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[Qemu-devel] Re: [PATCH 4/6] tcg-i386: Implement small forward branches.
From: |
Laurent Desnogues |
Subject: |
[Qemu-devel] Re: [PATCH 4/6] tcg-i386: Implement small forward branches. |
Date: |
Fri, 18 Dec 2009 12:39:54 +0100 |
On Thu, Dec 17, 2009 at 6:55 PM, Richard Henderson <address@hidden> wrote:
> There are places, like brcond2, where we know that the destination
> of a forward branch will be within 127 bytes. Add the R_386_PC8
> relocation type to support this, and add a flag to tcg_out_jxx to
> generate it. Set the flag in the small forward branches in brcond2.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> elf.h | 2 ++
> tcg/i386/tcg-target.c | 36 +++++++++++++++++++++++++-----------
> 2 files changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/elf.h b/elf.h
> index 11674d7..c84c8ab 100644
> --- a/elf.h
> +++ b/elf.h
> @@ -243,6 +243,8 @@ typedef struct {
> #define R_386_GOTOFF 9
> #define R_386_GOTPC 10
> #define R_386_NUM 11
> +/* Not a dynamic reloc, so not included in R_386_NUM. Used in TCG. */
> +#define R_386_PC8 23
>
> #define R_MIPS_NONE 0
> #define R_MIPS_16 1
> diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
> index 972b102..cc3d28f 100644
> --- a/tcg/i386/tcg-target.c
> +++ b/tcg/i386/tcg-target.c
> @@ -61,6 +61,9 @@ static void patch_reloc(uint8_t *code_ptr, int type,
> case R_386_PC32:
> *(uint32_t *)code_ptr = value - (long)code_ptr;
> break;
> + case R_386_PC8:
> + *(uint8_t *)code_ptr = value - (long)code_ptr;
> + break;
> default:
> tcg_abort();
> }
> @@ -305,7 +308,8 @@ static void tcg_out_addi(TCGContext *s, int reg,
> tcg_target_long val)
> tgen_arithi(s, ARITH_ADD, reg, val, 0);
> }
>
> -static void tcg_out_jxx(TCGContext *s, int opc, int label_index)
> +/* Use SMALL != 0 to force a short forward branch. */
> +static void tcg_out_jxx(TCGContext *s, int opc, int label_index, int small)
> {
> int32_t val, val1;
> TCGLabel *l = &s->labels[label_index];
> @@ -320,6 +324,7 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
> label_index)
> tcg_out8(s, 0x70 + opc);
> tcg_out8(s, val1);
> } else {
> + assert (!small);
To be consistent with the rest I'd use:
if (small)
tcg_abort();
> if (opc == -1) {
> tcg_out8(s, 0xe9);
> tcg_out32(s, val - 5);
> @@ -329,6 +334,15 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
> label_index)
> tcg_out32(s, val - 6);
> }
> }
> + } else if (small) {
> + if (opc == -1) {
> + tcg_out8(s, 0xeb);
> + } else {
> + tcg_out8(s, 0x0f);
I don't think this prefix should be output.
Laurent
> + tcg_out8(s, 0x70 + opc);
> + }
> + tcg_out_reloc(s, s->code_ptr, R_386_PC8, label_index, -1);
> + s->code_ptr += 1;
> } else {
> if (opc == -1) {
> tcg_out8(s, 0xe9);
> @@ -355,7 +369,7 @@ static void tcg_out_brcond(TCGContext *s, int cond,
> } else {
> tcg_out_modrm(s, 0x01 | (ARITH_CMP << 3), arg2, arg1);
> }
> - tcg_out_jxx(s, tcg_cond_to_jcc[cond], label_index);
> + tcg_out_jxx(s, tcg_cond_to_jcc[cond], label_index, 0);
> }
>
> /* XXX: we implement it at the target level to avoid having to
> @@ -376,42 +390,42 @@ static void tcg_out_brcond2(TCGContext *s,
> break;
> case TCG_COND_LT:
> tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_LE:
> tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_GT:
> tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_GE:
> tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_LTU:
> tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_LEU:
> tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_GTU:
> tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
> args[5]);
> break;
> case TCG_COND_GEU:
> tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
> args[5]);
> - tcg_out_jxx(s, JCC_JNE, label_next);
> + tcg_out_jxx(s, JCC_JNE, label_next, 1);
> tcg_out_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
> args[5]);
> break;
> default:
> @@ -913,7 +927,7 @@ static inline void tcg_out_op(TCGContext *s, int opc,
> }
> break;
> case INDEX_op_br:
> - tcg_out_jxx(s, JCC_JMP, args[0]);
> + tcg_out_jxx(s, JCC_JMP, args[0], 0);
> break;
> case INDEX_op_movi_i32:
> tcg_out_movi(s, TCG_TYPE_I32, args[0], args[1]);
> --
> 1.6.5.2
>
>
- [Qemu-devel] [PATCH 0/6] tcg conditional set/move, round 2, Richard Henderson, 2009/12/17
- [Qemu-devel] [PATCH 4/6] tcg-i386: Implement small forward branches., Richard Henderson, 2009/12/17
- [Qemu-devel] Re: [PATCH 4/6] tcg-i386: Implement small forward branches.,
Laurent Desnogues <=
- [Qemu-devel] [PATCH 6/6] tcg-i386: Implement setcond, movcond, setcond2., Richard Henderson, 2009/12/17
- [Qemu-devel] [PATCH 2/6] tcg: Add tcg_invert_cond., Richard Henderson, 2009/12/17
- [Qemu-devel] [PATCH 3/6] tcg-x86_64: Implement setcond and movcond., Richard Henderson, 2009/12/17
- [Qemu-devel] [PATCH 1/6] tcg: Generic support for conditional set and conditional move., Richard Henderson, 2009/12/17