[InstCombine] add tests to show likely unwanted select widening; NFC

This is a prerequisite patch for D26556:
https://reviews.llvm.org/D26556

...because there was no direct coverage for these folds (which in some cases are adding instructions).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287400 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed