[PATCH] Add new debug kind LocTrackingOnly.

[David Blaikie]

Looks good - though I'd prefer to separate the discussion about column info so as to isolate the changes/tests/etc and not delay this review.

================
Comment at: lib/Frontend/CompilerInvocation.cpp:571
@@ +570,3 @@
+      Opts.setDebugInfo(CodeGenOptions::LocTrackingOnly);
+      Opts.DebugColumnInfo = true;
+    }
----------------
Perhaps we could leave this out for now & just have a separate CR/discussion about the semantics/ramifications of having this difference between -R and -gmlt?

================
Comment at: test/Frontend/optimization-remark.c:13
@@ +12,3 @@
+// CHECK: , !dbg !
+// CHECK-NOT: DW_TAG_base_type
+
----------------
Could have a brief comment here "Ensure -Rpass, like -gmlt, doesn't produce debug info metadata for types".

http://reviews.llvm.org/D4235