On Wed, May 10, 2023 at 5:10 PM liuhongt <hongtao....@intel.com> wrote:
>
> > The quoted patch shows -shared in context and you didn't post a
> > backport version
> > to look at. But yes, we shouldn't change -shared behavior on a
> > branch, even less so make it
> > inconsistent between targets.
> Here's the patch.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> Ok for GCC 11/12 backport?
I'm going to push the patch next week if there's no objection.
>
> if (mdaz-ftz)
> link crtfastmath.o
> else if ((Ofast || ffast-math || funsafe-math-optimizations)
> && !mno-daz-ftz)
> link crtfastmath.o
> else
> Don't link crtfastmath.o
>
> gcc/ChangeLog:
>
> * config/i386/cygwin.h (ENDFILE_SPEC): Link crtfastmath.o
> whenever -mdaz-ftz is specified. Don't link crtfastmath.o
> when -mno-daz-ftz is specified.
> * config/i386/darwin.h (ENDFILE_SPEC): Ditto.
> * config/i386/gnu-user-common.h
> (GNU_USER_TARGET_MATHFILE_SPEC): Ditto.
> * config/i386/mingw32.h (ENDFILE_SPEC): Ditto.
> * config/i386/i386.opt (mdaz-ftz): New option.
> * doc/invoke.texi (x86 options): Document mftz-daz.
> ---
> gcc/config/i386/cygwin.h | 2 +-
> gcc/config/i386/darwin.h | 4 ++--
> gcc/config/i386/gnu-user-common.h | 2 +-
> gcc/config/i386/i386.opt | 4 ++++
> gcc/config/i386/mingw32.h | 2 +-
> gcc/doc/invoke.texi | 11 ++++++++++-
> 6 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/config/i386/cygwin.h b/gcc/config/i386/cygwin.h
> index d06eda369cf..5412c5d4479 100644
> --- a/gcc/config/i386/cygwin.h
> +++ b/gcc/config/i386/cygwin.h
> @@ -57,7 +57,7 @@ along with GCC; see the file COPYING3. If not see
>
> #undef ENDFILE_SPEC
> #define ENDFILE_SPEC \
> - "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s}\
> +
> "%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}
> \
> %{!shared:%:if-exists(default-manifest.o%s)}\
> %{fvtable-verify=none:%s; \
> fvtable-verify=preinit:vtv_end.o%s; \
> diff --git a/gcc/config/i386/darwin.h b/gcc/config/i386/darwin.h
> index a55f6b2b874..2f773924d6e 100644
> --- a/gcc/config/i386/darwin.h
> +++ b/gcc/config/i386/darwin.h
> @@ -109,8 +109,8 @@ along with GCC; see the file COPYING3. If not see
> "%{!force_cpusubtype_ALL:-force_cpusubtype_ALL} "
>
> #undef ENDFILE_SPEC
> -#define ENDFILE_SPEC \
> - "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
> +#define ENDFILE_SPEC
> +\
> "%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}
> \
> %{mpc32:crtprec32.o%s} \
> %{mpc64:crtprec64.o%s} \
> %{mpc80:crtprec80.o%s}" TM_DESTRUCTOR
> diff --git a/gcc/config/i386/gnu-user-common.h
> b/gcc/config/i386/gnu-user-common.h
> index 23b54c5be52..3d2a33f1714 100644
> --- a/gcc/config/i386/gnu-user-common.h
> +++ b/gcc/config/i386/gnu-user-common.h
> @@ -47,7 +47,7 @@ along with GCC; see the file COPYING3. If not see
>
> /* Similar to standard GNU userspace, but adding -ffast-math support. */
> #define GNU_USER_TARGET_MATHFILE_SPEC \
> - "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
> +
> "%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}
> \
> %{mpc32:crtprec32.o%s} \
> %{mpc64:crtprec64.o%s} \
> %{mpc80:crtprec80.o%s}"
> diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
> index a3675e515bc..5cfb7cdcbc2 100644
> --- a/gcc/config/i386/i386.opt
> +++ b/gcc/config/i386/i386.opt
> @@ -420,6 +420,10 @@ mpc80
> Target RejectNegative
> Set 80387 floating-point precision to 80-bit.
>
> +mdaz-ftz
> +Target
> +Set the FTZ and DAZ Flags.
> +
> mpreferred-stack-boundary=
> Target RejectNegative Joined UInteger Var(ix86_preferred_stack_boundary_arg)
> Attempt to keep stack aligned to this power of 2.
> diff --git a/gcc/config/i386/mingw32.h b/gcc/config/i386/mingw32.h
> index d3ca0cd0279..ddbe6a4054b 100644
> --- a/gcc/config/i386/mingw32.h
> +++ b/gcc/config/i386/mingw32.h
> @@ -197,7 +197,7 @@ along with GCC; see the file COPYING3. If not see
>
> #undef ENDFILE_SPEC
> #define ENDFILE_SPEC \
> - "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
> +
> "%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}
> \
> %{!shared:%:if-exists(default-manifest.o%s)}\
> %{fvtable-verify=none:%s; \
> fvtable-verify=preinit:vtv_end.o%s; \
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index cb83dd8a1cc..87eedfffa6c 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -1434,7 +1434,7 @@ See RS/6000 and PowerPC Options.
> -m96bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128
> @gol
> -mregparm=@var{num} -msseregparm @gol
> -mveclibabi=@var{type} -mvect8-ret-in-mem @gol
> --mpc32 -mpc64 -mpc80 -mstackrealign @gol
> +-mpc32 -mpc64 -mpc80 -mdaz-ftz -mstackrealign @gol
> -momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
> -mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
> -m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=@var{num} @gol
> @@ -32078,6 +32078,15 @@ are enabled by default; routines in such libraries
> could suffer significant
> loss of accuracy, typically through so-called ``catastrophic cancellation'',
> when this option is used to set the precision to less than extended
> precision.
>
> +@item -mdaz-ftz
> +@opindex mdaz-ftz
> +
> +The flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR
> register
> +are used to control floating-point calculations.SSE and AVX instructions
> +including scalar and vector instructions could benefit from enabling the FTZ
> +and DAZ flags when @option{-mdaz-ftz} is specified. Don't set FTZ/DAZ flags
> +when @option{-mno-daz-ftz} is specified.
> +
> @item -mstackrealign
> @opindex mstackrealign
> Realign the stack at entry. On the x86, the @option{-mstackrealign}
> --
> 2.39.1.388.g2fc9e9ca3c
>
--
BR,
Hongtao
