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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>
This commit is contained in:
Richard Henderson 2015-09-14 14:39:48 +01:00 committed by Peter Maydell
parent 259cb68491
commit 7dd03d773e
1 changed files with 58 additions and 16 deletions
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74
target-arm/translate-a64.c
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@ -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