Reduce memory consumption of coverage dumps
Reduce memory consumption of coverage dumps

Avoiding an intermediate join operation removes the need for an
intermediate buffer that may be quite large, as showcased by

        https://bugs.llvm.org/show_bug.cgi?id=41965

Differential Revision: https://reviews.llvm.org/D62623

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@362584 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang