Give up on array allocas in getPointerDereferenceableBytes

Summary:
As suggested by Eli Friedman, don't try to handle array allocas here,
because of possible overflows, instead rely on instcombine converting
them to allocations of array types.

Reviewers: efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D41398

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321159 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed