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Re: [Qemu-devel] [RFC v1 09/13] target-ppc: add cmpeqb instruction
From: |
Nikunj A Dadhania |
Subject: |
Re: [Qemu-devel] [RFC v1 09/13] target-ppc: add cmpeqb instruction |
Date: |
Thu, 21 Jul 2016 13:32:02 +0530 |
User-agent: |
Notmuch/0.21 (https://notmuchmail.org) Emacs/25.0.94.1 (x86_64-redhat-linux-gnu) |
Richard Henderson <address@hidden> writes:
> On 07/18/2016 10:35 PM, Nikunj A Dadhania wrote:
>> + tcg_gen_andi_tl(src1, cpu_gpr[rA(ctx->opcode)], 0xFF);
>> + for (i = 0; i < 64; i += 8) {
>> + tcg_gen_shri_tl(t0, arg1, i);
>> + tcg_gen_andi_tl(t0, t0, 0xFF);
>> + tcg_gen_brcond_tl(TCG_COND_EQ, src1, t0, l1);
>> + }
>> + tcg_gen_movi_i32(cpu_crf[crfD(ctx->opcode)], 0);
>> + tcg_gen_br(l2);
>> + gen_set_label(l1);
>> + /* Set match bit, i.e. CRF_GT */
>> + tcg_gen_movi_i32(cpu_crf[crfD(ctx->opcode)], 1 << CRF_GT);
>
> Ew. This can be done much better as
>
> http://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord
>
> Which still might be best done in a helper, because of the constants involved
> (tcg is not nearly so good as gcc in building full 64-bit constants).
>
> C.f. target-alpha/int_helper.c, helper_cmpbe0 (which computes different
> information than cmpeqb, but is still helpful as an example).
Sure, I will have a look.
Nikunj
- Re: [Qemu-devel] [RFC v1 07/13] target-ppc: add cnttzd[.] instruction, (continued)
Re: [Qemu-devel] [RFC v1 09/13] target-ppc: add cmpeqb instruction, David Gibson, 2016/07/22
[Qemu-devel] [RFC v1 10/13] target-ppc: add setb instruction, Nikunj A Dadhania, 2016/07/18
[Qemu-devel] [RFC v1 11/13] target-ppc: add maddld instruction, Nikunj A Dadhania, 2016/07/18