On Fri Feb 27, 2026 at 10:20:19PM +0100, Mark Kettenis wrote:
> > Date: Fri, 27 Feb 2026 10:16:02 +0100
> > From: Mark Kettenis <mark.kettenis@xs4all.nl>
> > 
> > > Date: Fri, 27 Feb 2026 08:05:21 +0100
> > > From: Rafael Sadowski <rafael@sizeofvoid.org>
> > > 
> > > On Thu Feb 19, 2026 at 10:39:24PM -0500, Brad Smith wrote:
> > > > Enable the Quad-precision float support for amd64
> > > > 
> > > > https://github.com/llvm/llvm-project/commit/910a4bf5b70ae14e7262677a8880ee98056e44e1
> > > > https://github.com/llvm/llvm-project/commit/d2ce3e9621411f3391def327f89e3a650918989f
> > > > 
> > > > 
> > > > This fixes an issue I ran into quite awhile ago with fmt and float128 support.
> > > > 
> > > > This was all fixed with compiler-rt as of LLVM 18.
> > > > 
> > > > ld: error: undefined symbol: __unordtf2
> > > > >>> referenced by format-test.cc
> > > > >>>               test/CMakeFiles/format-test.dir/format-test.cc.o:(fmt::v11::basic_appender<char> fmt::v11::detail::write_float<char, fmt::v11::basic_appender<char>, __float128>(fmt::v11::basic_appender<char>, __float128, fmt::v11::format_specs, fmt::v11::detail::locale_ref))
> > > > 
> > > > ld: error: undefined symbol: __netf2
> > > > >>> referenced by format-test.cc
> > > > >>>               test/CMakeFiles/format-test.dir/format-test.cc.o:(int fmt::v11::detail::format_float<__float128>(__float128, int, fmt::v11::format_specs const&, bool, fmt::v11::detail::buffer<char>&))
> > > > 
> > > > ld: error: undefined symbol: __trunctfsf2
> > > > >>> referenced by format-test.cc
> > > > >>>               test/CMakeFiles/format-test.dir/format-test.cc.o:(int fmt::v11::detail::format_float<__float128>(__float128, int, fmt::v11::format_specs const&, bool, fmt::v11::detail::buffer<char>&))
> > > > c++: error: linker command failed with exit code 1 (use -v to see invocation)
> > > > ninja: build stopped: subcommand failed.
> > > > 
> > > > 
> > > 
> > > Thanks Brad,
> > > 
> > > I can confirm that. I think the problem happened because
> > > "GEN_SRCS+=${GEN_TF_SRCS}" was present above and at first glance it did
> > > not appear to be in the if block of aarch64.
> > > 
> > > Let's put it all in one place so that these problems do not occur again.
> > 
> > Please no.  Enabling the quad-precision float support is a
> > per-architecture decision.  The reasons for enabling that differ from
> > architecture to architecture.  So lumping it all together makes no
> > sense.
> > 
> > > Index: Makefile
> > > ===================================================================
> > > RCS file: /cvs/src/gnu/lib/libcompiler_rt/Makefile,v
> > > diff -u -p -r1.14 Makefile
> > > --- Makefile	10 Sep 2025 03:38:56 -0000	1.14
> > > +++ Makefile	27 Feb 2026 06:59:07 -0000
> > > @@ -211,9 +211,6 @@ GEN_SRCS+=	floatdidf \
> > >  .PATH: ${.CURDIR}/../../llvm/compiler-rt/lib/builtins/cpu_model
> > >  SRCS+=	aarch64.c
> > >  
> > > -# Quad-precision float support
> > > -GEN_SRCS+=	${GEN_TF_SRCS}
> > > -
> > >  # Prepare multiple versions of the LSE-helper
> > >  CPPFLAGS+=-DHAS_ASM_LSE
> > >  .for pat in cas swp ldadd ldclr ldeor ldset
> > > @@ -305,25 +302,17 @@ SRCS+=	divxc3.c \
> > >  	trunctfxf2.c
> > >  .endif
> > >  
> > > -.if ${RTARCH} == "mips64" || ${RTARCH} == "mips64el"
> > > -# Quad-precision float support
> > > -GEN_SRCS+=	${GEN_TF_SRCS}
> > > -.endif
> > > -
> > > -.if ${RTARCH} == "ppc"
> > > -# Omit "double-double" functions since long double is the same as
> > > -# double on OpenBSD.
> > > -.endif
> > > -
> > >  .if ${RTARCH} == "riscv"
> > > -# Quad-precision float support
> > > -GEN_SRCS+=	${GEN_TF_SRCS}
> > >  SRCS+=	restore.S \
> > >  	save.S
> > >  .endif
> > >  
> > > -.if ${RTARCH} == "sparc64"
> > >  # Quad-precision float support
> > > +# Omit "double-double" functions since long double is the same as
> > > +# double on ppc
> > > +.if ${RTARCH} == "mips64" || ${RTARCH} == "mips64el"  \
> > > +	|| ${RTARCH} == "sparc64" || ${RTARCH} == "aarch64" \
> > > +	|| ${RTARCH} == "x86_64" || ${RTARCH} == "riscv"
> > >  GEN_SRCS+=	${GEN_TF_SRCS}
> > >  .endif
> > >  
> 
> Like this.  Apparently there is no __float128/_Float128 support for
> i386 in llvm.
> 
> Index: gnu/lib/libcompiler_rt/Makefile
> ===================================================================
> RCS file: /cvs/src/gnu/lib/libcompiler_rt/Makefile,v
> diff -u -p -r1.14 Makefile
> --- gnu/lib/libcompiler_rt/Makefile	10 Sep 2025 03:38:56 -0000	1.14
> +++ gnu/lib/libcompiler_rt/Makefile	27 Feb 2026 21:18:25 -0000
> @@ -303,6 +303,11 @@ SRCS+=	divxc3.c \
>  	mulxc3.c \
>  	powixf2.c \
>  	trunctfxf2.c
> +
> +.if ${RTARCH} == "x86_64"
> +# Quad-precision float support (for __float128)
> +GEN_SRCS+=	${GEN_TF_SRCS}
> +.endif
>  .endif
>  
>  .if ${RTARCH} == "mips64" || ${RTARCH} == "mips64el"
> 

Thanks Mark,

So, I've read through this Makefile again and I understand what
you mean. OK for your / Brad's diff!