[InstCombine] Fix bug in pointer replacement

This optimisation was crashing when there was a chain of more than one bitcast
instruction to replace, as a result of the changes in D27283.

Patch by James Price.

Differential Revision: https://reviews.llvm.org/D30347


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296163 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed