Fix the bug when -compile-twice is specified, the PSI will be invalidated.

Fix the bug when -compile-twice is specified, the PSI will be invalidated.

Summary:
When using llc with -compile-twice, module is generated twice, but getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI will still get the old PSI with the original (invalidated) Module. This patch checks if the module has changed when calling getPSI, if yes, update the module and invalidate the Summary.
The bug does not show up in the current llc because PSI is not used in CodeGen yet. But with https://reviews.llvm.org/D24989, the bug will be exposed by test/CodeGen/PowerPC/pr26378.ll

Reviewers: eraman, davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D24993

llvm-svn: 282616