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[RFC] Unconditionally clean up CFG before emitting prologue


with the numerous checks generated in Ada, the gimplification process can 
generated dead branches that aren't easily eliminated at -O0 and can impair 
the debugging experience.  We have found that unconditionally cleaning up the 
CFG before emitting the prologue/epilogue can help in some cases.  This is the 
same idiom already used in rest_of_handle_jump2 for example.

Tested on x86_64-suse-linux.  Comments?

2012-04-09  Eric Botcazou  <>

	* function.c (rest_of_handle_thread_prologue_and_epilogue): Clean up
	the CFG before generating prologue/epilogue even when not optimizing.

Eric Botcazou
Index: function.c
--- function.c	(revision 186176)
+++ function.c	(working copy)
@@ -6877,8 +6877,7 @@ struct rtl_opt_pass pass_leaf_regs =
 static unsigned int
 rest_of_handle_thread_prologue_and_epilogue (void)
-  if (optimize)
-    cleanup_cfg (CLEANUP_EXPENSIVE);
+  cleanup_cfg (optimize ? CLEANUP_EXPENSIVE : 0);
   /* On some machines, the prologue and epilogue code, or parts thereof,
      can be represented as RTL.  Doing so lets us schedule insns between

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