[Bug rtl-optimization/46649] [4.6 Regression] ICE: in move_bb_info, at sel-sched-ir.c:5080 with -fschedule-insns -fselective-scheduling

[amonakov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46649

--- Comment #7 from Alexander Monakov <amonakov at gcc dot gnu.org> 2010-12-14 
14:38:38 UTC ---
After a discussion with Andrey and refreshing my memory on that code I think
it's actually better to unbreak purge_empty_blocks in this case.  It used to be
correct, i.e. it never attempted to delete the first BB in the region; then I
broke it because I wasn't aware of the limitation w.r.t. removal of the first
BB.

Sorry for the spam.

diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
index 427fd22..9f0c4a3 100644
--- a/gcc/sel-sched-ir.c
+++ b/gcc/sel-sched-ir.c
@@ -3749,10 +3749,10 @@ tidy_control_flow (basic_block xbb, bool full_tidying)
 void
 purge_empty_blocks (void)
 {
-  /* Do not attempt to delete preheader.  */
-  int i = sel_is_loop_preheader_p (BASIC_BLOCK (BB_TO_BLOCK (0))) ? 1 : 0;
+  int i;

-  while (i < current_nr_blocks)
+  /* Do not attempt to delete the first basic block in the region.  */
+  for (i = 1; i < current_nr_blocks; i++)
     {
       basic_block b = BASIC_BLOCK (BB_TO_BLOCK (i));