From: Richard Henderson <richard.henderson@linaro.org>
To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: qemu-stable@nongnu.org
Subject: Re: [PATCH] target/i386: fix operand size for DATA16 REX.W POPCNT
Date: Fri, 10 May 2024 11:20:48 +0200 [thread overview]
Message-ID: <c27b0759-3a40-42da-88c7-88c3c8c6b245@linaro.org> (raw)
In-Reply-To: <20240509152526.141855-1-pbonzini@redhat.com>
On 5/9/24 17:25, Paolo Bonzini wrote:
> 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(-)
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
next prev parent reply other threads:[~2024-05-10 9:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-09 15:25 [PATCH] target/i386: fix operand size for DATA16 REX.W POPCNT Paolo Bonzini
2024-05-10 9:20 ` Richard Henderson [this message]
2024-05-10 11:25 ` Zhao Liu
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