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tcg/i386: use movbe instruction in qemu_ldst routines
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The movbe instruction has been added on some Intel Atom CPUs and on
recent Intel Haswell CPUs. It allows to load/store a value and at the
same time bswap it.

This patch detects the avaibility of this instruction and when available
use it in the qemu load/store routines in replacement of load/store +
bswap. Note that for 16-bit unsigned loads, movbe + movzw is basically the
same as movzw + bswap, so the patch doesn't touch this case.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
[RTH: Reduced the number of conditionals using "movop".]
Signed-off-by: Richard Henderson <rth@twiddle.net>
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@aurel32 @rth7680
aurel32 authored and rth7680 committed Jan 25, 2014
1 parent 2a11377 commit 085bb5b
Showing 1 changed file with 80 additions and 37 deletions.
117 changes: 80 additions & 37 deletions tcg/i386/tcg-target.c
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Expand Up @@ -99,18 +99,31 @@ static const int tcg_target_call_oarg_regs[] = {
# define TCG_REG_L1 TCG_REG_EDX
#endif

/* The host compiler should supply <cpuid.h> to enable runtime features
detection, as we're not going to go so far as our own inline assembly.
If not available, default values will be assumed. */
#if defined(CONFIG_CPUID_H)
#include <cpuid.h>
#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. */
is available. */
#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

/* If bit_MOVBE is defined in cpuid.h (added in GCC version 4.6), we are
going to attempt to determine at runtime whether movbe is available. */
#if defined(CONFIG_CPUID_H) && defined(bit_MOVBE)
static bool have_movbe;
#else
# define have_movbe 0
#endif

static uint8_t *tb_ret_addr;

static void patch_reloc(uint8_t *code_ptr, int type,
Expand Down Expand Up @@ -280,6 +293,8 @@ static inline int tcg_target_const_match(tcg_target_long val,
#define OPC_MOVB_EvIz (0xc6)
#define OPC_MOVL_EvIz (0xc7)
#define OPC_MOVL_Iv (0xb8)
#define OPC_MOVBE_GyMy (0xf0 | P_EXT38)
#define OPC_MOVBE_MyGy (0xf1 | P_EXT38)
#define OPC_MOVSBL (0xbe | P_EXT)
#define OPC_MOVSWL (0xbf | P_EXT)
#define OPC_MOVSLQ (0x63 | P_REXW)
Expand Down Expand Up @@ -1344,7 +1359,14 @@ static void tcg_out_qemu_ld_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
TCGReg base, intptr_t ofs, int seg,
TCGMemOp memop)
{
const TCGMemOp bswap = memop & MO_BSWAP;
const TCGMemOp real_bswap = memop & MO_BSWAP;
TCGMemOp bswap = real_bswap;
int movop = OPC_MOVL_GvEv;

if (have_movbe && real_bswap) {
bswap = 0;
movop = OPC_MOVBE_GyMy;
}

switch (memop & MO_SSIZE) {
case MO_UB:
Expand All @@ -1355,31 +1377,38 @@ static void tcg_out_qemu_ld_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
break;
case MO_UW:
tcg_out_modrm_offset(s, OPC_MOVZWL + seg, datalo, base, ofs);
if (bswap) {
if (real_bswap) {
tcg_out_rolw_8(s, datalo);
}
break;
case MO_SW:
if (bswap) {
tcg_out_modrm_offset(s, OPC_MOVZWL + seg, datalo, base, ofs);
tcg_out_rolw_8(s, datalo);
if (real_bswap) {
if (have_movbe) {
tcg_out_modrm_offset(s, OPC_MOVBE_GyMy + P_DATA16 + seg,
datalo, base, ofs);
} else {
tcg_out_modrm_offset(s, OPC_MOVZWL + seg, datalo, base, ofs);
tcg_out_rolw_8(s, datalo);
}
tcg_out_modrm(s, OPC_MOVSWL + P_REXW, datalo, datalo);
} else {
tcg_out_modrm_offset(s, OPC_MOVSWL + P_REXW + seg,
datalo, base, ofs);
}
break;
case MO_UL:
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg, datalo, base, ofs);
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
if (bswap) {
tcg_out_bswap32(s, datalo);
}
break;
#if TCG_TARGET_REG_BITS == 64
case MO_SL:
if (bswap) {
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg, datalo, base, ofs);
tcg_out_bswap32(s, datalo);
if (real_bswap) {
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
if (bswap) {
tcg_out_bswap32(s, datalo);
}
tcg_out_ext32s(s, datalo, datalo);
} else {
tcg_out_modrm_offset(s, OPC_MOVSLQ + seg, datalo, base, ofs);
Expand All @@ -1388,27 +1417,22 @@ static void tcg_out_qemu_ld_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
#endif
case MO_Q:
if (TCG_TARGET_REG_BITS == 64) {
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + P_REXW + seg,
datalo, base, ofs);
tcg_out_modrm_offset(s, movop + P_REXW + seg, datalo, base, ofs);
if (bswap) {
tcg_out_bswap64(s, datalo);
}
} else {
if (bswap) {
if (real_bswap) {
int t = datalo;
datalo = datahi;
datahi = t;
}
if (base != datalo) {
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg,
datalo, base, ofs);
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg,
datahi, base, ofs + 4);
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
tcg_out_modrm_offset(s, movop + seg, datahi, base, ofs + 4);
} else {
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg,
datahi, base, ofs + 4);
tcg_out_modrm_offset(s, OPC_MOVL_GvEv + seg,
datalo, base, ofs);
tcg_out_modrm_offset(s, movop + seg, datahi, base, ofs + 4);
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
}
if (bswap) {
tcg_out_bswap32(s, datalo);
Expand Down Expand Up @@ -1484,13 +1508,19 @@ static void tcg_out_qemu_st_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
TCGReg base, intptr_t ofs, int seg,
TCGMemOp memop)
{
const TCGMemOp bswap = memop & MO_BSWAP;

/* ??? Ideally we wouldn't need a scratch register. For user-only,
we could perform the bswap twice to restore the original value
instead of moving to the scratch. But as it is, the L constraint
means that TCG_REG_L0 is definitely free here. */
const TCGReg scratch = TCG_REG_L0;
const TCGMemOp real_bswap = memop & MO_BSWAP;
TCGMemOp bswap = real_bswap;
int movop = OPC_MOVL_EvGv;

if (have_movbe && real_bswap) {
bswap = 0;
movop = OPC_MOVBE_MyGy;
}

switch (memop & MO_SIZE) {
case MO_8:
Expand All @@ -1509,16 +1539,15 @@ static void tcg_out_qemu_st_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
tcg_out_rolw_8(s, scratch);
datalo = scratch;
}
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + P_DATA16 + seg,
datalo, base, ofs);
tcg_out_modrm_offset(s, movop + P_DATA16 + seg, datalo, base, ofs);
break;
case MO_32:
if (bswap) {
tcg_out_mov(s, TCG_TYPE_I32, scratch, datalo);
tcg_out_bswap32(s, scratch);
datalo = scratch;
}
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + seg, datalo, base, ofs);
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
break;
case MO_64:
if (TCG_TARGET_REG_BITS == 64) {
Expand All @@ -1527,8 +1556,7 @@ static void tcg_out_qemu_st_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
tcg_out_bswap64(s, scratch);
datalo = scratch;
}
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + P_REXW + seg,
datalo, base, ofs);
tcg_out_modrm_offset(s, movop + P_REXW + seg, datalo, base, ofs);
} else if (bswap) {
tcg_out_mov(s, TCG_TYPE_I32, scratch, datahi);
tcg_out_bswap32(s, scratch);
Expand All @@ -1537,8 +1565,13 @@ static void tcg_out_qemu_st_direct(TCGContext *s, TCGReg datalo, TCGReg datahi,
tcg_out_bswap32(s, scratch);
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + seg, scratch, base, ofs+4);
} else {
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + seg, datalo, base, ofs);
tcg_out_modrm_offset(s, OPC_MOVL_EvGv + seg, datahi, base, ofs+4);
if (real_bswap) {
int t = datalo;
datalo = datahi;
datahi = t;
}
tcg_out_modrm_offset(s, movop + seg, datalo, base, ofs);
tcg_out_modrm_offset(s, movop + seg, datahi, base, ofs+4);
}
break;
default:
Expand Down Expand Up @@ -2165,13 +2198,23 @@ 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
#if !(defined(have_cmov) && defined(have_movbe))
{
unsigned a, b, c, d;
have_cmov = (__get_cpuid(1, &a, &b, &c, &d) && (d & bit_CMOV));
int ret = __get_cpuid(1, &a, &b, &c, &d);

# ifndef have_cmov
/* 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. */
have_cmov = ret && (d & bit_CMOV);
# endif

# ifndef have_movbe
/* MOVBE is only available on Intel Atom and Haswell CPUs, so we
need to probe for it. */
have_movbe = ret && (c & bit_MOVBE);
# endif
}
#endif

Expand Down

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