[all-commits] [llvm/llvm-project] 6b1365: [BOLT][AArch64] Transform cmpbr ~> cmp + br when i...

[Alexandros Lamprineas via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6b13656fd8386f979e061cc97e32b607ee3fcdf4
      https://github.com/llvm/llvm-project/commit/6b13656fd8386f979e061cc97e32b607ee3fcdf4
  Author: Alexandros Lamprineas <alexandros.lamprineas at arm.com>
  Date:   2026-06-04 (Thu, 04 Jun 2026)

  Changed paths:
    M bolt/include/bolt/Core/BinaryFunction.h
    M bolt/include/bolt/Core/MCPlusBuilder.h
    M bolt/include/bolt/Passes/LongJmp.h
    M bolt/include/bolt/Utils/CommandLineOpts.h
    M bolt/lib/Core/BinaryFunction.cpp
    M bolt/lib/Passes/BinaryPasses.cpp
    M bolt/lib/Passes/LongJmp.cpp
    M bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp
    M bolt/lib/Target/AArch64/CMakeLists.txt
    M bolt/lib/Target/RISCV/RISCVMCPlusBuilder.cpp
    M bolt/lib/Target/X86/X86MCPlusBuilder.cpp
    M bolt/lib/Utils/CommandLineOpts.cpp
    M bolt/test/AArch64/compare-and-branch-inversion.S
    M bolt/unittests/Core/CMakeLists.txt
    M bolt/unittests/Core/MCPlusBuilder.cpp

  Log Message:
  -----------
  [BOLT][AArch64] Transform cmpbr ~> cmp + br when inversion not possible (#185731)

When reordering blocks we may have to invert branches. Sometimes this
isn't possible for compare-and-branch instructions because the immediate
value would overflow/underflow after the adjustment. In such cases I am
splitting the instruction into a compare followed by a branch. For this
to be legal we should be sure that the condition flags are not being
clobbered. Liveness analysis may help here.



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