[PATCH] D41133: [X86] Make the code that creates fmaddsub from build_vector of extracts and inserts functional and add tests.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, zvi, spatel.

We had no tests for this and we couldn't do the optimization because of a bad use count check. We need to know how many non-undef pieces of the build vector were filled in and ensure our use count is equal to that. But on the shuffle combine version we need the use count to be 2.

The missing coverage was noticed during the review of https://reviews.llvm.org/D40335.


https://reviews.llvm.org/D41133

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/fmaddsub-combine.ll

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