https://gcc.gnu.org/g:95b6ee96348041eaee9133f082b57f3e57ef0b11
commit r14-9350-g95b6ee96348041eaee9133f082b57f3e57ef0b11
Author: Jakub Jelinek <ja...@redhat.com>
Date: Thu Mar 7 08:43:16 2024 +0100
match.pd: Optimize a * !a to 0 [PR114009]
The following patch attempts to fix an optimization regression through
adding a simple simplification. We already have the
/* (m1 CMP m2) * d -> (m1 CMP m2) ? d : 0 */
(if (!canonicalize_math_p ())
(for cmp (tcc_comparison)
(simplify
(mult:c (convert (cmp@0 @1 @2)) @3)
(if (INTEGRAL_TYPE_P (type)
&& INTEGRAL_TYPE_P (TREE_TYPE (@0)))
(cond @0 @3 { build_zero_cst (type); })))
optimization which otherwise triggers during the a * !a multiplication,
but that is done only late and we aren't able through range assumptions
optimize it yet anyway.
The patch adds a specific simplification for it.
If a is zero, then a * !a will be 0 * 1 (or for signed 1-bit 0 * -1)
and so 0.
If a is non-zero, then a * !a will be a * 0 and so again 0.
THe pattern is valid for scalar integers, complex integers and vector types,
but I think will actually trigger only for the scalar integers. For
vector types I've added other two with VEC_COND_EXPR in it, for complex
there are different GENERIC trees to match and it is something that likely
would be never matched in GIMPLE, so I didn't handle that.
2024-03-07 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/114009
* genmatch.cc (decision_tree::gen): Emit ARG_UNUSED for captures
argument even for GENERIC, not just for GIMPLE.
* match.pd (a * !a -> 0): New simplifications.
* gcc.dg/tree-ssa/pr114009.c: New test.
Diff:
---
gcc/genmatch.cc | 2 +-
gcc/match.pd | 11 +++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr114009.c | 33 ++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 1 deletion(-)
diff --git a/gcc/genmatch.cc b/gcc/genmatch.cc
index 61c4c8c0294..c982c95b70f 100644
--- a/gcc/genmatch.cc
+++ b/gcc/genmatch.cc
@@ -4071,7 +4071,7 @@ decision_tree::gen (vec <FILE *> &files, bool gimple)
for (unsigned i = 0;
i < as_a <expr *>(s->s->s->match)->ops.length (); ++i)
fp_decl (f, " tree ARG_UNUSED (_p%d),", i);
- fp_decl (f, " tree *captures");
+ fp_decl (f, " tree *ARG_UNUSED (captures)");
}
for (unsigned i = 0; i < s->s->s->for_subst_vec.length (); ++i)
{
diff --git a/gcc/match.pd b/gcc/match.pd
index 4edba7c84fb..9ce313323a3 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1219,6 +1219,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& tree_nop_conversion_p (type, TREE_TYPE (@1)))
(lshift @0 @2)))
+/* Fold a * !a into 0. */
+(simplify
+ (mult:c @0 (convert? (eq @0 integer_zerop)))
+ { build_zero_cst (type); })
+(simplify
+ (mult:c @0 (vec_cond (eq @0 integer_zerop) @1 integer_zerop))
+ { build_zero_cst (type); })
+(simplify
+ (mult:c @0 (vec_cond (ne @0 integer_zerop) integer_zerop @1))
+ { build_zero_cst (type); })
+
/* Shifts by precision or greater result in zero. */
(for shift (lshift rshift)
(simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr114009.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr114009.c
new file mode 100644
index 00000000000..3b0486e16ad
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr114009.c
@@ -0,0 +1,33 @@
+/* PR tree-optimization/114009 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wno-psabi -fdump-tree-forwprop1" } */
+/* { dg-final { scan-tree-dump-times " return 0;" 3 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times " (?:return|<retval> =) { 0, 0, 0, 0 };"
1 "forwprop1" } } */
+
+int
+foo (int x)
+{
+ x = (x / 2) * 2;
+ return (!x) * x;
+}
+
+int
+bar (int x, int y)
+{
+ (void) x;
+ return y * !y;
+}
+
+unsigned long long
+baz (unsigned long long x)
+{
+ return (!x) * x;
+}
+
+typedef int V __attribute__((vector_size (4 * sizeof (int))));
+
+V
+qux (V x)
+{
+ return x * (x == 0);
+}
