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Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4 |
Date: |
Mon, 21 Dec 2009 16:02:18 -0800 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 |
On 12/21/2009 03:08 PM, Laurent Desnogues wrote:
If you wanted to use movcond, you'd have to make
cond + move a special case...
You'd certainly want the ARM front-end to use movcond more often than
that. For instance:
addeq r1,r2,r3
-->
add_i32 tmp,r2,r3
movcond_i32 r1,ZF,0,tmp,r1,eq
You'd want to continue to use a branch around if the instruction has
side effects like cpu fault (e.g. load, store) or updating flags.
It ought not be very hard to arrange for something like
if (cond != 0xe) {
if (may_use_movcond(insn)) {
s->condlabel = -1;
/* Save the true destination register. */
s->conddest = cpu_R[dest];
/* Implement the instruction into a temporary. */
cpu_R[dest] = tcg_temp_new();
} else {
s->condlabel = gen_new_label();
ArmConditional cmp = gen_test_cc(cond ^ 1);
tcg_gen_brcondi_i32(cmp.cond, cmp.reg, 0, s->condlabel);
}
s->condjmp = 1;
}
// ... implement the instruction as we currently do.
if (s->condjmp) {
if (s->condlabel == -1) {
/* Conditionally move the temporary result into the
true destination register. */
ArmConditional cmp = gen_test_cc(cond);
tcg_gen_movcond_i32(cmp.cond, s->conddest, cmp.reg, 0,
cpu_R[dest], s->conddest);
tcg_temp_free(cpu_R[dest]);
/* Restore the true destination register. */
cpu_R[dest] = s->conddest;
} else {
tcg_set_label(d->condlabel);
}
}
r~
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, (continued)
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Paul Brook, 2009/12/20
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Richard Henderson, 2009/12/20
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Richard Henderson, 2009/12/21
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Laurent Desnogues, 2009/12/21
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Richard Henderson, 2009/12/21
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Laurent Desnogues, 2009/12/21
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4,
Richard Henderson <=
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Laurent Desnogues, 2009/12/22
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Laurent Desnogues, 2009/12/23
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Aurelien Jarno, 2009/12/22
- Re: [Qemu-devel] [PATCH 0/5] tcg conditional set, round 4, Aurelien Jarno, 2009/12/21