[all-commits] [llvm/llvm-project] 3d0a68: [llvm-cov] Simplify and optimize MC/DC computation...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3d0a689eb72aef639347edbec4608e631d5208a1
      https://github.com/llvm/llvm-project/commit/3d0a689eb72aef639347edbec4608e631d5208a1
  Author: Fangrui Song <i at maskray.me>
  Date:   2024-01-29 (Mon, 29 Jan 2024)

  Changed paths:
    M llvm/lib/ProfileData/Coverage/CoverageMapping.cpp

  Log Message:
  -----------
  [llvm-cov] Simplify and optimize MC/DC computation (#79727)

Update code from https://reviews.llvm.org/D138847

`buildTestVector` is a standard DFS (walking a reduced ordered binary
decision diagram). Avoid shouldCopyOffTestVectorFor{True,False}Path
complexity and redundant `Map[ID]` lookups.

`findIndependencePairs` unnecessarily uses four nested loops (n<=6) to
find independence pairs. Instead, enumerate the two execution vectors
and find the number of mismatches. This algorithm can be optimized using
the marking function technique described in _Efficient Test Coverage
Measurement for MC/DC,  2013_, but this may be overkill.