From: Jakub Jelinek <jakub@redhat.com>
Date: Mon, 2 Feb 2026 09:07:15 +0000 (+0100)
Subject: widening_mul: Fix UADDC/USUBC pattern matching [PR121104]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49c7fc2d534cb7e16f0e95fd89f47eb0b0d34762;p=thirdparty%2Fgcc.git

widening_mul: Fix UADDC/USUBC pattern matching [PR121104]

As the following testcase shows, I've missed a check that element type
of lhs type of ovf1/ovf2 (.ADD_OVERFLOW/.SUB_OVERFLOW) matches type (there
are some casts accepted on the way for the case of values in [0-1] range),
so the following testcase got also matched as .SUBC and we get an ICE on
type mismatch in there.  The other .{ADD,SUB}_OVERFLOW cases already check
even the result type, both
                    if (gimple_call_internal_p (ovf, code == PLUS_EXPR
                                                     ? IFN_ADD_OVERFLOW
                                                     : IFN_SUB_OVERFLOW))
...
                        ovf_lhs = gimple_call_lhs (ovf);
                        tree ovf_lhs_type = TREE_TYPE (TREE_TYPE (ovf_lhs));
                        ovf_arg1 = gimple_call_arg (ovf, 0);
                        ovf_arg2 = gimple_call_arg (ovf, 1);
                        /* In that case we need to punt if the types don't
                           mismatch.  */
                        if (!types_compatible_p (type, ovf_lhs_type)
                            || !types_compatible_p (type, TREE_TYPE (ovf_arg1))
                            || !types_compatible_p (type,
                                                    TREE_TYPE (ovf_arg2)))
                          ovf_lhs = NULL_TREE;
and
          gimple *ovf3
            = SSA_NAME_DEF_STMT (TREE_OPERAND (gimple_assign_rhs1 (im3), 0));
          if (gimple_call_internal_p (ovf3, ifn))
            {
              lhs = gimple_call_lhs (ovf3);
              arg1 = gimple_call_arg (ovf3, 0);
              arg2 = gimple_call_arg (ovf3, 1);
              if (types_compatible_p (type, TREE_TYPE (TREE_TYPE (lhs)))
                  && types_compatible_p (type, TREE_TYPE (arg1))
                  && types_compatible_p (type, TREE_TYPE (arg2)))

2026-02-02  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/121104
	* tree-ssa-math-opts.cc (match_uaddc_usubc): Punt if
	lhs of ovf1 or ovf2 doesn't have element type compatible with type.

	* gcc.dg/pr121104.c: New test.
---

diff --git a/gcc/testsuite/gcc.dg/pr121104.c b/gcc/testsuite/gcc.dg/pr121104.c
new file mode 100644
index 00000000000..a972faac037
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr121104.c
@@ -0,0 +1,23 @@
+/* PR tree-optimization/121104 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+static unsigned long
+foo (unsigned long x, unsigned long y,
+     unsigned long z, unsigned long *w)
+{
+  int r;
+  unsigned long a = __builtin_sub_overflow (x, y, &r);
+  unsigned long b = __builtin_sub_overflow (r, z, &r);
+  *w = a + b;
+  return r;
+}
+
+unsigned long
+bar (unsigned long *p, unsigned long *q)
+{
+  unsigned long c;
+  p[0] = foo (p[0], q[0], 0, &c);
+  p[1] = foo (p[1], q[1], c, &c);
+  return c;
+}
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index 4b50a96ad3a..1b642e915fb 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -5411,7 +5411,11 @@ match_uaddc_usubc (gimple_stmt_iterator *gsi, gimple *stmt, tree_code code)
 			TYPE_MODE (type)) == CODE_FOR_nothing
       || (rhs[2]
 	  && optab_handler (code == PLUS_EXPR ? uaddc5_optab : usubc5_optab,
-			    TYPE_MODE (type)) == CODE_FOR_nothing))
+			    TYPE_MODE (type)) == CODE_FOR_nothing)
+      || !types_compatible_p (type,
+			      TREE_TYPE (TREE_TYPE (gimple_call_lhs (ovf1))))
+      || !types_compatible_p (type,
+			      TREE_TYPE (TREE_TYPE (gimple_call_lhs (ovf2)))))
     return false;
   tree arg1, arg2, arg3 = NULL_TREE;
   gimple *re1 = NULL, *re2 = NULL;