[StructurizeCFG] Fix infinite loop in rebuildSSA.

Michel Dänzer reported that r288051, "[StructurizeCFG] Use range-based
for loops", introduced a bug into rebuildSSA, wherein we were iterating
over an instruction's use list while modifying it, without taking care
to do this correctly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288200 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed