Merging r242433:

Merging r242433:
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r242433 | tstellar | 2015-07-16 12:40:07 -0700 (Thu, 16 Jul 2015) | 11 lines

AMDPGU/SI: Use AssertZext node to mask high bit for scratch offsets

Summary:
We can safely assume that the high bit of scratch offsets will never
be set, because this would require at least 128 GB of GPU memory.

Reviewers: arsenm

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11225
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_37@242683 91177308-0d34-0410-b5e6-96231b3b80d8