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x/arch/x86/x86asm: Inst.MemBytes is 0 for movsb/movsw/movsd/movsq instructions #47626

TACIXAT opened this issue Aug 10, 2021 · 1 comment


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@TACIXAT TACIXAT commented Aug 10, 2021

What version of Go are you using (go version)?

$ go version
1.15.8 windows/amd64

Does this issue reproduce with the latest release?

Checked on, yes.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env

What did you do?

package main

import (


func main() {
	// rep movsw [rdi], [rsi]
	bs := []byte{ 0x66, 0xf3, 0xa5 }
	inst, err := x86asm.Decode(bs, 64)
	if err != nil {

What did you expect to see?


What did you see instead?


@seankhliao seankhliao changed the title x86asm.Inst.MemBytes is 0 for movsb/movsw/movsd/movsq instructions x/arch/x86/x86asm: Inst.MemBytes is 0 for movsb/movsw/movsd/movsq instructions Aug 12, 2021
@gopherbot gopherbot added this to the Unreleased milestone Aug 12, 2021
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@seankhliao seankhliao commented Aug 12, 2021


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