Message-ID: <50886FFB.8070802@gmail.com>
Date: Wed, 24 Oct 2012 15:47:23 -0700
From: Juri Lelli <juri.lelli@gmail.com>
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To: "H. Peter Anvin" <hpa@zytor.com>
CC: peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com,
        rostedt@goodmis.org, oleg@redhat.com, fweisbec@gmail.com,
        darren@dvhart.com, johan.eker@ericsson.com, p.faure@akatech.ch,
        linux-kernel@vger.kernel.org, claudio@evidence.eu.com,
        michael@amarulasolutions.com, fchecconi@gmail.com,
        tommaso.cucinotta@sssup.it, nicola.manica@disi.unitn.it,
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        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 02/16] math128, x86_64: Implement {mul,add}_u128 in 64bit
 asm
References: <1351115634-8420-1-git-send-email-juri.lelli@gmail.com> <1351115634-8420-3-git-send-email-juri.lelli@gmail.com> <50886B43.3080001@zytor.com>
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On 10/24/2012 03:27 PM, H. Peter Anvin wrote:
> On 10/24/2012 02:53 PM, Juri Lelli wrote:
>> diff --git a/arch/x86/include/asm/math128.h b/arch/x86/include/asm/math128.h
>> new file mode 100644
>> index 0000000..c0e2a6c
>> --- /dev/null
>> +++ b/arch/x86/include/asm/math128.h
>> @@ -0,0 +1,39 @@
>> +#ifndef _ASM_MATH128_H
>> +#define _ASM_MATH128_H
>> +
>> +#ifdef CONFIG_X86_64
>> +
>> +#ifdef __SIZEOF_INT128__
>> +#define ARCH_HAS_INT128
>> +#endif
>> +
>> +#ifndef ARCH_HAS_INT128
>> +
>> +static inline u128 mul_u64_u64(u64 a, u64 b)
>> +{
>> +       u128 res;
>> +
>> +       asm("mulq %2"
>> +               : "=a" (res.lo), "=d" (res.hi)
>> +               :  "rm" (b), "0" (a));
>> +
>> +       return res;
>> +}
>> +#define mul_u64_u64 mul_u64_u64
>> +
>> +static inline u128 add_u128(u128 a, u128 b)
>> +{
>> +       u128 res;
>> +
>> +       asm("addq %2,%0;\n"
>> +           "adcq %3,%1;\n"
>> +               : "=rm" (res.lo), "=rm" (res.hi)
>> +               : "r" (b.lo), "r" (b.hi), "0" (a.lo), "1" (a.hi));
>> +
>> +       return res;
>> +}
>> +#define add_u128 add_u128
>> +
>
> How could this work since u128 presumably has not yet been defined as a
> structure?  After all, isn't it the absence of ARCH_HAS_INT128 which
> makes that happen?

Sorry, you were not in the Cc list of the previous patch in the patchset,
so you probably missed that. I should have triple checked git send-email
Cc list. Sorry about that.

I'll add you there.

Thanks and Regards,

- Juri
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