stor-layout.c (layout_decl): Use the field's type to determine the mode and keep…

stor-layout.c (layout_decl): Use the field's type to determine the mode and keep DECL_BIT_FIELD for a...

	* 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.

	testsuite/
	* 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.

From-SVN: r165934

gcc/ChangeLog

+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.
+
 2010-10-25  Paul Koning  <ni1d@arrl.net>
 
 	* config/pdp11/pdp11.md: Add define_constants for register

gcc/config/arm/arm.c

@@ -1971,6 +1971,10 @@ arm_option_override (void)
 			   global_options.x_param_values,
 			   global_options_set.x_param_values);
 
+  /* 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 ();
 }

gcc/stor-layout.c

@@ -661,11 +661,14 @@ layout_decl (tree decl, unsigned int known_align)
 	    }
 
 	  /* 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);

gcc/testsuite/ChangeLog

+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.
+
 2010-10-25  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/pointer_discr1.adb: New test.

gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c

+/* { 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\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */

gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c

+/* { 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\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */

gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c

+/* { 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\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" } } */