On Mon, Jan 21, 2019 at 5:15 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> TI->SF and TI->DF conversions in libgcc2.c:
>
> FSTYPE
> FUNC (DWtype u)
> {
> ...
> }
>
> have no rounding mode support. We should replace __floattisf, __floattidf,
> __floatuntisf and __floatuntidf in libgcc2.c with these from soft-fp.
>
> PR libgcc/88931
> * config/i386/64/t-softfp-compat (libgcc2-ti-functions): New.
> (LIB2FUNCS_EXCLUDE): Likewise.
> (libgcc2-ti-softp): Likewise.
> (LIB2ADD): Likewise.
> ---
> libgcc/config/i386/64/t-softfp-compat | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/libgcc/config/i386/64/t-softfp-compat
> b/libgcc/config/i386/64/t-softfp-compat
> index 0978695c3a4..abb78032bf5 100644
> --- a/libgcc/config/i386/64/t-softfp-compat
> +++ b/libgcc/config/i386/64/t-softfp-compat
> @@ -13,3 +13,11 @@ libgcc2-tf-functions = _divtc3 _multc3 _powitf2
> LIB2FUNCS_EXCLUDE += $(libgcc2-tf-functions)
> libgcc2-tf-compats = $(addsuffix .c, $(libgcc2-tf-functions))
> LIB2ADD += $(addprefix $(srcdir)/config/i386/64/, $(libgcc2-tf-compats))
> +
> +# Replace _floatdisf, _floatdidf, _floatundisf and _floatundidf in
> +# libgcc2.c, which have no rounding mode support, with floattisf.c,
> +# floattidf.c, floatundisf.c and floatundidf.c from soft-fp.
> +libgcc2-ti-functions = _floatdisf _floatdidf _floatundisf _floatundidf
> +LIB2FUNCS_EXCLUDE += $(libgcc2-ti-functions)
> +libgcc2-ti-softp = floattisf.c floattidf.c floatuntisf.c floatuntidf.c
> +LIB2ADD += $(addprefix $(srcdir)/soft-fp/, $(libgcc2-ti-softp))
It is not that simple. Please note that libgcc2 functions use FP
instructions in narrower mode (so, in effect still use FPU), while
soft-fp functions don't even touch the FPU, and do everything using
bit twiddling. I think that your change would introduce qoute
noticeable runtime regressions.
Uros.
> --
> 2.20.1
>
