* basic-block.h (could_fall_through): Declare.

	* cfganal.c (can_fallthru): Succeed if the target is EXIT_BLOCK_PTR.
	Fail if the source already has a fallthrough edge to the exit
	block pointer.
	(could_fall_through): New function.
	* cfgbuild.c (make_edges): Check if we already have a fallthrough
	edge to the exit block pointer.
	* cfglayout.c (fixup_fallthru_exit_predecessor): Check that it is
	not called before reload has completed.
	Handle special case of first block having a fall-through exit edge.
	(cfg_layout_finalize): Don't call it before reload or if we have
	rtl epilogues.
	(fixup_reorder_chain): A fall through to the exit block does not
	require the block to come last.  Add sanity checks.
	* cfgrtl.c (rtl_split_edge): Add special handling of fall through
	edges to the exit block.
	* function.c (cfglayout.h): #include.
	(thread_prologue_and_epilogue_insns): If we have neither return nor
	epilogue, but a fall through to the exit block from mid-function,
	force a non-fall-through exit.
	* Makefile.in (function.o): Depend on CFGLAYOUT_H.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@83089 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 31 insertions, 11 deletions

diff --git a/gcc/function.c b/gcc/function.c
index 00c56e322af..b59da9a4160 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -63,6 +63,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "integrate.h"
 #include "langhooks.h"
 #include "target.h"
+#include "cfglayout.h"
 
 #ifndef LOCAL_ALIGNMENT
 #define LOCAL_ALIGNMENT(TYPE, ALIGNMENT) ALIGNMENT
@@ -7558,20 +7559,20 @@ thread_prologue_and_epilogue_insns (rtx f ATTRIBUTE_UNUSED)
 	}
     }
 #endif
+  /* Find the edge that falls through to EXIT.  Other edges may exist
+     due to RETURN instructions, but those don't need epilogues.
+     There really shouldn't be a mixture -- either all should have
+     been converted or none, however...  */
+
+  for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next)
+    if (e->flags & EDGE_FALLTHRU)
+      break;
+  if (e == NULL)
+    goto epilogue_done;
+
 #ifdef HAVE_epilogue
   if (HAVE_epilogue)
     {
-      /* Find the edge that falls through to EXIT.  Other edges may exist
-	 due to RETURN instructions, but those don't need epilogues.
-	 There really shouldn't be a mixture -- either all should have
-	 been converted or none, however...  */
-
-      for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next)
-	if (e->flags & EDGE_FALLTHRU)
-	  break;
-      if (e == NULL)
-	goto epilogue_done;
-
       start_sequence ();
       epilogue_end = emit_note (NOTE_INSN_EPILOGUE_BEG);
 
@@ -7597,7 +7598,26 @@ thread_prologue_and_epilogue_insns (rtx f ATTRIBUTE_UNUSED)
       insert_insn_on_edge (seq, e);
       inserted = 1;
     }
+  else
 #endif
+    {
+      basic_block cur_bb;
+
+      if (! next_active_insn (BB_END (e->src)))
+	goto epilogue_done;
+      /* We have a fall-through edge to the exit block, the source is not
+         at the end of the function, and there will be an assembler epilogue
+         at the end of the function.
+         We can't use force_nonfallthru here, because that would try to
+         use return.  Inserting a jump 'by hand' is extremely messy, so
+	 we take advantage of cfg_layout_finalize using
+	fixup_fallthru_exit_predecessor.  */
+      cfg_layout_initialize ();
+      FOR_EACH_BB (cur_bb)
+	if (cur_bb->index >= 0 && cur_bb->next_bb->index >= 0)
+	  cur_bb->rbi->next = cur_bb->next_bb;
+      cfg_layout_finalize ();
+    }
 epilogue_done:
 
   if (inserted)