From: Paolo Bonzini <pbonzini@redhat.com>
To: Richard Henderson <rth@twiddle.net>
Cc: Laszlo Ersek <lersek@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] i386/translate: ignore 0x67 (PREFIX_ADR) on TARGET_X86_64 && CODE64()
Date: Sun, 26 May 2013 10:33:35 +0200 [thread overview]
Message-ID: <51A1C8DF.506@redhat.com> (raw)
In-Reply-To: <51A147DB.2020606@twiddle.net>
Il 26/05/2013 01:23, Richard Henderson ha scritto:
> On 2013-05-24 14:37, Laszlo Ersek wrote:
>> @@ -4813,7 +4813,11 @@ static target_ulong disas_insn(CPUX86State
>> *env, DisasContext *s,
>> /* 0x66 is ignored if rex.w is set */
>> dflag = 2;
>> }
>> - if (!(prefixes & PREFIX_ADR)) {
>> + if (prefixes & PREFIX_ADR) {
>> + /* flip it back, 0x67 should have no effect */
>> + aflag ^= 1;
>> + }
>> + else {
>> aflag = 2;
>> }
>> }
>>
>
> Agreed that there's a bug here. I'm thinking it would be clearer to not
> write this as yet another flip, but understand that unlike dflag, aflag
> can only be either 1 or 2 in 64-bit mode.
>
> I'm thinking of something more like this:
>
> diff --git a/target-i386/translate.c b/target-i386/translate.c
> index 0aeccdb..bf772aa 100644
> --- a/target-i386/translate.c
> +++ b/target-i386/translate.c
> @@ -4813,9 +4813,8 @@ static target_ulong disas_insn(CPUX86State *env,
> DisasContext *s,
> /* 0x66 is ignored if rex.w is set */
> dflag = 2;
> }
> - if (!(prefixes & PREFIX_ADR)) {
> - aflag = 2;
> - }
> + /* 0x67 toggles between 64-bit and 32-bit addressing. */
> + aflag = (prefixes & PREFIX_ADR ? 1 : 2);
Isn't that just "aflag++"? Needs a comment of course ("toggle between
32- and 64-bit, not 16- and 32-bit.").
Paolo
next prev parent reply other threads:[~2013-05-26 8:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-24 21:37 [Qemu-devel] [PATCH] i386/translate: ignore 0x67 (PREFIX_ADR) on TARGET_X86_64 && CODE64() Laszlo Ersek
2013-05-25 23:23 ` Richard Henderson
2013-05-26 8:33 ` Paolo Bonzini [this message]
2013-05-26 23:45 ` Laszlo Ersek
2013-05-27 6:29 ` Paolo Bonzini
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