[PATCH] D35492: [DAGCombiner] Match non-uniform constant vectors using predicates (RFC).

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.

Most combines currently recognise scalar and splat-vector constants, but not non-uniform vector constants.

This is a proposal to introduce a matching mechanism that uses predicates to check against BUILD_VECTOR of ConstantSDNode, as well as scalar ConstantSDNode cases.

I've changed a couple of predicates to demonstrate - the combine-shl changes add currently unsupported cases, while the MatchRotate replaces an existing mechanism.


Repository:
  rL LLVM

https://reviews.llvm.org/D35492

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/combine-shl.ll

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