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tcg-i386: Perform cmov detection at runtime for 32-bit. 

Existing compile-time detection is spotty at best.  Convert
it all to runtime detection instead.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Richard Henderson 2012-12-28 14:17:02 -08:00 committed by Blue Swirl
parent afcb92beac
commit 76a347e1cd
3 changed files with 49 additions and 6 deletions
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19
configure vendored
View File

@ -3086,6 +3086,21 @@ if compile_prog "" "" ; then
has_environ=yes
fi
########################################
# check if cpuid.h is usable.
cpuid_h=no
cat > $TMPC << EOF
#include <cpuid.h>
int main(void) {
return 0;
}
EOF
if compile_prog "" "" ; then
cpuid_h=yes
fi
##########################################
# End of CC checks
# After here, no more $cc or $ld runs
@ -3611,6 +3626,10 @@ if test "$has_environ" = "yes" ; then
echo "CONFIG_HAS_ENVIRON=y" >> $config_host_mak
fi
if test "$cpuid_h" = "yes" ; then
echo "CONFIG_CPUID_H=y" >> $config_host_mak
fi
if test "$glusterfs" = "yes" ; then
echo "CONFIG_GLUSTERFS=y" >> $config_host_mak
fi

31
tcg/i386/tcg-target.c
View File

@ -97,6 +97,18 @@ static const int tcg_target_call_oarg_regs[] = {
# define TCG_REG_L1 TCG_REG_EDX
#endif
/* For 32-bit, we are going to attempt to determine at runtime whether cmov
is available. However, the host compiler must supply <cpuid.h>, as we're
not going to go so far as our own inline assembly. */
#if TCG_TARGET_REG_BITS == 64
# define have_cmov 1
#elif defined(CONFIG_CPUID_H)
#include <cpuid.h>
static bool have_cmov;
#else
# define have_cmov 0
#endif
static uint8_t *tb_ret_addr;
static void patch_reloc(uint8_t *code_ptr, int type,
@ -943,7 +955,14 @@ static void tcg_out_movcond32(TCGContext *s, TCGCond cond, TCGArg dest,
TCGArg v1)
{
tcg_out_cmp(s, c1, c2, const_c2, 0);
tcg_out_modrm(s, OPC_CMOVCC | tcg_cond_to_jcc[cond], dest, v1);
if (have_cmov) {
tcg_out_modrm(s, OPC_CMOVCC | tcg_cond_to_jcc[cond], dest, v1);
} else {
int over = gen_new_label();
tcg_out_jxx(s, tcg_cond_to_jcc[tcg_invert_cond(cond)], over, 1);
tcg_out_mov(s, TCG_TYPE_I32, dest, v1);
tcg_out_label(s, over, s->code_ptr);
}
}
#if TCG_TARGET_REG_BITS == 64
@ -2243,6 +2262,16 @@ static void tcg_target_qemu_prologue(TCGContext *s)
static void tcg_target_init(TCGContext *s)
{
/* For 32-bit, 99% certainty that we're running on hardware that supports
cmov, but we still need to check. In case cmov is not available, we'll
use a small forward branch. */
#ifndef have_cmov
{
unsigned a, b, c, d;
have_cmov = (__get_cpuid(1, &a, &b, &c, &d) && (d & bit_CMOV));
}
#endif
#if !defined(CONFIG_USER_ONLY)
/* fail safe */
if ((1 << CPU_TLB_ENTRY_BITS) != sizeof(CPUTLBEntry))

5
tcg/i386/tcg-target.h
View File

@ -91,12 +91,7 @@ typedef enum {
#define TCG_TARGET_HAS_nand_i32 0
#define TCG_TARGET_HAS_nor_i32 0
#define TCG_TARGET_HAS_deposit_i32 1
#if defined(__x86_64__) || defined(__i686__)
/* Use cmov only if the compiler is already doing so. */
#define TCG_TARGET_HAS_movcond_i32 1
#else
#define TCG_TARGET_HAS_movcond_i32 0
#endif
#if TCG_TARGET_REG_BITS == 64
#define TCG_TARGET_HAS_div2_i64 1