On Sun, May 20, 2012 at 7:47 AM, H.J. Lu <hongjiu...@intel.com> wrote:
> Hi,
>
> This patch allows -mpreferred-stack-boundary=3 on x86-64 when SSE is
> disabled. Since this option changes ABI, I also added a warning for
> -mpreferred-stack-boundary=3. OK for trunk?
>
> Thanks.
>
>
> H.J.
> ----
> PR target/53383
> * doc/invoke.texi: Add a warning for -mpreferred-stack-boundary=3.
>
> * config/i386/i386.c (ix86_option_override_internal): Allow
> -mpreferred-stack-boundary=3 for 64-bit if SSE is disenabled.
>
> * config/i386/i386.h (MIN_STACK_BOUNDARY): Set to 64 for 64-bit
> if SSE is disenabled.
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index eca542c..338d387 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -3660,7 +3660,7 @@ ix86_option_override_internal (bool main_args_p)
> ix86_preferred_stack_boundary = PREFERRED_STACK_BOUNDARY_DEFAULT;
> if (global_options_set.x_ix86_preferred_stack_boundary_arg)
> {
> - int min = (TARGET_64BIT ? 4 : 2);
> + int min = (TARGET_64BIT ? (TARGET_SSE ? 4 : 3) : 2);
> int max = (TARGET_SEH ? 4 : 12);
>
> if (ix86_preferred_stack_boundary_arg < min
> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
> index ddb3645..f7f13d2 100644
> --- a/gcc/config/i386/i386.h
> +++ b/gcc/config/i386/i386.h
> @@ -708,7 +708,7 @@ enum target_cpu_default
> #define MAIN_STACK_BOUNDARY (TARGET_64BIT ? 128 : 32)
>
> /* Minimum stack boundary. */
> -#define MIN_STACK_BOUNDARY (TARGET_64BIT ? 128 : 32)
> +#define MIN_STACK_BOUNDARY (TARGET_64BIT ? (TARGET_SSE ? 128 : 64) : 32)
>
> /* Boundary (in *bits*) on which the stack pointer prefers to be
> aligned; the compiler cannot rely on having this alignment. */
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 4c5c79f..daa1f3a 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -13521,6 +13521,12 @@ Attempt to keep the stack boundary aligned to a 2
> raised to @var{num}
> byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
> the default is 4 (16 bytes or 128 bits).
>
> +@strong{Warning:} When generating code for the x86-64 architecture with
> +SSE extensions disabled, @option{-mpreferred-stack-boundary=3} can be
> +used to keep the stack boundary aligned to 8 byte boundary. You must
> +build all modules with @option{-mpreferred-stack-boundary=3}, including
> +any libraries. This includes the system libraries and startup modules.
> +
> @item -mincoming-stack-boundary=@var{num}
> @opindex mincoming-stack-boundary
> Assume the incoming stack is aligned to a 2 raised to @var{num} byte
I applied the above patch to GCC 4.7 and the following patch to
Linux kernel 3.4.0. Kernel boots and runs correctly. Is the patch
OK for trunk?
Thanks.
--
H.J.
---
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 94e91e4..cd4a4f7 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -49,6 +49,9 @@ else
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
+ # Use -mpreferred-stack-boundary=3 if supported.
+ KBUILD_CFLAGS += $(call cc-option,-mno-sse -mpreferred-stack-boundary=3)
+
# FIXME - should be integrated in Makefile.cpu (Makefile_32.cpu)
cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)
cflags-$(CONFIG_MPSC) += $(call cc-option,-march=nocona)
