[Mesa-dev] [PATCH V2] mesa: use build flag to ensure stack is realigned on x86

[Jose Fonseca]

I'm not particularly knowledgeable about autoconf/make, but it looks 
correct AFAICT.  Thanks for doing this.

I think it would be useful to also add a comment somewhere on why 
-mstackrealign is necessary for 32-bits, for future reference.

Reviewed-by: Jose Fonseca <jfonseca at vmware.com>

Jose

On 07/12/14 12:13, Timothy Arceri wrote:
> Nowadays GCC assumes stack pointer is 16-byte aligned even on 32-bits, but that is an assumption OpenGL drivers (or any dynamic library for that matter) can't afford to make as there are many closed- and open- source application binaries out there that only assume 4-byte stack alignment.
>
> V2: use $target_cpu rather than $host_cpu
>   and setup build flags in config rather than makefile
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D86788&d=AAIBAQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=zfmBZnnVGHeYde45pMKNnVyzeaZbdIqVLprmZCM2zzE&m=weeQ6GJvnQZRjCkjJDlt2roe8RkioxRFO4Rstd2I7Qc&s=w8hG15bIjKbRUDArovpsg5FkTcM8R5Jb7bayyaXGWis&e=
> Signed-off-by: Timothy Arceri <t_arceri at yahoo.com.au>
> ---
>   Tested by cross compiling and running 32-bit version of
>   UrbanTerror.
>
>   Please note if this patch is ok it should also be applied to 10.4 with
>   the last hunk removed.
>
>   configure.ac               | 11 ++++++++++-
>   src/mesa/Makefile.am       |  2 +-
>   src/mesa/main/sse_minmax.c |  3 ---
>   3 files changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index b0df1bb..7dc435a 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -253,8 +253,9 @@ AC_SUBST([VISIBILITY_CXXFLAGS])
>   dnl
>   dnl Optional flags, check for compiler support
>   dnl
> +SSE41_CFLAGS="-msse4.1"
>   save_CFLAGS="$CFLAGS"
> -CFLAGS="-msse4.1 $CFLAGS"
> +CFLAGS="$SSE41_CFLAGS $CFLAGS"
>   AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
>   #include <smmintrin.h>
>   int main () {
> @@ -474,6 +475,12 @@ fi
>   dnl
>   dnl Arch/platform-specific settings
>   dnl
> +case "$target_cpu" in
> +    i?86)
> +        SSE41_CFLAGS="$SSE41_CFLAGS -mstackrealign"
> +;;
> +esac
> +
>   AC_ARG_ENABLE([asm],
>       [AS_HELP_STRING([--disable-asm],
>           [disable assembly usage @<:@default=enabled on supported plaforms@:>@])],
> @@ -2091,6 +2098,8 @@ AM_CONDITIONAL(HAVE_X86_ASM, test "x$asm_arch" = xx86 -o "x$asm_arch" = xx86_64)
>   AM_CONDITIONAL(HAVE_X86_64_ASM, test "x$asm_arch" = xx86_64)
>   AM_CONDITIONAL(HAVE_SPARC_ASM, test "x$asm_arch" = xsparc)
>
> +AC_SUBST([SSE41_CFLAGS], $SSE41_CFLAGS)
> +
>   AC_SUBST([NINE_MAJOR], 1)
>   AC_SUBST([NINE_MINOR], 0)
>   AC_SUBST([NINE_TINY], 0)
> diff --git a/src/mesa/Makefile.am b/src/mesa/Makefile.am
> index 932db4f..3b68573 100644
> --- a/src/mesa/Makefile.am
> +++ b/src/mesa/Makefile.am
> @@ -153,7 +153,7 @@ libmesagallium_la_LIBADD = \
>   libmesa_sse41_la_SOURCES = \
>   	main/streaming-load-memcpy.c \
>   	main/sse_minmax.c
> -libmesa_sse41_la_CFLAGS = $(AM_CFLAGS) -msse4.1
> +libmesa_sse41_la_CFLAGS = $(AM_CFLAGS) $(SSE41_CFLAGS)
>
>   pkgconfigdir = $(libdir)/pkgconfig
>   pkgconfig_DATA = gl.pc
> diff --git a/src/mesa/main/sse_minmax.c b/src/mesa/main/sse_minmax.c
> index 93cf2a6..222ac14 100644
> --- a/src/mesa/main/sse_minmax.c
> +++ b/src/mesa/main/sse_minmax.c
> @@ -31,9 +31,6 @@
>   #include <stdint.h>
>
>   void
> -#if !defined(__x86_64__)
> -   __attribute__((force_align_arg_pointer))
> -#endif
>   _mesa_uint_array_min_max(const unsigned *ui_indices, unsigned *min_index,
>                            unsigned *max_index, const unsigned count)
>   {
>