[PATCH] Add new debug kind LocTrackingOnly.

[David Blaikie]

As to the other comments about whether to add a value to the enum or use a flag in createCompileUnit - for now I think I'm going to err on the side of preferring a flag in createCompileUnit.

The Clang-side support for this should obviously look a fair bit like GMLT (indeed if you put the enum value for this mode before GMLT, it should get most/all the right behavior by default (though you might have to fix up some comparisons for == GMLT to <= GMLT)). At some point we can probably simplify this even further so all the scopes are just simple line/file info without having to create any compile units, functions, lexical scopes, etc.

================
Comment at: test/Transforms/LoopVectorize/X86/vectorization-remarks.ll:7
@@ +6,3 @@
+; emitting debug info in the final output.
+; RUN: llc -mtriple x86_64-pc-linux-gnu %s -o - | FileCheck -check-prefix=DEBUG-OUTPUT %s
+; DEBUG-OUTPUT-NOT: .loc
----------------
My instinct would've been to -filetype=obj and run this through objdump -h and FileCheck that instead, but this seems OK too.

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Comment at: test/Transforms/LoopVectorize/X86/vectorization-remarks.ll:9
@@ +8,3 @@
+; DEBUG-OUTPUT-NOT: .loc
+; DEBUG-OUTPUT-NOT: {{.*}}.debug_info{{.*}}
+
----------------
You don't need the {{.*}} on either side here, FileCheck looks for subline matches by default (which is why the .loc as you've written it is correct).

http://reviews.llvm.org/D4234