[llvm-commits] [llvm] r72507 - in /llvm/trunk: include/llvm/Target/TargetLowering.h lib/CodeGen/SelectionDAG/DAGCombiner.cpp lib/Target/X86/X86ISelLowering.cpp lib/Target/X86/X86ISelLowering.h test/CodeGen/X86/narrow_op-1.ll test/CodeGen/X86/narrow_op-2.ll

[Evan Cheng]

On May 28, 2009, at 1:48 PM, Sebastian Redl wrote:

> Evan Cheng wrote:
>> On May 27, 2009, at 11:38 PM, Duncan Sands wrote:
>>
>>
>>> Hi Evan, nice transform!  But I think you shouldn't do it if the
>>> original store was volatile.
>>>
>>
>> Why not? This would just reduce the store width.
>>
>
> Wouldn't it be better to default the "is profitable" check to false  
> for
> platforms that don't override it? It seems to me that the problems  
> from
> incorrectly allowing the narrowing outweigh the problems from
> incorrectly disallowing it. I think there are more platforms that only
> support full-word stores efficiently (e.g. the Alpha) than there are
> architectures where every narrowing is profitable.

Makes sense. Done.

Evan

>
> Sebastian
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