* [Qemu-devel] [PATCH] tcg-i386: Perform cmov detection at runtime for 32-bit.
@ 2012-12-28 22:17 Richard Henderson
2012-12-29 15:51 ` Blue Swirl
0 siblings, 1 reply; 2+ messages in thread
From: Richard Henderson @ 2012-12-28 22:17 UTC (permalink / raw)
To: qemu-devel; +Cc: Blue Swirl, Aurelien Jarno
Existing compile-time detection is spotty at best. Convert
it all to runtime detection instead.
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
configure | 19 +++++++++++++++++++
tcg/i386/tcg-target.c | 31 ++++++++++++++++++++++++++++++-
tcg/i386/tcg-target.h | 5 -----
3 files changed, 49 insertions(+), 6 deletions(-)
diff --git a/configure b/configure
index 99c1ec3..b0c7e54 100755
--- a/configure
+++ b/configure
@@ -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
diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index ae82746..e083874 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -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))
diff --git a/tcg/i386/tcg-target.h b/tcg/i386/tcg-target.h
index 5352ac0..e63db9c 100644
--- a/tcg/i386/tcg-target.h
+++ b/tcg/i386/tcg-target.h
@@ -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
--
1.7.11.7
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH] tcg-i386: Perform cmov detection at runtime for 32-bit.
2012-12-28 22:17 [Qemu-devel] [PATCH] tcg-i386: Perform cmov detection at runtime for 32-bit Richard Henderson
@ 2012-12-29 15:51 ` Blue Swirl
0 siblings, 0 replies; 2+ messages in thread
From: Blue Swirl @ 2012-12-29 15:51 UTC (permalink / raw)
To: Richard Henderson; +Cc: qemu-devel, Aurelien Jarno
Thanks, applied.
On Fri, Dec 28, 2012 at 10:17 PM, Richard Henderson <rth@twiddle.net> wrote:
> Existing compile-time detection is spotty at best. Convert
> it all to runtime detection instead.
>
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
> configure | 19 +++++++++++++++++++
> tcg/i386/tcg-target.c | 31 ++++++++++++++++++++++++++++++-
> tcg/i386/tcg-target.h | 5 -----
> 3 files changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/configure b/configure
> index 99c1ec3..b0c7e54 100755
> --- a/configure
> +++ b/configure
> @@ -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
> diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
> index ae82746..e083874 100644
> --- a/tcg/i386/tcg-target.c
> +++ b/tcg/i386/tcg-target.c
> @@ -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))
> diff --git a/tcg/i386/tcg-target.h b/tcg/i386/tcg-target.h
> index 5352ac0..e63db9c 100644
> --- a/tcg/i386/tcg-target.h
> +++ b/tcg/i386/tcg-target.h
> @@ -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
> --
> 1.7.11.7
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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