From patchwork Wed Jul 21 07:15:17 2010
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Subject: Fix PR44941
Date: Tue, 20 Jul 2010 21:15:17 -0000
From: IainS <developer@sandoe-acoustics.co.uk>
X-Patchwork-Id: 59405
Message-Id: <9DA9D36B-6A09-48E0-8B14-E4E41EE0A2D0@sandoe-acoustics.co.uk>
To: Richard Guenther <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org

Hi Richard,

On 19 Jul 2010, at 13:42, Richard Guenther wrote:

>
> This fixes PR44941 by early handling arguments of size zero.  With
> MEM_REF type-punned cases can now be registers which we do not handle
> properly.  After fixing this you can now see that we can avoid  
> generating
> the stack slot for the zero-sized arg completely.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.  Comments?


> 2010-07-19  Richard Guenther  <rguenther@suse.de>
>
> 	PR middle-end/44941
> 	* expr.c (emit_block_move_hints): Move zero size check first.
> 	Move asserts to more useful places.
> 	* calls.c (load_register_parameters): Check for zero size.
>
> 	* gcc.c-torture/compile/pr44941.c: New testcase.
>  	    {
>  	      rtx mem = validize_mem (args[i].value);

The change to calls.c caused some compat/* fails on powerpc*-darwin9.

As discussed on irc, (hopefully I understood what was wanted)
the attached patch restores powerpc...
...  whilst compile.exp=pr44941.c still passes on i686-darwin9.
bootstrapped on {i686,powerpc}-darwin9
OK for trunk?
Iain




  	      /* Handle a BLKmode that needs shifting.  */


Index: gcc/calls.c
===================================================================
--- gcc/calls.c	(revision 162339)
+++ gcc/calls.c	(working copy)
@@ -1668,15 +1668,16 @@ load_register_parameters (struct arg_data  
*args, i
  	      emit_move_insn (gen_rtx_REG (word_mode, REGNO (reg) + j),
  			      args[i].aligned_regs[j]);

-	  else if ((partial == 0 || args[i].pass_on_stack)
-		   && size != 0)
+	  else if (partial == 0 || args[i].pass_on_stack)
  	    {
  	      rtx mem = validize_mem (args[i].value);

-	      /* Check for overlap with already clobbered argument area.  */
+	      /* Check for overlap with already clobbered argument area,
+	         providing that this has finite size.  */
  	      if (is_sibcall
-		  && mem_overlaps_already_clobbered_arg_p (XEXP (args[i].value, 0),
-							   size))
+		  && (size == 0
+		      || mem_overlaps_already_clobbered_arg_p (
+					    XEXP (args[i].value, 0), size)))
  		*sibcall_failure = 1;