match.pd: Fix up __imag__ .MUL_OVERFLOW simplification [PR123864]

The integer_minus_onep case is really meant for multiplication by
-1, not by (unsigned char)0xff or (unsigned short)0xffff or 0xffffffffU etc.
We've already tested that the first operand is signed (otherwise the
earlier case is used) and also that int_fits_type_p (@1, TREE_TYPE (@0)),
but if @0 is signed and @1 is unsigned all ones with smaller precision
than that, it fits into @0's type, integer_minus_onep will be true
and it still should be handled through the ranges, not as @0 == min.

2026-01-30  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/123864
	* match.pd (__builtin_mul_overflow_p (x, cst, (stype) 0) ->
	x > stype_max / cst || x < stype_min / cst): Only check
	integer_minus_onep for signed types.

	* gcc.c-torture/execute/pr123864.c: New test.
	* gcc.dg/torture/pr123864.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index 75511c459fa2024ec7d66cc2225d02e4cd16b83f..05e8ea7a229d55cbf3660b16a176e582c03a8911 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -8798,7 +8798,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
     (convert (gt @0 (trunc_div! { TYPE_MAX_VALUE (TREE_TYPE (@0)); } @1)))
     (if (TYPE_MIN_VALUE (TREE_TYPE (@0)))
-     (if (integer_minus_onep (@1))
+     (if (!TYPE_UNSIGNED (TREE_TYPE (@1)) && integer_minus_onep (@1))
       (convert (eq @0 { TYPE_MIN_VALUE (TREE_TYPE (@0)); }))
       (with
        {

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr123864.c b/gcc/testsuite/gcc.c-torture/execute/pr123864.c
new file mode 100644 (file)
index 0000000..c70d1ca
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr123864.c
@@ -0,0 +1,24 @@
+/* PR tree-optimization/123864 */
+
+[[gnu::noipa]] static int
+foo (long long x)
+{
+  return __builtin_mul_overflow_p (x, ~0U, x);
+}
+
+int
+main ()
+{
+  if (foo (0))
+    __builtin_abort ();
+#if __SIZEOF_INT__ == 4 && __SIZEOF_LONG_LONG__ == 8 && __CHAR_BIT__ == 8
+  if (foo (__INT_MAX__ + 1LL))
+    __builtin_abort ();
+  if (!foo (__INT_MAX__ + 2LL))
+    __builtin_abort ();
+  if (foo (-__INT_MAX__ - 1LL))
+    __builtin_abort ();
+  if (!foo (-__INT_MAX__ - 2LL))
+    __builtin_abort ();
+#endif
+}

diff --git a/gcc/testsuite/gcc.dg/torture/pr123864.c b/gcc/testsuite/gcc.dg/torture/pr123864.c
new file mode 100644 (file)
index 0000000..8f2e375
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr123864.c
@@ -0,0 +1,28 @@
+/* PR tree-optimization/123864 */
+/* { dg-do run { target int128 } } */
+
+int u, v, x;
+
+[[gnu::noipa]] static void
+foo ()
+{
+  __int128 c = (__int128) 0xa5ee4bc88ULL << 64;
+  long long b = 0x207b8a7f7LL;
+  int a = 4;
+  long long y;
+  __builtin_add_overflow (a, v, &y);
+  c *= y;
+  
+  unsigned z;
+  if (__builtin_add_overflow (b, u, &z))
+    z = 0xffffffffU;
+  x = __builtin_mul_overflow_p (z, c, c);
+}
+
+int
+main ()
+{
+  foo ();
+  if (!x)
+    __builtin_abort ();
+}