunc_div @0 @1) @1) @0)
+ (eq (trunc_mod @0 @1) { build_zero_cst TREE_TYPE(@0); }))
diff --git a/gcc/testsuite/gcc.dg/pr104992-1.c
b/gcc/testsuite/gcc.dg/pr104992-1.c
new file mode 100644
index 00000000000..a80e5e180ce
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104992-1.c
@@ -0,0 +1,30 @@
+/* PR tree-optimization/104992 */
+/* { dg-do run } */
+/* { dg-options "-O2"} */
+
+#include "pr104992.c"
+
+int main () {
+
+ /* Should be true. */
+ if (!foo(6, 3)
+ || !bar(12, 2)
+ || !baz(34, 17)
+ || !qux(50, 10)
+ || !fred(16, 8)
+ || !baz(-9, 3)
+ || !baz(9, -3)
+ || !baz(-9, -3)
+ ) {
+ __builtin_abort();
+ }
+
+ /* Should be false. */
+ if (foo(5, 30)
+ || bar(72, 27)
+ || baz(42, 15)) {
+ __builtin_abort();
+ }
+
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/pr104992.c b/gcc/testsuite/gcc.dg/pr104992.c
new file mode 100644
index 00000000000..b4b0ca53118
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104992.c
@@ -0,0 +1,35 @@
+/* PR tree-optimization/104992 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* Form from PR. */
+__attribute__((noipa)) unsigned foo(unsigned x, unsigned y)
+{
+ return x / y * y == x;
+}
+
+__attribute__((noipa)) unsigned bar(unsigned x, unsigned y) {
+ return x == x / y * y;
+}
+
+/* Signed test case. */
+__attribute__((noipa)) unsigned baz (int x, int y) {
+ return x / y * y == x;
+}
+
+/* Changed order. */
+__attribute__((noipa)) unsigned qux (unsigned x, unsigned y) {
+ return y * (x / y) == x;
+}
+
+/* Wrong order. */
+__attribute__((noipa)) unsigned fred (unsigned x, unsigned y) {
+ return y * x / y == x;
+}
+
+/* Wrong pattern. */
+__attribute__((noipa)) unsigned waldo (unsigned x, unsigned y, unsigned z) {
+ return x / y * z == x;
+}
+
+/* { dg-final {scan-tree-dump-times " % " 4 "optimized" } } */
base-commit: 633e9920589ddfaf2d6da1c24ce99b18a2638db4
--
2.31.1
