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Subject: Re: [Qemu-devel] [PATCH] i386/translate: ignore 0x67 (PREFIX_ADR)
 on TARGET_X86_64 && CODE64()
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To: Laszlo Ersek <lersek@redhat.com>
Cc: qemu-devel@nongnu.org

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:


r~


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);
      }
  #endif