This patch contains the complete implementation of DIArgList, DBG_VALUE_LIST, and salvaging of Binary Operator and GEP instructions with non-constant operands. This is not intended to be an actual review (the stack of patches culimating in D91722 are the review patches), but an easy-to-apply patch for anyone seeking to test, poke around on, or add to the new feature.
Note that currently one of the tests added by this patch fails; the test is being rewritten. All the other tests (added by this patch or otherwise) should pass. The patch is currently up-to-date with revision 993c488ed.