2010-10-26  Jie Zhang  <jie@codesourcery.com>

	Issue #1259

	Backport from mainline:

	gcc/
	2010-10-26  Jie Zhang  <jie@codesourcery.com>

	* stor-layout.c (layout_decl): Use the field's type to
	determine the mode and keep DECL_BIT_FIELD for a volatile
	bit-field.
	* config/arm/arm.c (arm_override_options): Default to
	-fstrict-volatile-bitfields.

	gcc/testsuite/
	2010-10-26  Jie Zhang  <jie@codesourcery.com>

	* gcc.target/arm/volatile-bitfields-1.c: New test.
	* gcc.target/arm/volatile-bitfields-2.c: New test.
	* gcc.target/arm/volatile-bitfields-3.c: New test.

=== modified file 'gcc/config/arm/arm.c'
--- old/gcc/config/arm/arm.c	2010-11-04 10:45:05 +0000
+++ new/gcc/config/arm/arm.c	2010-11-04 12:49:37 +0000
@@ -1933,6 +1933,10 @@
        calculation, which is 2 instructions.  */
     set_param_value ("gcse-unrestricted-cost", 2);
 
+  /* ARM EABI defaults to strict volatile bitfields.  */
+  if (TARGET_AAPCS_BASED && flag_strict_volatile_bitfields < 0)
+    flag_strict_volatile_bitfields = 1;
+
   /* Register global variables with the garbage collector.  */
   arm_add_gc_roots ();
 

=== modified file 'gcc/stor-layout.c'
--- old/gcc/stor-layout.c	2010-04-02 18:54:46 +0000
+++ new/gcc/stor-layout.c	2010-11-04 12:49:37 +0000
@@ -593,11 +593,14 @@
 	    }
 
 	  /* See if we can use an ordinary integer mode for a bit-field.
-	     Conditions are: a fixed size that is correct for another mode
-	     and occupying a complete byte or bytes on proper boundary.  */
+	     Conditions are: a fixed size that is correct for another mode,
+	     occupying a complete byte or bytes on proper boundary,
+	     and not volatile or not -fstrict-volatile-bitfields.  */
 	  if (TYPE_SIZE (type) != 0
 	      && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
-	      && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT)
+	      && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT
+	      && !(TREE_THIS_VOLATILE (decl)
+		   && flag_strict_volatile_bitfields > 0))
 	    {
 	      enum machine_mode xmode
 		= mode_for_size_tree (DECL_SIZE (decl), MODE_INT, 1);

=== added file 'gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c'
--- old/gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c	1970-01-01 00:00:00 +0000
+++ new/gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c	2010-11-04 12:49:37 +0000
@@ -0,0 +1,18 @@
+/* { dg-require-effective-target arm_eabi } */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef struct {
+  char a:1;
+  char b:7;
+  int c;
+} BitStruct;
+
+volatile BitStruct bits;
+
+int foo ()
+{
+  return bits.b;
+}
+
+/* { dg-final { scan-assembler "ldrb\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */

=== added file 'gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c'
--- old/gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c	1970-01-01 00:00:00 +0000
+++ new/gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c	2010-11-04 12:49:37 +0000
@@ -0,0 +1,18 @@
+/* { dg-require-effective-target arm_eabi } */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef struct {
+  volatile unsigned long a:8;
+  volatile unsigned long b:8;
+  volatile unsigned long c:16;
+} BitStruct;
+
+BitStruct bits;
+
+unsigned long foo ()
+{
+  return bits.b;
+}
+
+/* { dg-final { scan-assembler "ldr\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */

=== added file 'gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c'
--- old/gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c	1970-01-01 00:00:00 +0000
+++ new/gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c	2010-11-04 12:49:37 +0000
@@ -0,0 +1,18 @@
+/* { dg-require-effective-target arm_eabi } */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef struct {
+  volatile unsigned long a:8;
+  volatile unsigned long b:8;
+  volatile unsigned long c:16;
+} BitStruct;
+
+BitStruct bits;
+
+unsigned long foo ()
+{
+  return bits.c;
+}
+
+/* { dg-final { scan-assembler "ldr\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */