[llvm] llvm-tapi-diff

[spowell]

Summary

This patch introduces a new tool, llvm-tapi-diff, that compares and returns the diff of two TBD files.

[spowell]

clang-format fixes and included getOSAndEnvironmentName.

[spowell]

fixed issue with ... at end of tbd files that caused malformed file for testing

[spowell]

fix clang-tidy warnings

[spowell]

uploaded with -U999999

[cishida]

llvm/include/llvm/TextAPI/Target.h

63

nit: s/getTargetTriple/getTripleName or getTargetTripleName
Triple is already a type so this could be conflicting if there are similar functions that have that return type

llvm/tools/llvm-tapi-diff/DiffEngine.h

133

I'd prefer this emit an empty string

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

2

Please update these header descriptions

80

This path should never be possible, right? Could we instead error out if Bin* can't be casted & early return.

and have this be return Engine.compareFiles()

[JDevlieghere]

llvm/include/llvm/Object/TapiUniversal.h

104

It looks like the TapiUniversal guarantees that ParsedFile isn't NULL and indeed, some other functions seems to be unconditionally dereferencing this member. Should this return function a (const) reference instead?

llvm/include/llvm/TextAPI/Target.h

63

You're passing Target by value, so this is going to make a copy. Is that intentional? Should this take a const Target& instead?

llvm/lib/TextAPI/Platform.cpp

117

GCC used to complain about a missing return even after an exhaustive switch. Many places add an llvm_unreachable at the end of the function to avoid that.

llvm/test/tools/llvm-tapi-diff/tapi-diff-mismatched-number-of-inlines.test

2

The not binary is all lowercase. I suspect this will fail when running the test on a case-sensitive file system.

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

25–27

I was under the impression std::equal already ensured that the two ranges are of equal length. Is this meant as an optimization to quickly discard cases where the number of element are different? If so, keep in mind that for some iterator types like forward iterators, this is going to be O(n). Unless you know this is only going to be called with a random access iterator for which this operation is O(1) this might actually hurt performance.

32

T, U and V are pretty cryptic. It looks like U is some sort of TargetVec type, so maybe call it TargetVecT.

llvm/tools/llvm-tapi-diff/DiffEngine.h

24–43

The enums and classes in this header could use a Doxygen comment explaining what they are used for. To me it's not clear from their name what their purpose is.

186

Above you use LHS and RHS. Is there a reason to use One and Two here? Personally I'd stick with the former.

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

33

Please use WithColor::error() for consistency with other tools (and color output :-)

43

Instead of dumping the error here, why not return it and let the caller deal with it? Below there's a call to convertFileToBinary and without checking the implementation it looks like it's lacking error handling.

67

Some/most llvm tools use EXIT_SUCCESS and EXIT_FAILURE, which make it much easier to quickly spot exit codes.

[spowell]

changed getTargetTriple to getTargetTripleName; fixed header descriptions; fixed unreachable path; return const reference from getInterfaceFile; passing Target as const reference into getTargetTripleName; added llvm_unreachable to getOSAndEnvironmentName; NOT -> not in tests; removed unnecessary comparison in checkSymbolEquality; refactored typenames for addValToDiffVec template function; added Doxygen comments for DiffEngine.h; One and Two => LHS and RHS in llvm-tapi-diff; added WithColor; return llvm::Error or std::unique_ptr<Binary> for convertFileToBinary instead of only dumping error; used EXIT_FAILURE instead of returning 1;

[spowell]

resubmitted patch because of failure

[spowell]

fixed issue with applying patch

[spowell]

fixed issue with getOSAndEnvironmentName

[cishida]

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

2

we should also replace symbol table comparator with something like (tapi|tbd) file comparator

12

s/llvm-nm/llvm-tapi-diff

80

Please add a testcase that goes through an error path.
When I ran the tool with a misspelled input it crashes.
If I understood @JDevlieghere comment correctly, we should be handling the error at this call site instead of inside convertFileToBinary and currently we don't capture the possible error from the wrapped Expected<T> object.

bin/llvm-tapi-diff: error: src/llvm-project/llvm/test/tools/llvm-tapi-diff/Inputs/vC.tbd: No such file or directory
Expected<T> must be checked before access or destruction.
Unchecked Expected<T> contained error:
No such file or directoryPLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0.      Program arguments: bin/llvm-tapi-diff  src/llvm-project/llvm/test/tools/llvm-tapi-diff/Inputs/v4B.tbd  src/llvm-project/llvm/test/tools/llvm-tapi-diff/Inputs/vC.tbd
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  llvm-tapi-diff           0x00000001084d4dd7 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 39
1  llvm-tapi-diff           0x00000001084d3ff8 llvm::sys::RunSignalHandlers() + 248
<omitted>
[1]    85533 abort      bin/llvm-tapi-diff

See https://llvm.org/docs/ProgrammersManual.html#error-handling for more details.

[spowell]

updated header descriptions, updated error handling for convertFileToBinary and if a file cannot be cast as TapiUniversal.

[spowell]

fixed patch upload for -U999999

[spowell]

clang-format fixes and replaced macho.dylib for macho.yaml

[JDevlieghere]

llvm/lib/TextAPI/Platform.cpp

134

Should this be llvm::MachO::PlatformKind?

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

2

This seems to be missing a few dashes.

221–222

This is still using 1 and 2 while everything else is now using LHS and RHS.

325–327

The llvm style guidelines say no braces around single-line ifs.

llvm/tools/llvm-tapi-diff/DiffEngine.h

49–59

Rather than documenting the class as a whole, it's good practice to document the individual members like this. This is much more maintainable when a member gets added or removed, and Doxygen will associate the comment with the variable for you, which means you don't have to repeat the type etc.

55–57

Should these members really be public? If the answer is yes, you'd want to use struct instead of class, which has public visibility by default. It's not so much about avoiding the access specifier on line 53, but more about conveying your intention to other developers.

147

This probably also needs an unreachable. Same for the function below. There might be more in this patch.

202

Several files seem to be missing newlines at the end.

[spowell]

llvm.MachO.PlatformKind => llvm::MachO::PlatformKind in platform.cpp; removed 1 and 2 in favor of LHS and RHS in DiffEngine.cpp; refactored comments in DiffEngine.h; changed DiffOutput from class to struct; added llvm_unreachable in switch statements in DiffEngine.h; Added new lines at end of files.

[spowell]

added new lines to test input files.

[spowell]

rebased patch from main to fix patch apply issue, added new line for CMakeLists.txt

[spowell]

uploading patch again to trigger rebuild

[spowell]

update separators in tests

[spowell]

use regex to try to fix windows failure.

[spowell]

fixed brackets for regex in test

[JDevlieghere]

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

10–11

This is not a header tho :-)

93–96

Could we reduce the density of this code by adding a helper that looks something like:

void DiffAttribute(StringRef Name, std::vector<DiffOutput>& Output, AttributeDiff Attr) {
  Output.push_back(getSingleAttrDiff(Attr, Name));
}

and then simplify these calls to:

DiffAttribute("Install Name", ReturnedOutput, DiffScalarVal<StringRef, AD_Diff_Scalar_Str>(Order, Interface->getInstallName()));

Having the name of the attribute first makes it clear what you're diffing. I'd probably also rename ReturnedOutput to something shorter (Output) to reduce the length of those calls.

llvm/tools/llvm-tapi-diff/DiffEngine.h

65–66

Can these two be private? These members look like implementation details. Same in the other classes.

73

I see (this->Order == lhs) ? "< " : "> ") in several places. How about creating a helper that takes a InterfaceInputOrder and returns a StringRef to avoid this duplication?

133

Why are these functions implemented in the header?

172

The LLVM Coding Guide says that comments should be sentences, i.e. capitalized and with a period at the end.

223

You're passing the vector by value, so this will copy all its element for printing. Can this be a const ref?

[cishida]

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

129

you don't need this conditional, the body of the for loop would never run if its empty

172

These don't need to be scoped

llvm/tools/llvm-tapi-diff/DiffEngine.h

57

Most, if not all, instances of this type are named Diff Diff.DiffVec is redundant and is also used as a variable name in other places.
What about Values?

82

nit: this-> calls are unecessarcy

102

Remove the typo at the end.

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

2

sorry for the confusion on notation, I mean either tapi or tbd should be in the description.

[sgraenitz]

Hey, just a few notes on proper error handling.

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

41

The idiomatic solution for this is ExitOnErr as described here:
https://llvm.org/docs/ProgrammersManual.html#using-exitonerror-to-simplify-tool-code

53

Could the result be returned directly here? Like this?

return createBinary(BufferOrErr.get()->getMemBufferRef());

74

I think with ExitOnError this could be:

std::unique_ptr<Binary> BinLHS = ExitOnErr(convertFileToBinary(InputFileNameLHS));

It is not uncommon to have it as a static global in a tool's driver cpp and use it directly all over the place. There is a number of good examples, e.g. llvm-link https://github.com/llvm/llvm-project/blob/81bc732816107f6aff4fd61980f7b03cc92332b5/llvm/tools/llvm-link/llvm-link.cpp#L296

[spowell]

fixed heading on DiffEngine.cpp; made helper to collect single scalar values; ReturnedOutput => Output; made implementation details private for class variables; made helper to set order indicator for print functions; moved functions that did not need to be in header; removed unneeded conditional; removed unneeded scope; DiffVec => Values, TargValues, DocValues; addValToDiffVec => addDiffToTargetSlice; removed unnecessary this-> calls; removed typo in comment; fixed heading on llvm-tapi-diff.cpp; fixed error handling in llvm-tapi-diff.cpp

[spowell]

removed import that was auto-added by text editor causing failure of tests.

[spowell]

fix error handling in llvm-tapi-diff.cpp

[JDevlieghere]

A few small nits and this should be ready to go.

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

384–387

LHS? DocLHS?

458

This line got me thinking that it might be nice to make the raw_ostream an argument to printDifferences and do the same for compareFiles below. That aligns nicely with LLVM's library design, where the actual implementation (the DiffEngine) can remain unaware of where its output is being printed while centralize the fact that it's going to stdout in llvm-tapi-diff.cpp.

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

30–33

This is generally lowercase.

[spowell]

Doc1 => DocLHS; Doc2 => DocRHS; made raw_ostream argument in compareFiles and printDifferences; lowercase argument prompts;

[JDevlieghere]

LGTM! Thanks for bearing with me :-)

[spowell]

formatting fixes

[ributzka]

LGTM

[thakis]

llvm/test/tools/llvm-tapi-diff/tapi-diff-matching-tbd.test

2

Shouldn't you add llvm-tapi-diff to llvm/test/CMakeLists.txt to make sure it gets built when you build check-llvm? And to the tools.extend( bit in llvm/test/lit.cfg.py?

[jyknight]

llvm/tools/llvm-tapi-diff/DiffEngine.h

58

std::vector<std::unique_ptr<AttributeDiff>>

Storing a subclass of AttributeDiff into a unique_ptr<AttributeDiff> is not OK, because AttributeDiff does not have a virtual destructor. So, this tool is invoking UB.

Just adding the virtual destructor to AttributeDiff is probably ok -- there doesn't seem to be any reason to avoid using virtual dispatch in this tool's class hierarchy, afaict.

[hubert.reinterpretcast]

The tests for this tool are observed to be failing on multiple big-endian platforms:
clang-s390x-linux: https://lab.llvm.org/buildbot/#/builders/94/builds/4116
clang-ppc64be-linux: https://lab.llvm.org/buildbot/#/builders/52/builds/8035

[cishida]

In D101835#2798031, @hubert.reinterpretcast wrote:

The tests for this tool are observed to be failing on multiple big-endian platforms:
clang-s390x-linux: https://lab.llvm.org/buildbot/#/builders/94/builds/4116
clang-ppc64be-linux: https://lab.llvm.org/buildbot/#/builders/52/builds/8035

Thanks for letting us know! @spowell from reading the lit output, it appears like the output order for the target slices isn't stable. I've reverted while we investigate and fix.

[danilaml]

I'm pretty sure this also causes a build failure on older, but supported versions of GCC due to this bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480):

../tools/llvm-tapi-diff/DiffEngine.cpp:35:71: error: specialization of template<class T, llvm::DiffAttrKind U> void llvm::DiffScalarVal<T, U>::print(llvm::raw_ostream&, std::__cxx11::string) in different namespace [-fpermissive]
                                                     std::string Indent) {
                                                                       ^

llvm/include/llvm/Object/TapiUniversal.h

     return make_range(begin_objects(), end_objects());
   }
 
+  MachO::InterfaceFile *getInterfaceFile() { return ParsedFile.get(); }
+
   uint32_t getNumberOfObjects() const { return Libraries.size(); }
 
   static bool classof(const Binary *v) { return v->isTapiUniversal(); }

llvm/include/llvm/TextAPI/Platform.h

 PlatformKind mapToPlatformKind(const Triple &Target);
 PlatformSet mapToPlatformSet(ArrayRef<Triple> Targets);
 StringRef getPlatformName(PlatformKind Platform);
+std::string getOSAndEnvironmentName(PlatformKind Platform,
+                                    std::string Version = "");
 
 } // end namespace MachO.
 } // end namespace llvm.

llvm/include/llvm/TextAPI/Symbol.h

 #endif
 
   bool operator==(const Symbol &O) const {
-    return (Kind == O.Kind) && (Name == O.Name) && (Targets == O.Targets) &&
-           (Flags == O.Flags);
+    return std::tie(Name, Kind, Targets, Flags) ==
+           std::tie(O.Name, O.Kind, O.Targets, O.Flags);
   }
 
   bool operator!=(const Symbol &O) const { return !(*this == O); }
 
+  bool operator<(const Symbol &O) const {
+    return std::tie(Name, Kind, Targets, Flags) <
+           std::tie(O.Name, O.Kind, O.Targets, O.Flags);
+  }
+
 private:
   StringRef Name;
   TargetList Targets;

llvm/include/llvm/TextAPI/Target.h

 PlatformSet mapToPlatformSet(ArrayRef<Target> Targets);
 ArchitectureSet mapToArchitectureSet(ArrayRef<Target> Targets);
 
+std::string getTargetTriple(Target Targ);
+
 raw_ostream &operator<<(raw_ostream &OS, const Target &Target);
 
 } // namespace MachO

llvm/lib/TextAPI/Platform.cpp

   llvm_unreachable("Unknown llvm.MachO.PlatformKind enum");
 }
 
+std::string getOSAndEnvironmentName(PlatformKind Platform,
+                                    std::string Version) {
+  switch (Platform) {
+  case PlatformKind::unknown:
+    return "darwin" + Version;
+  case PlatformKind::macOS:
+    return "macos" + Version;
+  case PlatformKind::iOS:
+    return "ios" + Version;
+  case PlatformKind::tvOS:
+    return "tvos" + Version;
+  case PlatformKind::watchOS:
+    return "watchos" + Version;
+  case PlatformKind::bridgeOS:
+    return "bridgeos" + Version;
+  case PlatformKind::macCatalyst:
+    return "ios" + Version + "-macabi";
+  case PlatformKind::iOSSimulator:
+    return "ios" + Version + "-simulator";
+  case PlatformKind::tvOSSimulator:
+    return "tvos" + Version + "-simulator";
+  case PlatformKind::watchOSSimulator:
+    return "watchos" + Version + "-simulator";
+  case PlatformKind::driverKit:
+    return "driverkit" + Version;
+  }
+}
+
 } // end namespace MachO.
 } // end namespace llvm.

llvm/lib/TextAPI/Target.cpp

   return Result;
 }
 
+std::string getTargetTriple(Target Targ) {
+  return (getArchitectureName(Targ.Arch) + "-apple-" +
+          getOSAndEnvironmentName(Targ.Platform))
+      .str();
+}
+
 } // end namespace MachO.
 } // end namespace llvm.

llvm/test/tools/llvm-tapi-diff/Inputs/v4A.tbd

+--- !tapi-tbd
+tbd-version: 4
+targets:  [ i386-macos, x86_64-macos, x86_64-ios ]
+uuids:
+  - target: i386-macos
+    value: 00000000-0000-0000-0000-000000000000
+  - target: x86_64-macos
+    value: 11111111-1111-1111-1111-111111111111
+  - target: x86_64-ios
+    value: 11111111-1111-1111-1111-111111111111
+flags: [ flat_namespace, installapi ]
+install-name: Umbrella.framework/Umbrella
+current-version: 1.2.3
+compatibility-version: 1.2
+swift-abi-version: 5
+parent-umbrella:
+  - targets: [ i386-macos, x86_64-macos, x86_64-ios ]
+    umbrella: System
+allowable-clients:
+  - targets: [ i386-macos, x86_64-macos, x86_64-ios ]
+    clients: [ ClientA ]
+exports:
+  - targets: [ i386-macos ]
+    symbols: [ _symA ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+  - targets: [ x86_64-ios ]
+    symbols: [_symB]
+  - targets: [ x86_64-macos, x86_64-ios ]
+    symbols: [_symAB]
+reexports:
+  - targets: [ i386-macos ]
+    symbols: [_symC]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+undefineds:
+  - targets: [ i386-macos ]
+    symbols: [ _symD ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+...
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/Inputs/v4B.tbd

+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           [ installapi ]
+install-name:    'Umbrella.framework/Umbrella'
+current-version: 1.2.3
+compatibility-version: 0
+swift-abi-version: 5
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientA ]
+reexported-libraries:
+  - targets: [ i386-macos ]
+    libraries: [ 'Alpine.framework/Alpine' ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symA ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symC ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           []
+install-name:    'Alpine.framework/Alpine'
+current-version: 1.2.3
+compatibility-version: 0
+swift-abi-version: 5
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientD ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symA ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symC ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+...
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/Inputs/v4C.tbd

+--- !tapi-tbd
+tbd-version: 4
+targets:  [ i386-macos, x86_64-ios ]
+uuids:
+  - target: i386-macos
+    value: 00000000-0000-0000-0000-000000000000
+  - target: x86_64-macos
+    value: 11111111-1111-1111-1111-111111111111
+  - target: x86_64-ios
+    value: 22222222-2222-2222-2222-222222222222
+flags: [ installapi ]
+install-name: Umbrella.framework/Umbrella
+current-version: 1.3.3
+compatibility-version: 1.2
+swift-abi-version: 3
+parent-umbrella:
+  - targets: [ i386-macos, x86_64-ios ]
+    umbrella: System
+allowable-clients:
+  - targets: [ i386-macos, x86_64-ios ]
+    clients: [ ClientA ]
+exports:
+  - targets: [ i386-macos ]
+    symbols: [ _symA ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+  - targets: [ x86_64-ios ]
+    symbols: [_symB]
+  - targets: [ x86_64-ios ]
+    symbols: [_symAB]
+reexports:
+  - targets: [ i386-macos ]
+    symbols: [_symC]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+undefineds:
+  - targets: [ i386-macos ]
+    symbols: [ _symD ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+...
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/Inputs/v4D.tbd

+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           [ installapi ]
+install-name:    'Umbrella.framework/Umbrella'
+current-version: 1.2.3
+compatibility-version: 0
+swift-abi-version: 5
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientA ]
+reexported-libraries:
+  - targets: [ i386-macos, x86_64-ios-simulator ]
+    libraries: [ 'Alpine.framework/Alpine', 'System.framework/System' ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symA ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symC ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           []
+install-name:    'Alpine.framework/Alpine'
+current-version: 1.2.3
+compatibility-version: 0
+swift-abi-version: 5
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientD ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symA ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symC ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+--- !tapi-tbd
+tbd-version: 4
+targets:  [ i386-macos, x86_64-ios ]
+uuids:
+  - target: i386-macos
+    value: 00000000-0000-0000-0000-000000000000
+  - target: x86_64-macos
+    value: 11111111-1111-1111-1111-111111111111
+  - target: x86_64-ios
+    value: 22222222-2222-2222-2222-222222222222
+flags: []
+install-name: 'System.framework/System'
+current-version: 1.3.3
+compatibility-version: 1.2
+swift-abi-version: 3
+parent-umbrella:
+  - targets: [ i386-macos, x86_64-ios ]
+    umbrella: System
+allowable-clients:
+  - targets: [ i386-macos, x86_64-ios ]
+    clients: [ ClientA ]
+exports:
+  - targets: [ i386-macos ]
+    symbols: [ _symA ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+  - targets: [ x86_64-ios ]
+    symbols: [_symB]
+  - targets: [ x86_64-ios ]
+    symbols: [_symAB]
+reexports:
+  - targets: [ i386-macos ]
+    symbols: [_symC]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+undefineds:
+  - targets: [ i386-macos ]
+    symbols: [ _symD ]
+    objc-classes: []
+    objc-eh-types: []
+    objc-ivars: []
+    weak-symbols: []
+    thread-local-symbols: []
+...
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/Inputs/v4E.tbd

+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           [ installapi ]
+install-name:    'Umbrella.framework/Umbrella'
+current-version: 1.2.3
+compatibility-version: 0
+swift-abi-version: 4
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientC ]
+reexported-libraries:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    libraries:       [ Alpine.framework/Alpine ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symA ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symQ ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+--- !tapi-tbd
+tbd-version:     4
+targets:         [ i386-macos, x86_64-ios-simulator ]
+uuids:
+  - target:          i386-macos
+    value:           00000000-0000-0000-0000-000000000000
+  - target:          x86_64-ios-simulator
+    value:           11111111-1111-1111-1111-111111111111
+flags:           []
+install-name:    'Alpine.framework/Alpine'
+current-version: 1.4.3
+compatibility-version: 0
+swift-abi-version: 3
+parent-umbrella:
+  - targets:         [ i386-macos, x86_64-ios-simulator ]
+    umbrella:        System
+allowable-clients:
+  - targets:         [ i386-macos ]
+    clients:         [ ClientB ]
+exports:
+  - targets:         [ i386-macos ]
+    symbols:         [ _symE ]
+    objc-classes:    [ Class1 ]
+    weak-symbols:    [ _symC ]
+  - targets:         [ x86_64-ios-simulator ]
+    symbols:         [ _symB ]
+...
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-matching-tbd.test

+; RUN: llvm-tapi-diff %S/Inputs/v4A.tbd %S/Inputs/v4A.tbd 2>&1 | FileCheck %s --allow-empty
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-mismatched-number-of-inlines.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4B.tbd %S/Inputs/v4D.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4B.tbd
+; CHECK:> {{.*}}/Inputs/v4D.tbd
+
+; CHECK:     Reexported Libraries
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:               > Alpine.framework/Alpine
+; CHECK-NEXT:               > System.framework/System
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:               > System.framework/System
+; CHECK-NEXT:Inlined Reexported Frameworks/Libraries
+; CHECK-NEXT:    System.framework/System
+; CHECK-NEXT:        Current Version
+; CHECK-NEXT:                > 1.3.3
+; CHECK-NEXT:        Compatibility Version
+; CHECK-NEXT:                > 1.2
+; CHECK-NEXT:        Swift ABI Version
+; CHECK-NEXT:                > 3
+; CHECK-NEXT:        InstallAPI
+; CHECK-NEXT:                > false
+; CHECK-NEXT:        Two Level Namespace
+; CHECK-NEXT:                > true
+; CHECK-NEXT:        Application Extension Safe
+; CHECK-NEXT:                > true
+; CHECK-NEXT:        Allowable Clients
+; CHECK-NEXT:                i386-apple-macos
+; CHECK-NEXT:                       > ClientA
+; CHECK-NEXT:                x86_64-apple-ios
+; CHECK-NEXT:                       > ClientA
+; CHECK-NEXT:        Parent Umbrellas
+; CHECK-NEXT:                i386-apple-macos
+; CHECK-NEXT:                       > System
+; CHECK-NEXT:                x86_64-apple-ios
+; CHECK-NEXT:                       > System
+; CHECK-NEXT:        Symbols
+; CHECK-NEXT:                i386-apple-macos
+; CHECK-NEXT:                        > _symC - Reexported
+; CHECK-NEXT:                        > _symD - Undefined
+; CHECK-NEXT:                        > _symA - None
+; CHECK-NEXT:                x86_64-apple-ios
+; CHECK-NEXT:                        > _symAB - None
+; CHECK-NEXT:                        > _symB - None
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-no-inlines.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4A.tbd %S/Inputs/v4C.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4A.tbd
+; CHECK:> {{.*}}/Inputs/v4C.tbd
+
+; CHECK:Current Version
+; CHECK-NEXT:< 1.2.3
+; CHECK-NEXT:> 1.3.3
+; CHECK-NEXT:Swift ABI Version
+; CHECK-NEXT:< 5
+; CHECK-NEXT:> 3
+; CHECK-NEXT:Two Level Namespace
+; CHECK-NEXT:< false
+; CHECK-NEXT:> true
+; CHECK-NEXT:Allowable Clients
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:Parent Umbrellas
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < System
+; CHECK-NEXT:Symbols
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK:                < _symAB - None
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:

llvm/test/tools/llvm-tapi-diff/tapi-diff-same-number-of-inlines.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4B.tbd %S/Inputs/v4E.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4B.tbd
+; CHECK:> {{.*}}/Inputs/v4E.tbd
+
+; CHECK:Swift ABI Version
+; CHECK-NEXT:< 5
+; CHECK-NEXT:> 4
+; CHECK-NEXT:Reexported Libraries
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:               > Alpine.framework/Alpine
+; CHECK-NEXT:Allowable Clients
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:               > ClientC
+; CHECK-NEXT:Symbols
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:                < _symC - Weak-Defined
+; CHECK-NEXT:                > _symQ - Weak-Defined
+; CHECK-NEXT:Inlined Reexported Frameworks/Libraries
+; CHECK-NEXT:        Alpine.framework/Alpine
+; CHECK-NEXT:                Current Version
+; CHECK-NEXT:                   < 1.2.3
+; CHECK-NEXT:                   > 1.4.3
+; CHECK-NEXT:                Swift ABI Version
+; CHECK-NEXT:                   < 5
+; CHECK-NEXT:                   > 3
+; CHECK-NEXT:                Allowable Clients
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               < ClientD
+; CHECK-NEXT:                               > ClientB
+; CHECK-NEXT:                Symbols
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                                < _symA - None
+; CHECK-NEXT:                                > _symE - None
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-tbd-has-multiple-inlines.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4A.tbd %S/Inputs/v4D.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4A.tbd
+; CHECK:> {{.*}}/Inputs/v4D.tbd
+
+; CHECK:Compatibility Version
+; CHECK-NEXT:< 1.2
+; CHECK-NEXT:> 0
+; CHECK-NEXT:Two Level Namespace
+; CHECK-NEXT:< false
+; CHECK-NEXT:> true
+; CHECK-NEXT:Reexported Libraries
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:               > Alpine.framework/Alpine
+; CHECK-NEXT:               > System.framework/System
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:               > Alpine.framework/Alpine
+; CHECK-NEXT:               > System.framework/System
+; CHECK-NEXT:Allowable Clients
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:Parent Umbrellas
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < System
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:               < System
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:               > System
+; CHECK-NEXT:Symbols
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:                < _symC - Reexported
+; CHECK-NEXT:                < _symD - Undefined
+; CHECK-NEXT:                > _symC - Weak-Defined
+; CHECK-NEXT:                > .objc_class_name_Class1 - None
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:                < _symAB - None
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:                < _symAB - None
+; CHECK-NEXT:                < _symB - None
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:                > _symB - None
+; CHECK-NEXT:Inlined Reexported Frameworks/Libraries
+; CHECK-NEXT:        Alpine.framework/Alpine
+; CHECK-NEXT:                Current Version
+; CHECK-NEXT:                        >  1.2.3
+; CHECK-NEXT:                Compatibility Version
+; CHECK-NEXT:                        >  0
+; CHECK-NEXT:                Swift ABI Version
+; CHECK-NEXT:                        >  5
+; CHECK-NEXT:                InstallAPI
+; CHECK-NEXT:                        >  false
+; CHECK-NEXT:                Two Level Namespace
+; CHECK-NEXT:                        >  true
+; CHECK-NEXT:                Application Extension Safe
+; CHECK-NEXT:                        >  true
+; CHECK-NEXT:                Allowable Clients
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > ClientD
+; CHECK-NEXT:                Parent Umbrellas
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                        x86_64-apple-ios-simulator
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                Symbols
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                                >  _symC - Weak-Defined
+; CHECK-NEXT:                                >  .objc_class_name_Class1 - None
+; CHECK-NEXT:                                >  _symA - None
+; CHECK-NEXT:                        x86_64-apple-ios-simulator
+; CHECK-NEXT:                                >  _symB - None
+; CHECK-NEXT:        System.framework/System
+; CHECK-NEXT:                Current Version
+; CHECK-NEXT:                        >  1.3.3
+; CHECK-NEXT:                Compatibility Version
+; CHECK-NEXT:                        >  1.2
+; CHECK-NEXT:                Swift ABI Version
+; CHECK-NEXT:                        >  3
+; CHECK-NEXT:                InstallAPI
+; CHECK-NEXT:                        >  false
+; CHECK-NEXT:                Two Level Namespace
+; CHECK-NEXT:                        >  true
+; CHECK-NEXT:                Application Extension Safe
+; CHECK-NEXT:                        >  true
+; CHECK-NEXT:                Allowable Clients
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > ClientA
+; CHECK-NEXT:                        x86_64-apple-ios
+; CHECK-NEXT:                               > ClientA
+; CHECK-NEXT:                Parent Umbrellas
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                        x86_64-apple-ios
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                Symbols
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                                >  _symC - Reexported
+; CHECK-NEXT:                                >  _symD - Undefined
+; CHECK-NEXT:                                >  _symA - None
+; CHECK-NEXT:                        x86_64-apple-ios
+; CHECK-NEXT:                                >  _symAB - None
+; CHECK-NEXT:                                >  _symB - None
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-tbd-has-single-inlineA.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4A.tbd %S/Inputs/v4B.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4A.tbd
+; CHECK:> {{.*}}/Inputs/v4B.tbd
+
+; CHECK:Compatibility Version
+; CHECK-NEXT:< 1.2
+; CHECK-NEXT:> 0
+; CHECK-NEXT:Two Level Namespace
+; CHECK-NEXT:< false
+; CHECK-NEXT:> true
+; CHECK-NEXT:Reexported Libraries
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:               > Alpine.framework/Alpine
+; CHECK-NEXT:Allowable Clients
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:               < ClientA
+; CHECK-NEXT:Parent Umbrellas
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:               < System
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:               < System
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:               > System
+; CHECK-NEXT:Symbols
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:                < _symC - Reexported
+; CHECK-NEXT:                < _symD - Undefined
+; CHECK-NEXT:                > _symC - Weak-Defined
+; CHECK-NEXT:                > .objc_class_name_Class1 - None
+; CHECK-NEXT:        x86_64-apple-macos
+; CHECK-NEXT:                < _symAB - None
+; CHECK-NEXT:        x86_64-apple-ios
+; CHECK-NEXT:                < _symAB - None
+; CHECK-NEXT:                < _symB - None
+; CHECK-NEXT:        x86_64-apple-ios-simulator
+; CHECK-NEXT:                > _symB
+; CHECK-NEXT:Inlined Reexported Frameworks/Libraries
+; CHECK-NEXT:        Alpine.framework/Alpine
+; CHECK-NEXT:                Current Version
+; CHECK-NEXT:                   > 1.2.3
+; CHECK-NEXT:                Compatibility Version
+; CHECK-NEXT:                   > 0
+; CHECK-NEXT:                Swift ABI Version
+; CHECK-NEXT:                   > 5
+; CHECK-NEXT:                InstallAPI
+; CHECK-NEXT:                   > false
+; CHECK-NEXT:                Two Level Namespace
+; CHECK-NEXT:                   > true
+; CHECK-NEXT:                Application Extension Safe
+; CHECK-NEXT:                   > true
+; CHECK-NEXT:                Allowable Clients
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > ClientD
+; CHECK-NEXT:                Parent Umbrellas
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                        x86_64-apple-ios-simulator
+; CHECK-NEXT:                               > System
+; CHECK-NEXT:                Symbols
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                                > _symC - Weak-Defined
+; CHECK-NEXT:                                > .objc_class_name_Class1 - None
+; CHECK-NEXT:                                > _symA - None
+; CHECK-NEXT:                        x86_64-apple-ios-simulator
+; CHECK-NEXT:                                > _symB - None
+
+
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/test/tools/llvm-tapi-diff/tapi-diff-tbd-has-single-inlineB.test

+; RUN: NOT llvm-tapi-diff %S/Inputs/v4B.tbd %S/Inputs/v4C.tbd 2>&1 | FileCheck %s
+
+; CHECK:< {{.*}}/Inputs/v4B.tbd
+; CHECK:> {{.*}}/Inputs/v4C.tbd
+
+; CHECK:Current Version
+; CHECK-NEXT:< 1.2.3
+; CHECK-NEXT:> 1.3.3
+; CHECK-NEXT:Compatibility Version
+; CHECK-NEXT:< 0
+; CHECK-NEXT:> 1.2
+; CHECK-NEXT:Swift ABI Version
+; CHECK-NEXT:< 5
+; CHECK-NEXT:> 3
+; CHECK-NEXT:Reexported Libraries
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:               < Alpine.framework/Alpine
+; CHECK-NEXT:Allowable Clients
+; CHECK-NEXT:       x86_64-apple-ios
+; CHECK-NEXT:               > ClientA
+; CHECK-NEXT:Parent Umbrellas
+; CHECK-NEXT:       x86_64-apple-ios-simulator
+; CHECK-NEXT:               < System
+; CHECK-NEXT:       x86_64-apple-ios
+; CHECK-NEXT:               > System
+; CHECK-NEXT:Symbols
+; CHECK-NEXT:        i386-apple-macos
+; CHECK-NEXT:                < _symC - Weak-Defined
+; CHECK-NEXT:                < .objc_class_name_Class1 - None
+; CHECK-NEXT:                > _symC - Reexported
+; CHECK-NEXT:                > _symD - Undefined
+; CHECK-NEXT:       x86_64-apple-ios-simulator
+; CHECK-NEXT:                < _symB - None
+; CHECK-NEXT:       x86_64-apple-ios
+; CHECK-NEXT:                > _symAB - None
+; CHECK-NEXT:                > _symB - None
+; CHECK-NEXT:Inlined Reexported Frameworks/Libraries
+; CHECK-NEXT:        Alpine.framework/Alpine
+; CHECK-NEXT:                Current Version
+; CHECK-NEXT:                        <  1.2.3
+; CHECK-NEXT:                Compatibility Version
+; CHECK-NEXT:                        <  0
+; CHECK-NEXT:                Swift ABI Version
+; CHECK-NEXT:                        <  5
+; CHECK-NEXT:                InstallAPI
+; CHECK-NEXT:                        <  false
+; CHECK-NEXT:                Two Level Namespace
+; CHECK-NEXT:                        <  true
+; CHECK-NEXT:                Application Extension Safe
+; CHECK-NEXT:                        <  true
+; CHECK-NEXT:                Allowable Clients
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               < ClientD
+; CHECK-NEXT:                Parent Umbrellas
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                               < System
+; CHECK-NEXT:                       x86_64-apple-ios-simulator
+; CHECK-NEXT:                               < System
+; CHECK-NEXT:                Symbols
+; CHECK-NEXT:                        i386-apple-macos
+; CHECK-NEXT:                                <  _symC - Weak-Defined
+; CHECK-NEXT:                                <  .objc_class_name_Class1 - None
+; CHECK-NEXT:                                <  _symA - None
+; CHECK-NEXT:                       x86_64-apple-ios-simulator
+; CHECK-NEXT:                                <  _symB - None
+
+; CHECK-NOT: error:
+; CHECK-NOT: warning:
 No newline at end of file

llvm/tools/llvm-tapi-diff/CMakeLists.txt

+set(LLVM_LINK_COMPONENTS
+  Object
+  Support
+  TextAPI
+  )
+
+add_llvm_tool(llvm-tapi-diff
+  llvm-tapi-diff.cpp
+  DiffEngine.cpp
+  )
 No newline at end of file

llvm/tools/llvm-tapi-diff/DiffEngine.h

+//===-- DiffEngine.h - File comparator ------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines the interface to the llvm-nm difference engine,
+// which structurally compares two tbd files. (To be updated)
+//
+//===----------------------------------------------------------------------===/
+#ifndef LLVM_TOOLS_LLVM_NM_DIFF_DIFFENGINE_H
+#define LLVM_TOOLS_LLVM_NM_DIFF_DIFFENGINE_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Object/TapiUniversal.h"
+#include "llvm/TextAPI/Symbol.h"
+#include "llvm/TextAPI/Target.h"
+
+namespace llvm {
+
+enum InterfaceInputOrder { lhs, rhs };
+
+enum DiffAttrKind {
+  AD_Diff_Scalar_PackedVersion,
+  AD_Diff_Scalar_Unsigned,
+  AD_Diff_Scalar_Bool,
+  AD_Diff_Scalar_Str,
+  AD_Str_Vec,
+  AD_Sym_Vec,
+  AD_Inline_Doc,
+};
+
+class AttributeDiff {
+public:
+  AttributeDiff(DiffAttrKind Kind) : Kind(Kind){};
+  DiffAttrKind getKind() const { return Kind; }
+
+private:
+  const DiffAttrKind Kind;
+};
+
+class DiffOutput {
+public:
+  std::string Name;
+  DiffAttrKind Kind;
+  std::vector<std::unique_ptr<AttributeDiff>> DiffVec;
+  DiffOutput(std::string Name) : Name(Name){};
+};
+
+template <class T, DiffAttrKind U> class DiffScalarVal : public AttributeDiff {
+public:
+  InterfaceInputOrder Order;
+  T Val;
+  DiffScalarVal(InterfaceInputOrder Order, T Val)
+      : AttributeDiff(U), Order(Order), Val(Val){};
+
+  static bool classof(const AttributeDiff *A) { return A->getKind() == U; }
+
+  void print(raw_ostream &OS, std::string Indent) {
+    OS << Indent << "\t" << ((this->Order == lhs) ? "< " : "> ") << this->Val
+       << "\n";
+  }
+};
+
+template <>
+inline void
+DiffScalarVal<StringRef, AD_Diff_Scalar_Str>::print(raw_ostream &OS,
+                                                    std::string Indent) {
+  OS << Indent << "\t\t" << ((this->Order == lhs) ? "< " : "> ") << this->Val
+     << "\n";
+}
+
+template <>
+inline void
+DiffScalarVal<uint8_t, AD_Diff_Scalar_Unsigned>::print(raw_ostream &OS,
+                                                       std::string Indent) {
+  OS << Indent << "\t" << ((this->Order == lhs) ? "< " : "> ")
+     << std::to_string(this->Val) << "\n";
+}
+
+template <>
+inline void
+DiffScalarVal<bool, AD_Diff_Scalar_Bool>::print(raw_ostream &OS,
+                                                std::string Indent) {
+  OS << Indent << "\t" << ((this->Order == lhs) ? "< " : "> ")
+     << ((this->Val == true) ? "true" : "false") << "\n";
+}
+
+class SymScalar {
+public:
+  InterfaceInputOrder Order;
+  const MachO::Symbol *Val;
+  SymScalar(InterfaceInputOrder Order, const MachO::Symbol *Sym)
+      : Order(Order), Val(Sym){};
+
+  void print(raw_ostream &OS, std::string Indent, MachO::Target Targ) {
+    if (Val->getKind() == MachO::SymbolKind::ObjectiveCClass) {
+      if (Targ.Arch == MachO::AK_i386 &&
+          Targ.Platform == MachO::PlatformKind::macOS) {
+        OS << Indent << "\t\t" << ((this->Order == lhs) ? "< " : "> ")
+           << ".objc_class_name_" << Val->getName() << " - "
+           << stringifySymbolFlag(Val->getFlags()) << "\n";
+        return;
+      }
+      OS << Indent << "\t\t" << ((this->Order == lhs) ? "< " : "> ")
+         << "_OBJC_CLASS_$_" << Val->getName() << " - "
+         << stringifySymbolFlag(Val->getFlags()) << "\n";
+    }
+    OS << Indent << "\t\t" << ((this->Order == lhs) ? "< " : "> ")
+       << stringifySymbolKind(Val->getKind()) << Val->getName() << " - "
+       << stringifySymbolFlag(Val->getFlags()) << "\n";
+  }
+
+private:
+  std::string stringifySymbolKind(MachO::SymbolKind Kind) {
+    switch (Kind) {
+    case MachO::SymbolKind::GlobalSymbol:
+      return "";
+    case MachO::SymbolKind::ObjectiveCClass:
+      return "_OBJC_METACLASS_$_";
+    case MachO::SymbolKind ::ObjectiveCClassEHType:
+      return "_OBJC_EHTYPE_$_";
+    case MachO::SymbolKind ::ObjectiveCInstanceVariable:
+      return "_OBJC_IVAR_$_";
+    }
+  }
+
+  std::string stringifySymbolFlag(MachO::SymbolFlags Flag) {
+    switch (Flag) {
+    case MachO::SymbolFlags::None:
+      return "None";
+    case MachO::SymbolFlags::ThreadLocalValue:
+      return "Thread-Local";
+    case MachO::SymbolFlags::WeakDefined:
+      return "Weak-Defined";
+    case MachO::SymbolFlags::WeakReferenced:
+      return "Weak-Referenced";
+    case MachO::SymbolFlags::Undefined:
+      return "Undefined";
+    case MachO::SymbolFlags::Rexported:
+      return "Reexported";
+    }
+  }
+};
+
+class DiffStrVec : public AttributeDiff {
+public:
+  MachO::Target Targ;
+  std::vector<DiffScalarVal<StringRef, AD_Diff_Scalar_Str>> DiffVec;
+  DiffStrVec(MachO::Target Targ) : AttributeDiff(AD_Str_Vec), Targ(Targ){};
+
+  static bool classof(const AttributeDiff *A) {
+    return A->getKind() == AD_Str_Vec;
+  }
+};
+
+class DiffSymVec : public AttributeDiff {
+public:
+  MachO::Target Targ;
+  std::vector<SymScalar> DiffVec;
+  DiffSymVec(MachO::Target Targ) : AttributeDiff(AD_Sym_Vec), Targ(Targ){};
+
+  static bool classof(const AttributeDiff *A) {
+    return A->getKind() == AD_Sym_Vec;
+  }
+};
+
+class InlineDoc : public AttributeDiff {
+public:
+  std::string InstallName;
+  std::vector<DiffOutput> DiffVec;
+  InlineDoc(StringRef InstName, std::vector<DiffOutput> Diff)
+      : AttributeDiff(AD_Inline_Doc), InstallName(InstName),
+        DiffVec(std::move(Diff)){};
+
+  static bool classof(const AttributeDiff *A) {
+    return A->getKind() == AD_Inline_Doc;
+  }
+};
+
+class DiffEngine {
+public:
+  DiffEngine(object::TapiUniversal *InputFileNameOne,
+             object::TapiUniversal *InputFileNameTwo)
+      : FileOne(InputFileNameOne), FileTwo(InputFileNameTwo){};
+  bool compareFiles();
+
+private:
+  object::TapiUniversal *FileOne;
+  object::TapiUniversal *FileTwo;
+
+  void printDifferences(std::vector<DiffOutput>, int);
+  std::vector<DiffOutput> findDifferences(MachO::InterfaceFile *,
+                                          MachO::InterfaceFile *);
+};
+
+} // namespace llvm
+
+#endif
 No newline at end of file

llvm/tools/llvm-tapi-diff/DiffEngine.cpp

+//===-- DiffEngine.cpp - Structural file comparison ------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines the implementation of the llvm-nm difference
+// engine, which structurally compares two tbd files. (To be updated)
+//
+//===----------------------------------------------------------------------===/
+#include "DiffEngine.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/TextAPI/InterfaceFile.h"
+#include "llvm/TextAPI/Target.h"
+
+using namespace llvm;
+using namespace MachO;
+using namespace object;
+
+bool checkSymbolEquality(llvm::MachO::InterfaceFile::const_symbol_range LHS,
+                         llvm::MachO::InterfaceFile::const_symbol_range RHS) {
+  if (std::distance(LHS.begin(), LHS.end()) !=
+      (std::distance(RHS.begin(), RHS.end())))
+    return false;
+  return std::equal(LHS.begin(), LHS.end(), RHS.begin(),
+                    [&](auto LHS, auto RHS) { return *LHS == *RHS; });
+}
+
+template <typename T, typename U, typename V>
+void addValToDiffVec(V Val, Target Targ, DiffOutput &Diff,
+                     InterfaceInputOrder Order) {
+  auto TargetVector = llvm::find_if(
+      Diff.DiffVec, [&](const std::unique_ptr<AttributeDiff> &RawTVec) {
+        if (T *TVec = dyn_cast<T>(RawTVec.get()))
+          return TVec->Targ == Targ;
+        return false;
+      });
+  if (TargetVector != Diff.DiffVec.end()) {
+    U NewTargetVec(Order, Val);
+    cast<T>(TargetVector->get())->DiffVec.push_back(NewTargetVec);
+  } else {
+    auto NewTargetVec = std::make_unique<T>(Targ);
+    U NewNameVec(Order, Val);
+    NewTargetVec->DiffVec.push_back(NewNameVec);
+    Diff.DiffVec.push_back(std::move(NewTargetVec));
+  }
+}
+
+DiffOutput getSingleAttrDiff(const std::vector<InterfaceFileRef> &IRefVec,
+                             std::string Name, InterfaceInputOrder Order) {
+  DiffOutput Diff(Name);
+  Diff.Kind = AD_Str_Vec;
+  for (const auto &IRef : IRefVec)
+    for (auto Targ : IRef.targets())
+      addValToDiffVec<DiffStrVec, DiffScalarVal<StringRef, AD_Diff_Scalar_Str>>(
+          IRef.getInstallName(), Targ, Diff, Order);
+  return Diff;
+}
+
+DiffOutput
+getSingleAttrDiff(const std::vector<std::pair<Target, std::string>> &PairVec,
+                  std::string Name, InterfaceInputOrder Order) {
+  DiffOutput Diff(Name);
+  Diff.Kind = AD_Str_Vec;
+  for (const auto &Pair : PairVec)
+    addValToDiffVec<DiffStrVec, DiffScalarVal<StringRef, AD_Diff_Scalar_Str>>(
+        StringRef(Pair.second), Pair.first, Diff, Order);
+  return Diff;
+}
+
+DiffOutput
+getSingleAttrDiff(llvm::MachO::InterfaceFile::const_symbol_range SymRange,
+                  std::string Name, InterfaceInputOrder Order) {
+  DiffOutput Diff(Name);
+  Diff.Kind = AD_Sym_Vec;
+  for (const auto *Sym : SymRange)
+    for (auto Targ : Sym->targets())
+      addValToDiffVec<DiffSymVec, SymScalar>(Sym, Targ, Diff, Order);
+  return Diff;
+}
+
+template <typename T>
+DiffOutput getSingleAttrDiff(T SingleAttr, std::string Attribute) {
+  DiffOutput Diff(Attribute);
+  Diff.Kind = SingleAttr.getKind();
+  Diff.DiffVec.push_back(std::make_unique<T>(SingleAttr));
+  return Diff;
+}
+
+std::vector<DiffOutput> getSingleIF(InterfaceFile *Interface,
+                                    InterfaceInputOrder Order) {
+  std::vector<DiffOutput> ReturnedOutput;
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(DiffScalarVal<StringRef, AD_Diff_Scalar_Str>(
+                            Order, Interface->getInstallName()),
+                        "Install Name"));
+  ReturnedOutput.push_back(getSingleAttrDiff(
+      DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+          Order, Interface->getCurrentVersion()),
+      "Current Version"));
+  ReturnedOutput.push_back(getSingleAttrDiff(
+      DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+          Order, Interface->getCompatibilityVersion()),
+      "Compatibility Version"));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(DiffScalarVal<uint8_t, AD_Diff_Scalar_Unsigned>(
+                            Order, Interface->getSwiftABIVersion()),
+                        "Swift ABI Version"));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(DiffScalarVal<bool, AD_Diff_Scalar_Bool>(
+                            Order, Interface->isInstallAPI()),
+                        "InstallAPI"));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(DiffScalarVal<bool, AD_Diff_Scalar_Bool>(
+                            Order, Interface->isTwoLevelNamespace()),
+                        "Two Level Namespace"));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(DiffScalarVal<bool, AD_Diff_Scalar_Bool>(
+                            Order, Interface->isApplicationExtensionSafe()),
+                        "Application Extension Safe"));
+  ReturnedOutput.push_back(getSingleAttrDiff(Interface->reexportedLibraries(),
+                                             "Reexported Libraries", Order));
+  ReturnedOutput.push_back(getSingleAttrDiff(Interface->allowableClients(),
+                                             "Allowable Clients", Order));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(Interface->umbrellas(), "Parent Umbrellas", Order));
+  ReturnedOutput.push_back(
+      getSingleAttrDiff(Interface->symbols(), "Symbols", Order));
+  if (!Interface->documents().empty())
+    for (auto Doc : Interface->documents()) {
+      DiffOutput Documents("Inlined Reexported Frameworks/Libraries");
+      Documents.Kind = AD_Inline_Doc;
+      Documents.DiffVec.push_back(std::make_unique<InlineDoc>(
+          InlineDoc(Doc->getInstallName(), getSingleIF(Doc.get(), Order))));
+      ReturnedOutput.push_back(std::move(Documents));
+    }
+  return ReturnedOutput;
+}
+
+void findAndAddDiff(const std::vector<InterfaceFileRef> &CollectedIRefVec,
+                    const std::vector<InterfaceFileRef> &LookupIRefVec,
+                    DiffOutput &Result, InterfaceInputOrder Order) {
+  Result.Kind = AD_Str_Vec;
+  for (const auto &IRef : CollectedIRefVec)
+    for (auto Targ : IRef.targets()) {
+      auto FoundIRef = llvm::find_if(LookupIRefVec, [&](const auto LIRef) {
+        auto FoundTarg = llvm::find(LIRef.targets(), Targ);
+        return (FoundTarg != LIRef.targets().end() &&
+                IRef.getInstallName() == LIRef.getInstallName());
+      });
+      if (FoundIRef == LookupIRefVec.end())
+        addValToDiffVec<DiffStrVec,
+                        DiffScalarVal<StringRef, AD_Diff_Scalar_Str>>(
+            IRef.getInstallName(), Targ, Result, Order);
+    }
+}
+
+void findAndAddDiff(
+    const std::vector<std::pair<Target, std::string>> &CollectedPairs,
+    const std::vector<std::pair<Target, std::string>> &LookupPairs,
+    DiffOutput &Result, InterfaceInputOrder Order) {
+  Result.Kind = AD_Str_Vec;
+  for (const auto &Pair : CollectedPairs) {
+    auto FoundPair = llvm::find(LookupPairs, Pair);
+    if (FoundPair == LookupPairs.end())
+      addValToDiffVec<DiffStrVec, DiffScalarVal<StringRef, AD_Diff_Scalar_Str>>(
+          StringRef(Pair.second), Pair.first, Result, Order);
+  }
+}
+
+void findAndAddDiff(
+    llvm::MachO::InterfaceFile::const_symbol_range CollectedSyms,
+    llvm::MachO::InterfaceFile::const_symbol_range LookupSyms,
+    DiffOutput &Result, InterfaceInputOrder Order) {
+  Result.Kind = AD_Sym_Vec;
+  for (const auto *Sym : CollectedSyms)
+    for (const auto Targ : Sym->targets()) {
+      auto FoundSym = llvm::find_if(LookupSyms, [&](const auto LSym) {
+        auto FoundTarg = llvm::find(LSym->targets(), Targ);
+        return (Sym->getName() == LSym->getName() &&
+                Sym->getKind() == LSym->getKind() &&
+                Sym->getFlags() == LSym->getFlags() &&
+                FoundTarg != LSym->targets().end());
+      });
+      if (FoundSym == LookupSyms.end())
+        addValToDiffVec<DiffSymVec, SymScalar>(Sym, Targ, Result, Order);
+    }
+}
+
+template <typename T>
+DiffOutput recordDifferences(T LHS, T RHS, std::string Attr) {
+  DiffOutput Diff(Attr);
+  if (LHS.getKind() == RHS.getKind()) {
+    Diff.Kind = LHS.getKind();
+    Diff.DiffVec.push_back(std::make_unique<T>(LHS));
+    Diff.DiffVec.push_back(std::make_unique<T>(RHS));
+  }
+  return Diff;
+}
+
+template <typename T>
+DiffOutput recordDifferences(const std::vector<T> &LHS,
+                             const std::vector<T> &RHS, std::string Attr) {
+  DiffOutput Diff(Attr);
+  Diff.Kind = AD_Str_Vec;
+  findAndAddDiff(LHS, RHS, Diff, lhs);
+  findAndAddDiff(RHS, LHS, Diff, rhs);
+  return Diff;
+}
+
+DiffOutput recordDifferences(llvm::MachO::InterfaceFile::const_symbol_range LHS,
+                             llvm::MachO::InterfaceFile::const_symbol_range RHS,
+                             std::string Attr) {
+  DiffOutput Diff(Attr);
+  Diff.Kind = AD_Sym_Vec;
+  findAndAddDiff(LHS, RHS, Diff, lhs);
+  findAndAddDiff(RHS, LHS, Diff, rhs);
+  return Diff;
+}
+
+std::vector<DiffOutput> DiffEngine::findDifferences(InterfaceFile *IF1,
+                                                    InterfaceFile *IF2) {
+  std::vector<DiffOutput> ReturnedOutput;
+  if (IF1->getInstallName() != IF2->getInstallName())
+    ReturnedOutput.push_back(recordDifferences(
+        DiffScalarVal<StringRef, AD_Diff_Scalar_Str>(lhs,
+                                                     IF1->getInstallName()),
+        DiffScalarVal<StringRef, AD_Diff_Scalar_Str>(rhs,
+                                                     IF2->getInstallName()),
+        "Install Name"));
+
+  if (IF1->getCurrentVersion() != IF2->getCurrentVersion())
+    ReturnedOutput.push_back(recordDifferences(
+        DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+            lhs, IF1->getCurrentVersion()),
+        DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+            rhs, IF2->getCurrentVersion()),
+        "Current Version"));
+  if (IF1->getCompatibilityVersion() != IF2->getCompatibilityVersion())
+    ReturnedOutput.push_back(recordDifferences(
+        DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+            lhs, IF1->getCompatibilityVersion()),
+        DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>(
+            rhs, IF2->getCompatibilityVersion()),
+        "Compatibility Version"));
+  if (IF1->getSwiftABIVersion() != IF2->getSwiftABIVersion())
+    ReturnedOutput.push_back(
+        recordDifferences(DiffScalarVal<uint8_t, AD_Diff_Scalar_Unsigned>(
+                              lhs, IF1->getSwiftABIVersion()),
+                          DiffScalarVal<uint8_t, AD_Diff_Scalar_Unsigned>(
+                              rhs, IF2->getSwiftABIVersion()),
+                          "Swift ABI Version"));
+  if (IF1->isInstallAPI() != IF2->isInstallAPI())
+    ReturnedOutput.push_back(recordDifferences(
+        DiffScalarVal<bool, AD_Diff_Scalar_Bool>(lhs, IF1->isInstallAPI()),
+        DiffScalarVal<bool, AD_Diff_Scalar_Bool>(rhs, IF2->isInstallAPI()),
+        "InstallAPI"));
+
+  if (IF1->isTwoLevelNamespace() != IF2->isTwoLevelNamespace())
+    ReturnedOutput.push_back(recordDifferences(
+        DiffScalarVal<bool, AD_Diff_Scalar_Bool>(lhs,
+                                                 IF1->isTwoLevelNamespace()),
+        DiffScalarVal<bool, AD_Diff_Scalar_Bool>(rhs,
+                                                 IF2->isTwoLevelNamespace()),
+        "Two Level Namespace"));
+
+  if (IF1->isApplicationExtensionSafe() != IF2->isApplicationExtensionSafe())
+    ReturnedOutput.push_back(
+        recordDifferences(DiffScalarVal<bool, AD_Diff_Scalar_Bool>(
+                              lhs, IF1->isApplicationExtensionSafe()),
+                          DiffScalarVal<bool, AD_Diff_Scalar_Bool>(
+                              rhs, IF2->isApplicationExtensionSafe()),
+                          "Application Extension Safe"));
+
+  if (IF1->reexportedLibraries() != IF2->reexportedLibraries())
+    ReturnedOutput.push_back(recordDifferences(IF1->reexportedLibraries(),
+                                               IF2->reexportedLibraries(),
+                                               "Reexported Libraries"));
+
+  if (IF1->allowableClients() != IF2->allowableClients())
+    ReturnedOutput.push_back(recordDifferences(
+        IF1->allowableClients(), IF2->allowableClients(), "Allowable Clients"));
+
+  if (IF1->umbrellas() != IF2->umbrellas())
+    ReturnedOutput.push_back(recordDifferences(
+        IF1->umbrellas(), IF2->umbrellas(), "Parent Umbrellas"));
+
+  if (!checkSymbolEquality(IF1->symbols(), IF2->symbols()))
+    ReturnedOutput.push_back(
+        recordDifferences(IF1->symbols(), IF2->symbols(), "Symbols"));
+
+  if (IF1->documents() != IF2->documents()) {
+    DiffOutput Docs("Inlined Reexported Frameworks/Libraries");
+    Docs.Kind = AD_Inline_Doc;
+    std::vector<StringRef> DocsInserted;
+    // Iterate through inline frameworks/libraries from interface file and find
+    // match based on install name.
+    for (auto Doc1 : IF1->documents()) {
+      auto Pair = llvm::find_if(IF2->documents(), [&](const auto &Doc2) {
+        return (Doc1->getInstallName() == Doc2->getInstallName());
+      });
+      // If a match found, recursively get differences between the pair.
+      if (Pair != IF2->documents().end()) {
+        InlineDoc PairDiff = InlineDoc(
+            Doc1->getInstallName(), findDifferences(Doc1.get(), Pair->get()));
+        if (!PairDiff.DiffVec.empty())
+          Docs.DiffVec.push_back(
+              std::make_unique<InlineDoc>(std::move(PairDiff)));
+      }
+      // If a match is not found, get attributes from single item.
+      else
+        Docs.DiffVec.push_back(std::make_unique<InlineDoc>(
+            InlineDoc(Doc1->getInstallName(), getSingleIF(Doc1.get(), lhs))));
+      DocsInserted.push_back(Doc1->getInstallName());
+    }
+    for (auto Doc2 : IF2->documents()) {
+      auto WasGathered =
+          llvm::find_if(DocsInserted, [&](const auto &GatheredDoc) {
+            return (GatheredDoc == Doc2->getInstallName());
+          });
+      if (WasGathered == DocsInserted.end())
+        Docs.DiffVec.push_back(std::make_unique<InlineDoc>(
+            InlineDoc(Doc2->getInstallName(), getSingleIF(Doc2.get(), rhs))));
+    }
+    if (!Docs.DiffVec.empty()) {
+      ReturnedOutput.push_back(std::move(Docs));
+    }
+  }
+  return ReturnedOutput;
+}
+
+template <typename T>
+void printSingleVal(std::string Indent, DiffOutput &Attr, raw_ostream &OS) {
+  if (Attr.DiffVec.empty())
+    return;
+  OS << Indent << Attr.Name << "\n";
+  for (auto &RawItem : Attr.DiffVec)
+    if (T *Item = dyn_cast<T>(RawItem.get()))
+      Item->print(OS, Indent);
+}
+
+template <typename T>
+void printVecVal(std::string Indent, DiffOutput &Attr, raw_ostream &OS) {
+  if (Attr.DiffVec.empty())
+    return;
+  OS << Indent << Attr.Name << "\n";
+  for (auto &Item : Attr.DiffVec)
+    if (T *Vec = dyn_cast<T>(Item.get())) {
+      OS << Indent << "\t" << getTargetTriple(Vec->Targ) << "\n";
+      for (auto &Item : Vec->DiffVec)
+        Item.print(OS, Indent);
+    }
+}
+
+template <>
+void printVecVal<DiffSymVec>(std::string Indent, DiffOutput &Attr,
+                             raw_ostream &OS) {
+  if (Attr.DiffVec.empty())
+    return;
+  OS << Indent << Attr.Name << "\n";
+  for (auto &RawSymVec : Attr.DiffVec)
+    if (DiffSymVec *SymVec = dyn_cast<DiffSymVec>(RawSymVec.get())) {
+      OS << Indent << "\t" << getTargetTriple(SymVec->Targ) << "\n";
+      for (auto &Item : SymVec->DiffVec)
+        Item.print(OS, Indent, SymVec->Targ);
+    }
+}
+
+void DiffEngine::printDifferences(std::vector<DiffOutput> Diffs,
+                                  int IndentCounter) {
+  std::string Indent = std::string(IndentCounter, '\t');
+  raw_ostream &OS = outs();
+  for (auto &Attr : Diffs) {
+    switch (Attr.Kind) {
+    case AD_Diff_Scalar_Str:
+      if (IndentCounter == 0)
+        printSingleVal<DiffScalarVal<StringRef, AD_Diff_Scalar_Str>>(Indent,
+                                                                     Attr, OS);
+      break;
+    case AD_Diff_Scalar_PackedVersion:
+      printSingleVal<
+          DiffScalarVal<PackedVersion, AD_Diff_Scalar_PackedVersion>>(Indent,
+                                                                      Attr, OS);
+      break;
+    case AD_Diff_Scalar_Unsigned:
+      printSingleVal<DiffScalarVal<uint8_t, AD_Diff_Scalar_Unsigned>>(Indent,
+                                                                      Attr, OS);
+      break;
+    case AD_Diff_Scalar_Bool:
+      printSingleVal<DiffScalarVal<bool, AD_Diff_Scalar_Bool>>(Indent, Attr,
+                                                               OS);
+      break;
+    case AD_Str_Vec:
+      printVecVal<DiffStrVec>(Indent, Attr, OS);
+      break;
+    case AD_Sym_Vec:
+      printVecVal<DiffSymVec>(Indent, Attr, OS);
+      break;
+    case AD_Inline_Doc:
+      if (!Attr.DiffVec.empty()) {
+        OS << Indent << Attr.Name << "\n";
+        for (auto &Item : Attr.DiffVec)
+          if (InlineDoc *Doc = dyn_cast<InlineDoc>(Item.get()))
+            if (!Doc->DiffVec.empty()) {
+              OS << Indent << "\t" << Doc->InstallName << "\n";
+              printDifferences(std::move(Doc->DiffVec), 2);
+            }
+      }
+      break;
+    }
+  }
+}
+
+bool DiffEngine::compareFiles() {
+  auto *IF1 = FileOne->getInterfaceFile();
+  auto *IF2 = FileTwo->getInterfaceFile();
+  if (*IF1 == *IF2)
+    return false;
+  outs() << "< " << std::string(IF1->getPath().data()) << "\n> "
+         << std::string(IF2->getPath().data()) << "\n\n";
+  std::vector<DiffOutput> Diffs = findDifferences(IF1, IF2);
+  printDifferences(std::move(Diffs), 0);
+  return true;
+}

llvm/tools/llvm-tapi-diff/llvm-tapi-diff.cpp

+//===-- llvm-nm-diff.cpp - symbol table comparator command-line driver ---*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the command-line driver for the llvm-nm difference engine.
+//
+//===----------------------------------------------------------------------===//
+#include "DiffEngine.h"
+#include "llvm/Object/TapiUniversal.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/InitLLVM.h"
+
+using namespace llvm;
+using namespace MachO;
+using namespace object;
+
+namespace {
+cl::OptionCategory NMCat("llvm-tapi-diff Options");
+cl::opt<std::string> InputFileNameOne(cl::Positional, cl::desc("<First File>"),
+                                      cl::cat(NMCat));
+cl::opt<std::string> InputFileNameTwo(cl::Positional, cl::desc("<Second File>"),
+                                      cl::cat(NMCat));
+} // anonymous namespace
+
+static bool error(std::error_code EC, std::string Path) {
+  if (EC) {
+    errs() << Path << ": " << EC.message() << "\n";
+    return true;
+  }
+  return false;
+}
+
+static void error(llvm::Error E, std::string FileName) {
+  logAllUnhandledErrors(std::move(E), errs(), (FileName + ": "));
+}
+
+std::unique_ptr<Binary> convertFileToBinary(std::string &Filename) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
+      MemoryBuffer::getFileOrSTDIN(Filename);
+  if (error(BufferOrErr.getError(), Filename))
+    return {};
+
+  Expected<std::unique_ptr<Binary>> BinaryOrErr =
+      createBinary(BufferOrErr.get()->getMemBufferRef());
+  if (!BinaryOrErr) {
+    error(BinaryOrErr.takeError(), Filename);
+    return {};
+  }
+  return std::move(*BinaryOrErr);
+}
+
+int main(int argc, char **argv) {
+  InitLLVM X(argc, argv);
+  cl::HideUnrelatedOptions(NMCat);
+  cl::ParseCommandLineOptions(
+      argc, argv,
+      "This tool will compare two tbd files and return the "
+      "differences in those files.");
+  if (InputFileNameOne.empty() || InputFileNameTwo.empty()) {
+    cl::PrintHelpMessage();
+    return 1;
+  }
+
+  auto BinOne = convertFileToBinary(InputFileNameOne);
+  auto BinTwo = convertFileToBinary(InputFileNameTwo);
+
+  if (!BinOne || !BinTwo)
+    return 1;
+  if (TapiUniversal *FileOne = dyn_cast<TapiUniversal>(BinOne.get()))
+    if (TapiUniversal *FileTwo = dyn_cast<TapiUniversal>(BinTwo.get())) {
+      DiffEngine Engine(FileOne, FileTwo);
+      return Engine.compareFiles();
+    }
+  return 1;
+}