[all-commits] [llvm/llvm-project] 557ef0: [RISCV] Copy AVLs whose LiveIntervals aren't exten...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 557ef043afd04da91e79425133f14c94831a646c
      https://github.com/llvm/llvm-project/commit/557ef043afd04da91e79425133f14c94831a646c
  Author: Luke Lau <luke at igalia.com>
  Date:   2024-07-15 (Mon, 15 Jul 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
    M llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
    M llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir
    M llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll

  Log Message:
  -----------
  [RISCV] Copy AVLs whose LiveIntervals aren't extendable in insertVSETVLI (#98342)

Currently before forwarding an AVL we do a simple non-exhaustive check
to see if its LiveInterval is extendable. But we also need to check for
this when we're extending an AVL's LiveInterval via merging the
VSETVLIInfos in transferBefore with equally zero AVLs.

Rather than trying to conservatively prevent these cases, this inserts a
copy of the AVL instead if we don't know we'll be able to extend it.
This is likely to be more robust, and even if the extra copy is
undesirable these cases should be rare in practice.



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