Comparing operands should not require the same ValueID

Summary: When comparing basic blocks, there is an additional check that two Value*'s should have the same ID, which interferes with merging equivalent constants of different kinds (such as a ConstantInt and a ConstantPointerNull in the included testcase). The cmpValues function already ensures that the two values in each function are the same, so removing this check should not cause incorrect merging.

Also, the type comparison is redundant, based on reviewing the code and testing on the test suite and several large LTO bitcodes.

Author: jrkoenig
Reviewers: nlewycky, jfb, dschuff
Subscribers: llvm-commits
Differential revision: http://reviews.llvm.org/D12302

llvm-svn: 246001