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Re: [PATCH] Fix PR44941

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 <>

	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?

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),

-	  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;

/* Handle a BLKmode that needs shifting. */

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