Merging r291968 and r291979:

Merging r291968 and r291979:
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r291968 | dannyb | 2017-01-13 14:40:01 -0800 (Fri, 13 Jan 2017) | 23 lines

NewGVN: Move leaders around properly to ensure we have a canonical dominating leader. Fixes PR 31613.

Summary:
This is a testcase where phi node cycling happens, and because we do
not order the leaders by domination or anything similar, the leader
keeps changing.

Using std::set for the members is too expensive, and we actually don't
need them sorted all the time, only at leader changes.

We could keep both a set and a vector, and keep them mostly sorted and
resort as necessary, or use a set and a fibheap, but all of this seems
premature.

After running some statistics, we are able to avoid the vast majority
of sorting by keeping a "next leader" field.  Most congruence classes only have
leader changes once or twice during GVN.

Reviewers: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28594
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r291979 | dannyb | 2017-01-13 15:54:10 -0800 (Fri, 13 Jan 2017) | 1 line

NewGVN: Fix PR31613 test regex naming
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@292307 91177308-0d34-0410-b5e6-96231b3b80d8