On Thu, 2020-10-22 at 18:05 -0400, Michael Meissner via Gcc-patches wrote:
> PowerPC: Add -mno-gnu-attributes to ibm-ldouble.o.
> 
> I have split all of these patches into separate patches to hopefully get them
> into the tree.
> 
> This patch is split off from the patch adding __float128 <-> Decimal
> conversions.  This patch is needed to prevent the linker from issuing a
> warning when the long double format is IEEE 128-bit.
> 
> I have tested this patch with bootstrap builds on a little endian power9 
> system
> running Linux.  With the other patches, I have built two full bootstrap builds
> using this patch and the patches after this patch.  One build used the current
> default for long double (IBM extended double) and the other build switched the
> default to IEEE 128-bit.  I used the Advance Toolchain AT 14.0 compiler as the
> library used by this compiler.  There are no regressions between the tests.
> There are 3 fortran benchmarks (ieee/large_2.f90, default_format_2.f90, and
> default_format_denormal_2.f90) that now pass.
> 
> Can I install this into the trunk?
> 
> We have gotten some requests to back port these changes to GCC 10.x.  At the
> moment, I am not planning to do the back port, but I may need to in the 
> future.
> 
> libgcc/
> 2020-10-22  Michael Meissner  <meiss...@linux.ibm.com>
> 
>       * config/rs6000/t-float128: Compile ibm-ldouble.o with
>       -mno-gnu-attributes.
> ---
>  libgcc/config/rs6000/t-float128 | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/libgcc/config/rs6000/t-float128 b/libgcc/config/rs6000/t-float128
> index d5413445189..c2cb3e2b705 100644
> --- a/libgcc/config/rs6000/t-float128
> +++ b/libgcc/config/rs6000/t-float128
> @@ -69,6 +69,11 @@ $(fp128_ppc_obj)    : INTERNAL_CFLAGS += $(FP128_CFLAGS_SW)
>  $(fp128_obj)          : $(fp128_includes)
>  $(fp128_obj)          : $(srcdir)/config/rs6000/quad-float128.h
> 
> +
> +# Turn off gnu attributes to allow using the IBM extended double support for
> +# __ibm128 if long double uses the IEEE 128-bit representation.
> +ibm-ldouble$(objext) : INTERNAL_CFLAGS += -mno-gnu-attribute
> +

I think from context you can drop the "if long double uses the IEEE
128-bit representation." portion of that comment. 

(Though this corrects
a condition based on the configury, etc, there is no conditional logic
here..)



>  $(fp128_softfp_src) : $(srcdir)/soft-fp/$(subst -sw,,$(subst kf,tf,$@)) 
> $(fp128_dep)
>       @src="$(srcdir)/soft-fp/$(subst -sw,,$(subst kf,tf,$@))"; \
>       echo "Create $@"; \
> -- 
> 2.22.0
> 
> 

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