[Mesa-dev] [PATCH] configure.ac/swr: build swr with -fno-strict-aliasing

[Matt Turner]

On Tue, Aug 2, 2016 at 10:53 AM, Tim Rowley <timothy.o.rowley at intel.com> wrote:
> swr rasterizer contains numerous data transfers between vectors
> and ordinary C types.  Fixing for strict aliasing will take time.

Oh, sorry! I forgot about swr.

> ---
>  configure.ac                        | 7 +++++++
>  src/gallium/drivers/swr/Makefile.am | 1 +
>  2 files changed, 8 insertions(+)
>
> diff --git a/configure.ac b/configure.ac
> index aea5890..fb4a12a 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -312,6 +312,8 @@ if test "x$GCC" = xyes; then
>      MSVC2013_COMPAT_CFLAGS="-Werror=pointer-arith"
>      MSVC2013_COMPAT_CXXFLAGS="-Werror=pointer-arith"
>
> +    NO_STRICT_ALIASING_CFLAGS="-fno-strict-aliasing"
> +
>      # Enable -Werror=vla if compiler supports it
>      save_CFLAGS="$CFLAGS"
>      AC_MSG_CHECKING([whether $CC supports -Werror=vla])
> @@ -341,11 +343,16 @@ if test "x$GXX" = xyes; then
>
>      # We don't want floating-point math functions to set errno or trap
>      CXXFLAGS="$CXXFLAGS -fno-math-errno -fno-trapping-math"
> +
> +    NO_STRICT_ALIASING_CXXFLAGS="-fno-strict-aliasing"
>  fi
>
>  AC_SUBST([MSVC2013_COMPAT_CFLAGS])
>  AC_SUBST([MSVC2013_COMPAT_CXXFLAGS])
>
> +AC_SUBST([NO_STRICT_ALIASING_CFLAGS])
> +AC_SUBST([NO_STRICT_ALIASING_CXXFLAGS])
> +
>  dnl even if the compiler appears to support it, using visibility attributes isn't
>  dnl going to do anything useful currently on cygwin apart from emit lots of warnings
>  case "$host_os" in
> diff --git a/src/gallium/drivers/swr/Makefile.am b/src/gallium/drivers/swr/Makefile.am
> index 3459af3..fa02349 100644
> --- a/src/gallium/drivers/swr/Makefile.am
> +++ b/src/gallium/drivers/swr/Makefile.am
> @@ -29,6 +29,7 @@ noinst_LTLIBRARIES = libmesaswr.la
>  libmesaswr_la_SOURCES = $(LOADER_SOURCES)
>
>  COMMON_CXXFLAGS = \
> +       $(NO_STRICT_ALIASING_CXXFLAGS) \

I think you should just put -fno-strict-aliasing here instead. I don't
think the variable and substitutions in configure.ac add anything.