On Mon, Feb 20, 2017 at 10:51:04AM +0100, Richard Biener wrote:
> On Fri, Feb 17, 2017 at 2:53 PM, Marek Polacek <pola...@redhat.com> wrote:
> > We are crashing with a label as a value without accompanying goto.
> > The problem is that TREE_SIDE_EFFECTS and FORCED_LABEL use the same
> > ->base.side_effects_flag, so gimplify_expr is confused. We don't
> > ICE with 'goto *&&L;' becase then we take this path:
> > 11406 case GOTO_EXPR:
> > 11407 /* If the target is not LABEL, then it is a computed jump
> > 11408 and the target needs to be gimplified. */
> > 11409 if (TREE_CODE (GOTO_DESTINATION (*expr_p)) != LABEL_DECL)
> > 11410 {
> > 11411 ret = gimplify_expr (&GOTO_DESTINATION (*expr_p), pre_p,
> > 11412 NULL, is_gimple_val, fb_rvalue);
> > and because of that fb_rvalue we won't go to the switch where the ICE
> > occured. Because '*&&L;' on its own is useless, I think we can simply
> > discard it, which is what the following does.
> >
> > Bootstrapped/regtested on x86_64-linux, ok for trunk and 6?
>
> I think I prefer
>
> Index: gcc/gimplify.c
> ===================================================================
> --- gcc/gimplify.c (revision 245594)
> +++ gcc/gimplify.c (working copy)
> @@ -11977,7 +11977,8 @@ gimplify_expr (tree *expr_p, gimple_seq
> {
> /* We aren't looking for a value, and we don't have a valid
> statement. If it doesn't have side-effects, throw it away. */
> - if (!TREE_SIDE_EFFECTS (*expr_p))
> + if (TREE_CODE (*expr_p) == LABEL_DECL
> + || !TREE_SIDE_EFFECTS (*expr_p))
> *expr_p = NULL;
> else if (!TREE_THIS_VOLATILE (*expr_p))
> {
>
> (with a comment). Ideally we'd have TREE_NOT_CHECK (NON_TYPE_CHEC
> (NODE), LABEL_DECL) on
> TREE_SIDE_EFFECTS but that may have unwanted fallout at this point.
>
> Ok with the above change.
All right, I'll commit this after testing. Thanks,
2017-02-20 Marek Polacek <pola...@redhat.com>
PR middle-end/79537
* gimplify.c (gimplify_expr): Handle unused *&&L;.
* gcc.dg/comp-goto-4.c: New.
diff --git gcc/gimplify.c gcc/gimplify.c
index 1b9c8d2..820459c 100644
--- gcc/gimplify.c
+++ gcc/gimplify.c
@@ -11976,8 +11976,11 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p,
gimple_seq *post_p,
if (fallback == fb_none && *expr_p && !is_gimple_stmt (*expr_p))
{
/* We aren't looking for a value, and we don't have a valid
- statement. If it doesn't have side-effects, throw it away. */
- if (!TREE_SIDE_EFFECTS (*expr_p))
+ statement. If it doesn't have side-effects, throw it away.
+ We can also get here with code such as "*&&L;", where L is
+ a LABEL_DECL that is marked as FORCED_LABEL. */
+ if (TREE_CODE (*expr_p) == LABEL_DECL
+ || !TREE_SIDE_EFFECTS (*expr_p))
*expr_p = NULL;
else if (!TREE_THIS_VOLATILE (*expr_p))
{
diff --git gcc/testsuite/gcc.dg/comp-goto-4.c gcc/testsuite/gcc.dg/comp-goto-4.c
index e69de29..51a6a86 100644
--- gcc/testsuite/gcc.dg/comp-goto-4.c
+++ gcc/testsuite/gcc.dg/comp-goto-4.c
@@ -0,0 +1,21 @@
+/* PR middle-end/79537 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+/* { dg-require-effective-target indirect_jumps } */
+/* { dg-require-effective-target label_values } */
+
+void
+f (void)
+{
+L:
+ *&&L;
+}
+
+void
+f2 (void)
+{
+ void *p;
+L:
+ p = &&L;
+ *p; /* { dg-warning "dereferencing 'void \\*' pointer" } */
+}
Marek
