[PATCH] D57336: [DAGCombiner] fold extract_subvector of extract_subvector

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: RKSimon, craig.topper.
Herald added a subscriber: mcrosier.

This is the sibling fold for insert-of-insert that was added with D56604 <https://reviews.llvm.org/D56604>.

Now that we have x86 shuffle narrowing (D57156 <https://reviews.llvm.org/D57156>), this change shows improvements for lots of AVX512 reduction code (not sure that we would ever expect extract-of-extract otherwise).

There's a small regression in some of the partial-permute tests (extracting followed by splat). I'll try to reduce that and file a bug.


https://reviews.llvm.org/D57336

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/avx512-hadd-hsub.ll
  test/CodeGen/X86/avx512-shuffles/partial_permute.ll
  test/CodeGen/X86/madd.ll
  test/CodeGen/X86/min-legal-vector-width.ll
  test/CodeGen/X86/sad.ll
  test/CodeGen/X86/vector-reduce-add-widen.ll
  test/CodeGen/X86/vector-reduce-add.ll
  test/CodeGen/X86/vector-reduce-and-widen.ll
  test/CodeGen/X86/vector-reduce-and.ll
  test/CodeGen/X86/vector-reduce-fadd-fast.ll
  test/CodeGen/X86/vector-reduce-fmul-fast.ll
  test/CodeGen/X86/vector-reduce-mul-widen.ll
  test/CodeGen/X86/vector-reduce-mul.ll
  test/CodeGen/X86/vector-reduce-or-widen.ll
  test/CodeGen/X86/vector-reduce-or.ll
  test/CodeGen/X86/vector-reduce-xor-widen.ll
  test/CodeGen/X86/vector-reduce-xor.ll
  test/CodeGen/X86/vector-shuffle-512-v16.ll

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