tree-optimization/108164 - undefined overflow with IV vectorization

vect_update_ivs_after_vectorizer can end up emitting a signed
IV update when the loop body performed an unsigned computation.
The following makes sure to perform that update in the type
of the loop update type to avoid undefined behavior on overflow.

	PR tree-optimization/108164
	* tree-vect-loop-manip.cc (vect_update_ivs_after_vectorizer):
	Perform vect_step_op_add update in the appropriate type.

	* gcc.dg/pr108164.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/pr108164.c b/gcc/testsuite/gcc.dg/pr108164.c
new file mode 100644 (file)
index 0000000..d76d557
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108164.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fno-tree-dce" } */
+
+int a, b, c;
+int main()
+{
+  int e = -1;
+  short f = -1;
+  for (; c < 1; c++)
+    while (f >= e)
+      f++;
+  for (; a < 2; a++) {
+    short g = ~(~b | ~f);
+    int h = -g;
+    int i = (3 / ~h) / ~b;
+    b = i;
+  }
+  return 0;
+}

diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 1d96130..5ec739e 100644 (file)
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -1576,14 +1576,16 @@ vect_update_ivs_after_vectorizer (loop_vec_info loop_vinfo,
 
       if (induction_type == vect_step_op_add)
        {
-         off = fold_build2 (MULT_EXPR, TREE_TYPE (step_expr),
-                            fold_convert (TREE_TYPE (step_expr), niters),
-                            step_expr);
+         tree stype = TREE_TYPE (step_expr);
+         off = fold_build2 (MULT_EXPR, stype,
+                            fold_convert (stype, niters), step_expr);
          if (POINTER_TYPE_P (type))
            ni = fold_build_pointer_plus (init_expr, off);
          else
-           ni = fold_build2 (PLUS_EXPR, type,
-                             init_expr, fold_convert (type, off));
+           ni = fold_convert (type,
+                              fold_build2 (PLUS_EXPR, stype,
+                                           fold_convert (stype, init_expr),
+                                           off));
        }
       /* Don't bother call vect_peel_nonlinear_iv_init.  */
       else if (induction_type == vect_step_op_neg)