[trunk<-vta] Re: [vtab] Permit coalescing of user variables

Alexandre Oliva aoliva@redhat.com
Mon Jun 6 02:42:00 GMT 2011


On Jun  5, 2011, Alexandre Oliva <aoliva@redhat.com> wrote:

> On Jun  4, 2011, Jakub Jelinek <jakub@redhat.com> wrote:
>> The following changes all look wrong to me, they make the tests totally
>> useless.  If both f and g are used in real code after the asm volatile, then
>> the both f and g will likely live in some register or memory.
>> The whole point of the construct in the tests is that f has at that spot
>> a reg or mem location, but g isn't present anywhere anymore (as the compiler
>> doesn't or shouldn't know that asm volatile hasn't changed f), thus it
>> should represent them as bswap/clz/ctz/rotate.

> I see.  I'll try to figure out why that didn't work.

So, I tried to duplicate the problem and failed.  The cut&pasto fix
r174632 fixed the only two cases that had failed, on x86_64-linux-gnu
and only at -O1.  I suppose the wrong bit width made the expression
unsuitable for a rotate or debug expr, but the fix made the tests pass
again, so I withdraw the “fixes” for those testcases: they work even
with coalescing fully enabled.  Thanks for catching this.

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer



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