[PATCH] D74180: AMDGPU: Limit the search in finding the instruction pattern for v_swap generation.

[Changpeng Fang via Phabricator via llvm-commits]

cfang created this revision.
cfang added reviewers: arsenm, rampitec.
Herald added subscribers: kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.

Current implementation of matchSwap in SIShrinkInstructions searches the entire use_nodbg_operands set to find the possible
pattern to generate v_swap instruction. This approach will lead to a O(N^3) in compile time for SIShrinkInstructions.

But in reality, the matching pattern only exists within nearby instructions in the same basic block. This work limits the search to a maximum of
16 instructions, and has a linear compile time comsumption.


https://reviews.llvm.org/D74180

Files:
  llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp
  llvm/test/CodeGen/AMDGPU/v_swap_b32.mir

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