[PATCH] [CodeGen] Combine shuffle from concat+bitcast scalar to avoid the smaller vector type.

[Simon Pilgrim]

> Now that I look at this again, it seems to me that for the concat problem, a cleaner solution would be to combine (only when the intermediate type is illegal, perhaps?):

> 

>   (v8i8 concat_vectors (v2i8 bitcast (i16)) x4)

> 

> into:

> 

>   (v8i8 (bitcast (v4i16 BUILD_VECTOR (i16) x4)))

>    

> 

> Is that what you're proposing?


Yes that seems the cleanest approach and gives us the best chance of further optimization later on.


http://reviews.llvm.org/D8884

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