[patch] Fix m32c breakage caused by fix for PR 32773

[Zdenek Dvorak <rakdver at kam dot mff dot cuni dot cz>]

Hello,

> > The patch below makes us create a forwarder block in case exit has
> > several fallthru predecessors.  Bootstrapped & regtested on i686.
> 
>    It breaks on m32c-unknown-elf:

when an epilogue is inserted, a fallthru to texit may be converted
to a non-fallthru edge.  However, we keep the EDGE_FALLTHRU flag on
the exit edges.  force_one_exit_fallthru then may try to redirect such
edges, thus causing this ICE.

The fix is to clean up the fallthru flag from the exit edges.
Bootstrapped & regtested on i686.

Zdenek

	* function.c (thread_prologue_and_epilogue_insns): Fix exit
	predecessor fallthru flags.

Index: function.c
===================================================================
*** function.c	(revision 126718)
--- function.c	(working copy)
*************** thread_prologue_and_epilogue_insns (void
*** 5256,5262 ****
  epilogue_done:
  
    if (inserted)
!     commit_edge_insertions ();
  
  #ifdef HAVE_sibcall_epilogue
    /* Emit sibling epilogues before any sibling call sites.  */
--- 5256,5273 ----
  epilogue_done:
  
    if (inserted)
!     {
!       commit_edge_insertions ();
! 
!       /* The epilogue insns we inserted may cause the exit edge to no longer
! 	 be fallthru.  */
!       FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
! 	{
! 	  if (((e->flags & EDGE_FALLTHRU) != 0)
! 	      && returnjump_p (BB_END (e->src)))
! 	    e->flags &= ~EDGE_FALLTHRU;
! 	}
!     }
  
  #ifdef HAVE_sibcall_epilogue
    /* Emit sibling epilogues before any sibling call sites.  */