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configure: move -mcx16 flag out of CPU_CFLAGS

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The point of CPU_CFLAGS is really just to select the appropriate multilib,
for example for library linking tests, and -mcx16 is not needed for
that purpose.

Furthermore, if -mcx16 is part of QEMU's choice of a basic x86_64
instruction set, it should be applied to cross-compiled x86_64 code too;
it is plausible that tests/tcg would want to cover cmpxchg16b as well,
for example.  In the end this makes just as much sense as a per sub-build
tweak, so move the flag to meson.build and cross_cc_cflags_x86_64.

This leaves out contrib/plugins, which would fail when attempting to use
__sync_val_compare_and_swap_16 (note it does not do yet); while minor,
this *is* a disadvantage of this change.  But building contrib/plugins
with a Makefile instead of meson.build is something self-inflicted just
for the sake of showing that it can be done, and if this kind of papercut
started becoming a problem we could make the directory part of the meson
build.  Until then, we can live with the limitation.

Signed-off-by: Artyom Kunakovsky <artyomkunakovsky@gmail.com>
Message-ID: <20240523051118.29367-1-artyomkunakovsky@gmail.com>
[rewrite commit message, remove from configure. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Artyom Kunakovsky 2024-05-23 08:11:18 +03:00 committed by Paolo Bonzini
parent 70581940ca
commit c2bf2ccb26
2 changed files with 9 additions and 5 deletions
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7
configure vendored
View File

@ -512,10 +512,7 @@ case "$cpu" in
cpu="x86_64"
host_arch=x86_64
linux_arch=x86
# ??? Only extremely old AMD cpus do not have cmpxchg16b.
# If we truly care, we should simply detect this case at
# runtime and generate the fallback to serial emulation.
CPU_CFLAGS="-m64 -mcx16"
CPU_CFLAGS="-m64"
;;
esac
@ -1203,7 +1200,7 @@ fi
: ${cross_cc_cflags_sparc64="-m64 -mcpu=ultrasparc"}
: ${cross_cc_sparc="$cross_cc_sparc64"}
: ${cross_cc_cflags_sparc="-m32 -mcpu=supersparc"}
: ${cross_cc_cflags_x86_64="-m64"}
: ${cross_cc_cflags_x86_64="-m64 -mcx16"}
compute_target_variable() {
eval "$2="

7
meson.build
View File

@ -336,6 +336,13 @@ if host_arch == 'i386' and not cc.links('''
qemu_common_flags = ['-march=i486'] + qemu_common_flags
endif
# ??? Only extremely old AMD cpus do not have cmpxchg16b.
# If we truly care, we should simply detect this case at
# runtime and generate the fallback to serial emulation.
if host_arch == 'x86_64'
qemu_common_flags = ['-mcx16'] + qemu_common_flags
endif
if get_option('prefer_static')
qemu_ldflags += get_option('b_pie') ? '-static-pie' : '-static'
endif