[gcc r15-11489] tree-optimization/125786 - do not rewrite stmts in reassoc

https://gcc.gnu.org/g:7902a49cfca20a69e9dbe757bfba426eeaeab552

commit r15-11489-g7902a49cfca20a69e9dbe757bfba426eeaeab552
Author: Richard Biener <[email protected]>
Date:   Mon Jun 15 10:37:29 2026 +0200

    tree-optimization/125786 - do not rewrite stmts in reassoc
    
    We may not simply rewrite def stmts of associative operands as
    they might have multiple uses.  The following appropriately
    creates a new stmt instead.
    
            PR tree-optimization/125786
            * tree-ssa-reassoc.cc (optimize_vec_cond_expr): Create a new
            stmt instead of rewriting an existing possibly multi-use one.
    
            * gcc.dg/torture/pr125786.c: New testcase.
    
    (cherry picked from commit b3763e32ea4b0bf9e68bb89eac9bf2d7ab92680c)

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr125786.c | 30 ++++++++++++++++++++++++++++++
 gcc/tree-ssa-reassoc.cc                 | 14 ++++++++------
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr125786.c b/gcc/testsuite/gcc.dg/torture/pr125786.c
new file mode 100644
index 000000000000..4b432f9d2f00
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr125786.c
@@ -0,0 +1,30 @@
+/* { dg-do run } */
+
+#define length 16
+typedef int type;
+typedef type v8i64 __attribute__((vector_size(sizeof(type)*length)));
+v8i64 g6, g27;
+_Bool main_c14;
+
+__attribute__((noipa))
+static
+void f(v8i64 *a)
+{
+  for(int i =0;i<length;i++)
+    if ((*a)[i] != -1)
+      __builtin_abort();
+}
+
+int main()
+{
+  if (main_c14) goto lbl_br43;
+lbl_bf7:
+  g6 = 0 <= g27;
+  g27 = g27 <= g27;
+  g27 = g6 > g27;
+lbl_br43:
+  g6 = g6 | g27;
+  if (main_c14) goto lbl_bf7;
+  g6 = g6 * g27 == 0;
+  f(&g6);
+}
diff --git a/gcc/tree-ssa-reassoc.cc b/gcc/tree-ssa-reassoc.cc
index 8f7e41b24b18..18ebd2c65fe6 100644
--- a/gcc/tree-ssa-reassoc.cc
+++ b/gcc/tree-ssa-reassoc.cc
@@ -4272,7 +4272,7 @@ optimize_vec_cond_expr (tree_code opcode, vec<operand_entry *> *ops)
 
   for (i = 0; i < length; ++i)
     {
-      tree elt0 = (*ops)[i]->op;
+      tree &elt0 = (*ops)[i]->op;
 
       gassign *stmt0, *vcond0;
       bool invert;
@@ -4320,11 +4320,13 @@ optimize_vec_cond_expr (tree_code opcode, vec<operand_entry *> *ops)
 	  gimple_stmt_iterator gsi = gsi_for_stmt (vcond0);
 	  tree exp = force_gimple_operand_gsi (&gsi, comb, true, NULL_TREE,
 					       true, GSI_SAME_STMT);
-	  if (invert)
-	    swap_ssa_operands (vcond0, gimple_assign_rhs2_ptr (vcond0),
-			       gimple_assign_rhs3_ptr (vcond0));
-	  gimple_assign_set_rhs1 (vcond0, exp);
-	  update_stmt (vcond0);
+	  tree res = gimple_build (&gsi, true, GSI_SAME_STMT, UNKNOWN_LOCATION,
+				   VEC_COND_EXPR, TREE_TYPE (elt0), exp,
+				   constant_boolean_node (true,
+							  TREE_TYPE (elt0)),
+				   constant_boolean_node (false,
+							  TREE_TYPE (elt0)));
+	  elt0 = res;
 
 	  elt1 = error_mark_node;
 	  any_changes = true;