From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Huth <thuth@redhat.com>,
Laurent Vivier <lvivier@redhat.com>,
kvm@vger.kernel.org
Cc: kvm-ppc@vger.kernel.org, drjones@redhat.com
Subject: Re: [kvm-unit-test PATCH v2] powerpc: Add emulator test for the lswi instruction
Date: Tue, 10 May 2016 12:05:47 +0000 [thread overview]
Message-ID: <5731CE9B.9060904@redhat.com> (raw)
In-Reply-To: <57174AB9.2090900@redhat.com>
On 20/04/2016 11:24, Thomas Huth wrote:
>>> + ".long 0x7fe154aa\n" /* lswi r31, r1, 10 */
>>
>> Perhaps you can add a comment explaining why you are using a .long
>> instead of the mnemonic?
>
> The compiler is smart enough to detect that r1 is in the range of
> registers that get clobbered, and thus rejects that mnemonic. You
> quickly notice that when replacing the .long with the mnemonic, so I'm
> not sure whether it's worth to add a verbose comment here... Paolo, what
> do you prefer?
The assembler does this, not the compiler. Is this a valid operation at
all, or is it undefined? (aka, what does it do on real hardware)? O_o
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Huth <thuth@redhat.com>,
Laurent Vivier <lvivier@redhat.com>,
kvm@vger.kernel.org
Cc: kvm-ppc@vger.kernel.org, drjones@redhat.com
Subject: Re: [kvm-unit-test PATCH v2] powerpc: Add emulator test for the lswi instruction
Date: Tue, 10 May 2016 14:05:47 +0200 [thread overview]
Message-ID: <5731CE9B.9060904@redhat.com> (raw)
In-Reply-To: <57174AB9.2090900@redhat.com>
On 20/04/2016 11:24, Thomas Huth wrote:
>>> + ".long 0x7fe154aa\n" /* lswi r31, r1, 10 */
>>
>> Perhaps you can add a comment explaining why you are using a .long
>> instead of the mnemonic?
>
> The compiler is smart enough to detect that r1 is in the range of
> registers that get clobbered, and thus rejects that mnemonic. You
> quickly notice that when replacing the .long with the mnemonic, so I'm
> not sure whether it's worth to add a verbose comment here... Paolo, what
> do you prefer?
The assembler does this, not the compiler. Is this a valid operation at
all, or is it undefined? (aka, what does it do on real hardware)? O_o
Paolo
next prev parent reply other threads:[~2016-05-10 12:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 14:49 [kvm-unit-test PATCH v2] powerpc: Add emulator test for the lswi instruction Thomas Huth
2016-04-14 14:49 ` Thomas Huth
2016-04-19 12:51 ` Laurent Vivier
2016-04-19 12:51 ` Laurent Vivier
2016-04-20 9:24 ` Thomas Huth
2016-04-20 9:24 ` Thomas Huth
2016-05-10 12:05 ` Paolo Bonzini [this message]
2016-05-10 12:05 ` Paolo Bonzini
2016-05-10 15:23 ` Thomas Huth
2016-05-10 15:23 ` Thomas Huth
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