[PATCH] D49636: [X86] Add matching for another pattern of PMADDWD.

[Craig Topper via Phabricator via llvm-commits]

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

This is the pattern you get from the loop vectorizer for something like this

int16_t A[1024];
int16_t B[1024];
int32_t C[512];

void pmaddwd() {

  for (int i = 0; i != 512; ++i)
    C[i] = (A[2*i]*B[2*i]) + (A[2*i+1]*B[2*i+1]);

}

In this case we will have (add (mul (build_vector), (build_vector)), (mul (build_vector), (build_vector))). This is different than the pattern we currently match which has the build_vectors between an add and a single multiply. I'm not sure what C code would get you that pattern.


Repository:
  rL LLVM

https://reviews.llvm.org/D49636

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/madd.ll

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