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From: Richard Henderson <richard.henderson@linaro.org>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>, qemu-devel@nongnu.org
Cc: Thomas Huth <thuth@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	Cornelia Huck <cohuck@redhat.com>,
	"Richard W . M . Jones" <rjones@redhat.com>,
	qemu-s390x@nongnu.org, Miroslav Rezanina <mrezanin@redhat.com>
Subject: Re: [PATCH] tcg/s390: Fix compare instruction from extended-immediate facility
Date: Thu, 4 Feb 2021 08:54:45 -1000	[thread overview]
Message-ID: <3328ae06-976f-5240-a538-6156cdbc71dc@linaro.org> (raw)
In-Reply-To: <20210204182902.1742826-1-f4bug@amsat.org>

On 2/4/21 8:29 AM, Philippe Mathieu-Daudé wrote:
> The code is currently comparing c2 to the type promotion of
> uint32_t and int32_t. That is, the conversion rules are as:
> 
>   (common_type) c2 == (common_type) (uint32_t)
>                         (is_unsigned
>                         ? (uint32_t)c2
>                         : (uint32_t)(int32_t)c2)
> 
> In the signed case we lose the desired sign extensions because
> of the argument promotion rules of the ternary operator.
> 
> Solve the problem by doing the round-trip parsing through the
> intermediate type and back to the desired common type (all at
> one expression).
> 
> Fixes: a534bb15f30 ("tcg/s390: Use constant pool for cmpi")
> Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  tcg/s390/tcg-target.c.inc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

A most excellent catch, thanks.  Queued.


r~


  reply	other threads:[~2021-02-04 19:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-04 18:29 [PATCH] tcg/s390: Fix compare instruction from extended-immediate facility Philippe Mathieu-Daudé
2021-02-04 18:54 ` Richard Henderson [this message]
2021-02-04 19:25 ` David Hildenbrand
2021-02-04 22:06 ` Richard W.M. Jones

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