Merging r221318:

Merging r221318:
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r221318 | majnemer | 2014-11-04 15:49:08 -0800 (Tue, 04 Nov 2014) | 10 lines

Analysis: Make isSafeToSpeculativelyExecute fire less for divides

Divides and remainder operations do not behave like other operations
when they are given poison: they turn into undefined behavior.

It's really hard to know if the operands going into a div are or are not
poison.  Because of this, we should only choose to speculate if there
are constant operands which we can easily reason about.

This fixes PR21412.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_35@223647 91177308-0d34-0410-b5e6-96231b3b80d8