Merging r310481, r310492 and r310510:

Merging r310481, r310492 and r310510:
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r310481 | davide | 2017-08-09 08:13:50 -0700 (Wed, 09 Aug 2017) | 8 lines

[ValueTracking] Honour recursion limit.

The recently improved support for `icmp` in ValueTracking
(r307304) exposes the fact that `isImplied` condition doesn't
really bail out if we hit the recursion limit (and calls
`computeKnownBits` which increases the depth and asserts).

Differential Revision:  https://reviews.llvm.org/D36512
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r310492 | davide | 2017-08-09 09:06:04 -0700 (Wed, 09 Aug 2017) | 1 line

[ValueTracking] Update tests to unbreak the bots.
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r310510 | spatel | 2017-08-09 11:56:26 -0700 (Wed, 09 Aug 2017) | 6 lines

[SimplifyCFG] remove checks for crasher test from r310481

Not sure why the earlier version would fail, but trying to get the bots
(and my local machine) to pass again.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@310634 91177308-0d34-0410-b5e6-96231b3b80d8