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?
2017-02-17 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..5524357 100644
--- gcc/gimplify.c
+++ gcc/gimplify.c
@@ -12003,6 +12003,11 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p,
gimple_seq *post_p,
gimple_test_f, fallback);
break;
+ case LABEL_DECL:
+ /* We can get here with code such as "*&&L;", where L is
+ a LABEL_DECL that is marked as FORCED_LABEL. Skip it. */
+ break;
+
default:
/* Anything else with side-effects must be converted to
a valid statement before we get here. */
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
