diff options
author | Richard Henderson <rth@twiddle.net> | 2015-09-14 14:39:48 +0100 |
---|---|---|
committer | Peter Maydell <peter.maydell@linaro.org> | 2015-09-14 14:39:48 +0100 |
commit | 7dd03d773e0dafae9271318fc8d6b2b14de74403 (patch) | |
tree | 3a1b73b986895f7ea2cac8ce462df143808ff7c3 | |
parent | 259cb68491ab36427e7e5d820fe543d53b006ec6 (diff) |
target-arm: Implement ccmp branchless
This can allow much of a ccmp to be elided when particular
flags are subsequently dead.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-id: 1441909103-24666-6-git-send-email-rth@twiddle.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
-rw-r--r-- | target-arm/translate-a64.c | 74 |
1 files changed, 58 insertions, 16 deletions
diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c index 1ab2c8d9aa..b48cd97314 100644 --- a/target-arm/translate-a64.c +++ b/target-arm/translate-a64.c @@ -3570,8 +3570,9 @@ static void disas_adc_sbc(DisasContext *s, uint32_t insn) static void disas_cc(DisasContext *s, uint32_t insn) { unsigned int sf, op, y, cond, rn, nzcv, is_imm; - TCGLabel *label_continue = NULL; + TCGv_i32 tcg_t0, tcg_t1, tcg_t2; TCGv_i64 tcg_tmp, tcg_y, tcg_rn; + DisasCompare c; if (!extract32(insn, 29, 1)) { unallocated_encoding(s); @@ -3589,19 +3590,13 @@ static void disas_cc(DisasContext *s, uint32_t insn) rn = extract32(insn, 5, 5); nzcv = extract32(insn, 0, 4); - if (cond < 0x0e) { /* not always */ - TCGLabel *label_match = gen_new_label(); - label_continue = gen_new_label(); - arm_gen_test_cc(cond, label_match); - /* nomatch: */ - tcg_tmp = tcg_temp_new_i64(); - tcg_gen_movi_i64(tcg_tmp, nzcv << 28); - gen_set_nzcv(tcg_tmp); - tcg_temp_free_i64(tcg_tmp); - tcg_gen_br(label_continue); - gen_set_label(label_match); - } - /* match, or condition is always */ + /* Set T0 = !COND. */ + tcg_t0 = tcg_temp_new_i32(); + arm_test_cc(&c, cond); + tcg_gen_setcondi_i32(tcg_invert_cond(c.cond), tcg_t0, c.value, 0); + arm_free_cc(&c); + + /* Load the arguments for the new comparison. */ if (is_imm) { tcg_y = new_tmp_a64(s); tcg_gen_movi_i64(tcg_y, y); @@ -3610,6 +3605,7 @@ static void disas_cc(DisasContext *s, uint32_t insn) } tcg_rn = cpu_reg(s, rn); + /* Set the flags for the new comparison. */ tcg_tmp = tcg_temp_new_i64(); if (op) { gen_sub_CC(sf, tcg_tmp, tcg_rn, tcg_y); @@ -3618,9 +3614,55 @@ static void disas_cc(DisasContext *s, uint32_t insn) } tcg_temp_free_i64(tcg_tmp); - if (cond < 0x0e) { /* continue */ - gen_set_label(label_continue); + /* If COND was false, force the flags to #nzcv. Compute two masks + * to help with this: T1 = (COND ? 0 : -1), T2 = (COND ? -1 : 0). + * For tcg hosts that support ANDC, we can make do with just T1. + * In either case, allow the tcg optimizer to delete any unused mask. + */ + tcg_t1 = tcg_temp_new_i32(); + tcg_t2 = tcg_temp_new_i32(); + tcg_gen_neg_i32(tcg_t1, tcg_t0); + tcg_gen_subi_i32(tcg_t2, tcg_t0, 1); + + if (nzcv & 8) { /* N */ + tcg_gen_or_i32(cpu_NF, cpu_NF, tcg_t1); + } else { + if (TCG_TARGET_HAS_andc_i32) { + tcg_gen_andc_i32(cpu_NF, cpu_NF, tcg_t1); + } else { + tcg_gen_and_i32(cpu_NF, cpu_NF, tcg_t2); + } + } + if (nzcv & 4) { /* Z */ + if (TCG_TARGET_HAS_andc_i32) { + tcg_gen_andc_i32(cpu_ZF, cpu_ZF, tcg_t1); + } else { + tcg_gen_and_i32(cpu_ZF, cpu_ZF, tcg_t2); + } + } else { + tcg_gen_or_i32(cpu_ZF, cpu_ZF, tcg_t0); + } + if (nzcv & 2) { /* C */ + tcg_gen_or_i32(cpu_CF, cpu_CF, tcg_t0); + } else { + if (TCG_TARGET_HAS_andc_i32) { + tcg_gen_andc_i32(cpu_CF, cpu_CF, tcg_t1); + } else { + tcg_gen_and_i32(cpu_CF, cpu_CF, tcg_t2); + } + } + if (nzcv & 1) { /* V */ + tcg_gen_or_i32(cpu_VF, cpu_VF, tcg_t1); + } else { + if (TCG_TARGET_HAS_andc_i32) { + tcg_gen_andc_i32(cpu_VF, cpu_VF, tcg_t1); + } else { + tcg_gen_and_i32(cpu_VF, cpu_VF, tcg_t2); + } } + tcg_temp_free_i32(tcg_t0); + tcg_temp_free_i32(tcg_t1); + tcg_temp_free_i32(tcg_t2); } /* C3.5.6 Conditional select |