[all-commits] [llvm/llvm-project] e48916: [ARM][ConstantIslands] Correct MinNoSplitDisp calc...

[pzhengqc via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e48916f615e0ad2b994b2b785d4fe1b8a98bc322
      https://github.com/llvm/llvm-project/commit/e48916f615e0ad2b994b2b785d4fe1b8a98bc322
  Author: pzhengqc <55604844+pzhengqc at users.noreply.github.com>
  Date:   2024-12-14 (Sat, 14 Dec 2024)

  Changed paths:
    M llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
    A llvm/test/CodeGen/Thumb2/constant-islands-no-split.mir

  Log Message:
  -----------
  [ARM][ConstantIslands] Correct MinNoSplitDisp calculation (#114590)

MinNoSplitDisp was first introduced in D16890 to handle cases where the
ConstantIslands pass fails to converge in the presence of big basic
blocks. However, the computation of the variable seems to be wrong as it
currently computes the offset immediately following UserBB. In other
words, it represents the distance from the beginning of the function to
the end of UserBB. The distance from the beginning of the function does
not seem to be a good indicator of how big the basic block is unless the
basic block is close to the beginning of the function. I think
MinNoSplitDisp should compute the distance between UserOffset and the
end of UserBB instead.



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