Since my previous idea of resolving conflicts between
-fstrict-volatile-bitfields behavior and the new C/C++ memory model
depending on the selected -std= option was shot down
http://gcc.gnu.org/ml/gcc-patches/2013-06/msg01163.html
it appears that the only way to make -fstrict-volatile-bitfields do
something remotely resembling what it is supposed to do in a way that is
acceptable to the maintainers is to make it not be the default on any
target any more, so that the new memory model always takes precedence
over ABI specifications by default. So, here is a patch to do it.
The affected targets are aarch64, arm, h8300, m32c, rx, and sh. The
code change is identical on all targets, but I have only been able to
test on arm (arm-none-eabi). I have included tweaks to pass
-fstrict-volatile-bitfields explicitly on the test cases that failed
when the default was removed. It might be that some tests for other
targets need similar changes as well.
OK to commit in conjunction with the other patches in this series?
-Sandra
2013-06-30 Sandra Loosemore <san...@codesourcery.com>
gcc/
* config/aarch64/aarch64.c (aarch64_override_options): Don't
override flag_strict_volatile_bitfields.
* config/arm/arm.c (arm_option_override): Likewise.
* config/h8300/h8300.c (h8300_option_override): Likewise.
* config/m32c/m32c.c (m32c_option_override): Likewise.
* config/rx/rx.c (rx_option_override): Likewise.
* config/sh/sh.c (sh_option_override): Likewise.
* doc/invoke.texi (Code Gen Options): Document that
-fstrict-volatile-bitfields is no longer the default on any target.
gcc/testsuite/
* gcc.target/arm/volatile-bitfields-1.c: Add explicit
-fstrict-volatile-bitfields.
* gcc.target/arm/volatile-bitfields-2.c: Likewise.
* gcc.target/arm/volatile-bitfields-3.c: Likewise.
* gcc.target/arm/volatile-bitfields-4.c: Likewise.
Index: gcc/config/aarch64/aarch64.c
===================================================================
--- gcc/config/aarch64/aarch64.c (revision 199963)
+++ gcc/config/aarch64/aarch64.c (working copy)
@@ -4890,10 +4890,6 @@ aarch64_override_options (void)
aarch64_build_bitmask_table ();
- /* This target defaults to strict volatile bitfields. */
- if (flag_strict_volatile_bitfields < 0 && abi_version_at_least (2))
- flag_strict_volatile_bitfields = 1;
-
/* If the user did not specify a processor, choose the default
one for them. This will be the CPU set during configuration using
--with-cpu, otherwise it is "generic". */
Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c (revision 199963)
+++ gcc/config/arm/arm.c (working copy)
@@ -2136,11 +2136,6 @@ 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
- && abi_version_at_least(2))
- flag_strict_volatile_bitfields = 1;
-
/* Enable sw prefetching at -O3 for CPUS that have prefetch, and we have deemed
it beneficial (signified by setting num_prefetch_slots to 1 or more.) */
if (flag_prefetch_loop_arrays < 0
Index: gcc/config/h8300/h8300.c
===================================================================
--- gcc/config/h8300/h8300.c (revision 199963)
+++ gcc/config/h8300/h8300.c (working copy)
@@ -437,10 +437,6 @@ h8300_option_override (void)
restore er6 though, so bump up the cost. */
h8300_move_ratio = 6;
}
-
- /* This target defaults to strict volatile bitfields. */
- if (flag_strict_volatile_bitfields < 0 && abi_version_at_least(2))
- flag_strict_volatile_bitfields = 1;
}
/* Return the byte register name for a register rtx X. B should be 0
Index: gcc/config/m32c/m32c.c
===================================================================
--- gcc/config/m32c/m32c.c (revision 199963)
+++ gcc/config/m32c/m32c.c (working copy)
@@ -416,10 +416,6 @@ m32c_option_override (void)
if (TARGET_A24)
flag_ivopts = 0;
- /* This target defaults to strict volatile bitfields. */
- if (flag_strict_volatile_bitfields < 0 && abi_version_at_least(2))
- flag_strict_volatile_bitfields = 1;
-
/* r8c/m16c have no 16-bit indirect call, so thunks are involved.
This is always worse than an absolute call. */
if (TARGET_A16)
Index: gcc/config/rx/rx.c
===================================================================
--- gcc/config/rx/rx.c (revision 199963)
+++ gcc/config/rx/rx.c (working copy)
@@ -2691,10 +2691,6 @@ rx_option_override (void)
}
}
- /* This target defaults to strict volatile bitfields. */
- if (flag_strict_volatile_bitfields < 0 && abi_version_at_least(2))
- flag_strict_volatile_bitfields = 1;
-
rx_override_options_after_change ();
if (align_jumps == 0 && ! optimize_size)
Index: gcc/config/sh/sh.c
===================================================================
--- gcc/config/sh/sh.c (revision 199963)
+++ gcc/config/sh/sh.c (working copy)
@@ -1020,10 +1020,6 @@ sh_option_override (void)
if (sh_fixed_range_str)
sh_fix_range (sh_fixed_range_str);
- /* This target defaults to strict volatile bitfields. */
- if (flag_strict_volatile_bitfields < 0 && abi_version_at_least(2))
- flag_strict_volatile_bitfields = 1;
-
/* Parse atomic model option and make sure it is valid for the current
target CPU. */
selected_atomic_model_
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 199963)
+++ gcc/doc/invoke.texi (working copy)
@@ -20895,8 +20895,11 @@ attribute, the access is done honoring t
GCC assumes that the user knows something about the target hardware
that it is unaware of.
-The default value of this option is determined by the application binary
-interface for the target processor.
+Note that in some cases this option overrides the memory model
+specified in recent versions of the C and C++ standards. For this
+reason, @option{-fstrict-volatile-bitfields} is not enabled by default
+on any target, even those where the application binary interface for
+the target processor requires this behavior.
@item -fsync-libcalls
@opindex fsync-libcalls
Index: gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c
===================================================================
--- gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c (revision 199963)
+++ gcc/testsuite/gcc.target/arm/volatile-bitfields-1.c (working copy)
@@ -1,6 +1,6 @@
/* { dg-require-effective-target arm_eabi } */
/* { dg-do compile } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -fstrict-volatile-bitfields" } */
typedef struct {
char a:1;
Index: gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c
===================================================================
--- gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c (revision 199963)
+++ gcc/testsuite/gcc.target/arm/volatile-bitfields-2.c (working copy)
@@ -1,6 +1,6 @@
/* { dg-require-effective-target arm_eabi } */
/* { dg-do compile } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -fstrict-volatile-bitfields" } */
typedef struct {
volatile unsigned long a:8;
Index: gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c
===================================================================
--- gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c (revision 199963)
+++ gcc/testsuite/gcc.target/arm/volatile-bitfields-3.c (working copy)
@@ -1,6 +1,6 @@
/* { dg-require-effective-target arm_eabi } */
/* { dg-do compile } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -fstrict-volatile-bitfields" } */
typedef struct {
volatile unsigned long a:8;
Index: gcc/testsuite/gcc.target/arm/volatile-bitfields-4.c
===================================================================
--- gcc/testsuite/gcc.target/arm/volatile-bitfields-4.c (revision 199963)
+++ gcc/testsuite/gcc.target/arm/volatile-bitfields-4.c (working copy)
@@ -1,6 +1,6 @@
/* { dg-require-effective-target arm_eabi } */
/* { dg-do compile } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -fstrict-volatile-bitfields" } */
/* { dg-final { scan-assembler-times "ldr\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" 2 } } */
/* { dg-final { scan-assembler-times "str\[\\t \]+\[^\n\]*,\[\\t \]*\\\[\[^\n\]*\\\]" 2 } } */
/* { dg-final { scan-assembler-not "strb" } } */
