On Thu, Jan 14, 2010 at 02:59:51PM -0800, Richard Henderson wrote:
> The existing P_REXB internal opcode flag unconditionally emits
> the REX prefix. Technically it's not needed if the register in
> question is %al, %bl, %cl, %dl.
>
> Eliding the prefix requires splitting the P_REXB flag into two,
> in order to indicate whether the byte register in question is
> in the REG or the R/M field. Within TCG, the byte register is
> in the REG field only for stores.
Thanks, applied.
> Signed-off-by: Richard Henderson <r...@twiddle.net>
> ---
> tcg/x86_64/tcg-target.c | 46 ++++++++++++++++++++++++++++++----------------
> 1 files changed, 30 insertions(+), 16 deletions(-)
>
> diff --git a/tcg/x86_64/tcg-target.c b/tcg/x86_64/tcg-target.c
> index 8c7e738..cbaabef 100644
> --- a/tcg/x86_64/tcg-target.c
> +++ b/tcg/x86_64/tcg-target.c
> @@ -217,9 +217,10 @@ static inline int tcg_target_const_match(tcg_target_long
> val,
> #define JCC_JLE 0xe
> #define JCC_JG 0xf
>
> -#define P_EXT 0x100 /* 0x0f opcode prefix */
> -#define P_REXW 0x200 /* set rex.w = 1 */
> -#define P_REXB 0x400 /* force rex use for byte registers */
> +#define P_EXT 0x100 /* 0x0f opcode prefix */
> +#define P_REXW 0x200 /* set rex.w = 1 */
> +#define P_REXB_R 0x400 /* REG field as byte register */
> +#define P_REXB_RM 0x800 /* R/M field as byte register */
>
> static const uint8_t tcg_cond_to_jcc[10] = {
> [TCG_COND_EQ] = JCC_JE,
> @@ -234,16 +235,29 @@ static const uint8_t tcg_cond_to_jcc[10] = {
> [TCG_COND_GTU] = JCC_JA,
> };
>
> -static inline void tcg_out_opc(TCGContext *s, int opc, int r, int rm, int x)
> +static void tcg_out_opc(TCGContext *s, int opc, int r, int rm, int x)
> {
> - int rex;
> - rex = ((opc >> 6) & 0x8) | ((r >> 1) & 0x4) |
> - ((x >> 2) & 2) | ((rm >> 3) & 1);
> - if (rex || (opc & P_REXB)) {
> - tcg_out8(s, rex | 0x40);
> + int rex = 0;
> +
> + rex |= (opc & P_REXW) >> 6; /* REX.W */
> + rex |= (r & 8) >> 1; /* REX.R */
> + rex |= (x & 8) >> 2; /* REX.X */
> + rex |= (rm & 8) >> 3; /* REX.B */
> +
> + /* P_REXB_{R,RM} indicates that the given register is the low byte.
> + For %[abcd]l we need no REX prefix, but for %{si,di,bp,sp}l we do,
> + as otherwise the encoding indicates %[abcd]h. Note that the values
> + that are ORed in merely indicate that the REX byte must be present;
> + those bits get discarded in output. */
> + rex |= opc & (r >= 4 ? P_REXB_R : 0);
> + rex |= opc & (rm >= 4 ? P_REXB_RM : 0);
> +
> + if (rex) {
> + tcg_out8(s, (uint8_t)(rex | 0x40));
> }
> - if (opc & P_EXT)
> + if (opc & P_EXT) {
> tcg_out8(s, 0x0f);
> + }
> tcg_out8(s, opc & 0xff);
> }
>
> @@ -408,7 +422,7 @@ static inline void tgen_arithi32(TCGContext *s, int c,
> int r0, int32_t val)
> tcg_out8(s, val);
> } else if (c == ARITH_AND && val == 0xffu) {
> /* movzbl */
> - tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB, r0, r0);
> + tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB_RM, r0, r0);
> } else if (c == ARITH_AND && val == 0xffffu) {
> /* movzwl */
> tcg_out_modrm(s, 0xb7 | P_EXT, r0, r0);
> @@ -776,7 +790,7 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg
> *args,
> switch(opc) {
> case 0:
> /* movzbl */
> - tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB, TCG_REG_RSI, data_reg);
> + tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB_RM, TCG_REG_RSI, data_reg);
> break;
> case 1:
> /* movzwl */
> @@ -829,7 +843,7 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg
> *args,
> switch(opc) {
> case 0:
> /* movb */
> - tcg_out_modrm_offset(s, 0x88 | P_REXB, data_reg, r0, offset);
> + tcg_out_modrm_offset(s, 0x88 | P_REXB_R, data_reg, r0, offset);
> break;
> case 1:
> if (bswap) {
> @@ -964,7 +978,7 @@ static inline void tcg_out_op(TCGContext *s, int opc,
> const TCGArg *args,
> case INDEX_op_st8_i32:
> case INDEX_op_st8_i64:
> /* movb */
> - tcg_out_modrm_offset(s, 0x88 | P_REXB, args[0], args[1], args[2]);
> + tcg_out_modrm_offset(s, 0x88 | P_REXB_R, args[0], args[1], args[2]);
> break;
> case INDEX_op_st16_i32:
> case INDEX_op_st16_i64:
> @@ -1161,7 +1175,7 @@ static inline void tcg_out_op(TCGContext *s, int opc,
> const TCGArg *args,
> break;
>
> case INDEX_op_ext8s_i32:
> - tcg_out_modrm(s, 0xbe | P_EXT | P_REXB, args[0], args[1]);
> + tcg_out_modrm(s, 0xbe | P_EXT | P_REXB_RM, args[0], args[1]);
> break;
> case INDEX_op_ext16s_i32:
> tcg_out_modrm(s, 0xbf | P_EXT, args[0], args[1]);
> @@ -1177,7 +1191,7 @@ static inline void tcg_out_op(TCGContext *s, int opc,
> const TCGArg *args,
> break;
> case INDEX_op_ext8u_i32:
> case INDEX_op_ext8u_i64:
> - tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB, args[0], args[1]);
> + tcg_out_modrm(s, 0xb6 | P_EXT | P_REXB_RM, args[0], args[1]);
> break;
> case INDEX_op_ext16u_i32:
> case INDEX_op_ext16u_i64:
> --
> 1.6.5.2
>
>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurel...@aurel32.net http://www.aurel32.net
