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Subject: Re: [OMPI users] Problems building Open MPI 1.4.1 with Pathscale
From: Barrett, Brian W (bwbarre_at_[hidden])
Date: 2010-02-10 10:42:54

Adding the memory and cc will certainly do no harm, and someone tried to remove them as an optimization. I wouldn't change the input and output lines - the differences are mainly syntactic sugar.


On Feb 10, 2010, at 7:04 AM, Ake Sandgren wrote:

> On Wed, 2010-02-10 at 08:21 -0500, Jeff Squyres wrote:
>> On Feb 10, 2010, at 7:47 AM, Ake Sandgren wrote:
>>> According to people who knows asm statements fairly well (compiler
>>> developers), it should be
>>> static inline int opal_atomic_cmpset_32( volatile int32_t *addr,
>>> int32_t oldval, int32_t newval)
>>> {
>>> unsigned char ret;
>>> __asm__ __volatile__ (
>>> SMPLOCK "cmpxchgl %3,%2 \n\t"
>>> "sete %0 \n\t"
>>> : "=qm" (ret), "=a" (oldval), "=m" (*addr)
>>> : "q"(newval), "2"(*addr), "1"(oldval)
>>> : "memory", "cc");
>>> return (int)ret;
>>> }
>> Disclaimer: I know almost nothing about assembly.
>> I know that OMPI's asm is a carefully crafted set of assembly that works across a broad range of compilers. So what might not be "quite right" for one compiler may actually be there because another compiler needs it.
>> That being said, if the changes above are for correctness, not neatness/style/etc., I can't speak for that...
> The above should be correct for gcc style unless i misunderstood them.
> Quoting from their reply:
> 'it should be "memory", "cc" since you also have to tell gcc you're
> clobbering the EFLAGS'
> And i don't know asm either so...