[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 5/5] tcg/i386: Use SHLX/SHRX/SARX instructions
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 5/5] tcg/i386: Use SHLX/SHRX/SARX instructions |
Date: |
Sun, 16 Feb 2014 09:57:41 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 |
On 02/16/2014 06:21 AM, Paolo Bonzini wrote:
> Il 31/01/2014 15:43, Richard Henderson ha scritto:
>> + gen_shift_maybe_vex:
>> + if (have_bmi2 && !const_args[2]) {
>> + tcg_out_vex_modrm(s, vexop + rexw, args[0], args[2], args[1]);
>> + break;
>> + }
>> + /* FALLTHRU */
>
> What if args[2] happens to be ECX?
shlx handles that just fine. I don't think it's worth an extra check to
fall back to shl on the off-chance that ecx is used; it's pretty far down
on the register allocation order list, so it wouldn't happen often.
r~