[all-commits] [llvm/llvm-project] 0ae6cf: [RegAllocFast] Handle single-vdef instrs faster (#...

[Alexis Engelke via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0ae6cfc5990b0b739166bd7db370125ca66494c2
      https://github.com/llvm/llvm-project/commit/0ae6cfc5990b0b739166bd7db370125ca66494c2
  Author: Alexis Engelke <engelke at in.tum.de>
  Date:   2024-06-21 (Fri, 21 Jun 2024)

  Changed paths:
    M llvm/lib/CodeGen/RegAllocFast.cpp

  Log Message:
  -----------
  [RegAllocFast] Handle single-vdef instrs faster (#96284)

On x86, many instructions have tied operands, so allocateInstruction
uses the more complex assignment strategy, which computes the assignment
order of virtual defs first. This involves iterating over all register
classes (or register aliases for physical defs) to compute the possible
number of defs per register class.

However, this information is only used for sorting virtual defs and
therefore not required when there's only one virtual def -- which is a
very common case. As iterating over all register classes/aliases is not
cheap, do this only when there's more than one virtual def.



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