search for: 857742d7

Hi, I've prototyped a pair of passes which 1) add synthetic debug info to a Module and 2) determine how much of that info is lost. The idea is to make it easier to write targeted test cases for debug info preservation. For example, here is a quick way to test that Mem2Reg doesn't drop debug info from one test input: > ; RUN: opt < %s -debugify -mem2reg -check-debugify -S