Hi all,
This patch addresses the issue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126693.
The optimization is not valid for the following cases:
- fp with -frounding-math.
- Integers with wrapping arithmetic and signed integer overflow.
- values to be folded must have single use otherwise we may end up adding an
extra ABS_EXPR.
e.g.
int gx, gy, mul;
void f (int x, int y)
{
int ax = __builtin_abs (x);
int ay = __builtin_abs (y);
mul = ax * ay;
gx = ax; // use of ax
gy = ay; // use of ay
}
regtested and bootstraped on x86_64-linux-gnu. ok for trunk ?
gcc/ChangeLog:
PR tree-optimization/126693.
* match.pd: Fold abs(x) * abs(y) into abs(x * y).
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/mult-abs-3.c: New test.
* gcc.dg/tree-ssa/mult-abs-4.c: New test.
* gcc.dg/tree-ssa/mult-abs-5.c: New test.
---
gcc/match.pd | 10 +++++++
gcc/testsuite/gcc.dg/tree-ssa/mult-abs-3.c | 17 ++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/mult-abs-4.c | 32 ++++++++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/mult-abs-5.c | 7 +++++
4 files changed, 66 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/mult-abs-3.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/mult-abs-4.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/mult-abs-5.c
diff --git a/gcc/match.pd b/gcc/match.pd
index a2a48e1b475..379fa98a692 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1254,6 +1254,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(mult (absu@1 @0) @1)
(mult (convert@2 @0) @2))
+/* abs(x) * abs(y) -> abs(x * y). */
+(simplify
+ (mult (abs:s @0) (abs:s @1))
+ (if ((FLOAT_TYPE_P (type)
+ && !HONOR_SIGN_DEPENDENT_ROUNDING (type))
+ || (ANY_INTEGRAL_TYPE_P (type)
+ && TYPE_OVERFLOW_UNDEFINED (type)
+ && !TYPE_OVERFLOW_SANITIZED (type)))
+ (abs (mult @0 @1))))
+
#if GIMPLE
/* Simplify SAD(x, x, acc) -> acc since the absolute difference is zero. */
(simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-3.c
b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-3.c
new file mode 100644
index 00000000000..2bebafc65b0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-3.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target c99_runtime } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+#include <stdlib.h>
+
+double f (double x, double y) { return __builtin_fabs (x) *
__builtin_fabs (y); }
+float g (float x, float y) { return __builtin_fabsf (x) *
__builtin_fabsf (y); }
+int h (int x, int y) { return __builtin_abs (x) *
__builtin_abs (y); }
+long i (long x, long y) { return __builtin_labs (x) *
__builtin_labs (y); }
+long long j (long long x, long long y) { return __builtin_llabs (x) *
__builtin_llabs (y); }
+
+int k (int x, int y) { return abs (x) * abs (y); }
+long l (long x, long y) { return labs (x) * labs (y); }
+long long m (long long x, long long y) { return llabs (x) * llabs (y); }
+
+/* { dg-final { scan-tree-dump-times "ABS_EXPR" 8 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-4.c
b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-4.c
new file mode 100644
index 00000000000..4979dfd5207
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-4.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+double __attribute__((optimize ("-frounding-math")))
+frnd (double x, double y)
+{
+ return __builtin_fabs (x) * __builtin_fabs (y);
+}
+
+int __attribute__((optimize ("-fwrapv")))
+wrap (int x, int y)
+{
+ return __builtin_abs (x) * __builtin_abs (y);
+}
+
+int __attribute__((optimize ("-ftrapv")))
+trap (int x, int y)
+{
+ return __builtin_abs (x) * __builtin_abs (y);
+}
+
+int gx, gy;
+int shared (int x, int y)
+{
+ int ax = __builtin_abs (x);
+ int ay = __builtin_abs (y);
+ gx = ax;
+ gy = ay;
+ return ax * ay;
+}
+
+/* { dg-final { scan-tree-dump-times "ABS_EXPR" 8 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-5.c
b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-5.c
new file mode 100644
index 00000000000..860b931c376
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-5.c
@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fsanitize=signed-integer-overflow -fdump-tree-optimized"
} */
+
+int f (int x, int y) { return __builtin_abs (x) * __builtin_abs (y); }
+long g (long x, long y) { return __builtin_labs (x) * __builtin_labs (y); }
+
+/* { dg-final { scan-tree-dump-times "ABS_EXPR" 4 "optimized" } } */
--
2.34.1
