[all-commits] [llvm/llvm-project] 342acf: [AMDGPU] Turn off pass to rewrite partially used v...

[Valery via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 342acfc9bbc67d81e452b7edc29777bc920f5fd6
      https://github.com/llvm/llvm-project/commit/342acfc9bbc67d81e452b7edc29777bc920f5fd6
  Author: Valery Pykhtin <valery.pykhtin at gmail.com>
  Date:   2023-06-07 (Wed, 07 Jun 2023)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
    M llvm/test/CodeGen/AMDGPU/GlobalISel/extractelement-stack-lower.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/extractelement.i128.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/extractelement.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/insertelement.i16.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/insertelement.large.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/insertelement.ll
    M llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll
    M llvm/test/CodeGen/AMDGPU/coalesce-identity-copies-undef-subregs.mir
    M llvm/test/CodeGen/AMDGPU/dead-lane.mir
    M llvm/test/CodeGen/AMDGPU/llc-pipeline.ll
    M llvm/test/CodeGen/AMDGPU/llvm.mulo.ll
    M llvm/test/CodeGen/AMDGPU/load-global-i16.ll
    M llvm/test/CodeGen/AMDGPU/loop-live-out-copy-undef-subrange.ll
    M llvm/test/CodeGen/AMDGPU/mad_64_32.ll
    M llvm/test/CodeGen/AMDGPU/mul.ll
    M llvm/test/CodeGen/AMDGPU/promote-constOffset-to-imm.ll
    M llvm/test/CodeGen/AMDGPU/rewrite-partial-reg-uses-dbg.mir
    M llvm/test/CodeGen/AMDGPU/rewrite-partial-reg-uses-gen.mir
    M llvm/test/CodeGen/AMDGPU/rewrite-partial-reg-uses.mir
    M llvm/test/CodeGen/AMDGPU/sdiv64.ll
    M llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir
    M llvm/test/CodeGen/AMDGPU/spill-vgpr.ll
    M llvm/test/CodeGen/AMDGPU/srem64.ll
    M llvm/test/CodeGen/AMDGPU/udiv64.ll
    M llvm/test/CodeGen/AMDGPU/urem64.ll

  Log Message:
  -----------
  [AMDGPU] Turn off pass to rewrite partially used virtual superregisters after RenameIndependentSubregs pass with registers of minimal size.

There is a failure with this pass in the case when target register class for a subregister isn't known from instruction description (for ex. COPY).
Currently in this situation the RC is obtained using TargetRegisterInfo::getSubRegisterClass but in general it's not working.

In order to fix this two things should be done:
1. Stop processing a subregister if the target register class is unknown (conservative approach)
2. Improve deduction of subregister' target register class (i.e by processing COPY chain)

I was going to implement point 1 but my tests use implicit operands for S_NOP and they don't have associated target register class and all tests fail.
Therefore I decided to turn off the pass now, implement point 1 and fix my tests.

Reviewed By: arsenm, #amdgpu

Differential Revision: https://reviews.llvm.org/D152291