• Jakob Gruber's avatar
    [coverage] Filter out singleton ranges that alias full ranges · aac2f8c9
    Jakob Gruber authored
    Block coverage is based on a system of ranges that can either have
    both a start and end position, or only a start position (so-called
    singleton ranges). When formatting coverage information, singletons
    are expanded until the end of the immediate full parent range. E.g.
    in:
    
    {0, 10}  // Full range.
    {5, -1}  // Singleton range.
    
    the singleton range is expanded to {5, 10}.
    
    Singletons are produced mostly for continuation counters that track
    whether we execute past a specific language construct.
    
    Unfortunately, continuation counters can turn up in spots that confuse
    our post-processing. For example:
    
    if (true) { ... block1 ... } else { ... block2 ... }
    
    If block1 produces a continuation counter, it could end up with the
    same start position as the else-branch counter. Since we merge
    identical blocks, the else-branch could incorrectly end up with an
    execution count of one.
    
    We need to avoid merging such cases. A full range should always take
    precedence over a singleton range; a singleton range should never
    expand to completely fill a full range. An additional post-processing
    pass ensures this.
    
    Bug: v8:8237
    Change-Id: Idb3ec7b2feddc0585313810b9c8be1e9f4ec64bf
    Reviewed-on: https://chromium-review.googlesource.com/c/1273095Reviewed-by: 's avatarGeorg Neis <neis@chromium.org>
    Reviewed-by: 's avatarYang Guo <yangguo@chromium.org>
    Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#56531}
    aac2f8c9
debug-coverage.cc 21.1 KB