treat invoke like call

Summary:
InvokeInst should be treated like CallInst and
assigned a separate discriminator. This is particularly
import when an Invoke is converted to a Call
during compilation and so can invalidate sample profile
data collected wtih different link time optimizations

Reviewers: twoh, Kader, danielcdh, wmi

Reviewed By: wmi

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D56491

llvm-svn: 351251