tree: Avoid variable sharing in get_narrower [PR94724]

On Thu, May 07, 2020 at 02:45:29PM +0200, Thomas Schwinge wrote:
> >>+      for (tree op = win; TREE_CODE (op) == COMPOUND_EXPR;
>
> ..., and new 'op' variable here.
>
> >>+        op = TREE_OPERAND (op, 1))
> >>+     v.safe_push (op);
> >>+      FOR_EACH_VEC_ELT_REVERSE (v, i, op)
> >>+     ret = build2_loc (EXPR_LOCATION (op), COMPOUND_EXPR,
> >>+                       TREE_TYPE (win), TREE_OPERAND (op, 0),
> >>+                       ret);
> >>+      return ret;
> >>     }
> >>   while (TREE_CODE (op) == NOP_EXPR)
> >>     {

There is no reason for the shadowing and op at this point acts as a
temporary and will be overwritten in FOR_EACH_VEC_ELT_REVERSE anyway.
So, we can just s/tree // here.

2020-05-08  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/94724
	* tree.c (get_narrower): Reuse the op temporary instead of
	shadowing it.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 75b0ed1..2e5a051 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2020-05-08  Jakub Jelinek  <jakub@redhat.com>
 
+       PR middle-end/94724
+       * tree.c (get_narrower): Reuse the op temporary instead of
+       shadowing it.
+
        PR tree-optimization/94783
        * match.pd ((X + (X >> (prec - 1))) ^ (X >> (prec - 1)) to abs (X)):
        New simplification.

diff --git a/gcc/tree.c b/gcc/tree.c
index e451401..3974749 100644 (file)
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -8889,7 +8889,7 @@ get_narrower (tree op, int *unsignedp_ptr)
        return win;
       auto_vec <tree, 16> v;
       unsigned int i;
-      for (tree op = win; TREE_CODE (op) == COMPOUND_EXPR;
+      for (op = win; TREE_CODE (op) == COMPOUND_EXPR;
           op = TREE_OPERAND (op, 1))
        v.safe_push (op);
       FOR_EACH_VEC_ELT_REVERSE (v, i, op)