[Bug middle-end/79537] [5/6/7 Regression] ICE in gimplify_expr, at gimplify.c:12009

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79537

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
gimplify_expr has code to handle taking the address of a label:
11610         case LABEL_DECL:
11611           /* We get here when taking the address of a label.  We mark
11612              the label as "forced"; meaning it can never be removed and
11613              it is a potential target for any computed goto.  */
11614           FORCED_LABEL (*expr_p) = 1;
11615           ret = GS_ALL_DONE;
11616           break;

but we crash later on in the switch here:

11978       /* We aren't looking for a value, and we don't have a valid
11979          statement.  If it doesn't have side-effects, throw it away.  */
11980       if (!TREE_SIDE_EFFECTS (*expr_p))
11981         *expr_p = NULL;
11982       else if (!TREE_THIS_VOLATILE (*expr_p))
11983         {
11984           /* This is probably a _REF that contains something nested that
11985              has side effects.  Recurse through the operands to find it. 
*/
11986           enum tree_code code = TREE_CODE (*expr_p);

The problem is that the LABEL_DECL L is considered TREE_SIDE_EFFECTS, because
the definition of FORCED_LABEL is:

#define FORCED_LABEL(NODE) (LABEL_DECL_CHECK (NODE)->base.side_effects_flag)