[PATCH 37/59] math: Fix modf{f} build on clang

[H.J. Lu]

On Thu, Oct 23, 2025 at 12:26 AM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 20/10/25 19:09, H.J. Lu wrote:
> > On Tue, Oct 21, 2025 at 1:58 AM Adhemerval Zanella Netto
> > <adhemerval.zanella@linaro.org> wrote:
> >>
> >>
> >>
> >> On 18/10/25 03:28, H.J. Lu wrote:
> >>> On Sat, Oct 18, 2025 at 3:58 AM Adhemerval Zanella
> >>> <adhemerval.zanella@linaro.org> wrote:
> >>>>
> >>>> We need to disable the internal optimize for math builtins
> >>>> (NO_MATH_REDIRECT) for the USE_TRUNC_BUILTIN case.
> >>>
> >>> Does it change GCC codegen?
> >>
> >> No, both with clang and gcc either the builtin is issues (on
> >> aarch64 for instance) or the internal symbol is called.
> >
> > Why does NO_MATH_REDIRECT make no difference here?
> > Why is this macro needed?
>
> With clang the internal optimization to avoid PLT usage for symbol
> that might be inline will make clang to *not* emit the builtin:
>
> include/math.h
>
> 177 MATH_REDIRECT (trunc, "__", MATH_REDIRECT_UNARY_ARGS)
>
> Without NO_MATH_REDIRECT, which disables it; build with clang
> fails:
>
> >>> referenced by s_modf.c:34 ([...]/../sysdeps/ieee754/dbl-64/s_modf.c:34)
> >>>               [...]/aarch64-linux-gnu-clang-21/libc_pic.os.clean:(__modf)
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> gcc is not affected by this, it will emit the 'frintz' regardless
> of MATH_REDIRECT.

So clang won't inline trunc without NO_MATH_REDIRECT?
Why isn't gcc impacted?

-- 
H.J.