[PATCH] D22199: AMDGPU: Leave WQM earlier before VMEM loads

[Nicolai Hähnle via llvm-commits]

nhaehnle created this revision.
nhaehnle added reviewers: arsenm, tstellarAMD, mareko.
nhaehnle added a subscriber: llvm-commits.
Herald added subscribers: kzhuravl, arsenm.

When the initial propagation determines that a VMEM load does not have to run
in WQM, make it run in Exact mode instead if the remainder of the shader
doesn't care. This can reduce the bandwidth required for loads.

This typically introduces two additional SALU instructions and uses two
additional SGPRs in pixel shaders for the livemask.

http://reviews.llvm.org/D22199

Files:
  lib/Target/AMDGPU/SIWholeQuadMode.cpp
  test/CodeGen/AMDGPU/wqm.ll

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