[llvm-commits] [llvm] r166642 - in /llvm/trunk: include/llvm/Target/TargetLowering.h include/llvm/Target/TargetTransformImpl.h lib/Target/TargetTransformImpl.cpp lib/Transforms/IPO/PassManagerBuilder.cpp lib/Transforms/Vectorize/LoopVectorize.cpp test/Transforms/LoopVectorize/cost-model.ll

[Nadav Rotem]

On Oct 24, 2012, at 9:54 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> Fair enough. Nevertheless, this does not seem like an argument for giving them a zero cost. Is it? I'd think that we'd want to give them some cost by default, and then lower that cost on targets where that makes sense.

We need to have a way for targets to control the cost of different instructions, without relying in IsCustomOrLegal.  I think that I will add a hook right *before* the call that checks which ISD is used. 

> Also, should we add something like:
> bool useVectorGEP(), which by default returns false, so that we can only emit these on targets where it makes sense. That, combined with the cost information, will allow us to reason about creating vector GEPs for MIC, etc.

Yes, I think that this is a good idea. 
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