[PATCH] D26561: [AArch64] Split 0 vector stores into scalar store pairs.

[Geoff Berry via llvm-commits]

gberry created this revision.
gberry added reviewers: t.p.northover, mcrosier, MatzeB, jmolloy.
gberry added a subscriber: llvm-commits.
Herald added subscribers: rengolin, aemerson.

Replace a splat of zeros to a vector store by scalar stores of WZR/XZR.
The load store optimizer pass will merge them to store pair stores.
This should be better than a movi to create the vector zero followed by
a vector store if the zero constant is not re-used, since one
instructions and one register live range will be removed.

For example, the final generated code should be:

  stp xzr, xzr, [x0]

instead of:

  movi v0.2d, #0
  str q0, [x0]


https://reviews.llvm.org/D26561

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  test/CodeGen/AArch64/arm64-misched-basic-A53.ll
  test/CodeGen/AArch64/ldst-opt.ll
  test/CodeGen/AArch64/ldst-paired-aliasing.ll

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