[backport proposed 4.8/trunk fix for M68K PR52573 <mikpe@it.uu.se>]

Date: Wed, 11 Jul 2012 23:31:07 +0200
From: Bernd Schmidt <bernds at codesourcery dot com>
Subject: Re: regrename creates invalid insn
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

On 03/26/2012 06:03 PM, Andreas Schwab wrote:
> Bernd Schmidt <bernds@codesourcery.com> writes:
> 
>> Does 4.7 still have the failure at all?
> 
> Yes, see PR52573.

Well, I still think having both REG_DEAD and REG_UNUSED for the same reg
is bogus, but fixing that causes trouble in reg-stack. It seems the path
of least resistance is to just cope with the situation in regrename.

The following seems to cure the problem with a 4.7 m68k cross. Also
bootstrapped and tested with -frename-registers enabled at -O2 on
x86_64-linux. Ok everywhere?


Bernd

gcc/

	PR rtl-optimization/52573
	* regrename.c (build_def_use): Ignore REG_DEAD notes if there is a
	REG_UNUSED for the same register.

--- gcc-4.6.3/gcc/regrename.c.~1~	2011-01-02 18:28:24.000000000 +0100
+++ gcc-4.6.3/gcc/regrename.c	2012-07-14 15:59:06.000000000 +0200
@@ -1328,7 +1328,8 @@ build_def_use (basic_block bb)
 
 	  /* Step 4: Close chains for registers that die here.  */
 	  for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
-	    if (REG_NOTE_KIND (note) == REG_DEAD)
+	    if (REG_NOTE_KIND (note) == REG_DEAD
+		&& !find_regno_note (insn, REG_UNUSED, REGNO (XEXP (note, 0))))
 	      {
 		remove_from_hard_reg_set (&live_hard_regs,
 					  GET_MODE (XEXP (note, 0)),