re PR bootstrap/65060 (r220696 breaks bootstrap on Linux/x86-32)

       PR bootstrap/65060
        Revert my change for tree-optimization/64823.

From-SVN: r220701

1 files changed, 7 insertions, 32 deletions

diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index 7187d065e91..4f839910a84 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -110,15 +110,6 @@ potentially_threadable_block (basic_block bb)
 {
   gimple_stmt_iterator gsi;
 
-  /* Special case.  We can get blocks that are forwarders, but are
-     not optimized away because they forward from outside a loop
-     to the loop header.   We want to thread through them as we can
-     sometimes thread to the loop exit, which is obviously profitable. 
-     the interesting case here is when the block has PHIs.  */
-  if (gsi_end_p (gsi_start_nondebug_bb (bb))
-      && !gsi_end_p (gsi_start_phis (bb)))
-    return true;
-  
   /* If BB has a single successor or a single predecessor, then
      there is no threading opportunity.  */
   if (single_succ_p (bb) || single_pred_p (bb))
@@ -1290,32 +1281,16 @@ thread_through_normal_block (edge e,
     = record_temporary_equivalences_from_stmts_at_dest (e, stack, simplify,
 							*backedge_seen_p);
 
-  /* There's two reasons STMT might be null, and distinguishing
-     between them is important.
+  /* If we didn't look at all the statements, the most likely reason is
+     there were too many and thus duplicating this block is not profitable.
 
-     First the block may not have had any statements.  For example, it
-     might have some PHIs and unconditionally transfer control elsewhere.
-     Such blocks are suitable for jump threading, particularly as a
-     joiner block.
-
-     The second reason would be if we did not process all the statements
-     in the block (because there were too many to make duplicating the
-     block profitable.   If we did not look at all the statements, then
-     we may not have invalidated everything needing invalidation.  Thus
-     we must signal to our caller that this block is not suitable for
-     use as a joiner in a threading path.  */
+     Also note if we do not look at all the statements, then we may not
+     have invalidated equivalences that are no longer valid if we threaded
+     around a loop.  Thus we must signal to our caller that this block
+     is not suitable for use as a joiner in a threading path.  */
   if (!stmt)
-    {
-      /* First case.  The statement simply doesn't have any instructions, but
-	 does have PHIs.  */
-      if (gsi_end_p (gsi_start_nondebug_bb (e->dest))
-	  && !gsi_end_p (gsi_start_phis (e->dest)))
-	return 0;
+    return -1;
 
-      /* Second case.  */
-      return -1;
-    }
-  
   /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
      will be taken.  */
   if (gimple_code (stmt) == GIMPLE_COND