Fangrui Song 3d0a689eb7 [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.

2024-01-29 12:07:13 -08:00

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