[InstCombine][NFC] Tests for 'signed truncation check' optimization

See D50465 for the actual opt itself.

Differential Revision: https://reviews.llvm.org/D50464

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339602 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed