Merging r296992:

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r296992 | sanjoy | 2017-03-05 15:49:17 -0800 (Sun, 05 Mar 2017) | 7 lines

[SCEV] Decrease the recursion threshold for CompareValueComplexity

Fixes PR32142.

r287232 accidentally increased the recursion threshold for
CompareValueComplexity from 2 to 32.  This change reverses that change
by introducing a separate flag for CompareValueComplexity's threshold.
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llvm-svn: 297164