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Sender: Richard Henderson <rth7680@gmail.com>
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Date: Sun, 16 Feb 2014 09:57:41 -0800
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [PATCH 5/5] tcg/i386: Use SHLX/SHRX/SARX
	instructions
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: aurelien@aurel32.net

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~