Merging r261441, r261447, and r261546:

Merging r261441, r261447, and r261546:

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r261441 | nemanjai | 2016-02-20 10:16:25 -0800 (Sat, 20 Feb 2016) | 12 lines

Fix for PR 26500

This patch corresponds to review:
http://reviews.llvm.org/D17294

It ensures that whatever block we are emitting the prologue/epilogue into, we
have the necessary scratch registers. It takes away the hard-coded register
numbers for use as scratch registers as registers that are guaranteed to be
available in the function prologue/epilogue are not guaranteed to be available
within the function body. Since we shrink-wrap, the prologue/epilogue may end
up in the function body.
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r261447 | nemanjai | 2016-02-20 12:45:37 -0800 (Sat, 20 Feb 2016) | 6 lines

Fix the build bot break caused by rL261441.

The patch has a necessary call to a function inside an assert. Which is fine
when you have asserts turned on. Not so much when they're off. Sorry about
the regression.
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r261546 | nemanjai | 2016-02-22 10:04:00 -0800 (Mon, 22 Feb 2016) | 6 lines

Fix for PR26690 take 2

This is what was meant to be in the initial commit to fix this bug. The
parens were missing. This commit also adds a test case for the bug and
has undergone full testing on PPC and X86.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_38@261572 91177308-0d34-0410-b5e6-96231b3b80d8