Merging r223500 (this time for real):

Merging r223500 (this time for real):
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r223500 | dexonsmith | 2014-12-05 11:13:42 -0800 (Fri, 05 Dec 2014) | 9 lines

BFI: Saturate when combining edges to a successor

When a loop gets bundled up, its outgoing edges are quite large, and can
just barely overflow 64-bits.  If one successor has multiple incoming
edges -- and that successor is getting all the incoming mass --
combining just its edges can overflow.  Handle that by saturating rather
than asserting.

This fixes PR21622.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_35@223716 91177308-0d34-0410-b5e6-96231b3b80d8