Merging r332302:

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r332302 | kfischer | 2018-05-14 15:05:01 -0700 (Mon, 14 May 2018) | 15 lines

[InstCombine] fix crash due to ignored addrspacecast

Summary:
Part of the InstCombine code for simplifying GEPs looks through
addrspacecasts. However, this was done by updating a variable
also used by the next transformation, for marking GEPs as
inbounds. This led to replacing a GEP with a similar instruction
in a different addrspace, which caused an assertion failure in RAUW.

This caused julia issue https://github.com/JuliaLang/julia/issues/27055

Patch by Jeff Bezanson <jeff@juliacomputing.com>

Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D46722
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llvm-svn: 333477