On Mon, 10 Feb 2025, Niels Möller wrote:
Marc Glisse <marc.gli...@inria.fr> writes:
Let's see. If I configure GMP with just --enable-fat, I still see in
config.h
#define HAVE_HOST_CPU_nehalem 1
and longlong.h enables mulx based on
#if X86_ASM_MULX \
&& (HAVE_HOST_CPU_haswell || HAVE_HOST_CPU_broadwell \
|| HAVE_HOST_CPU_skylake || HAVE_HOST_CPU_bd4 || HAVE_HOST_CPU_zen)
Torbjörn Granlund <t...@gmplib.org> writes:
Emmanuel Lonca <emmanuel.lo...@univ-artois.fr> writes:
To what I understand from the GMP documentation, compiling with the
--enable-fat flag should produce a library that can be used on any x86
architecture.
Yes, that's the idea IIRC.
It seems the above use in longlong.h is the only use of X86_ASM_MULX?
Then it seems right to completely disable that in fat builds, like
diff -r 1a2ad0e32507 configure.ac
--- a/configure.ac Mon Feb 03 17:52:54 2025 +0100
+++ b/configure.ac Mon Feb 10 16:21:35 2025 +0100
@@ -3843,7 +3843,9 @@ yes
X86_PATTERN | X86_64_PATTERN)
GMP_ASM_ALIGN_FILL_0x90
if test "$x86_have_mulx" = yes; then
- GMP_ASM_X86_MULX
+ if test "$enable_fat" = no; then
+ GMP_ASM_X86_MULX
+ fi
fi
GMP_ASM_COFF_TYPE
case $ABI in
I don't like it, GMP_ASM_X86_MULX is about the assembler supporting the
mulx instruction, not about the host processor being able to execute it.
Something simple might be in configure.ac to hide
tmp_host=`echo $host_cpu | sed 's/\./_/'`
AC_DEFINE_UNQUOTED(HAVE_HOST_CPU_$tmp_host)
GMP_DEFINE_RAW("define_not_for_expansion(\`HAVE_HOST_CPU_$tmp_host')", POST)
behind a test $enable_fat = no
since any use of HAVE_HOST_CPU_* (as opposed to HAVE_HOST_CPU_FAMILY_*) is
suspect in a fat build, but that prevents from having a fat build with a
non-basic baseline (say only support skylake or later).
I feel that somehow, with --enable-fat, we should avoid GMP's config.guess
and stick to the FSF version, but that doesn't look convenient.
--
Marc Glisse
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