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tcg: Add atomic128 helpers

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Force the use of cmpxchg16b on x86_64.

Wikipedia suggests that only very old AMD64 (circa 2004) did not have
this instruction.  Further, it's required by Windows 8 so no new cpus
will ever omit it.

If we truely care about these, then we could check this at startup time
and then avoid executing paths that use it.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2016-06-29 21:10:59 -07:00
parent c482cb117c
commit 7ebee43ee3
6 changed files with 119 additions and 3 deletions
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29
configure vendored
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@ -1216,7 +1216,10 @@ case "$cpu" in
cc_i386='$(CC) -m32'
;;
x86_64)
CPU_CFLAGS="-m64"
# ??? 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"
LDFLAGS="-m64 $LDFLAGS"
cc_i386='$(CC) -m32'
;;
@ -4521,6 +4524,26 @@ if compile_prog "" "" ; then
int128=yes
fi
#########################################
# See if 128-bit atomic operations are supported.
atomic128=no
if test "$int128" = "yes"; then
cat > $TMPC << EOF
int main(void)
{
unsigned __int128 x = 0, y = 0;
y = __atomic_load_16(&x, 0);
__atomic_store_16(&x, y, 0);
__atomic_compare_exchange_16(&x, &y, x, 0, 0, 0);
return 0;
}
EOF
if compile_prog "" "" ; then
atomic128=yes
fi
fi
########################################
# check if getauxval is available.
@ -5483,6 +5506,10 @@ if test "$int128" = "yes" ; then
echo "CONFIG_INT128=y" >> $config_host_mak
fi
if test "$atomic128" = "yes" ; then
echo "CONFIG_ATOMIC128=y" >> $config_host_mak
fi
if test "$getauxval" = "yes" ; then
echo "CONFIG_GETAUXVAL=y" >> $config_host_mak
fi