[PATCH] D45593: [DebugInfo][OPT] Fixing a couple of DI duplication bugs of CloneModule

[Roman Tereshin via Phabricator via llvm-commits]

rtereshin created this revision.
rtereshin added reviewers: aprantl, loladiro, GorNishanov, espindola, echristo, dexonsmith.
Herald added a subscriber: JDevlieghere.

As demonstrated by the regression tests added in this patch, the
following cases are valid cases:

1. A Function with no DISubprogram attached, but various debug info related to its instructions, coming, for instance, from an inlined function, also defined somewhere else in the same module;
2. ... or coming exclusively from the functions inlined and eliminated from the module entirely.

The ValueMap shared between CloneFunctionInto calls within CloneModule
needs to contain identity mappings for all of the DISubprogram's to
prevent them from being duplicated by MapMetadata / RemapInstruction
calls, this is achieved via DebugInfoFinder collecting all the
DISubprogram's. However, CloneFunctionInto was missing calls into
DebugInfoFinder for functions w/o DISubprogram's attached, but still
referring DISubprogram's from within (case 1). This patch fixes that.

The fix above, however, exposes another issue: if a module contains a
DISubprogram referenced only indirectly from other debug info
metadata, but not attached to any Function defined within the module
(case 2), cloning such a module causes a DICompileUnit duplication: it
will be moved in indirecty via a DISubprogram by DebugInfoFinder first
(because of the first bug fix described above), without being
self-mapped within the shared ValueMap, and then will be copied during
named metadata cloning. So this patch makes sure DebugInfoFinder
visits DICompileUnit's referenced from DISubprogram's as it goes w/o
re-processing llvm.dbg.cu list over and over again for every function
cloned, and makes sure that CloneFunctionInto self-maps
DICompileUnit's referenced from the entire function, not just its own
DISubprogram attached that may also be missing.

The most convenient way of tesing CloneModule I found is to rely on
CloneModule call from `opt -run-twice`, instead of writing tedious
unit tests. That feature has a couple of properties that makes it hard
to use for this purpose though:

1. CloneModule doesn't copy source filename, making `opt -run-twice` report it as a difference.
2. `opt -run-twice` does the second run on the original module, not its clone, making the result of cloning completely invisible in opt's actual output with and without `-run-twice` both, which directly contradicts `opt -run-twice`s own error message.

This patch fixes this as well.


Repository:
  rL LLVM

https://reviews.llvm.org/D45593

Files:
  include/llvm/IR/DebugInfo.h
  lib/IR/DebugInfo.cpp
  lib/Transforms/Utils/CloneFunction.cpp
  lib/Transforms/Utils/CloneModule.cpp
  test/DebugInfo/X86/clone-module-2.ll
  test/DebugInfo/X86/clone-module.ll
  tools/opt/opt.cpp

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