commit b7c4b42cc3b3061be8ca3ee105a32e0fc0425d1d
author Vedant Kumar <vsk@apple.com> Fri Dec 07 20:23:52 2018 +0000
committer Vedant Kumar <vsk@apple.com> Fri Dec 07 20:23:52 2018 +0000
tree 43b001cffc47a1729f8fa244dce187592696093d
parent f66defb43a060b77765ca996474f7ea2ab8d917b

[HotColdSplitting] Outline more than once per function

Algorithm: Identify maximal cold regions and put them in a worklist. If
a candidate region overlaps with another, discard it. While the worklist
is full, remove a single-entry sub-region from the worklist and attempt
to outline it. By the non-overlap property, this should not invalidate
parts of the domtree pertaining to other outlining regions.

Testing: LNT results on X86 are clean. With test-suite + externals, llvm
outlines 134KB pre-patch, and 352KB post-patch (+ ~2.6x). The file
483.xalancbmk/src/Constants.cpp stands out as an extreme case where llvm
outlines over 100 times in some functions (mostly EH paths). There was
not a significant performance impact pre vs. post-patch.

Differential Revision: https://reviews.llvm.org/D53887

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348639 91177308-0d34-0410-b5e6-96231b3b80d8