[PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[liuhongt]

Don't add crtfastmath.o for -shared to avoid changing the MXCSR
register when loading a shared library.  crtfastmath.o will be used
only when building executables.

Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
Ok for trunk?

gcc/ChangeLog:

	PR target/55522
	PR target/36821
	* config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
	Link crtfastmath.o when -mdaz-ftz is specified, not link it
	when -shared is specified.
	* config/i386/i386.opt (mdaz-ftz): New option.
	* doc/invoke.texi (x86 options): Document mftz-daz.
---
 gcc/config/i386/gnu-user-common.h |  2 +-
 gcc/config/i386/i386.opt          |  4 ++++
 gcc/doc/invoke.texi               | 10 +++++++++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
index cab9be2bfb7..02e4a2192a4 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} \
+  "%{Ofast|ffast-math|funsafe-math-optimizations|mdaz-ftz:%{!shared: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 fb4e57ada7c..8fd222db857 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 RejectNegative
+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/doc/invoke.texi b/gcc/doc/invoke.texi
index cb40b38b73a..670e3767fbd 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1433,7 +1433,7 @@ 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
@@ -32752,6 +32752,14 @@ 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.
+
 @item -mstackrealign
 @opindex mstackrealign
 Realign the stack at entry.  On the x86, the @option{-mstackrealign}
-- 
2.27.0

Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Richard Biener]

On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> register when loading a shared library.  crtfastmath.o will be used
> only when building executables.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> Ok for trunk?

You reject negative -mdaz-ftz but wouldn't that be useful with
-Ofast -mno-daz-ftz since there's otherwise no way to avoid that?

Richard.

> gcc/ChangeLog:
>
>         PR target/55522
>         PR target/36821
>         * config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
>         Link crtfastmath.o when -mdaz-ftz is specified, not link it
>         when -shared is specified.
>         * config/i386/i386.opt (mdaz-ftz): New option.
>         * doc/invoke.texi (x86 options): Document mftz-daz.
> ---
>  gcc/config/i386/gnu-user-common.h |  2 +-
>  gcc/config/i386/i386.opt          |  4 ++++
>  gcc/doc/invoke.texi               | 10 +++++++++-
>  3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
> index cab9be2bfb7..02e4a2192a4 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} \
> +  "%{Ofast|ffast-math|funsafe-math-optimizations|mdaz-ftz:%{!shared: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 fb4e57ada7c..8fd222db857 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 RejectNegative
> +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/doc/invoke.texi b/gcc/doc/invoke.texi
> index cb40b38b73a..670e3767fbd 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -1433,7 +1433,7 @@ 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
> @@ -32752,6 +32752,14 @@ 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.

Maybe say that the MXCSR register is set at program start to achieve
this when the
flag is specified at _link_ time and say this switch is ignored when
-shared is specified?

> +
>  @item -mstackrealign
>  @opindex mstackrealign
>  Realign the stack at entry.  On the x86, the @option{-mstackrealign}
> --
> 2.27.0
>

Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Jakub Jelinek]

On Wed, Dec 14, 2022 at 09:08:02AM +0100, Richard Biener via Gcc-patches wrote:
> On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> > register when loading a shared library.  crtfastmath.o will be used
> > only when building executables.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > Ok for trunk?
> 
> You reject negative -mdaz-ftz but wouldn't that be useful with
> -Ofast -mno-daz-ftz since there's otherwise no way to avoid that?

Agreed.
I even wonder if the best wouldn't be to make the option effectively
three state, default, no and yes, where if the option isn't specified
at all, then crtfastmath.o* is linked as is now except for -shared,
if it is -mno-daz-ftz, then it is never linked in regardless of other
options and if it is -mdaz-ftz, then it is linked even for -shared.

> > --- 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 RejectNegative
> > +Set the FTZ and DAZ Flags.

As the option is only used in the driver, shouldn't it be marked Driver
and not Target?  It doesn't need to be saved/restored on every cfun switch
etc.

> > +@item -mdaz-ftz
> > +@opindex mdaz-ftz
> > +
> > +the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR register

Shouldn't description start with capital letter?

> > +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.
> 
> Maybe say that the MXCSR register is set at program start to achieve
> this when the
> flag is specified at _link_ time and say this switch is ignored when
> -shared is specified?

	Jakub

Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Richard Biener]

On Wed, Dec 14, 2022 at 9:16 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Wed, Dec 14, 2022 at 09:08:02AM +0100, Richard Biener via Gcc-patches wrote:
> > On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> > > register when loading a shared library.  crtfastmath.o will be used
> > > only when building executables.
> > >
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > > Ok for trunk?
> >
> > You reject negative -mdaz-ftz but wouldn't that be useful with
> > -Ofast -mno-daz-ftz since there's otherwise no way to avoid that?
>
> Agreed.
> I even wonder if the best wouldn't be to make the option effectively
> three state, default, no and yes, where if the option isn't specified
> at all, then crtfastmath.o* is linked as is now except for -shared,
> if it is -mno-daz-ftz, then it is never linked in regardless of other
> options and if it is -mdaz-ftz, then it is linked even for -shared.

Possibly.  I'd also suggest to split the changed -shared handling to
a separate patch since people may want to backport this and it
should be applicable to all other targets with similar handling.

> > > --- 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 RejectNegative
> > > +Set the FTZ and DAZ Flags.
>
> As the option is only used in the driver, shouldn't it be marked Driver
> and not Target?  It doesn't need to be saved/restored on every cfun switch
> etc.
>
> > > +@item -mdaz-ftz
> > > +@opindex mdaz-ftz
> > > +
> > > +the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR register
>
> Shouldn't description start with capital letter?
>
> > > +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.
> >
> > Maybe say that the MXCSR register is set at program start to achieve
> > this when the
> > flag is specified at _link_ time and say this switch is ignored when
> > -shared is specified?
>
>         Jakub
>

RE: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Liu, Hongtao]

> -----Original Message-----
> From: Richard Biener <richard.guenther@gmail.com>
> Sent: Wednesday, December 14, 2022 4:23 PM
> To: Jakub Jelinek <jakub@redhat.com>
> Cc: Liu, Hongtao <hongtao.liu@intel.com>; gcc-patches@gcc.gnu.org;
> crazylht@gmail.com; hjl.tools@gmail.com; ubizjak@gmail.com
> Subject: Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a
> new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.
> 
> On Wed, Dec 14, 2022 at 9:16 AM Jakub Jelinek <jakub@redhat.com> wrote:
> >
> > On Wed, Dec 14, 2022 at 09:08:02AM +0100, Richard Biener via Gcc-patches
> wrote:
> > > On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
> > > <gcc-patches@gcc.gnu.org> wrote:
> > > >
> > > > Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> > > > register when loading a shared library.  crtfastmath.o will be
> > > > used only when building executables.
> > > >
> > > > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > > > Ok for trunk?
> > >
> > > You reject negative -mdaz-ftz but wouldn't that be useful with
> > > -Ofast -mno-daz-ftz since there's otherwise no way to avoid that?
> >
> > Agreed.
> > I even wonder if the best wouldn't be to make the option effectively
> > three state, default, no and yes, where if the option isn't specified
> > at all, then crtfastmath.o* is linked as is now except for -shared, if
> > it is -mno-daz-ftz, then it is never linked in regardless of other
> > options and if it is -mdaz-ftz, then it is linked even for -shared.
> 
> Possibly.  I'd also suggest to split the changed -shared handling to a separate
> patch since people may want to backport this and it should be applicable to
> all other targets with similar handling.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522#c26
So patch in the upper link is ok for trunk?
I'll change -mdaz-ftz part as a separate patch.
> 
> > > > --- 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 RejectNegative
> > > > +Set the FTZ and DAZ Flags.
> >
> > As the option is only used in the driver, shouldn't it be marked
> > Driver and not Target?  It doesn't need to be saved/restored on every
> > cfun switch etc.
> >
> > > > +@item -mdaz-ftz
> > > > +@opindex mdaz-ftz
> > > > +
> > > > +the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the
> > > > +MXCSR register
> >
> > Shouldn't description start with capital letter?
> >
> > > > +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.
> > >
> > > Maybe say that the MXCSR register is set at program start to achieve
> > > this when the flag is specified at _link_ time and say this switch
> > > is ignored when -shared is specified?
> >
> >         Jakub
> >

Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Richard Biener]

On Wed, Dec 14, 2022 at 9:34 AM Liu, Hongtao <hongtao.liu@intel.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Richard Biener <richard.guenther@gmail.com>
> > Sent: Wednesday, December 14, 2022 4:23 PM
> > To: Jakub Jelinek <jakub@redhat.com>
> > Cc: Liu, Hongtao <hongtao.liu@intel.com>; gcc-patches@gcc.gnu.org;
> > crazylht@gmail.com; hjl.tools@gmail.com; ubizjak@gmail.com
> > Subject: Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a
> > new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.
> >
> > On Wed, Dec 14, 2022 at 9:16 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > >
> > > On Wed, Dec 14, 2022 at 09:08:02AM +0100, Richard Biener via Gcc-patches
> > wrote:
> > > > On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
> > > > <gcc-patches@gcc.gnu.org> wrote:
> > > > >
> > > > > Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> > > > > register when loading a shared library.  crtfastmath.o will be
> > > > > used only when building executables.
> > > > >
> > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > > > > Ok for trunk?
> > > >
> > > > You reject negative -mdaz-ftz but wouldn't that be useful with
> > > > -Ofast -mno-daz-ftz since there's otherwise no way to avoid that?
> > >
> > > Agreed.
> > > I even wonder if the best wouldn't be to make the option effectively
> > > three state, default, no and yes, where if the option isn't specified
> > > at all, then crtfastmath.o* is linked as is now except for -shared, if
> > > it is -mno-daz-ftz, then it is never linked in regardless of other
> > > options and if it is -mdaz-ftz, then it is linked even for -shared.
> >
> > Possibly.  I'd also suggest to split the changed -shared handling to a separate
> > patch since people may want to backport this and it should be applicable to
> > all other targets with similar handling.
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522#c26
> So patch in the upper link is ok for trunk?

It needs target maintainer approval but yes, I think that's what we want.

Richard.

> I'll change -mdaz-ftz part as a separate patch.
> >
> > > > > --- 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 RejectNegative
> > > > > +Set the FTZ and DAZ Flags.
> > >
> > > As the option is only used in the driver, shouldn't it be marked
> > > Driver and not Target?  It doesn't need to be saved/restored on every
> > > cfun switch etc.
> > >
> > > > > +@item -mdaz-ftz
> > > > > +@opindex mdaz-ftz
> > > > > +
> > > > > +the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the
> > > > > +MXCSR register
> > >
> > > Shouldn't description start with capital letter?
> > >
> > > > > +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.
> > > >
> > > > Maybe say that the MXCSR register is set at program start to achieve
> > > > this when the flag is specified at _link_ time and say this switch
> > > > is ignored when -shared is specified?
> > >
> > >         Jakub
> > >

Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Uros Bizjak]

On Wed, Dec 14, 2022 at 9:52 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Wed, Dec 14, 2022 at 9:34 AM Liu, Hongtao <hongtao.liu@intel.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Richard Biener <richard.guenther@gmail.com>
> > > Sent: Wednesday, December 14, 2022 4:23 PM
> > > To: Jakub Jelinek <jakub@redhat.com>
> > > Cc: Liu, Hongtao <hongtao.liu@intel.com>; gcc-patches@gcc.gnu.org;
> > > crazylht@gmail.com; hjl.tools@gmail.com; ubizjak@gmail.com
> > > Subject: Re: [PATCH] [x86] x86: Don't add crtfastmath.o for -shared and add a
> > > new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.
> > >
> > > On Wed, Dec 14, 2022 at 9:16 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > > >
> > > > On Wed, Dec 14, 2022 at 09:08:02AM +0100, Richard Biener via Gcc-patches
> > > wrote:
> > > > > On Wed, Dec 14, 2022 at 3:21 AM liuhongt via Gcc-patches
> > > > > <gcc-patches@gcc.gnu.org> wrote:
> > > > > >
> > > > > > Don't add crtfastmath.o for -shared to avoid changing the MXCSR
> > > > > > register when loading a shared library.  crtfastmath.o will be
> > > > > > used only when building executables.
> > > > > >
> > > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > > > > > Ok for trunk?
> > > > >
> > > > > You reject negative -mdaz-ftz but wouldn't that be useful with
> > > > > -Ofast -mno-daz-ftz since there's otherwise no way to avoid that?
> > > >
> > > > Agreed.
> > > > I even wonder if the best wouldn't be to make the option effectively
> > > > three state, default, no and yes, where if the option isn't specified
> > > > at all, then crtfastmath.o* is linked as is now except for -shared, if
> > > > it is -mno-daz-ftz, then it is never linked in regardless of other
> > > > options and if it is -mdaz-ftz, then it is linked even for -shared.
> > >
> > > Possibly.  I'd also suggest to split the changed -shared handling to a separate
> > > patch since people may want to backport this and it should be applicable to
> > > all other targets with similar handling.
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522#c26
> > So patch in the upper link is ok for trunk?
>
> It needs target maintainer approval but yes, I think that's what we want.

Yes, the one-liner is OK. Perhaps it also needs a corresponding
documentation change (haven't checked the documentation).

Uros.

>
> Richard.
>
> > I'll change -mdaz-ftz part as a separate patch.
> > >
> > > > > > --- 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 RejectNegative
> > > > > > +Set the FTZ and DAZ Flags.
> > > >
> > > > As the option is only used in the driver, shouldn't it be marked
> > > > Driver and not Target?  It doesn't need to be saved/restored on every
> > > > cfun switch etc.
> > > >
> > > > > > +@item -mdaz-ftz
> > > > > > +@opindex mdaz-ftz
> > > > > > +
> > > > > > +the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the
> > > > > > +MXCSR register
> > > >
> > > > Shouldn't description start with capital letter?
> > > >
> > > > > > +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.
> > > > >
> > > > > Maybe say that the MXCSR register is set at program start to achieve
> > > > > this when the flag is specified at _link_ time and say this switch
> > > > > is ignored when -shared is specified?
> > > >
> > > >         Jakub
> > > >

[PATCH V2 1/2] x86: Don't add crtfastmath.o for -shared

[liuhongt]

Update in V2:
Split -shared change into a separate commit and add some documentation
for it.
Bootstrapped and regtested on x86_64-pc-linu-gnu{-m32,}.
Ok of trunk?

Don't add crtfastmath.o for -shared to avoid changing the MXCSR register
when loading a shared library.  crtfastmath.o will be used only when
building executables.

	 PR target/55522
	* config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
	Don't add crtfastmath.o for -shared.
	* doc/invoke.texi (-shared): Add related documentation.
---
 gcc/config/i386/gnu-user-common.h | 2 +-
 gcc/doc/invoke.texi               | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
index cab9be2bfb7..9910cd64363 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} \
+  "%{Ofast|ffast-math|funsafe-math-optimizations:%{!shared:crtfastmath.o%s}} \
    %{mpc32:crtprec32.o%s} \
    %{mpc64:crtprec64.o%s} \
    %{mpc80:crtprec80.o%s}"
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index cb40b38b73a..cba4f19f4f4 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -17656,7 +17656,8 @@ needs to build supplementary stub code for constructors to work.  On
 multi-libbed systems, @samp{gcc -shared} must select the correct support
 libraries to link against.  Failing to supply the correct flags may lead
 to subtle defects.  Supplying them in cases where they are not necessary
-is innocuous.}
+is innocuous. For x86, crtfastmath.o will not be added when
+@option{-shared} is specified. }
 
 @item -shared-libgcc
 @itemx -static-libgcc
-- 
2.27.0

[PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[liuhongt]

Update in v2:
1. Support -mno-daz-ftz, and make the the option effectively three state as:

if (mdaz-ftz)
  link crtfastmath.o
else if ((Ofast || ffast-math || funsafe-math-optimizations)
     	 && !shared && !mno-daz-ftz)
  link crtfastmath.o
else
  Don't link crtfastmath.o

2. Still make the option Target since
   a. cc1: error: command-line option ‘-mdaz-ftz’ is valid for the driver but not for C
   b. Since there's no real variable speicified by mdaz-ftz, I saw in options.h, it's marked as
   #ifndef GENERATOR_FILE
  int x_VAR_mdaz_ftz;
  #define x_VAR_mdaz_ftz do_not_use
  #endif

and not be saved and restored in cl_target_option_save and cl_target_option_restore(am I missing something?)

3. Capital the first letter and add more descriptions about -mdaz-ftz and -shared.

gcc/ChangeLog:

	PR target/55522
	PR target/36821
	* config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
	Link crtfastmath.o whenever -mdaz-ftz is specified. Don't link
	crtfastmath.o when -share or -mno-daz-ftz is specified.
	* config/i386/i386.opt (mdaz-ftz): New option.
	* doc/invoke.texi (x86 options): Document mftz-daz.
---
 gcc/config/i386/gnu-user-common.h |  2 +-
 gcc/config/i386/i386.opt          |  4 ++++
 gcc/doc/invoke.texi               | 12 +++++++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
index 9910cd64363..f910524a6c3 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:%{!shared:crtfastmath.o%s}} \
+  "%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!shared:%{!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 fb4e57ada7c..0b7df429734 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/doc/invoke.texi b/gcc/doc/invoke.texi
index cba4f19f4f4..7f1d002f228 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1433,7 +1433,7 @@ 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
@@ -32753,6 +32753,16 @@ 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} or @option{-shared} is specified, @option{-mdaz-ftz}
+will set FTZ/DAZ flags even with @option{-shared}.
+
 @item -mstackrealign
 @opindex mstackrealign
 Realign the stack at entry.  On the x86, the @option{-mstackrealign}
-- 
2.27.0

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Jakub Jelinek]

On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> --- 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

s/Target/Driver/

> +Set the FTZ and DAZ Flags.

	Jakub

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, Dec 15, 2022 at 3:39 PM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> > --- 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
>
> s/Target/Driver/
Change to Driver and Got error like:cc1: error: command-line option
‘-mdaz-ftz’ is valid for the driver but not for C.
>
> > +Set the FTZ and DAZ Flags.
>
>         Jakub
>


-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, Dec 15, 2022 at 3:45 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, Dec 15, 2022 at 3:39 PM Jakub Jelinek <jakub@redhat.com> wrote:
> >
> > On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> > > --- 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
> >
> > s/Target/Driver/
> Change to Driver and Got error like:cc1: error: command-line option
> ‘-mdaz-ftz’ is valid for the driver but not for C.
Hi Jakub:
  I didn't find a good solution to handle this error after changing
*Target* to *Driver*, Could you give some hints how to solve this
problem?
Or is it ok for you to mark this as *Target*(there won't be any save
and restore in cfun since there's no variable defined here.)
> >
> > > +Set the FTZ and DAZ Flags.
> >
> >         Jakub
> >
>
>
> --
> BR,
> Hongtao



-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[H.J. Lu]

On Mon, Dec 19, 2022 at 8:52 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, Dec 15, 2022 at 3:45 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Thu, Dec 15, 2022 at 3:39 PM Jakub Jelinek <jakub@redhat.com> wrote:
> > >
> > > On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> > > > --- 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
> > >
> > > s/Target/Driver/
> > Change to Driver and Got error like:cc1: error: command-line option
> > ‘-mdaz-ftz’ is valid for the driver but not for C.
> Hi Jakub:
>   I didn't find a good solution to handle this error after changing
> *Target* to *Driver*, Could you give some hints how to solve this
> problem?
> Or is it ok for you to mark this as *Target*(there won't be any save
> and restore in cfun since there's no variable defined here.)

Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
as Driver.  We need to give it a different name to mark it as Driver.


-- 
H.J.

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Jakub Jelinek]

On Wed, Dec 21, 2022 at 12:20:23PM -0800, H.J. Lu wrote:
> On Mon, Dec 19, 2022 at 8:52 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Thu, Dec 15, 2022 at 3:45 PM Hongtao Liu <crazylht@gmail.com> wrote:
> > >
> > > On Thu, Dec 15, 2022 at 3:39 PM Jakub Jelinek <jakub@redhat.com> wrote:
> > > >
> > > > On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> > > > > --- 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
> > > >
> > > > s/Target/Driver/
> > > Change to Driver and Got error like:cc1: error: command-line option
> > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > Hi Jakub:
> >   I didn't find a good solution to handle this error after changing
> > *Target* to *Driver*, Could you give some hints how to solve this
> > problem?
> > Or is it ok for you to mark this as *Target*(there won't be any save
> > and restore in cfun since there's no variable defined here.)
> 
> Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> as Driver.  We need to give it a different name to mark it as Driver.

It is ok like that.

	Jakub

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[H.J. Lu]

[-- Attachment #1: Type: text/plain, Size: 1681 bytes --]

On Wed, Dec 21, 2022 at 2:35 PM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Wed, Dec 21, 2022 at 12:20:23PM -0800, H.J. Lu wrote:
> > On Mon, Dec 19, 2022 at 8:52 PM Hongtao Liu <crazylht@gmail.com> wrote:
> > >
> > > On Thu, Dec 15, 2022 at 3:45 PM Hongtao Liu <crazylht@gmail.com> wrote:
> > > >
> > > > On Thu, Dec 15, 2022 at 3:39 PM Jakub Jelinek <jakub@redhat.com> wrote:
> > > > >
> > > > > On Thu, Dec 15, 2022 at 02:21:37PM +0800, liuhongt via Gcc-patches wrote:
> > > > > > --- 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
> > > > >
> > > > > s/Target/Driver/
> > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > Hi Jakub:
> > >   I didn't find a good solution to handle this error after changing
> > > *Target* to *Driver*, Could you give some hints how to solve this
> > > problem?
> > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > and restore in cfun since there's no variable defined here.)
> >
> > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > as Driver.  We need to give it a different name to mark it as Driver.
>
> It is ok like that.
>
>         Jakub
>

The GCC driver handles -mno-XXX automatically for -mXXX.  Use
a different name needs to handle the negation.   Or we can do something
like this to check for CL_DRIVER before passing it to cc1.
-- 
H.J.

[-- Attachment #2: p.diff --]
[-- Type: text/x-patch, Size: 1594 bytes --]

diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index 2568d541196..87cbea11ae1 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -3851,7 +3851,7 @@ alloc_switch (void)
 
 static void
 save_switch (const char *opt, size_t n_args, const char *const *args,
-	     bool validated, bool known)
+	     bool validated, bool known, bool driver = false)
 {
   alloc_switch ();
   switches[n_switches].part1 = opt + 1;
@@ -3868,6 +3868,7 @@ save_switch (const char *opt, size_t n_args, const char *const *args,
   switches[n_switches].validated = validated;
   switches[n_switches].known = known;
   switches[n_switches].ordering = 0;
+  switches[n_switches].driver = driver;
   n_switches++;
 }
 
@@ -4575,7 +4576,8 @@ driver_handle_option (struct gcc_options *opts,
   if (do_save)
     save_switch (decoded->canonical_option[0],
 		 decoded->canonical_option_num_elements - 1,
-		 &decoded->canonical_option[1], validated, true);
+		 &decoded->canonical_option[1], validated, true,
+		 cl_options[opt_index].flags == CL_DRIVER);
   return true;
 }
 
@@ -7465,7 +7467,8 @@ check_live_switch (int switchnum, int prefix_length)
 static void
 give_switch (int switchnum, int omit_first_word)
 {
-  if ((switches[switchnum].live_cond & SWITCH_IGNORE) != 0)
+  if ((switches[switchnum].live_cond & SWITCH_IGNORE) != 0
+      || switches[switchnum].driver)
     return;
 
   if (!omit_first_word)
diff --git a/gcc/opts.h b/gcc/opts.h
index ce4fd5c39b9..2900f0d9168 100644
--- a/gcc/opts.h
+++ b/gcc/opts.h
@@ -561,6 +561,7 @@ struct switchstr
   bool known;
   bool validated;
   bool ordering;
+  bool driver;
 };
 
 #endif

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Jakub Jelinek]

On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > >  Target RejectNegative
> > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > >
> > > > > > > +mdaz-ftz
> > > > > > > +Target
> > > > > >
> > > > > > s/Target/Driver/
> > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > Hi Jakub:
> > > >   I didn't find a good solution to handle this error after changing
> > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > problem?
> > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > and restore in cfun since there's no variable defined here.)
> > >
> > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > as Driver.  We need to give it a different name to mark it as Driver.
> >
> > It is ok like that.
> >
> >         Jakub
> >
> 
> The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> a different name needs to handle the negation.   Or we can do something
> like this to check for CL_DRIVER before passing it to cc1.

I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.

	Jakub

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > >  Target RejectNegative
> > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > >
> > > > > > > > +mdaz-ftz
> > > > > > > > +Target
> > > > > > >
> > > > > > > s/Target/Driver/
> > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > Hi Jakub:
> > > > >   I didn't find a good solution to handle this error after changing
> > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > problem?
> > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > and restore in cfun since there's no variable defined here.)
> > > >
> > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > as Driver.  We need to give it a different name to mark it as Driver.
> > >
> > > It is ok like that.
> > >
> > >         Jakub
> > >
> >
> > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > a different name needs to handle the negation.   Or we can do something
> > like this to check for CL_DRIVER before passing it to cc1.
>
> I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
>
Thanks.
Uros, Is the patch for you?
>         Jakub
>


-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Uros Bizjak]

On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> >
> > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > >  Target RejectNegative
> > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > >
> > > > > > > > > +mdaz-ftz
> > > > > > > > > +Target
> > > > > > > >
> > > > > > > > s/Target/Driver/
> > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > Hi Jakub:
> > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > problem?
> > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > and restore in cfun since there's no variable defined here.)
> > > > >
> > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > >
> > > > It is ok like that.
> > > >
> > > >         Jakub
> > > >
> > >
> > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > a different name needs to handle the negation.   Or we can do something
> > > like this to check for CL_DRIVER before passing it to cc1.
> >
> > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> >
> Thanks.
> Uros, Is the patch for you?

The original patch is then OK.

Thanks,
Uros.

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, Dec 22, 2022 at 4:04 PM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > >
> > > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > > >  Target RejectNegative
> > > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > > >
> > > > > > > > > > +mdaz-ftz
> > > > > > > > > > +Target
> > > > > > > > >
> > > > > > > > > s/Target/Driver/
> > > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > > Hi Jakub:
> > > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > > problem?
> > > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > > and restore in cfun since there's no variable defined here.)
> > > > > >
> > > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > > >
> > > > > It is ok like that.
> > > > >
> > > > >         Jakub
> > > > >
> > > >
> > > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > > a different name needs to handle the negation.   Or we can do something
> > > > like this to check for CL_DRIVER before passing it to cc1.
> > >
> > > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> > >
> > Thanks.
> > Uros, Is the patch for you?
>
> The original patch is then OK.
Some users found the -mdaz-ftz option to be very useful, and want it
to be backport to GCC12 and GCC11.
But the patch is not a bugfix one, so i'd like to ask options from
other maintainers, if the patch is suitable for backport?

The backport patches include both this one and [1] which apply
-mdaz-ftz to all other x86 targets.

[1] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610053.html

>
> Thanks,
> Uros.



-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, May 4, 2023 at 1:35 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, Dec 22, 2022 at 4:04 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> >
> > On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
> > >
> > > On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > > >
> > > > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > > > >  Target RejectNegative
> > > > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > > > >
> > > > > > > > > > > +mdaz-ftz
> > > > > > > > > > > +Target
> > > > > > > > > >
> > > > > > > > > > s/Target/Driver/
> > > > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > > > Hi Jakub:
> > > > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > > > problem?
> > > > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > > > and restore in cfun since there's no variable defined here.)
> > > > > > >
> > > > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > > > >
> > > > > > It is ok like that.
> > > > > >
> > > > > >         Jakub
> > > > > >
> > > > >
> > > > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > > > a different name needs to handle the negation.   Or we can do something
> > > > > like this to check for CL_DRIVER before passing it to cc1.
> > > >
> > > > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> > > >
> > > Thanks.
> > > Uros, Is the patch for you?
> >
> > The original patch is then OK.
> Some users found the -mdaz-ftz option to be very useful, and want it
> to be backport to GCC12 and GCC11.
> But the patch is not a bugfix one, so i'd like to ask options from
s/options/opinions/g
> other maintainers, if the patch is suitable for backport?
>
> The backport patches include both this one and [1] which apply
> -mdaz-ftz to all other x86 targets.
>
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610053.html
>
> >
> > Thanks,
> > Uros.
>
>
>
> --
> BR,
> Hongtao



-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Richard Biener]

On Thu, May 4, 2023 at 7:37 AM Hongtao Liu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Thu, May 4, 2023 at 1:35 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Thu, Dec 22, 2022 at 4:04 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > >
> > > On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
> > > >
> > > > On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > > > >
> > > > > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > > > > >  Target RejectNegative
> > > > > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > > > > >
> > > > > > > > > > > > +mdaz-ftz
> > > > > > > > > > > > +Target
> > > > > > > > > > >
> > > > > > > > > > > s/Target/Driver/
> > > > > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > > > > Hi Jakub:
> > > > > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > > > > problem?
> > > > > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > > > > and restore in cfun since there's no variable defined here.)
> > > > > > > >
> > > > > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > > > > >
> > > > > > > It is ok like that.
> > > > > > >
> > > > > > >         Jakub
> > > > > > >
> > > > > >
> > > > > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > > > > a different name needs to handle the negation.   Or we can do something
> > > > > > like this to check for CL_DRIVER before passing it to cc1.
> > > > >
> > > > > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> > > > >
> > > > Thanks.
> > > > Uros, Is the patch for you?
> > >
> > > The original patch is then OK.
> > Some users found the -mdaz-ftz option to be very useful, and want it
> > to be backport to GCC12 and GCC11.
> > But the patch is not a bugfix one, so i'd like to ask options from
> s/options/opinions/g
> > other maintainers, if the patch is suitable for backport?
> >
> > The backport patches include both this one and [1] which apply
> > -mdaz-ftz to all other x86 targets.
> >
> > [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610053.html

Please make sure to not backport the -ffast-math linker spec change though.
Also note the 12 branch is currently frozen.

I'll defer to x86 maintainers on the -mdaz-ftz flag itself.

Richard.

> > >
> > > Thanks,
> > > Uros.
> >
> >
> >
> > --
> > BR,
> > Hongtao
>
>
>
> --
> BR,
> Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Thu, May 4, 2023 at 5:49 PM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Thu, May 4, 2023 at 7:37 AM Hongtao Liu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Thu, May 4, 2023 at 1:35 PM Hongtao Liu <crazylht@gmail.com> wrote:
> > >
> > > On Thu, Dec 22, 2022 at 4:04 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > >
> > > > On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
> > > > >
> > > > > On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > > > > >
> > > > > > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > > > > > >  Target RejectNegative
> > > > > > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > > > > > >
> > > > > > > > > > > > > +mdaz-ftz
> > > > > > > > > > > > > +Target
> > > > > > > > > > > >
> > > > > > > > > > > > s/Target/Driver/
> > > > > > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > > > > > Hi Jakub:
> > > > > > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > > > > > problem?
> > > > > > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > > > > > and restore in cfun since there's no variable defined here.)
> > > > > > > > >
> > > > > > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > > > > > >
> > > > > > > > It is ok like that.
> > > > > > > >
> > > > > > > >         Jakub
> > > > > > > >
> > > > > > >
> > > > > > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > > > > > a different name needs to handle the negation.   Or we can do something
> > > > > > > like this to check for CL_DRIVER before passing it to cc1.
> > > > > >
> > > > > > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> > > > > >
> > > > > Thanks.
> > > > > Uros, Is the patch for you?
> > > >
> > > > The original patch is then OK.
> > > Some users found the -mdaz-ftz option to be very useful, and want it
> > > to be backport to GCC12 and GCC11.
> > > But the patch is not a bugfix one, so i'd like to ask options from
> > s/options/opinions/g
> > > other maintainers, if the patch is suitable for backport?
> > >
> > > The backport patches include both this one and [1] which apply
> > > -mdaz-ftz to all other x86 targets.
> > >
> > > [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610053.html
>
> Please make sure to not backport the -ffast-math linker spec change though.
> Also note the 12 branch is currently frozen.
You're meaning don't backport -shared part since it will cause
different behavior between different backends. ?
I'm trying to backport the daz-ftz part, it won't change the existed
behavior for fast-math or shared.
%{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}
>
> I'll defer to x86 maintainers on the -mdaz-ftz flag itself.
>
> Richard.
>
> > > >
> > > > Thanks,
> > > > Uros.
> > >
> > >
> > >
> > > --
> > > BR,
> > > Hongtao
> >
> >
> >
> > --
> > BR,
> > Hongtao



-- 
BR,
Hongtao

Re: [PATCH V2 2/2] [x86] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Richard Biener]

On Wed, May 10, 2023 at 3:41 AM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, May 4, 2023 at 5:49 PM Richard Biener
> <richard.guenther@gmail.com> wrote:
> >
> > On Thu, May 4, 2023 at 7:37 AM Hongtao Liu via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > On Thu, May 4, 2023 at 1:35 PM Hongtao Liu <crazylht@gmail.com> wrote:
> > > >
> > > > On Thu, Dec 22, 2022 at 4:04 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > >
> > > > > On Thu, Dec 22, 2022 at 5:40 AM Hongtao Liu <crazylht@gmail.com> wrote:
> > > > > >
> > > > > > On Thu, Dec 22, 2022 at 6:46 AM Jakub Jelinek <jakub@redhat.com> wrote:
> > > > > > >
> > > > > > > On Wed, Dec 21, 2022 at 02:43:43PM -0800, H.J. Lu wrote:
> > > > > > > > > > > > > >  Target RejectNegative
> > > > > > > > > > > > > >  Set 80387 floating-point precision to 80-bit.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > +mdaz-ftz
> > > > > > > > > > > > > > +Target
> > > > > > > > > > > > >
> > > > > > > > > > > > > s/Target/Driver/
> > > > > > > > > > > > Change to Driver and Got error like:cc1: error: command-line option
> > > > > > > > > > > > ‘-mdaz-ftz’ is valid for the driver but not for C.
> > > > > > > > > > > Hi Jakub:
> > > > > > > > > > >   I didn't find a good solution to handle this error after changing
> > > > > > > > > > > *Target* to *Driver*, Could you give some hints how to solve this
> > > > > > > > > > > problem?
> > > > > > > > > > > Or is it ok for you to mark this as *Target*(there won't be any save
> > > > > > > > > > > and restore in cfun since there's no variable defined here.)
> > > > > > > > > >
> > > > > > > > > > Since all -m* options are passed to cc1, -mdaz-ftz can't be marked
> > > > > > > > > > as Driver.  We need to give it a different name to mark it as Driver.
> > > > > > > > >
> > > > > > > > > It is ok like that.
> > > > > > > > >
> > > > > > > > >         Jakub
> > > > > > > > >
> > > > > > > >
> > > > > > > > The GCC driver handles -mno-XXX automatically for -mXXX.  Use
> > > > > > > > a different name needs to handle the negation.   Or we can do something
> > > > > > > > like this to check for CL_DRIVER before passing it to cc1.
> > > > > > >
> > > > > > > I meant I'm ok with -m{,no-}daz-ftz option being Target rather than Driver.
> > > > > > >
> > > > > > Thanks.
> > > > > > Uros, Is the patch for you?
> > > > >
> > > > > The original patch is then OK.
> > > > Some users found the -mdaz-ftz option to be very useful, and want it
> > > > to be backport to GCC12 and GCC11.
> > > > But the patch is not a bugfix one, so i'd like to ask options from
> > > s/options/opinions/g
> > > > other maintainers, if the patch is suitable for backport?
> > > >
> > > > The backport patches include both this one and [1] which apply
> > > > -mdaz-ftz to all other x86 targets.
> > > >
> > > > [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610053.html
> >
> > Please make sure to not backport the -ffast-math linker spec change though.
> > Also note the 12 branch is currently frozen.
> You're meaning don't backport -shared part since it will cause
> different behavior between different backends. ?
> I'm trying to backport the daz-ftz part, it won't change the existed
> behavior for fast-math or shared.
> %{mdaz-ftz:crtfastmath.o%s;Ofast|ffast-math|funsafe-math-optimizations:%{!mno-daz-ftz:crtfastmath.o%s}}

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.

Richard.

> >
> > I'll defer to x86 maintainers on the -mdaz-ftz flag itself.
> >
> > Richard.
> >
> > > > >
> > > > > Thanks,
> > > > > Uros.
> > > >
> > > >
> > > >
> > > > --
> > > > BR,
> > > > Hongtao
> > >
> > >
> > >
> > > --
> > > BR,
> > > Hongtao
>
>
>
> --
> BR,
> Hongtao

[PATCH] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[liuhongt]

> 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?

    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

Re: [PATCH] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Wed, May 10, 2023 at 5:10 PM liuhongt <hongtao.liu@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

Re: [PATCH] x86: Add a new option -mdaz-ftz to enable FTZ and DAZ flags in MXCSR.

[Hongtao Liu]

On Fri, May 12, 2023 at 1:43 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Wed, May 10, 2023 at 5:10 PM liuhongt <hongtao.liu@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.
pushed to gcc-11/gcc-12 branch.
> >
> >     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



-- 
BR,
Hongtao

Re: [PATCH V2 1/2] x86: Don't add crtfastmath.o for -shared

[Uros Bizjak]

On Thu, Dec 15, 2022 at 7:23 AM liuhongt <hongtao.liu@intel.com> wrote:
>
> Update in V2:
> Split -shared change into a separate commit and add some documentation
> for it.
> Bootstrapped and regtested on x86_64-pc-linu-gnu{-m32,}.
> Ok of trunk?
>
> Don't add crtfastmath.o for -shared to avoid changing the MXCSR register
> when loading a shared library.  crtfastmath.o will be used only when
> building executables.
>
>          PR target/55522
>         * config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
>         Don't add crtfastmath.o for -shared.
>         * doc/invoke.texi (-shared): Add related documentation.

OK.

Thanks,
Uros.

> ---
>  gcc/config/i386/gnu-user-common.h | 2 +-
>  gcc/doc/invoke.texi               | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
> index cab9be2bfb7..9910cd64363 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} \
> +  "%{Ofast|ffast-math|funsafe-math-optimizations:%{!shared:crtfastmath.o%s}} \
>     %{mpc32:crtprec32.o%s} \
>     %{mpc64:crtprec64.o%s} \
>     %{mpc80:crtprec80.o%s}"
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index cb40b38b73a..cba4f19f4f4 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -17656,7 +17656,8 @@ needs to build supplementary stub code for constructors to work.  On
>  multi-libbed systems, @samp{gcc -shared} must select the correct support
>  libraries to link against.  Failing to supply the correct flags may lead
>  to subtle defects.  Supplying them in cases where they are not necessary
> -is innocuous.}
> +is innocuous. For x86, crtfastmath.o will not be added when
> +@option{-shared} is specified. }
>
>  @item -shared-libgcc
>  @itemx -static-libgcc
> --
> 2.27.0
>