[PATCH v2] math: Fix x86_64 build for -Os (BZ 33367)

Mon Sep 8 20:47:07 GMT 2025

On Mon, Sep 8, 2025 at 1:11 PM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 08/09/25 17:09, H.J. Lu wrote:
> > On Mon, Sep 8, 2025 at 12:56 PM Adhemerval Zanella
> > <adhemerval.zanella@linaro.org> wrote:
> >>
> >> The compiler might not inline the trunc function call for
> >> USE_TRUNC_BUILTIN [1].
> >>
> >> This patch adds an optimized __trunc/__truncf for x86 used
> >> on modf ifunc variant to avoid the trunc libcall.
> >>
> >> Checked on x86_64, x86_64-v2, x86_64-v3, and x86_64-v4. Used -O2 and
> >> -Os options. Performed a full make check on x86_64 with both
> >>  optimizations.
> >>
> >> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121861
> >> ---
> >>  sysdeps/x86/fpu/math_private.h                | 27 +++++++++++++++++++
> >>  sysdeps/x86_64/fpu/multiarch/s_modf-avx.c     |  4 +++
> >>  sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c  |  4 +++
> >>  sysdeps/x86_64/fpu/multiarch/s_modf.c         |  3 ++-
> >>  sysdeps/x86_64/fpu/multiarch/s_modff-avx.c    |  4 +++
> >>  sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c |  4 +++
> >>  sysdeps/x86_64/fpu/multiarch/s_modff.c        |  3 ++-
> >>  7 files changed, 47 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/sysdeps/x86/fpu/math_private.h b/sysdeps/x86/fpu/math_private.h
> >> index 132f011809..d30d580cea 100644
> >> --- a/sysdeps/x86/fpu/math_private.h
> >> +++ b/sysdeps/x86/fpu/math_private.h
> >> @@ -19,6 +19,7 @@
> >>  #ifndef X86_MATH_PRIVATE_H
> >>  #define X86_MATH_PRIVATE_H 1
> >>
> >> +#include <math.h>
> >>  #include_next <math_private.h>
> >>
> >>  __extern_always_inline long double
> >> @@ -29,4 +30,30 @@ __NTH (__ieee754_atan2l (long double y, long double x))
> >>    return ret;
> >>  }
> >>
> >> +__extern_always_inline double
> >> +__trunc (double x)
> >> +{
> >> +#ifdef __AVX__
> >> +  asm ("vroundsd $11, %1, %1, %0" : "=v" (x) : "v" (x));
> >> +#elif defined __SSE4_1__
> >> +  asm ("roundsd $11, %1, %0" : "=x" (x) : "x" (x));
> >> +#else
> >> +  x = trunc (x);
> >> +#endif
> >> +  return x;
> >> +}
> >
> > I will fix GCC 16.   Please make sure that inline asm isn't used for
> > GCC 16 or above.
>
> Would it make a lot of difference on modf implementation to add this extra
> switch?

I think an extra

#if GCC_COMPAT(16, 1)

is simple enough.  But it can wait.

> >
> >> +__extern_always_inline float
> >> +__truncf (float x)
> >> +{
> >> +#ifdef __AVX__
> >> +  asm ("vroundss $11, %1, %1, %0" : "=v" (x) : "v" (x));
> >> +#elif defined __SSE4_1__
> >> +  asm ("roundss $11, %1, %0" : "=x" (x) : "x" (x));
> >> +#else
> >> +  x = truncf (x);
> >> +#endif
> >> +  return x;
> >> +}
> >> +
> >>  #endif
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c b/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
> >> index ab4f03db0e..2f84d254a9 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
> >> @@ -1,3 +1,7 @@
> >> +#include <sysdeps/x86/isa-level.h>
> >> +#include <math_private.h>
> >> +
> >>  #define __modf __modf_avx
> >> +#define trunc __trunc
> >>
> >>  #include <sysdeps/ieee754/dbl-64/s_modf.c>
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c b/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
> >> index 00aa8cd736..dcf04097f2 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
> >> @@ -1,3 +1,7 @@
> >> +#include <sysdeps/x86/isa-level.h>
> >> +#include <math_private.h>
> >> +
> >>  #define __modf __modf_sse41
> >> +#define trunc __trunc
> >>
> >>  #include <sysdeps/ieee754/dbl-64/s_modf.c>
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf.c b/sysdeps/x86_64/fpu/multiarch/s_modf.c
> >> index e365bfcef7..61f77566b1 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modf.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modf.c
> >> @@ -18,7 +18,6 @@
> >>
> >>  #include <sysdeps/x86/isa-level.h>
> >>  #if MINIMUM_X86_ISA_LEVEL < AVX_X86_ISA_LEVEL
> >> -# define NO_MATH_REDIRECT

Why is this needed?

> >>  # include <libm-alias-double.h>
> >>
> >>  # define modf __redirect_modf
> >> @@ -38,4 +37,6 @@ libm_alias_double (__modf, modf)
> >>  #  define __modf __modf_sse2
> >>  # endif
> >>  #endif
> >> +#include <math_private.h>
> >> +#define trunc __trunc
> >>  #include <sysdeps/ieee754/dbl-64/s_modf.c>
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c b/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
> >> index 07cb9c1036..c121ec26e2 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
> >> @@ -1,3 +1,7 @@
> >> +#include <sysdeps/x86/isa-level.h>
> >> +#include <math_private.h>
> >> +
> >>  #define __modff __modff_avx
> >> +#define truncf __truncf
> >>
> >>  #include <sysdeps/ieee754/flt-32/s_modff.c>
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c b/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
> >> index 060c5e3979..30a785d385 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
> >> @@ -1,3 +1,7 @@
> >> +#include <sysdeps/x86/isa-level.h>
> >> +#include <math_private.h>
> >> +
> >>  #define __modff __modff_sse41
> >> +#define truncf __truncf
> >>
> >>  #include <sysdeps/ieee754/flt-32/s_modff.c>
> >> diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff.c b/sysdeps/x86_64/fpu/multiarch/s_modff.c
> >> index a4b5429037..ebf16777fd 100644
> >> --- a/sysdeps/x86_64/fpu/multiarch/s_modff.c
> >> +++ b/sysdeps/x86_64/fpu/multiarch/s_modff.c
> >> @@ -18,7 +18,6 @@
> >>
> >>  #include <sysdeps/x86/isa-level.h>
> >>  #if MINIMUM_X86_ISA_LEVEL < AVX_X86_ISA_LEVEL
> >> -# define NO_MATH_REDIRECT

Why is this needed?

> >>  # include <libm-alias-float.h>
> >>
> >>  # define modff __redirect_modff
> >> @@ -38,4 +37,6 @@ libm_alias_float (__modf, modf)
> >>  #  define __modff __modff_sse2
> >>  # endif
> >>  #endif
> >> +#include <math_private.h>
> >> +#define truncf __truncf
> >>  #include <sysdeps/ieee754/flt-32/s_modff.c>
> >> --
> >> 2.43.0
> >>
> >
> >
>

-- 
H.J.