[ConstantHoisting] Call cleanup() in ConstantHoistingPass::runImpl to avoid...

[ConstantHoisting] Call cleanup() in ConstantHoistingPass::runImpl to avoid dangling elements in ConstIntInfoVec for new PM

Summary:
ConstIntInfoVec contains elements extracted from the previous function.
In new PM, releaseMemory() is not called and the dangling elements can
cause segfault in findConstantInsertionPoint.

Rename releaseMemory() to cleanup() to deliver the idea that it is
mandatory and call cleanup() in ConstantHoistingPass::runImpl to fix
this.

Reviewers: ormris, zzheng, dmgreen, wmi

Reviewed By: ormris, wmi

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58589

llvm-svn: 355174