This simplifies (and for me robustifies) finding of the final_bb.
The current code is somewhat odd in that it requires at least one
non-forwarder successor of a switch to transform. The following
patch makes us simply pick the candidate from a random edge (I chose
the default edge) using either the successor or its successor if
the successor is a forwarder.
That fixes fallout of gcc.dg/tree-ssa/pr36881.c when removing
the early copyprop pass which happened to unconditionally run
a cfgcleanup.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2014-06-17 Richard Biener <rguent...@suse.de>
* tree-switch-conversion.c (collect_switch_conv_info): Simplify
and allow all blocks to be forwarders.
Index: gcc/tree-switch-conversion.c
===================================================================
*** gcc/tree-switch-conversion.c (revision 211727)
--- gcc/tree-switch-conversion.c (working copy)
*************** collect_switch_conv_info (gimple swtch,
*** 640,654 ****
info->other_count += e->count;
/* See if there is one common successor block for all branch
! targets. If it exists, record it in FINAL_BB. */
! FOR_EACH_EDGE (e, ei, info->switch_bb->succs)
! {
! if (! single_pred_p (e->dest))
! {
! info->final_bb = e->dest;
! break;
! }
! }
if (info->final_bb)
FOR_EACH_EDGE (e, ei, info->switch_bb->succs)
{
--- 640,655 ----
info->other_count += e->count;
/* See if there is one common successor block for all branch
! targets. If it exists, record it in FINAL_BB.
! Start with the destination of the default case as guess
! or its destination in case it is a forwarder block. */
! if (! single_pred_p (e_default->dest))
! info->final_bb = e_default->dest;
! else if (single_succ_p (e_default->dest)
! && ! single_pred_p (single_succ (e_default->dest)))
! info->final_bb = single_succ (e_default->dest);
! /* Require that all switch destinations are either that common
! FINAL_BB or a forwarder to it. */
if (info->final_bb)
FOR_EACH_EDGE (e, ei, info->switch_bb->succs)
{
