Separate the logic when handling indirect calls in SamplePGO ThinLTO compile...

Separate the logic when handling indirect calls in SamplePGO ThinLTO compile phase and other phases.

Summary: In SamplePGO ThinLTO compile phase, we will not invoke ICP as it may introduce confusion to the 2nd annotation. This patch extracted that logic and makes it clearer before profile annotation. In the mean time, we need to make function importing process both inlined callsites as well as not promoted indirect callsites.

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: sanjoy, mehdi_amini, llvm-commits, inglorion

Differential Revision: https://reviews.llvm.org/D38094

llvm-svn: 314619