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Re: [Qemu-devel] [RISU RFC PATCH v2 04/14] risugen_x86: add module

From: Richard Henderson
Subject: Re: [Qemu-devel] [RISU RFC PATCH v2 04/14] risugen_x86: add module
Date: Thu, 11 Jul 2019 11:26:35 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1

On 7/10/19 8:21 PM, Jan Bobek wrote:
> Doesn't B8 (without REX.W) work for x86_64, too? It zeroes the upper
> part of the destination, so it's effectively zero-extending, and it's
> one byte shorter than C7 (no ModR/M byte needed).

Sorry, I shouldn't have been quite so terse.  What I meant is

  if (!$is_x86_64 || (0 <= $imm && $imm <= 0xffffffff))

so that 32-bit always uses the 5-byte encoding instead of the 6-byte.

> That being said, I moved most of this function to risugen_x86_asm and
> included a bunch of comments regarding different cases, so it should
> be easier to understand.



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