[all-commits] [llvm/llvm-project] d0c51f: [LiveIns] Improve recomputeLiveIns() (#88951)

[Kai Nacke via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d0c51f7d5496015ce410cc758a7caf976ffaaec7
      https://github.com/llvm/llvm-project/commit/d0c51f7d5496015ce410cc758a7caf976ffaaec7
  Author: Kai Nacke <kai.peter.nacke at ibm.com>
  Date:   2024-04-17 (Wed, 17 Apr 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/LivePhysRegs.h
    M llvm/include/llvm/CodeGen/MachineBasicBlock.h
    M llvm/lib/CodeGen/MachineBasicBlock.cpp

  Log Message:
  -----------
  [LiveIns] Improve recomputeLiveIns() (#88951)

Some small changes to recomputeLiveIns() to improve performance:

- Instead of copying the list of old live-ins, and then clearing
  them, a new method swaps the list for an empty one.
- getLiveIns() now returns a constant reference to the list

As result, the list-data is never copied. Depending on the
implementation
details of the vector container, it can also save calls to allocate
and deallocate memory.
I see a small improvement on CTMark with these changes.

---------

Co-authored-by: Nikita Popov <github at npopov.com>



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