On 15.03.2014 03:48, Richard Henderson wrote:
> A compare and branch against zero happens at the start of
> every single TB.
>
> Signed-off-by: Richard Henderson <r...@twiddle.net>
> ---
> tcg/aarch64/tcg-target.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/tcg/aarch64/tcg-target.c b/tcg/aarch64/tcg-target.c
> index 44d53aa..0d6d495 100644
> --- a/tcg/aarch64/tcg-target.c
> +++ b/tcg/aarch64/tcg-target.c
> @@ -270,6 +270,10 @@ enum aarch64_ldst_op_type { /* type of operation */
> use the section number of the architecture reference manual in which the
> instruction group is described. */
> typedef enum {
> + /* Compare and branch (immediate). */
> + I3201_CBZ = 0x34000000,
> + I3201_CBNZ = 0x35000000,
> +
> /* Conditional branch (immediate). */
> I3202_B_C = 0x54000000,
>
> @@ -433,6 +437,12 @@ static inline uint32_t tcg_in32(TCGContext *s)
> #define tcg_out_insn(S, FMT, OP, ...) \
> glue(tcg_out_insn_,FMT)(S, glue(glue(glue(I,FMT),_),OP), ## __VA_ARGS__)
>
> +static void tcg_out_insn_3201(TCGContext *s, AArch64Insn insn, TCGType ext,
> + TCGReg rt, int imm19)
> +{
> + tcg_out32(s, insn | ext << 31 | (imm19 & 0x7ffff) << 5 | rt);
> +}
> +
> static void tcg_out_insn_3202(TCGContext *s, AArch64Insn insn,
> TCGCond c, int imm19)
> {
> @@ -910,8 +920,14 @@ static void tcg_out_brcond(TCGContext *s, TCGMemOp ext,
> TCGCond c, TCGArg a,
> {
> TCGLabel *l = &s->labels[label];
> intptr_t offset;
> + bool need_cmp;
>
> - tcg_out_cmp(s, ext, a, b, b_const);
> + if (b_const && b == 0 && (c == TCG_COND_EQ || c == TCG_COND_NE)) {
> + need_cmp = false;
> + } else {
> + need_cmp = true;
> + tcg_out_cmp(s, ext, a, b, b_const);
> + }
>
> if (!l->has_value) {
> tcg_out_reloc(s, s->code_ptr, R_AARCH64_CONDBR19, label, 0);
> @@ -922,7 +938,13 @@ static void tcg_out_brcond(TCGContext *s, TCGMemOp ext,
> TCGCond c, TCGArg a,
> assert(offset >= -0x40000 && offset < 0x40000);
> }
>
> - tcg_out_insn(s, 3202, B_C, c, offset);
> + if (need_cmp) {
> + tcg_out_insn(s, 3202, B_C, c, offset);
> + } else if (c == TCG_COND_EQ) {
> + tcg_out_insn(s, 3201, CBZ, ext, a, offset);
> + } else {
> + tcg_out_insn(s, 3201, CBNZ, ext, a, offset);
> + }
> }
>
> static inline void tcg_out_rev(TCGContext *s, TCGType ext,
>
Reviewed-by: Claudio Fontana <claudio.font...@huawei.com>
