[all-commits] [llvm/llvm-project] 22c8b1: [BranchRelaxation] Remove quadratic behavior in re...

[Daniel Hoekwater via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 22c8b1d853dfde925eb63c4907332c596048c631
      https://github.com/llvm/llvm-project/commit/22c8b1d853dfde925eb63c4907332c596048c631
  Author: Daniel Hoekwater <hoekwater at google.com>
  Date:   2024-09-27 (Fri, 27 Sep 2024)

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

  Log Message:
  -----------
  [BranchRelaxation] Remove quadratic behavior in relaxation pass (#96250)

Currently, we recompute block offsets after each relaxation. This causes
the complexity to be O(n^2) in the number of instructions, inflating
compile
time.

If we instead recompute block offsets after each iteration of the outer
loop, the complexity is O(n). Recomputing offsets in the outer loop will
cause some out-of-range branches to be missed in the inner loop, but
they will be relaxed in the next iteration of the outer loop.

This change may introduce unnecessary relaxations for an architecture
where the relaxed branch is smaller than the unrelaxed branch, but AFAIK
there is no such architecture.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications