Sanjay Patel f24900b934 [DAGCombiner] allow hoisting vector bitwise logic ahead of truncates ...

The transform performs a bitwise logic op in a wider type followed by
truncate when both inputs are truncated from the same source type:
logic_op (truncate x), (truncate y) --> truncate (logic_op x, y)

There are a bunch of other checks that should prevent doing this when 
it might be harmful.

We already do this transform for scalars in this spot. The vector 
limitation was shared with a check for the case when the operands are 
extended. I'm not sure if that limit is needed either, but that would 
be a separate patch.

Differential Revision: https://reviews.llvm.org/D55448

llvm-svn: 349303

2018-12-16 14:57:04 +00:00

2.1 KiB

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