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Re: [Qemu-devel] [PATCH] target-i386: Fix aflag logic for CODE64 and the
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH] target-i386: Fix aflag logic for CODE64 and the 0x67 prefix |
Date: |
Fri, 31 May 2013 08:03:01 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 |
Ping.
On 05/29/2013 12:30 PM, Richard Henderson wrote:
> The code reorganization in commit 4a6fd938 broke handling of PREFIX_ADR.
> While fixing this, tidy and comment the code so that it's more obvious
> what's going on in setting both aflag and dflag.
>
> The TARGET_X86_64 ifdef can be eliminated because CODE64 expands to the
> constant zero when TARGET_X86_64 is undefined.
>
> Cc: Paolo Bonzini <address@hidden>
> Reported-by: Laszlo Ersek <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> target-i386/translate.c | 30 +++++++++++++++---------------
> 1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/target-i386/translate.c b/target-i386/translate.c
> index 0aeccdb..14b0298 100644
> --- a/target-i386/translate.c
> +++ b/target-i386/translate.c
> @@ -4677,8 +4677,6 @@ static target_ulong disas_insn(CPUX86State *env,
> DisasContext *s,
> }
> s->pc = pc_start;
> prefixes = 0;
> - aflag = s->code32;
> - dflag = s->code32;
> s->override = -1;
> rex_w = -1;
> rex_r = 0;
> @@ -4801,23 +4799,25 @@ static target_ulong disas_insn(CPUX86State *env,
> DisasContext *s,
> }
>
> /* Post-process prefixes. */
> - if (prefixes & PREFIX_DATA) {
> - dflag ^= 1;
> - }
> - if (prefixes & PREFIX_ADR) {
> - aflag ^= 1;
> - }
> -#ifdef TARGET_X86_64
> if (CODE64(s)) {
> - if (rex_w == 1) {
> - /* 0x66 is ignored if rex.w is set */
> - dflag = 2;
> + /* In 64-bit mode, the default data size is 32-bit. Select 64-bit
> + data with rex_w, and 16-bit data with 0x66; rex_w takes precedence
> + over 0x66 if both are present. */
> + dflag = (rex_w > 0 ? 2 : prefixes & PREFIX_DATA ? 0 : 1);
> + /* In 64-bit mode, 0x67 selects 32-bit addressing. */
> + aflag = (prefixes & PREFIX_ADR ? 1 : 2);
> + } else {
> + /* In 16/32-bit mode, 0x66 selects the opposite data size. */
> + dflag = s->code32;
> + if (prefixes & PREFIX_DATA) {
> + dflag ^= 1;
> }
> - if (!(prefixes & PREFIX_ADR)) {
> - aflag = 2;
> + /* In 16/32-bit mode, 0x67 selects the opposite addressing. */
> + aflag = s->code32;
> + if (prefixes & PREFIX_ADR) {
> + aflag ^= 1;
> }
> }
> -#endif
>
> s->prefix = prefixes;
> s->aflag = aflag;
>