[PATCH] CodeGenPrepare: Avoid and/or i1 in select conditions.

[hfinkel at anl.gov]

In http://reviews.llvm.org/D7622#123459, @ab wrote:

> I should note that this would have been useful as a DAGCombine as
>  well, because for instance on X86, (select (fcmp oeq/une)) is lowered
>  into the pattern matched here.
>
> Matthias tells me doing it as a DAGCombine was frowned upon (why?),


I also don't understand why this would not be done in DAGCombine. It is basic-block local, and concerns itself with type legality, it seems appropriate for DAGCombine. One complication with DAGCombine is, if SELECT is not legal, then matching this might be hard.

> so

>  I'm doing pretty much the same thing on X86ISD::CMOV nodes, and will

>  submit shortly.

> -Ahmed



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