> From: Uros Bizjak <[email protected]>
> Sent: Friday, August 28, 2026 2:54 PM
>
> On Fri, Aug 28, 2026 at 3:53 AM Sun, Qin <[email protected]> wrote:
> >
> > When compiling with `-msoft-float -mfpmath=387`, `-msoft-float` turns off
> 387.
> > With neither FPMATH_SSE nor FPMATH_387 enabled, no unit can do FP
> arithmetics.
> > The i386-options.cc omits this kind of check, so ICE is triggered. We need
> > to add check in i386-options.cc to cover FPMATH_387 scenario when
> FPMATH_SSE
> > is false.
> >
> > gcc/ChangeLog:
> >
> > PR target/119300
> > * config/i386/i386-options.cc (ix86_option_override_internal):
> > Warn and use SSE arithmetics when -mfpmath=387 is set, 387 is turned
> > off but SSE is available.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR target/119300
> > * gcc.target/i386/pr119300.c: New test.
> > * gcc.target/i386/pr126148.c: Use -mno-sse instead of -mfpmath=387
> > to disable SSE math.
>
> OK.
Committed on behalf of Qin.
Thx,
Haochen
>
> Thanks,
> Uros.
>
> > ---
> > Changes in v3:
> > Removed the error() when 387 and SSE instruction set are both enabled,
> > because the error made g++.target/i386/pr88998.C fail. That test clears
> > both units.
> > Adjusted gcc.target/i386/pr126148.c to use -mno-sse instead of -
> mfpmath=387,
> > because -mno-80387 -mfpmath=387 will result in a SSE-available path with
> our
> > fix now. -mno-80387 -mno-sse can keep the FP disabled condition.
> >
> > gcc/config/i386/i386-options.cc | 7 +++++++
> > gcc/testsuite/gcc.target/i386/pr119300.c | 10 ++++++++++
> > gcc/testsuite/gcc.target/i386/pr126148.c | 2 +-
> > 3 files changed, 18 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr119300.c
> >
> > diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-
> options.cc
> > index 6bb5e1a08d9..e7f06154103 100644
> > --- a/gcc/config/i386/i386-options.cc
> > +++ b/gcc/config/i386/i386-options.cc
> > @@ -2793,6 +2793,13 @@ ix86_option_override_internal (bool
> main_args_p,
> > opts->x_ix86_fpmath = FPMATH_SSE;
> > }
> > }
> > + else if ((opts->x_ix86_fpmath & FPMATH_387)
> > + && !TARGET_80387_P (opts->x_target_flags)
> > + && TARGET_SSE_P (opts->x_ix86_isa_flags))
> > + {
> > + warning (0, "387 instruction set disabled, using SSE
> > arithmetics");
> > + opts->x_ix86_fpmath = FPMATH_SSE;
> > + }
> > }
> > /* For all chips supporting SSE2, -mfpmath=sse performs better than
> > fpmath=387. The second is however default at many targets since the
> > diff --git a/gcc/testsuite/gcc.target/i386/pr119300.c
> b/gcc/testsuite/gcc.target/i386/pr119300.c
> > new file mode 100644
> > index 00000000000..e5611cdd00e
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr119300.c
> > @@ -0,0 +1,10 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-msoft-float -mfpmath=387 -msse" } */
> > +
> > +float
> > +foo (float f)
> > +{
> > + return __builtin_ia32_rsqrtf (f);
> > +}
> > +
> > +/* { dg-warning "387 instruction set disabled, using SSE arithmetics" ""
> { target *-*-* } 0 } */
> > diff --git a/gcc/testsuite/gcc.target/i386/pr126148.c
> b/gcc/testsuite/gcc.target/i386/pr126148.c
> > index f706d303c4d..ab4009dd6a8 100644
> > --- a/gcc/testsuite/gcc.target/i386/pr126148.c
> > +++ b/gcc/testsuite/gcc.target/i386/pr126148.c
> > @@ -1,5 +1,5 @@
> > /* { dg-do compile { target { ! ia32 } } } */
> > -/* { dg-options "-O2 -ffast-math -mapxf -mno-80387 -mfpmath=387" } */
> > +/* { dg-options "-O2 -ffast-math -mapxf -mno-80387 -mno-sse" } */
> >
> > int foo (int a, double b) {
> > if (a || b)
> > --
> > 2.25.1
> >
