[PATCH] Add support for DebugFission to DWARF parser

[David Blaikie]

>>! In D1164#1, @samsonov wrote:
> Oh, and I would appreciate advice on writing tests for split-dwarf. Looks like debug info in the binaries built with -gsplit-dwarf always contains absolute paths to .dwo files, so checking in pre-built binaries is problematic... Generating .dwo files requires a fresh enough objcopy. Also, building binaries from source (or bytecode) in test cases would make it hard to predict the resulting object file layout and build (input, expected output) pairs for llvm-symbolizer...

Rafael recently (temporarily) broke some of this code while doing some unique_ptr refactoring and we were both a bit surprised by the lack of test coverage. You make a good point though, that this isn't easy to test, but let's see if there's some way:

What would happen if we build a dwo file somewhat manually - generating the assembly from Clang/LLVM, then hand-hacking the dwo file path (or just using clang -cc1 and specifying the dwo file name manually) as a relative path, rather than an absolute one. Would that produce a reusable test case we could commit to the lit suite?

Otherwise, at least, it'd be useful to have some manual test steps written down somewhere (maybe in the test/ directory, just in the form of a text file with a FIXME and manual steps).

http://reviews.llvm.org/D1164