[gcc r17-3200] match.pd: Fold abs(x) * abs(y) -> abs(x * y) [PR126693]

https://gcc.gnu.org/g:7c48d6a74693e1c64900f6aa203539ea1ca7b370

commit r17-3200-g7c48d6a74693e1c64900f6aa203539ea1ca7b370
Author: Dipesh Sharma <[email protected]>
Date:   Sat Aug 8 20:39:17 2026 +0530

    match.pd: Fold abs(x) * abs(y) -> abs(x * y) [PR126693]
    
    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.

Diff:
---
 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(+)

diff --git a/gcc/match.pd b/gcc/match.pd
index 50e731770228..beea45357e22 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1284,6 +1284,16 @@ 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 000000000000..121b437165ab
--- /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 000000000000..4979dfd5207c
--- /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 000000000000..860b931c376a
--- /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" } } */