[patch 2/5] hoist -fstrict-volatile-bitfields test

[Sandra Loosemore <sandra at codesourcery dot com>]

This patch makes parallel changes to store_bit_field_1 and 
extract_bit_field_1 to skip some register shortcuts if 
-fstrict-volatile-bitfields applies.  By itself, it doesn't fix any of 
the new test cases added in part 5, but it's required in conjunction 
with part 3 to make the new volatile-bitfields-3.c test pass on some 
targets (specifically, x86_64).

This part of the patch series has already been approved, but since it's 
probably not useful without the other pieces, I'm deferring checking it 
in for now.

-Sandra

2013-06-16  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* expmed.c (store_bit_field_1): Skip both cheap register alternatives
	if -fstrict-volatile-bitfields applies, not just the first one.
	(extract_bit_field_1): Likewise.

Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c	(revision 199963)
+++ gcc/expmed.c	(working copy)
@@ -810,15 +810,15 @@ store_bit_field_1 (rtx str_rtx, unsigned
     return true;
 
   /* If OP0 is a memory, try copying it to a register and seeing if a
-     cheap register alternative is available.  */
-  if (MEM_P (op0))
+     cheap register alternative is available.  Do not try these tricks if
+     -fstrict-volatile-bitfields is in effect, since they may not respect
+     the mode of the access.  */
+  if (MEM_P (op0)
+      && !(MEM_VOLATILE_P (op0)
+	   && flag_strict_volatile_bitfields > 0))
     {
-      /* Do not use unaligned memory insvs for volatile bitfields when
-	 -fstrict-volatile-bitfields is in effect.  */
-      if (!(MEM_VOLATILE_P (op0)
-	    && flag_strict_volatile_bitfields > 0)
-	  && get_best_mem_extraction_insn (&insv, EP_insv, bitsize, bitnum,
-					   fieldmode)
+      if (get_best_mem_extraction_insn (&insv, EP_insv, bitsize, bitnum,
+					fieldmode)
 	  && store_bit_field_using_insv (&insv, op0, bitsize, bitnum, value))
 	return true;
 
@@ -1592,14 +1592,14 @@ extract_bit_field_1 (rtx str_rtx, unsign
     }
 
   /* If OP0 is a memory, try copying it to a register and seeing if a
-     cheap register alternative is available.  */
-  if (MEM_P (op0))
+     cheap register alternative is available.  Do not try these tricks if
+     -fstrict-volatile-bitfields is in effect, since they may not respect
+     the mode of the access.  */
+  if (MEM_P (op0)
+      && !(MEM_VOLATILE_P (op0) && flag_strict_volatile_bitfields > 0))
     {
-      /* Do not use extv/extzv for volatile bitfields when
-         -fstrict-volatile-bitfields is in effect.  */
-      if (!(MEM_VOLATILE_P (op0) && flag_strict_volatile_bitfields > 0)
-	  && get_best_mem_extraction_insn (&extv, pattern, bitsize, bitnum,
-					   tmode))
+      if (get_best_mem_extraction_insn (&extv, pattern, bitsize, bitnum,
+					tmode))
 	{
 	  rtx result = extract_bit_field_using_extv (&extv, op0, bitsize,
 						     bitnum, unsignedp,