[Bug c/53881] [4.8 regression] ICE in hoist_edge_and_branch_if_true

["steven at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53881

--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-06 23:28:55 UTC ---
The problem is that the switch is not fully cleaned up, there are multiple case
labels going to the same target basic block:

(gdb) p debug_bb(e->src)
;; basic block 2, loop depth 0, count 0
;; prev block 0, next block 3
;; pred:       ENTRY (fallthru,exec)
;; succ:       3 (exec) 4 (exec)
<bb 2>:
a.0_1 = a;
switch (a.0_1) <default: <L4>, case 0 ... 1: <L6>, case 8: Label>

$13 = void
(gdb) p debug_bb(e->dest)
;; basic block 4, loop depth 0, count 0
;; prev block 3, next block 1
;; pred:       2 (exec) 3 (fallthru,exec)
;; succ:       EXIT
Label:
<L6>:
return;


Provisional patch:

Index: tree-switch-conversion.c
===================================================================
--- tree-switch-conversion.c    (revision 189341)
+++ tree-switch-conversion.c    (working copy)
@@ -329,14 +329,13 @@ emit_case_bit_tests (gimple swtch, tree index_expr
       unsigned int lo, hi;
       tree cs = gimple_switch_label (swtch, i);
       tree label = CASE_LABEL (cs);
+      edge e = find_edge (switch_bb, label_to_block (label));
       for (k = 0; k < count; k++)
-       if (label == test[k].label)
+       if (e == test[k].target_edge)
          break;

       if (k == count)
        {
-         edge e = find_edge (switch_bb, label_to_block (label));
-         gcc_assert (e);
          gcc_checking_assert (count < MAX_CASE_BIT_TESTS);
          test[k].hi = 0;
          test[k].lo = 0;