Re: [PATCH] target/i386: fix operand size for DATA16 REX.W POPCNT

[Zhao Liu]

On Thu, May 09, 2024 at 05:25:26PM +0200, Paolo Bonzini wrote:
> Date: Thu,  9 May 2024 17:25:26 +0200
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: [PATCH] target/i386: fix operand size for DATA16 REX.W POPCNT
> X-Mailer: git-send-email 2.45.0
> 
> According to the manual, 32-bit vs 64-bit is governed by REX.W
> and REX ignores the 0x66 prefix.  This can be confirmed with this
> program:
> 
>     #include <stdio.h>
>     int main()
>     {
>        int x = 0x12340000;
>        int y;
>        asm("popcntl %1, %0" : "=r" (y) : "r" (x)); printf("%x\n", y);
>        asm("mov $-1, %0; .byte 0x66; popcntl %1, %0" : "+r" (y) : "r" (x)); 
> printf("%x\n", y);
>        asm("mov $-1, %0; .byte 0x66; popcntq %q1, %q0" : "+r" (y) : "r" (x)); 
> printf("%x\n", y);
>     }
> 
> which prints 5/ffff0000/5 on real hardware and 5/ffff0000/ffff0000
> on QEMU.
> 
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  target/i386/tcg/translate.c | 17 +----------------
>  1 file changed, 1 insertion(+), 16 deletions(-)

Awesome!
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>