[patches] Re: infinite loop in SPEC's gcc after your patches

[Richard Henderson]

On Mon, Jul 23, 2001 at 10:57:48PM +0200, Jan Hubicka wrote:
> All the can_fallthrdu does as extra compared to the index test above is
> to verify, that there is no jump table lurking around.

Oh, right.  I keep reading that as a check that there's
no jump insn as well.  Which of course there would be.

> !   if (cbranch_block->end != PREV_INSN (cbranch_dest_block->head))
> !     flow_delete_insn_chain (NEXT_INSN (cbranch_block->end),
> ! 			    PREV_INSN (cbranch_dest_block->head));

Better.  Actually, would you check and see if this works
on your test case?  I was about to start bootstrapping it
here, but as I never saw the original problem on alpha...



r~


	* flow.c (try_simplify_condjump): Use tidy_fallthru_edge.

Index: flow.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/flow.c,v
retrieving revision 1.436
diff -c -p -d -u -r1.436 flow.c
--- flow.c	2001/07/23 15:27:33	1.436
+++ flow.c	2001/07/23 21:09:16
@@ -3073,17 +3073,18 @@ try_simplify_condjump (cbranch_block)
     fprintf (rtl_dump_file, "Simplifying condjump %i around jump %i\n",
 	     INSN_UID (cbranch_insn), INSN_UID (jump_block->end));
 
-  /* Success.  Update the CFG to match.  */
+  /* Success.  Update the CFG to match.  Note that after this point
+     the edge variable names appear backwards; the redirection is done
+     this way to preserve edge profile data.  */
   redirect_edge_succ (cbranch_jump_edge, cbranch_dest_block);
   redirect_edge_succ (cbranch_fallthru_edge, jump_dest_block);
   cbranch_jump_edge->flags |= EDGE_FALLTHRU;
   cbranch_fallthru_edge->flags &= ~EDGE_FALLTHRU;
   
+  /* Delete the block with the unconditional jump, and clean up the mess.  */
   flow_delete_block (jump_block);
-  /* Selectively unlink the sequence.  */
-  if (cbranch_jump_edge->src->end != PREV_INSN (cbranch_jump_edge->dest->head))
-    flow_delete_insn_chain (NEXT_INSN (cbranch_jump_edge->src->end),
-			    PREV_INSN (cbranch_jump_edge->dest->head));
+  tidy_fallthru_edge (cbranch_jump_edge, cbranch_block, cbranch_dest_block);
+
   return true;
 }