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.
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
>
