Implement Pass and Dialect plugins for mlir-opt

[fmorac]

Summary

Implementation of Pass and Dialect Plugins that mirrors LLVM Pass Plugin implementation from the new pass manager.

Currently the implementation only supports using the pass-pipeline option for adding passes. This restriction is imposed by the PassPipelineCLParser variable in mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:114 that loads the parse options statically before parsing the cmd line args.

mlir-opt stanalone-plugin.mlir --load-dialect-plugin=lib/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)"

[makslevental]

I don't have a lot substantial to say other than that this looks very viable to me (including the DialectPlugin). Bravo on an excellent job tracking everything down and well-manicured PR.

mlir/tools/mlir-opt/CMakeLists.txt

88

This is the key thing - good job tracking it down.

[rriddle]

Can you please reupload the full diff? The newest diff just looks like formatting changes.

[fmorac]

In D147053#4228125, @rriddle wrote:

Can you please reupload the full diff? The newest diff just looks like formatting changes.

Sure, don't know why I thought if I updated the patch it would also apply the first one.

[mehdi_amini]

Nice!

Does it work on MacOS and Windows?

mlir/examples/standalone/test/Standalone/standalone-plugin.mlir

2

Can you make an example of the load-pass-plugin as well?

mlir/include/mlir/IR/DialectPlugin.h

34 ↗

(On Diff #509088)

Seems like unfortunate copy/paste: MLIR_PLUGIN_API_VERSION

mlir/include/mlir/Pass/PassPlugin.h

32 ↗

(On Diff #509088)

I'm wondering if this is really that useful to version the plugin API when for all practical consideration we are rev-locked at the git-hash level almost. Any change to MLIR can break the plugin.

mlir/lib/Pass/PassPlugin.cpp

53 ↗

(On Diff #509088)

Can you make sure there is a newline here and in the other files?

mlir/lib/Tools/mlir-opt/MlirOptMain.cpp

112

Is the std::addressof doing anything different than & here?

127

Please document these

138–140

Please replace this one instead of adding a new one, otherwise we expose to the command line some options that we actually ignore.

144

Can't you just write clOptionsConfig->setDialectPluginsCallback(registry); here?

176

I understand why you made setDialectPluginsCallback a separate step (it needs the registry), but why this one?

180–182

I may miss something, but I'm not sure why the detour here

[fmorac]

In D147053#4228776, @mehdi_amini wrote:

Nice!

Does it work on MacOS and Windows?

@makslevental is testing it on MacOS and I know it builds on Windows, but I don't have a Windows box to test it.

mlir/examples/standalone/test/Standalone/standalone-plugin.mlir

2

Sure.

mlir/include/mlir/IR/DialectPlugin.h

34 ↗

(On Diff #509088)

Will change it, because I missed it.

mlir/include/mlir/Pass/PassPlugin.h

32 ↗

(On Diff #509088)

I decided to keep it to state that MLIR haven't modified the API plugin registration contract, so users know that the mechanism remains unchanged, and I would think this API is going to be more stable than many other components. But we can remove it.

mlir/lib/Pass/PassPlugin.cpp

53 ↗

(On Diff #509088)

Sure.

mlir/lib/Tools/mlir-opt/MlirOptMain.cpp

112

It's necessary because cl::opt overrides operator&.

127

Will do.

138–140

Ok I'll change it to:

void registerCLOptions(DialectRegistry &registry);

144

Yes, I was unsure it -> initialized the object, but I just checked and it does.

176

I saw the structure of the constructor and I preferred to outline the code so the body of the constructor remained cleaner, but I can inline it.

180–182

Don't know either, there's no need for it, I'll change it.

[rriddle]

mlir/examples/standalone/lib/Standalone/StandalonePasses.cpp

17–18

22–37

These should generally get defined within an anonymous namespace in the file

44–45

46

It'd be cleaner to signalPassFailure here .

49–50

mlir/examples/standalone/standalone-plugin/standalone-plugin.cpp

25–31

Why define this in a separate function, instead of inline below?

40–43

Same here

mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir

5

Can you use 2-space indents here?

mlir/examples/standalone/test/Standalone/standalone-plugin.mlir

5

Same here

mlir/include/mlir/IR/DialectPlugin.h

27 ↗

(On Diff #509309)

35 ↗

(On Diff #509309)

Please use camelCase for variable names

58 ↗

(On Diff #509309)

Why not StringRef here? Also please use camelCase for variable names.

103–104 ↗

(On Diff #509309)

struct results in C always feel problematic for composability, did you consider using out-param appraoch?

mlir/include/mlir/Pass/PassPlugin.h

43 ↗

(On Diff #509309)

Same comments as the other file, e.g. re: camelCase variables.

[fmorac]

The build is failing on Windows, due to an unrelated flang test see this other review: https://reviews.llvm.org/D147262 .

mlir/examples/standalone/standalone-plugin/standalone-plugin.cpp

25–31

Traditionally I've seen LLVM pass plugins split like that, but there's no good reason to not inlining them, so I did.

mlir/include/mlir/IR/DialectPlugin.h

58 ↗

(On Diff #509309)

The function internally requires the string to be null terminated, I could create the string inside the function, however I consider this would be an extra step.

103–104 ↗

(On Diff #509309)

Not really because the struct is simple and LLVM do it like this for their plugins. But I'm open to change it.

[devajithvs]

In D147053#4241021, @fmorac wrote:

The build is failing on Windows, due to an unrelated flang test see this other review: https://reviews.llvm.org/D147262 .

The build seems to be working fine here. I was wondering how you fixed the windows build issue.

[fmorac]

When I submitted the last diff Phabricator applied the patch on the latest commit at the time of submission, and apparently the flang bug had been resolved by then.

[fmorac]

Hi could someone help me land this commit? I forgot to signoff, my info is: "Fabian Mora <[e-mail]>" or "Fabian Mora <[e-mail]>". Thank you!

[jpienaar]

This seems to be causing failures

https://buildkite.com/llvm-project/upstream-bazel/builds/58808#0187576a-9661-42f7-b6a5-ad4b32599ea3

[stellaraccident]

In D147053#4249164, @jpienaar wrote:

This seems to be causing failures

https://buildkite.com/llvm-project/upstream-bazel/builds/58808#0187576a-9661-42f7-b6a5-ad4b32599ea3

Don't we fix forward for bazel failures?

[jpienaar]

In D147053#4249262, @stellaraccident wrote:

In D147053#4249164, @jpienaar wrote:

This seems to be causing failures

https://buildkite.com/llvm-project/upstream-bazel/builds/58808#0187576a-9661-42f7-b6a5-ad4b32599ea3

Don't we fix forward for bazel failures?

I apologize - I saw the failure and didn't realize it was bazel specific and didn't want to leave broken. My bad, let me reland.

[mehdi_amini]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

It's not clear to me why this file is in "IR"? Seems like something that should be part of the OptMainLib?

mlir/lib/Pass/PassPlugin.cpp

53 ↗

(On Diff #511449)

(same for this file)

[fmorac]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

When I was writing it I wasn't sure where to put these files, however my thinking process was that this functionality might be extended in the future beyond mlir-opt. For example mlir-translate could be modified to load dialect plugins, thus enabling plugin conversions and dialects at runtime. Also, these files in LLVM are kept in similar places, though this particular file has no equivalent in LLVM so with this one in particular I was unsure.

[rriddle]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

I'm not convinced we should be following LLVM here. Let's move these out of IR/. OptMainLib seems fine initially, we can hone in on a better place in followups.

[mehdi_amini]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

To me these are clearly not functionality of the IR or the Pass system. They are really command line tooling, you can also create a new library under the Tools/ folder if it needs to be shared.

[fmorac]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

Sure, what do you think about Tools/Plugins ?

[mehdi_amini]

mlir/include/mlir/IR/DialectPlugin.h

106 ↗

(On Diff #511449)

That would be fine with me

[fmorac]

Moved the Plugin related files to include/mlir/Tools/Plugins and lib/Tools/Plugins, and added the MLIRPluginsLib library.

[mehdi_amini]

The standalone test is now broken on my Mac:

Failed to load dialect plugin from '/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so'. Request ignored.
Expected<T> must be checked before access or destruction.
Unchecked Expected<T> contained error:
Could not load library '/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so': dlopen(/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so, 0x0009): tried: '/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so' (no such file), '/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so' (no such file)PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /build/bin/mlir-opt /mlir/examples/standalone/test/Standalone/standalone-plugin.mlir --load-dialect-plugin=/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so --pass-pipeline=builtin.module(standalone-switch-bar-foo)
 #0 0x0000000104d3ce98 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/build/bin/mlir-opt+0x1002a0e98)
 #1 0x0000000104d3b14c llvm::sys::RunSignalHandlers() (/build/bin/mlir-opt+0x10029f14c)
 #2 0x0000000104d3d538 SignalHandler(int) (/build/bin/mlir-opt+0x1002a1538)
 #3 0x00000001ae5982a4 (/usr/lib/system/libsystem_platform.dylib+0x1803fc2a4)
 #4 0x00000001ae569cec (/usr/lib/system/libsystem_pthread.dylib+0x1803cdcec)
 #5 0x00000001ae4a22c8 (/usr/lib/system/libsystem_c.dylib+0x1803062c8)
 #6 0x0000000106bac7f0 llvm::Expected<mlir::DialectPlugin>::fatalUncheckedExpected() const (/build/bin/mlir-opt+0x1021107f0)
 #7 0x0000000106bac6d4 std::__1::__function::__func<(anonymous namespace)::MlirOptMainConfigCLOptions::setDialectPluginsCallback(mlir::DialectRegistry&)::$_3, std::__1::allocator<(anonymous namespace)::MlirOptMainConfigCLOptions::setDialectPluginsCallback(mlir::DialectRegistry&)::$_3>, void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)>::operator()(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&) (/build/bin/mlir-opt+0x1021106d4)
 #8 0x0000000106baeb00 llvm::cl::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, bool, llvm::cl::parser<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>>::handleOccurrence(unsigned int, llvm::StringRef, llvm::StringRef) (/build/bin/mlir-opt+0x102112b00)
 #9 0x0000000104ca42cc llvm::cl::ParseCommandLineOptions(int, char const* const*, llvm::StringRef, llvm::raw_ostream*, char const*, bool) (/build/bin/mlir-opt+0x1002082cc)
#10 0x0000000106babc54 mlir::MlirOptMain(int, char**, llvm::StringRef, mlir::DialectRegistry&, bool) (build/bin/mlir-opt+0x10210fc54)
#11 0x0000000104a9e414 main (build/bin/mlir-opt+0x100002414)
#12 0x00000001ae23fe50

Thoughts on this?

[fmorac]

I believe it's caused by the first line in mlir/examples/standalone/test/Standalone/standalone-plugin.mlir :

// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s

so it uses the wrong extension. I don't have a mac to further test it (I might be able to borrow one), so the quickest fix is to deactivate the test on darwin.

[makslevental]

In D147053#4256907, @mehdi_amini wrote:

The standalone test is now broken on my Mac:

Failed to load dialect plugin from '/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.so'. Request ignored.
...

Thoughts on this?

Should be libStandalonePlugin.dylib right?

[makslevental]

In D147053#4256914, @fmorac wrote:

I believe it's caused by the first line in mlir/examples/standalone/test/Standalone/standalone-plugin.mlir :

// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s

so it uses the wrong extension. I don't have a mac to further test it (I might be able to borrow one), so the quickest fix is to deactivate the test on darwin.

Looks like it should be

// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s

according to https://github.com/llvm/llvm-project/blob/c98372725b5a3e56bb1c003ef9981d644b79bce7/mlir/test/Integration/Dialect/SparseTensor/CPU/concatenate_dim_1.mlir#L6

[fmorac]

In D147053#4256929, @makslevental wrote:

Looks like it should be

// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s

according to https://github.com/llvm/llvm-project/blob/c98372725b5a3e56bb1c003ef9981d644b79bce7/mlir/test/Integration/Dialect/SparseTensor/CPU/concatenate_dim_1.mlir#L6

yeah you're right, also I believe you said there was an extra flag need it. What's the way to solve this, do I just update the diff or do I need to create a new review?

[mehdi_amini]

We need a new review (you should only reuse a review if the commit is reverted).

There are a few different issues though:

• the assert is a problem: we shouldn't assert because it indicates an issue with the error checking.
• I tried the solution you mentioned, but we're still missing something in how we link the plugin I think:

******************** TEST 'STANDALONE :: Standalone/standalone-pass-plugin.mlir' FAILED ********************
Script:
--
: 'RUN: at line 1';   /Users/mehdi_amini/projects/upstream/build/bin/mlir-opt /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir --load-pass-plugin=/Users/mehdi_amini/projects/upstream/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.dylib --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | /Users/mehdi_amini/projects/upstream/build/bin/FileCheck /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
--
Exit Code: 2

Command Output (stderr):
--
<unknown>:0: error: MLIR Textual PassPipeline Parser:1:1: error: 'standalone-switch-bar-foo' does not refer to a registered pass or pass pipeline
standalone-switch-bar-foo
^

FileCheck error: '<stdin>' is empty.
FileCheck command line:  /Users/mehdi_amini/projects/upstream/build/bin/FileCheck /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir

--

********************
Testing:  0.. 10.. 20.. 30.. 40
FAIL: STANDALONE :: Standalone/standalone-plugin.mlir (7 of 7)
******************** TEST 'STANDALONE :: Standalone/standalone-plugin.mlir' FAILED ********************
Script:
--
: 'RUN: at line 1';   /Users/mehdi_amini/projects/upstream/build/bin/mlir-opt /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir --load-dialect-plugin=/Users/mehdi_amini/projects/upstream/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.dylib --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | /Users/mehdi_amini/projects/upstream/build/bin/FileCheck /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
--
Exit Code: 2

Command Output (stderr):
--
LLVM ERROR: can't create Attribute 'mlir::StringAttr' because storage uniquer isn't initialized: the dialect was likely not loaded, or the attribute wasn't added with addAttributes<...>() in the Dialect::initialize() method.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /Users/mehdi_amini/projects/upstream/build/bin/mlir-opt /Users/mehdi_amini/projects/upstream/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir --load-dialect-plugin=/Users/mehdi_amini/projects/upstream/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.dylib --pass-pipeline=builtin.module(standalone-switch-bar-foo)
1.	MLIR Parser: custom op parser 'builtin.module'
2.	MLIR Parser: custom op parser 'func.func'
 #0 0x00000001028b0e98 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/Users/mehdi_amini/projects/upstream/build/bin/mlir-opt+0x1002a0e98)
 #1 0x00000001028af14c llvm::sys::RunSignalHandlers() (/Users/mehdi_amini/projects/upstream/build/bin/mlir-opt+0x10029f14c)
 #2 0x00000001028b1538 SignalHandler(int) (/Users/mehdi_amini/projects/upstream/build/bin/mlir-opt+0x1002a1538)
 #3 0x00000001ae5982a4 (/usr/lib/system/libsystem_platform.dylib+0x1803fc2a4)
 #4 0x00000001ae569cec (/usr/lib/system/libsystem_pthread.dylib+0x1803cdcec)
 #5 0x00000001ae4a22c8 (/usr/lib/system/libsystem_c.dylib+0x1803062c8)
 #6 0x000000010a3dba50 llvm::report_fatal_error(llvm::Twine const&, bool) (/Users/mehdi_amini/projects/upstream/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.dylib+0x4fa50)
 #7 0x000000010a4b4498 bool llvm::function_ref<bool (mlir::StorageUniquer::BaseStorage const*)>::callback_fn<mlir::detail::StringAttrStorage* mlir::StorageUniquer::get<mlir::detail::StringAttrStorage, llvm::StringRef&, mlir::NoneType&>(llvm::function_ref<void (mlir::detail::StringAttrStorage*)>, mlir::TypeID, llvm::StringRef&, mlir::NoneType&)::'lambda'(mlir::StorageUniquer::BaseStorage const*)>(long, mlir::StorageUniquer::BaseStorage const*) (/Users/mehdi_amini/projects/upstream/build/tools/mlir/test/Examples/standalone/lib/libStandalonePlugin.dylib+0x128498)

[mehdi_amini]

The patch FYI:

diff --git a/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir b/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
index 5af4b3d92e34..868e22fe03bb 100644
--- a/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
+++ b/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s --load-pass-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+// RUN: mlir-opt %s --load-pass-plugin=%standalone_libs/libStandalonePlugin%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
 
 module {
   // CHECK-LABEL: func @foo()
diff --git a/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir b/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
index 3f935db8910c..0bdbfb50334e 100644
--- a/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
+++ b/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
 
 module {
   // CHECK-LABEL: func @foo()
diff --git a/mlir/examples/standalone/test/lit.cfg.py b/mlir/examples/standalone/test/lit.cfg.py
index 3e4ceee3865c..601ac8f769f9 100644
--- a/mlir/examples/standalone/test/lit.cfg.py
+++ b/mlir/examples/standalone/test/lit.cfg.py
@@ -30,6 +30,7 @@ config.test_source_root = os.path.dirname(__file__)
 config.test_exec_root = os.path.join(config.standalone_obj_root, 'test')
 
 config.substitutions.append(('%PATH%', config.environment['PATH']))
+config.substitutions.append(('%shlibext', config.llvm_shlib_ext))
 
 llvm_config.with_system_environment(
     ['HOME', 'INCLUDE', 'LIB', 'TMP', 'TEMP'])
diff --git a/mlir/examples/standalone/test/lit.site.cfg.py.in b/mlir/examples/standalone/test/lit.site.cfg.py.in
index 9a81c6b48343..eae93d0b122e 100644
--- a/mlir/examples/standalone/test/lit.site.cfg.py.in
+++ b/mlir/examples/standalone/test/lit.site.cfg.py.in
@@ -4,6 +4,7 @@ config.llvm_tools_dir = lit_config.substitute("@LLVM_TOOLS_DIR@")
 config.mlir_obj_dir = "@MLIR_BINARY_DIR@"
 config.enable_bindings_python = @MLIR_ENABLE_BINDINGS_PYTHON@
 config.standalone_obj_root = "@STANDALONE_BINARY_DIR@"
+config.llvm_shlib_ext = "@SHLIBEXT@"
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)

[fmorac]

In D147053#4256966, @mehdi_amini wrote:

We need a new review (you should only reuse a review if the commit is reverted).

There are a few different issues though:

• the assert is a problem: we shouldn't assert because it indicates an issue with the error checking.
• I tried the solution you mentioned, but we're still missing something in how we link the plugin I think:

I think @makslevental made it work by changing mlir/examples/standalone/standalone-plugin/CMakeLists.txt :

get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
set(LIBS
        MLIRStandalone
        )

add_mlir_dialect_library(StandalonePlugin
        SHARED
        standalone-plugin.cpp

        DEPENDS
        MLIRStandalone
        )

llvm_update_compile_flags(StandalonePlugin)
target_link_libraries(StandalonePlugin PRIVATE ${LIBS} "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")

mlir_check_all_link_libraries(StandalonePlugin)

I'll create the new review with both of these changes.

[mehdi_amini]

It does not work for me, I get the same result. I also got a warning while building: ld: warning: -undefined dynamic_lookup may not work with chained fixups

[fmorac]

In D147053#4256975, @mehdi_amini wrote:

It does not work for me, I get the same result. I also got a warning while building: ld: warning: -undefined dynamic_lookup may not work with chained fixups

I know he managed to get it to work on Mac, so there must be another flag that it's missing,, I think it works with shared libs. Officially LLVM Plugins are only supported on linux, because it's the only platform in which they reliably work, so I'll try to figure out what's missing, but maybe we should put a disclaimer and disable the test for non linux platforms even when we find the right flags.

[makslevental]

This does the trick for me

diff --git a/mlir/examples/standalone/lib/Standalone/CMakeLists.txt b/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
index 0e2d043665c3..4193bfda83e4 100644
--- a/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
+++ b/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
@@ -4,15 +4,15 @@ add_mlir_dialect_library(MLIRStandalone
         StandaloneOps.cpp
         StandalonePasses.cpp
 
         ADDITIONAL_HEADER_DIRS
         ${PROJECT_SOURCE_DIR}/include/Standalone
 
         DEPENDS
         MLIRStandaloneOpsIncGen
         MLIRStandalonePassesIncGen
 
-	LINK_LIBS PUBLIC
-	MLIRIR
-        MLIRInferTypeOpInterface
-        MLIRFuncDialect
+#		LINK_LIBS PUBLIC
+#		MLIRIR
+#        MLIRInferTypeOpInterface
+#        MLIRFuncDialect
 	)
diff --git a/mlir/examples/standalone/standalone-plugin/CMakeLists.txt b/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
index 961a3ea2c906..0c28a2e52a9f 100644
--- a/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
+++ b/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
@@ -1,22 +1,22 @@
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
 set(LIBS
-        MLIRIR
-        MLIRPass
-        MLIRPluginsLib
+#        MLIRIR
+#        MLIRPass
+#        MLIRPluginsLib
         MLIRStandalone
-        MLIRTransformUtils
+#        MLIRTransformUtils
         )
 
 add_mlir_dialect_library(StandalonePlugin
         SHARED
         standalone-plugin.cpp
 
         DEPENDS
         MLIRStandalone
         )
 
 llvm_update_compile_flags(StandalonePlugin)
-target_link_libraries(StandalonePlugin PRIVATE ${LIBS})
+target_link_libraries(StandalonePlugin PRIVATE ${LIBS} "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
 
 mlir_check_all_link_libraries(StandalonePlugin)

Key thing being not linking *anything* in mlir/examples/standalone/lib/Standalone/CMakeLists.txt (was getting "pass is not registered" before I made that change).

I don't know the right way to wire this up - I guess something needs to be a LLVM_ATTRIBUTE_WEAK symbol but it would be around mlir::standalone::registerPasses and that's in generated code.

[mehdi_amini]

Ah yes clearly the plugins shouldn't statically link anything and resolve all of their symbols through the main binary I believe.

(I don't really follow how you'd want to involve a "weak" annotation)

[makslevental]

In D147053#4257141, @mehdi_amini wrote:

(I don't really follow how you'd want to involve a "weak" annotation)

just purely going off of the wiki definition (and following along with @fmorac's use of them in standalone-plugin.cpp)

During linking, a strong symbol can override a weak symbol of the same name.

So I was imagining some situation where the symbols around e.g. StorageUniquer and mlir::Pass were marked weak and thus would work in cases where that code does need to be statically linked and alternatively would be overriden by strong symbols in mlir-opt for plugins. But maybe I've completely misunderstood the point of that attribute. And anyway it's not workable since it would take changing how stuff is generated so I guess CMake hacking is the only way?

[fmorac]

In D147053#4257153, @makslevental wrote:

So I was imagining some situation where the symbols around e.g. StorageUniquer and mlir::Pass were marked weak and thus would work in cases where that code does need to be statically linked and alternatively would be overriden by strong symbols in mlir-opt for plugins. But maybe I've completely misunderstood the point of that attribute. And anyway it's not workable since it would take changing how stuff is generated so I guess CMake hacking is the only way?

I think the best route is to modify those CMakes. Here's a full patch (It works on Linux):

diff --git a/mlir/examples/standalone/lib/Standalone/CMakeLists.txt b/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
index 0e2d043665c3..54fab25bcf52 100644
--- a/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
+++ b/mlir/examples/standalone/lib/Standalone/CMakeLists.txt
@@ -1,3 +1,18 @@
+if (APPLE)
+add_mlir_dialect_library(MLIRStandalone
+        StandaloneTypes.cpp
+        StandaloneDialect.cpp
+        StandaloneOps.cpp
+        StandalonePasses.cpp
+
+        ADDITIONAL_HEADER_DIRS
+        ${PROJECT_SOURCE_DIR}/include/Standalone
+
+        DEPENDS
+        MLIRStandaloneOpsIncGen
+        MLIRStandalonePassesIncGen
+	)
+else()
 add_mlir_dialect_library(MLIRStandalone
         StandaloneTypes.cpp
         StandaloneDialect.cpp
@@ -16,3 +31,4 @@ add_mlir_dialect_library(MLIRStandalone
         MLIRInferTypeOpInterface
         MLIRFuncDialect
 	)
+endif()
diff --git a/mlir/examples/standalone/standalone-plugin/CMakeLists.txt b/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
index 961a3ea2c906..bb76374a11f6 100644
--- a/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
+++ b/mlir/examples/standalone/standalone-plugin/CMakeLists.txt
@@ -1,5 +1,10 @@
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
+if (APPLE)
+set(LIBS
+        MLIRStandalone
+        )
+else()
 set(LIBS
         MLIRIR
         MLIRPass
@@ -7,6 +12,7 @@ set(LIBS
         MLIRStandalone
         MLIRTransformUtils
         )
+endif()
 
 add_mlir_dialect_library(StandalonePlugin
         SHARED
@@ -17,6 +23,6 @@ add_mlir_dialect_library(StandalonePlugin
         )
 
 llvm_update_compile_flags(StandalonePlugin)
-target_link_libraries(StandalonePlugin PRIVATE ${LIBS})
+target_link_libraries(StandalonePlugin PRIVATE ${LIBS} "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
 
 mlir_check_all_link_libraries(StandalonePlugin)
diff --git a/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir b/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
index 5af4b3d92e34..868e22fe03bb 100644
--- a/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
+++ b/mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir
@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s --load-pass-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+// RUN: mlir-opt %s --load-pass-plugin=%standalone_libs/libStandalonePlugin%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
 
 module {
   // CHECK-LABEL: func @foo()
diff --git a/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir b/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
index 3f935db8910c..0bdbfb50334e 100644
--- a/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
+++ b/mlir/examples/standalone/test/Standalone/standalone-plugin.mlir
@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin%shlibext --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
 
 module {
   // CHECK-LABEL: func @foo()
diff --git a/mlir/examples/standalone/test/lit.cfg.py b/mlir/examples/standalone/test/lit.cfg.py
index 3e4ceee3865c..601ac8f769f9 100644
--- a/mlir/examples/standalone/test/lit.cfg.py
+++ b/mlir/examples/standalone/test/lit.cfg.py
@@ -30,6 +30,7 @@ config.test_source_root = os.path.dirname(__file__)
 config.test_exec_root = os.path.join(config.standalone_obj_root, 'test')
 
 config.substitutions.append(('%PATH%', config.environment['PATH']))
+config.substitutions.append(('%shlibext', config.llvm_shlib_ext))
 
 llvm_config.with_system_environment(
     ['HOME', 'INCLUDE', 'LIB', 'TMP', 'TEMP'])
diff --git a/mlir/examples/standalone/test/lit.site.cfg.py.in b/mlir/examples/standalone/test/lit.site.cfg.py.in
index 9a81c6b48343..eae93d0b122e 100644
--- a/mlir/examples/standalone/test/lit.site.cfg.py.in
+++ b/mlir/examples/standalone/test/lit.site.cfg.py.in
@@ -4,6 +4,7 @@ config.llvm_tools_dir = lit_config.substitute("@LLVM_TOOLS_DIR@")
 config.mlir_obj_dir = "@MLIR_BINARY_DIR@"
 config.enable_bindings_python = @MLIR_ENABLE_BINDINGS_PYTHON@
 config.standalone_obj_root = "@STANDALONE_BINARY_DIR@"
+config.llvm_shlib_ext = "@SHLIBEXT@"
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)

[mehdi_amini]

Why does the linux build needs the extra dependencies?

[fmorac]

In D147053#4259501, @mehdi_amini wrote:

Why does the linux build needs the extra dependencies?

The immediate answer is that the building process fails without them (probably a missing flag, that tells the linker to go ahead without trying to resolve those symbols). I'll comeback with a better answer.

mlir/examples/standalone/CMakeLists.txt

 add_subdirectory(include)
 add_subdirectory(lib)
 if(MLIR_ENABLE_BINDINGS_PYTHON)
   message(STATUS "Enabling Python API")
   add_subdirectory(python)
 endif()
 add_subdirectory(test)
 add_subdirectory(standalone-opt)
+add_subdirectory(standalone-plugin)
 add_subdirectory(standalone-translate)

mlir/examples/standalone/include/Standalone/CMakeLists.txt

 add_mlir_dialect(StandaloneOps standalone)
 add_mlir_doc(StandaloneDialect StandaloneDialect Standalone/ -gen-dialect-doc)
 add_mlir_doc(StandaloneOps StandaloneOps Standalone/ -gen-op-doc)
+
+set(LLVM_TARGET_DEFINITIONS StandalonePasses.td)
+mlir_tablegen(StandalonePasses.h.inc --gen-pass-decls)
+add_public_tablegen_target(MLIRStandalonePassesIncGen)

mlir/examples/standalone/include/Standalone/StandalonePasses.h

+//===- StandalonePasses.h - Standalone passes  ------------------*- C++ -*-===//
+//
+// This file is licensed 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
+//
+//===----------------------------------------------------------------------===//
+#ifndef STANDALONE_STANDALONEPASSES_H
+#define STANDALONE_STANDALONEPASSES_H
+
+#include "Standalone/StandaloneDialect.h"
+#include "Standalone/StandaloneOps.h"
+#include "mlir/Pass/Pass.h"
+#include <memory>
+
+namespace mlir {
+namespace standalone {
+#define GEN_PASS_DECL
+#include "Standalone/StandalonePasses.h.inc"
+
+#define GEN_PASS_REGISTRATION
+#include "Standalone/StandalonePasses.h.inc"
+} // namespace standalone
+} // namespace mlir
+
+#endif

mlir/examples/standalone/include/Standalone/StandalonePasses.td

+//===- StandalonePsss.td - Standalone dialect passes -------*- tablegen -*-===//
+//
+// This file is licensed 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef STANDALONE_PASS
+#define STANDALONE_PASS
+
+include "mlir/Pass/PassBase.td"
+
+def StandaloneSwitchBarFoo: Pass<"standalone-switch-bar-foo", "::mlir::ModuleOp"> {
+  let summary = "Switches the name of a FuncOp named `bar` to `foo` and folds.";
+  let description = [{
+    Switches the name of a FuncOp named `bar` to `foo` and folds.
+    ```
+    func.func @bar() {
+      return
+    }
+    // Gets transformed to:
+    func.func @foo() {
+      return
+    }
+    ```
+  }];
+}
+
+#endif // STANDALONE_PASS

mlir/examples/standalone/lib/Standalone/CMakeLists.txt

 add_mlir_dialect_library(MLIRStandalone
         StandaloneTypes.cpp
         StandaloneDialect.cpp
         StandaloneOps.cpp
+        StandalonePasses.cpp
 
         ADDITIONAL_HEADER_DIRS
         ${PROJECT_SOURCE_DIR}/include/Standalone
 
         DEPENDS
         MLIRStandaloneOpsIncGen
+        MLIRStandalonePassesIncGen
 
   LINK_LIBS PUBLIC
   MLIRIR
         MLIRInferTypeOpInterface
+        MLIRFuncDialect
   )

mlir/examples/standalone/lib/Standalone/StandalonePasses.cpp

+//===- StandalonePasses.cpp - Standalone passes -----------------*- C++ -*-===//
+//
+// This file is licensed 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
+//
+//===----------------------------------------------------------------------===//
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/IR/BuiltinOps.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+#include "Standalone/StandalonePasses.h"
+
+namespace mlir::standalone {
+#define GEN_PASS_DEF_STANDALONESWITCHBARFOO
+#include "Standalone/StandalonePasses.h.inc"
+
+namespace {
+class StandaloneSwitchBarFooRewriter : public OpRewritePattern<func::FuncOp> {
+public:
+  using OpRewritePattern<func::FuncOp>::OpRewritePattern;
+  LogicalResult matchAndRewrite(func::FuncOp op,
+                                PatternRewriter &rewriter) const final {
+    if (op.getSymName() == "bar") {
+      rewriter.updateRootInPlace(op, [&op]() { op.setSymName("foo"); });
+      return success();
+    }
+    return failure();
+  }
+};
+
+class StandaloneSwitchBarFoo
+    : public impl::StandaloneSwitchBarFooBase<StandaloneSwitchBarFoo> {
+public:
+  using impl::StandaloneSwitchBarFooBase<
+      StandaloneSwitchBarFoo>::StandaloneSwitchBarFooBase;
+  void runOnOperation() final {
+    RewritePatternSet patterns(&getContext());
+    patterns.add<StandaloneSwitchBarFooRewriter>(&getContext());
+    FrozenRewritePatternSet patternSet(std::move(patterns));
+    if (failed(applyPatternsAndFoldGreedily(getOperation(), patternSet)))
+      signalPassFailure();
+  }
+};
+} // namespace
+} // namespace mlir::standalone

mlir/examples/standalone/standalone-opt/standalone-opt.cpp

 #include "mlir/Support/FileUtilities.h"
 #include "mlir/Tools/mlir-opt/MlirOptMain.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/ToolOutputFile.h"
 
 #include "Standalone/StandaloneDialect.h"
+#include "Standalone/StandalonePasses.h"
 
 int main(int argc, char **argv) {
   mlir::registerAllPasses();
+  mlir::standalone::registerPasses();
   // TODO: Register standalone passes here.
 
   mlir::DialectRegistry registry;
   registry.insert<mlir::standalone::StandaloneDialect,
                   mlir::arith::ArithDialect, mlir::func::FuncDialect>();
   // Add the following to include *all* MLIR Core dialects, or selectively
   // include what you need like above. You only need to register dialects that
   // will be *parsed* by the tool, not the one generated
   // registerAllDialects(registry);
 
   return mlir::asMainReturnCode(
       mlir::MlirOptMain(argc, argv, "Standalone optimizer driver\n", registry));
 }

mlir/examples/standalone/standalone-plugin/CMakeLists.txt

+get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
+get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
+set(LIBS
+        MLIRIR
+        MLIRPass
+        MLIRPluginsLib
+        MLIRStandalone
+        MLIRTransformUtils
+        )
+
+add_mlir_dialect_library(StandalonePlugin
+        SHARED
+        standalone-plugin.cpp
+
+        DEPENDS
+        MLIRStandalone
+        )
+
+llvm_update_compile_flags(StandalonePlugin)
+target_link_libraries(StandalonePlugin PRIVATE ${LIBS})
+
+mlir_check_all_link_libraries(StandalonePlugin)

mlir/examples/standalone/standalone-plugin/standalone-plugin.cpp

+//===- standalone-plugin.cpp ------------------------------------*- C++ -*-===//
+//
+// This file is licensed 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/Arith/IR/Arith.h"
+#include "mlir/IR/Dialect.h"
+#include "mlir/IR/MLIRContext.h"
+#include "mlir/InitAllDialects.h"
+#include "mlir/InitAllPasses.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Tools/Plugins/DialectPlugin.h"
+
+#include "Standalone/StandaloneDialect.h"
+#include "Standalone/StandalonePasses.h"
+
+using namespace mlir;
+
+/// Dialect plugin registration mechanism.
+/// Observe that it also allows to register passes.
+/// Necessary symbol to register the dialect plugin.
+extern "C" LLVM_ATTRIBUTE_WEAK DialectPluginLibraryInfo
+mlirGetDialectPluginInfo() {
+  return {MLIR_PLUGIN_API_VERSION, "Standalone", LLVM_VERSION_STRING,
+          [](DialectRegistry *registry) {
+            registry->insert<mlir::standalone::StandaloneDialect>();
+            mlir::standalone::registerPasses();
+          }};
+}
+
+/// Pass plugin registration mechanism.
+/// Necessary symbol to register the pass plugin.
+extern "C" LLVM_ATTRIBUTE_WEAK PassPluginLibraryInfo mlirGetPassPluginInfo() {
+  return {MLIR_PLUGIN_API_VERSION, "StandalonePasses", LLVM_VERSION_STRING,
+          []() { mlir::standalone::registerPasses(); }};
+}

mlir/examples/standalone/test/Standalone/standalone-pass-plugin.mlir

+// RUN: mlir-opt %s --load-pass-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+
+module {
+  // CHECK-LABEL: func @foo()
+  func.func @bar() {
+    return
+  }
+
+  // CHECK-LABEL: func @abar()
+  func.func @abar() {
+    return
+  }
+}

mlir/examples/standalone/test/Standalone/standalone-plugin.mlir

+// RUN: mlir-opt %s --load-dialect-plugin=%standalone_libs/libStandalonePlugin.so --pass-pipeline="builtin.module(standalone-switch-bar-foo)" | FileCheck %s
+
+module {
+  // CHECK-LABEL: func @foo()
+  func.func @bar() {
+    return
+  }
+
+  // CHECK-LABEL: func @standalone_types(%arg0: !standalone.custom<"10">)
+  func.func @standalone_types(%arg0: !standalone.custom<"10">) {
+    return
+  }
+}

mlir/examples/standalone/test/lit.cfg.py

 # excludes: A list of directories to exclude from the testsuite. The 'Inputs'
 # subdirectories contain auxiliary inputs for various tests in their parent
 # directories.
 config.excludes = ['Inputs', 'Examples', 'CMakeLists.txt', 'README.txt', 'LICENSE.txt']
 
 # test_exec_root: The root path where tests should be run.
 config.test_exec_root = os.path.join(config.standalone_obj_root, 'test')
 config.standalone_tools_dir = os.path.join(config.standalone_obj_root, 'bin')
+config.standalone_libs_dir = os.path.join(config.standalone_obj_root, 'lib')
+
+config.substitutions.append(('%standalone_libs', config.standalone_libs_dir))
 
 # Tweak the PATH to include the tools dir.
 llvm_config.with_environment('PATH', config.llvm_tools_dir, append_path=True)
 
 tool_dirs = [config.standalone_tools_dir, config.llvm_tools_dir]
 tools = [
+    'mlir-opt',
     'standalone-capi-test',
     'standalone-opt',
     'standalone-translate',
 ]
 
 llvm_config.add_tool_substitutions(tools, tool_dirs)
 
 llvm_config.with_environment('PYTHONPATH', [
     os.path.join(config.mlir_obj_dir, 'python_packages', 'standalone'),
 ], append_path=True)

mlir/include/mlir/Tools/Plugins/DialectPlugin.h

+//===- mlir/Tools/Plugins/DialectPlugin.h - Public Plugin API -------------===//
+//
+// 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 defines the public entry point for dialect plugins.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TOOLS_PLUGINS_DIALECTPLUGIN_H
+#define MLIR_TOOLS_PLUGINS_DIALECTPLUGIN_H
+
+#include "mlir/IR/DialectRegistry.h"
+#include "mlir/Tools/Plugins/PassPlugin.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/Error.h"
+#include <cstdint>
+#include <string>
+
+namespace mlir {
+extern "C" {
+/// Information about the plugin required to load its dialects & passes
+///
+/// This struct defines the core interface for dialect plugins and is supposed
+/// to be filled out by plugin implementors. MLIR-side users of a plugin are
+/// expected to use the \c DialectPlugin class below to interface with it.
+struct DialectPluginLibraryInfo {
+  /// The API version understood by this plugin, usually
+  /// \c MLIR_PLUGIN_API_VERSION
+  uint32_t apiVersion;
+  /// A meaningful name of the plugin.
+  const char *pluginName;
+  /// The version of the plugin.
+  const char *pluginVersion;
+
+  /// The callback for registering dialect plugin with a \c DialectRegistry
+  /// instance
+  void (*registerDialectRegistryCallbacks)(DialectRegistry *);
+};
+}
+
+/// A loaded dialect plugin.
+///
+/// An instance of this class wraps a loaded dialect plugin and gives access to
+/// its interface defined by the \c DialectPluginLibraryInfo it exposes.
+class DialectPlugin {
+public:
+  /// Attempts to load a dialect plugin from a given file.
+  ///
+  /// \returns Returns an error if either the library cannot be found or loaded,
+  /// there is no public entry point, or the plugin implements the wrong API
+  /// version.
+  static llvm::Expected<DialectPlugin> load(const std::string &filename);
+
+  /// Get the filename of the loaded plugin.
+  StringRef getFilename() const { return filename; }
+
+  /// Get the plugin name
+  StringRef getPluginName() const { return info.pluginName; }
+
+  /// Get the plugin version
+  StringRef getPluginVersion() const { return info.pluginVersion; }
+
+  /// Get the plugin API version
+  uint32_t getAPIVersion() const { return info.apiVersion; }
+
+  /// Invoke the DialectRegistry callback registration
+  void
+  registerDialectRegistryCallbacks(DialectRegistry &dialectRegistry) const {
+    info.registerDialectRegistryCallbacks(&dialectRegistry);
+  }
+
+private:
+  DialectPlugin(const std::string &filename,
+                const llvm::sys::DynamicLibrary &library)
+      : filename(filename), library(library), info() {}
+
+  std::string filename;
+  llvm::sys::DynamicLibrary library;
+  DialectPluginLibraryInfo info;
+};
+} // namespace mlir
+
+/// The public entry point for a dialect plugin.
+///
+/// When a plugin is loaded by the driver, it will call this entry point to
+/// obtain information about this plugin and about how to register its dialects.
+/// This function needs to be implemented by the plugin, see the example below:
+///
+/// ```
+/// extern "C" ::mlir::DialectPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
+/// mlirGetDialectPluginInfo() {
+///   return {
+///     MLIR_PLUGIN_API_VERSION, "MyPlugin", "v0.1", [](DialectRegistry) { ... }
+///   };
+/// }
+/// ```
+extern "C" ::mlir::DialectPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
+mlirGetDialectPluginInfo();
+
+#endif /* MLIR_TOOLS_PLUGINS_DIALECTPLUGIN_H */

mlir/include/mlir/Tools/Plugins/PassPlugin.h

+//===- mlir/Tools/Plugins/PassPlugin.h - Public Plugin API ----------------===//
+//
+// 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 defines the public entry point for pass plugins.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TOOLS_PLUGINS_PASSPLUGIN_H
+#define MLIR_TOOLS_PLUGINS_PASSPLUGIN_H
+
+#include "mlir/Support/LLVM.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/Error.h"
+#include <cstdint>
+#include <string>
+
+namespace mlir {
+/// \macro MLIR_PLUGIN_API_VERSION
+/// Identifies the API version understood by this plugin.
+///
+/// When a plugin is loaded, the driver will check it's supported plugin version
+/// against that of the plugin. A mismatch is an error. The supported version
+/// will be incremented for ABI-breaking changes to the \c PassPluginLibraryInfo
+/// struct, i.e. when callbacks are added, removed, or reordered.
+#define MLIR_PLUGIN_API_VERSION 1
+
+extern "C" {
+/// Information about the plugin required to load its passes
+///
+/// This struct defines the core interface for pass plugins and is supposed to
+/// be filled out by plugin implementors. LLVM-side users of a plugin are
+/// expected to use the \c PassPlugin class below to interface with it.
+struct PassPluginLibraryInfo {
+  /// The API version understood by this plugin, usually \c
+  /// MLIR_PLUGIN_API_VERSION
+  uint32_t apiVersion;
+  /// A meaningful name of the plugin.
+  const char *pluginName;
+  /// The version of the plugin.
+  const char *pluginVersion;
+
+  /// The callback for registering plugin passes.
+  void (*registerPassRegistryCallbacks)();
+};
+}
+
+/// A loaded pass plugin.
+///
+/// An instance of this class wraps a loaded pass plugin and gives access to
+/// its interface defined by the \c PassPluginLibraryInfo it exposes.
+class PassPlugin {
+public:
+  /// Attempts to load a pass plugin from a given file.
+  ///
+  /// \returns Returns an error if either the library cannot be found or loaded,
+  /// there is no public entry point, or the plugin implements the wrong API
+  /// version.
+  static llvm::Expected<PassPlugin> load(const std::string &filename);
+
+  /// Get the filename of the loaded plugin.
+  StringRef getFilename() const { return filename; }
+
+  /// Get the plugin name
+  StringRef getPluginName() const { return info.pluginName; }
+
+  /// Get the plugin version
+  StringRef getPluginVersion() const { return info.pluginVersion; }
+
+  /// Get the plugin API version
+  uint32_t getAPIVersion() const { return info.apiVersion; }
+
+  /// Invoke the PassRegistry callback registration
+  void registerPassRegistryCallbacks() const {
+    info.registerPassRegistryCallbacks();
+  }
+
+private:
+  PassPlugin(const std::string &filename,
+             const llvm::sys::DynamicLibrary &library)
+      : filename(filename), library(library), info() {}
+
+  std::string filename;
+  llvm::sys::DynamicLibrary library;
+  PassPluginLibraryInfo info;
+};
+} // namespace mlir
+
+/// The public entry point for a pass plugin.
+///
+/// When a plugin is loaded by the driver, it will call this entry point to
+/// obtain information about this plugin and about how to register its passes.
+/// This function needs to be implemented by the plugin, see the example below:
+///
+/// ```
+/// extern "C" ::mlir::PassPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
+/// mlirGetPassPluginInfo() {
+///   return {
+///     MLIR_PLUGIN_API_VERSION, "MyPlugin", "v0.1", []() { ... }
+///   };
+/// }
+/// ```
+extern "C" ::mlir::PassPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
+mlirGetPassPluginInfo();
+
+#endif /* MLIR_TOOLS_PLUGINS_PASSPLUGIN_H */

mlir/include/mlir/Tools/mlir-opt/MlirOptMain.h

 class PassPipelineCLParser;
 class PassManager;
 
 /// Configuration options for the mlir-opt tool.
 /// This is intended to help building tools like mlir-opt by collecting the
 /// supported options.
 /// The API is fluent, and the options are sorted in alphabetical order below.
 /// The options can be exposed to the LLVM command line by registering them
-/// with `MlirOptMainConfig::registerCLOptions();` and creating a config using
-/// `auto config = MlirOptMainConfig::createFromCLOptions();`.
+/// with `MlirOptMainConfig::registerCLOptions(DialectRegistry &);` and creating
+/// a config using `auto config = MlirOptMainConfig::createFromCLOptions();`.
 class MlirOptMainConfig {
 public:
   /// Register the options as global LLVM command line options.
-  static void registerCLOptions();
+  static void registerCLOptions(DialectRegistry &dialectRegistry);
 
   /// Create a new config with the default set from the CL options.
   static MlirOptMainConfig createFromCLOptions();
 
   ///
   /// Options.
   ///
 

mlir/lib/Tools/CMakeLists.txt

 add_subdirectory(lsp-server-support)
 add_subdirectory(mlir-lsp-server)
 add_subdirectory(mlir-opt)
 add_subdirectory(mlir-pdll-lsp-server)
 add_subdirectory(mlir-reduce)
 add_subdirectory(mlir-tblgen)
 add_subdirectory(mlir-translate)
 add_subdirectory(PDLL)
+add_subdirectory(Plugins)
 add_subdirectory(tblgen-lsp-server)

mlir/lib/Tools/Plugins/CMakeLists.txt

+add_mlir_library(MLIRPluginsLib
+  DialectPlugin.cpp
+  PassPlugin.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Tools/Plugins
+
+  LINK_LIBS PUBLIC
+  MLIRIR
+  MLIRPass
+  MLIRSupport
+  )

mlir/lib/Tools/Plugins/DialectPlugin.cpp

+//===- lib/Tools/Plugins/DialectPlugin.cpp - Load Dialect Plugins ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Tools/Plugins/DialectPlugin.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <cstdint>
+
+using namespace mlir;
+
+llvm::Expected<DialectPlugin> DialectPlugin::load(const std::string &filename) {
+  std::string error;
+  auto library =
+      llvm::sys::DynamicLibrary::getPermanentLibrary(filename.c_str(), &error);
+  if (!library.isValid())
+    return llvm::make_error<llvm::StringError>(
+        Twine("Could not load library '") + filename + "': " + error,
+        llvm::inconvertibleErrorCode());
+
+  DialectPlugin plugin{filename, library};
+
+  // mlirGetDialectPluginInfo should be resolved to the definition from the
+  // plugin we are currently loading.
+  intptr_t getDetailsFn =
+      (intptr_t)library.getAddressOfSymbol("mlirGetDialectPluginInfo");
+
+  if (!getDetailsFn)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Plugin entry point not found in '") + filename,
+        llvm::inconvertibleErrorCode());
+
+  plugin.info =
+      reinterpret_cast<decltype(mlirGetDialectPluginInfo) *>(getDetailsFn)();
+
+  if (plugin.info.apiVersion != MLIR_PLUGIN_API_VERSION)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Wrong API version on plugin '") + filename + "'. Got version " +
+            Twine(plugin.info.apiVersion) + ", supported version is " +
+            Twine(MLIR_PLUGIN_API_VERSION) + ".",
+        llvm::inconvertibleErrorCode());
+
+  if (!plugin.info.registerDialectRegistryCallbacks)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Empty entry callback in plugin '") + filename + "'.'",
+        llvm::inconvertibleErrorCode());
+
+  return plugin;
+}

mlir/lib/Tools/Plugins/PassPlugin.cpp

+//===- lib/Tools/Plugins/PassPlugin.cpp - Load Plugins for PR Passes ------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Tools/Plugins/PassPlugin.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <cstdint>
+
+using namespace mlir;
+
+llvm::Expected<PassPlugin> PassPlugin::load(const std::string &filename) {
+  std::string Error;
+  auto library =
+      llvm::sys::DynamicLibrary::getPermanentLibrary(filename.c_str(), &Error);
+  if (!library.isValid())
+    return llvm::make_error<llvm::StringError>(
+        Twine("Could not load library '") + filename + "': " + Error,
+        llvm::inconvertibleErrorCode());
+
+  PassPlugin plugin{filename, library};
+
+  // mlirGetPassPluginInfo should be resolved to the definition from the plugin
+  // we are currently loading.
+  intptr_t getDetailsFn =
+      (intptr_t)library.getAddressOfSymbol("mlirGetPassPluginInfo");
+
+  if (!getDetailsFn)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Plugin entry point not found in '") + filename,
+        llvm::inconvertibleErrorCode());
+
+  plugin.info =
+      reinterpret_cast<decltype(mlirGetPassPluginInfo) *>(getDetailsFn)();
+
+  if (plugin.info.apiVersion != MLIR_PLUGIN_API_VERSION)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Wrong API version on plugin '") + filename + "'. Got version " +
+            Twine(plugin.info.apiVersion) + ", supported version is " +
+            Twine(MLIR_PLUGIN_API_VERSION) + ".",
+        llvm::inconvertibleErrorCode());
+
+  if (!plugin.info.registerPassRegistryCallbacks)
+    return llvm::make_error<llvm::StringError>(
+        Twine("Empty entry callback in plugin '") + filename + "'.'",
+        llvm::inconvertibleErrorCode());
+
+  return plugin;
+}

mlir/lib/Tools/mlir-opt/CMakeLists.txt

 add_mlir_library(MLIROptLib
   MlirOptMain.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Tools/mlir-opt
 
   LINK_LIBS PUBLIC
   MLIRBytecodeWriter
   MLIRDebug
   MLIRObservers
   MLIRPass
   MLIRParser
+  MLIRPluginsLib
   MLIRSupport
   )

mlir/lib/Tools/mlir-opt/MlirOptMain.cpp

 #include "mlir/IR/MLIRContext.h"
 #include "mlir/Parser/Parser.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Pass/PassManager.h"
 #include "mlir/Support/FileUtilities.h"
 #include "mlir/Support/Timing.h"
 #include "mlir/Support/ToolUtilities.h"
 #include "mlir/Tools/ParseUtilities.h"
+#include "mlir/Tools/Plugins/DialectPlugin.h"
+#include "mlir/Tools/Plugins/PassPlugin.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/StringSaver.h"
static cl::opt<bool, /*ExternalStorage=*/true> verifyDiagnostics(
                  "expected-* lines on the corresponding line"),
         cl::location(verifyDiagnosticsFlag), cl::init(false));
 
     static cl::opt<bool, /*ExternalStorage=*/true> verifyPasses(
         "verify-each",
         cl::desc("Run the verifier after each transformation pass"),
         cl::location(verifyPassesFlag), cl::init(true));
 
+    static cl::list<std::string> passPlugins(
+        "load-pass-plugin", cl::desc("Load passes from plugin library"));
+    /// Set the callback to load a pass plugin.
+    passPlugins.setCallback([&](const std::string &pluginPath) {
+      auto plugin = PassPlugin::load(pluginPath);
+      if (!plugin) {
+        errs() << "Failed to load passes from '" << pluginPath
+               << "'. Request ignored.\n";
+        return;
+      }
+      plugin.get().registerPassRegistryCallbacks();
+    });
+
+    static cl::list<std::string> dialectPlugins(
+        "load-dialect-plugin", cl::desc("Load dialects from plugin library"));
+    this->dialectPlugins = std::addressof(dialectPlugins);
+
     static PassPipelineCLParser passPipeline("", "Compiler passes to run", "p");
     setPassPipelineParser(passPipeline);
   }
+
+  /// Set the callback to load a dialect plugin.
+  void setDialectPluginsCallback(DialectRegistry &registry);
+
+  /// Pointer to static dialectPlugins variable in constructor, needed by
+  /// setDialectPluginsCallback(DialectRegistry&).
+  cl::list<std::string> *dialectPlugins = nullptr;
 };
 } // namespace
 
 ManagedStatic<MlirOptMainConfigCLOptions> clOptionsConfig;
 
-void MlirOptMainConfig::registerCLOptions() { *clOptionsConfig; }
+void MlirOptMainConfig::registerCLOptions(DialectRegistry &registry) {
+  clOptionsConfig->setDialectPluginsCallback(registry);
+}
 
 MlirOptMainConfig MlirOptMainConfig::createFromCLOptions() {
   return *clOptionsConfig;
 }
 
 MlirOptMainConfig &MlirOptMainConfig::setPassPipelineParser(
     const PassPipelineCLParser &passPipeline) {
   passPipelineCallback = [&](PassManager &pm) {
     auto errorHandler = [&](const Twine &msg) {
       emitError(UnknownLoc::get(pm.getContext())) << msg;
       return failure();
     };
     if (failed(passPipeline.addToPipeline(pm, errorHandler)))
       return failure();
     if (this->shouldDumpPassPipeline()) {
 
       pm.dump();
       llvm::errs() << "\n";
     }
     return success();
   };
   return *this;
 }
 
+void MlirOptMainConfigCLOptions::setDialectPluginsCallback(
+    DialectRegistry &registry) {
+  dialectPlugins->setCallback([&](const std::string &pluginPath) {
+    auto plugin = DialectPlugin::load(pluginPath);
+    if (!plugin) {
+      errs() << "Failed to load dialect plugin from '" << pluginPath
+             << "'. Request ignored.\n";
+      return;
+    };
+    plugin.get().registerDialectRegistryCallbacks(registry);
+  });
+}
+
 /// Set the ExecutionContext on the context and handle the observers.
 class InstallDebugHandler {
 public:
   InstallDebugHandler(MLIRContext &context, const MlirOptMainConfig &config) {
     if (config.getLogActionsTo().empty()) {
       if (tracing::DebugCounter::isActivated())
         context.registerActionHandler(tracing::DebugCounter());
       return;
     }
     if (tracing::DebugCounter::isActivated())
       emitError(UnknownLoc::get(&context),
                 "Debug counters are incompatible with --log-actions-to option "
                 "and are disabled");
LogicalResult mlir::MlirOptMain(int argc, char **argv, llvm::StringRef toolName,
 
   static cl::opt<std::string> outputFilename("o", cl::desc("Output filename"),
                                              cl::value_desc("filename"),
                                              cl::init("-"));
 
   InitLLVM y(argc, argv);
 
   // Register any command line options.
-  MlirOptMainConfig::registerCLOptions();
+  MlirOptMainConfig::registerCLOptions(registry);
   registerAsmPrinterCLOptions();
   registerMLIRContextCLOptions();
   registerPassManagerCLOptions();
   registerDefaultTimingManagerCLOptions();
   tracing::DebugCounter::registerCLOptions();
 
   // Build the list of dialects as a header for the --help message.
   std::string helpHeader = (toolName + "\nAvailable Dialects: ").str();

mlir/tools/mlir-opt/CMakeLists.txt

add_mlir_library(MLIRMlirOptMain
   ${LIBS}
   )
 
 add_mlir_tool(mlir-opt
   mlir-opt.cpp
 
   DEPENDS
   ${LIBS}
+  SUPPORT_PLUGINS
   )
 target_link_libraries(mlir-opt PRIVATE ${LIBS})
 llvm_update_compile_flags(mlir-opt)
 
 mlir_check_all_link_libraries(mlir-opt)
+export_executable_symbols_for_plugins(mlir-opt)