[mlir python] Port Python core code to nanobind.

Why? https://nanobind.readthedocs.io/en/latest/why.html says it better
than I can, but my primary motivation for this change is to improve MLIR
IR construction time from JAX.

For a complicated Google-internal LLM model in JAX, this change improves the MLIR
lowering time by around 5s (out of around 30s), which is a significant
speedup for simply switching binding frameworks.

To a large extent, this is a mechanical change, for instance changing pybind11::
to nanobind::.

Notes:
* this PR needs wjakob/nanobind#806 to land in
  nanobind first. Without that fix, importing the MLIR modules will
  fail.
* this PR does not port the in-tree dialect extension modules. They can
  be ported in a future PR.
* I removed the py::sibling() annotations from def_static and def_class
  in PybindAdapters.h. These ask pybind11 to try to form an overload
  with an existing method, but it's not possible to form mixed
  pybind11/nanobind overloads this ways and the parent class is now defined in
  nanobind. Better solutions may be possible here.
* nanobind does not contain an exact equivalent of pybind11's buffer
  protocol support. It was not hard to add a nanobind implementation of
  a similar API.
* nanobind is pickier about casting to std::vector<bool>, expecting that
  the input is a sequence of bool types, not truthy values. In a couple
  of places I added code to support truthy values during casting.
* nanobind distinguishes bytes (nb::bytes) from strings (e.g.,
  std::string). This required nb::bytes overloads in a few places.

mlir/include/mlir/Bindings/Python/Diagnostics.h

@@ -12,17 +12,17 @@
 #include <cassert>
 #include <string>
 
+#include "llvm/ADT/StringRef.h"
 #include "mlir-c/Diagnostics.h"
 #include "mlir-c/IR.h"
-#include "llvm/ADT/StringRef.h"
 
 namespace mlir {
 namespace python {
 
 /// RAII scope intercepting all diagnostics into a string. The message must be
 /// checked before this goes out of scope.
 class CollectDiagnosticsToStringScope {
-public:
+ public:
   explicit CollectDiagnosticsToStringScope(MlirContext ctx) : context(ctx) {
     handlerID = mlirContextAttachDiagnosticHandler(ctx, &handler, &errorMessage,
                                                    /*deleteUserData=*/nullptr);
@@ -34,7 +34,7 @@ class CollectDiagnosticsToStringScope {
 
   [[nodiscard]] std::string takeMessage() { return std::move(errorMessage); }
 
-private:
+ private:
   static MlirLogicalResult handler(MlirDiagnostic diag, void *data) {
     auto printer = +[](MlirStringRef message, void *data) {
       *static_cast<std::string *>(data) +=
@@ -53,7 +53,7 @@ class CollectDiagnosticsToStringScope {
   std::string errorMessage = "";
 };
 
-} // namespace python
-} // namespace mlir
+}  // namespace python
+}  // namespace mlir
 
-#endif // MLIR_BINDINGS_PYTHON_DIAGNOSTICS_H
+#endif  // MLIR_BINDINGS_PYTHON_DIAGNOSTICS_H

mlir/include/mlir/Bindings/Python/IRTypes.h

@@ -9,7 +9,7 @@
 #ifndef MLIR_BINDINGS_PYTHON_IRTYPES_H
 #define MLIR_BINDINGS_PYTHON_IRTYPES_H
 
-#include "mlir/Bindings/Python/PybindAdaptors.h"
+#include "mlir/Bindings/Python/NanobindAdaptors.h"
 
 namespace mlir {
 

mlir/include/mlir/Bindings/Python/NanobindAdaptors.h

@@ -24,10 +24,10 @@
 
 #include <cstdint>
 
+#include "llvm/ADT/Twine.h"
 #include "mlir-c/Bindings/Python/Interop.h"
 #include "mlir-c/Diagnostics.h"
 #include "mlir-c/IR.h"
-#include "llvm/ADT/Twine.h"
 
 // Raw CAPI type casters need to be declared before use, so always include them
 // first.
@@ -233,8 +233,7 @@ struct type_caster<MlirOperation> {
   }
   static handle from_cpp(MlirOperation v, rv_policy,
                          cleanup_list *cleanup) noexcept {
-    if (v.ptr == nullptr)
-      return nanobind::none();
+    if (v.ptr == nullptr) return nanobind::none();
     nanobind::object capsule =
         nanobind::steal<nanobind::object>(mlirPythonOperationToCapsule(v));
     return nanobind::module_::import_(MAKE_MLIR_PYTHON_QUALNAME("ir"))
@@ -255,8 +254,7 @@ struct type_caster<MlirValue> {
   }
   static handle from_cpp(MlirValue v, rv_policy,
                          cleanup_list *cleanup) noexcept {
-    if (v.ptr == nullptr)
-      return nanobind::none();
+    if (v.ptr == nullptr) return nanobind::none();
     nanobind::object capsule =
         nanobind::steal<nanobind::object>(mlirPythonValueToCapsule(v));
     return nanobind::module_::import_(MAKE_MLIR_PYTHON_QUALNAME("ir"))
@@ -289,8 +287,7 @@ struct type_caster<MlirTypeID> {
   }
   static handle from_cpp(MlirTypeID v, rv_policy,
                          cleanup_list *cleanup) noexcept {
-    if (v.ptr == nullptr)
-      return nanobind::none();
+    if (v.ptr == nullptr) return nanobind::none();
     nanobind::object capsule =
         nanobind::steal<nanobind::object>(mlirPythonTypeIDToCapsule(v));
     return nanobind::module_::import_(MAKE_MLIR_PYTHON_QUALNAME("ir"))
@@ -321,8 +318,8 @@ struct type_caster<MlirType> {
   }
 };
 
-} // namespace detail
-} // namespace nanobind
+}  // namespace detail
+}  // namespace nanobind
 
 namespace mlir {
 namespace python {
@@ -340,7 +337,7 @@ namespace nanobind_adaptors {
 ///   (plus a fair amount of extra curricular poking)
 ///   TODO: If this proves useful, see about including it in nanobind.
 class pure_subclass {
-public:
+ public:
   pure_subclass(nanobind::handle scope, const char *derivedClassName,
                 const nanobind::object &superClass) {
     nanobind::object pyType =
@@ -382,7 +379,7 @@ class pure_subclass {
                   "function pointer");
     nanobind::object cf = nanobind::cpp_function(
         std::forward<Func>(f),
-        nanobind::name(name), // nanobind::scope(thisClass),
+        nanobind::name(name),  // nanobind::scope(thisClass),
         extra...);
     thisClass.attr(name) = cf;
     return *this;
@@ -396,7 +393,7 @@ class pure_subclass {
                   "function pointer");
     nanobind::object cf = nanobind::cpp_function(
         std::forward<Func>(f),
-        nanobind::name(name), // nanobind::scope(thisClass),
+        nanobind::name(name),  // nanobind::scope(thisClass),
         extra...);
     thisClass.attr(name) =
         nanobind::borrow<nanobind::object>(PyClassMethod_New(cf.ptr()));
@@ -405,15 +402,15 @@ class pure_subclass {
 
   nanobind::object get_class() const { return thisClass; }
 
-protected:
+ protected:
   nanobind::object superClass;
   nanobind::object thisClass;
 };
 
 /// Creates a custom subclass of mlir.ir.Attribute, implementing a casting
 /// constructor and type checking methods.
 class mlir_attribute_subclass : public pure_subclass {
-public:
+ public:
   using IsAFunctionTy = bool (*)(MlirAttribute);
   using GetTypeIDFunctionTy = MlirTypeID (*)();
 
@@ -445,7 +442,7 @@ class mlir_attribute_subclass : public pure_subclass {
     // have no additional members, we can just return the instance thus created
     // without amending it.
     std::string captureTypeName(
-        typeClassName); // As string in case if typeClassName is not static.
+        typeClassName);  // As string in case if typeClassName is not static.
     nanobind::object newCf = nanobind::cpp_function(
         [superCls, isaFunction, captureTypeName](
             nanobind::object cls, nanobind::object otherAttribute) {
@@ -491,7 +488,7 @@ class mlir_attribute_subclass : public pure_subclass {
 /// Creates a custom subclass of mlir.ir.Type, implementing a casting
 /// constructor and type checking methods.
 class mlir_type_subclass : public pure_subclass {
-public:
+ public:
   using IsAFunctionTy = bool (*)(MlirType);
   using GetTypeIDFunctionTy = MlirTypeID (*)();
 
@@ -523,7 +520,7 @@ class mlir_type_subclass : public pure_subclass {
     // have no additional members, we can just return the instance thus created
     // without amending it.
     std::string captureTypeName(
-        typeClassName); // As string in case if typeClassName is not static.
+        typeClassName);  // As string in case if typeClassName is not static.
     nanobind::object newCf = nanobind::cpp_function(
         [superCls, isaFunction, captureTypeName](nanobind::object cls,
                                                  nanobind::object otherType) {
@@ -573,7 +570,7 @@ class mlir_type_subclass : public pure_subclass {
 /// Creates a custom subclass of mlir.ir.Value, implementing a casting
 /// constructor and type checking methods.
 class mlir_value_subclass : public pure_subclass {
-public:
+ public:
   using IsAFunctionTy = bool (*)(MlirValue);
 
   /// Subclasses by looking up the super-class dynamically.
@@ -601,7 +598,7 @@ class mlir_value_subclass : public pure_subclass {
     // have no additional members, we can just return the instance thus created
     // without amending it.
     std::string captureValueName(
-        valueClassName); // As string in case if valueClassName is not static.
+        valueClassName);  // As string in case if valueClassName is not static.
     nanobind::object newCf = nanobind::cpp_function(
         [superCls, isaFunction, captureValueName](nanobind::object cls,
                                                   nanobind::object otherValue) {
@@ -629,12 +626,12 @@ class mlir_value_subclass : public pure_subclass {
   }
 };
 
-} // namespace nanobind_adaptors
+}  // namespace nanobind_adaptors
 
 /// RAII scope intercepting all diagnostics into a string. The message must be
 /// checked before this goes out of scope.
 class CollectDiagnosticsToStringScope {
-public:
+ public:
   explicit CollectDiagnosticsToStringScope(MlirContext ctx) : context(ctx) {
     handlerID = mlirContextAttachDiagnosticHandler(ctx, &handler, &errorMessage,
                                                    /*deleteUserData=*/nullptr);
@@ -646,7 +643,7 @@ class CollectDiagnosticsToStringScope {
 
   [[nodiscard]] std::string takeMessage() { return std::move(errorMessage); }
 
-private:
+ private:
   static MlirLogicalResult handler(MlirDiagnostic diag, void *data) {
     auto printer = +[](MlirStringRef message, void *data) {
       *static_cast<std::string *>(data) +=
@@ -665,7 +662,7 @@ class CollectDiagnosticsToStringScope {
   std::string errorMessage = "";
 };
 
-} // namespace python
-} // namespace mlir
+}  // namespace python
+}  // namespace mlir
 
-#endif // MLIR_BINDINGS_PYTHON_NANOBINDADAPTORS_H
+#endif  // MLIR_BINDINGS_PYTHON_NANOBINDADAPTORS_H

mlir/include/mlir/Bindings/Python/PybindAdaptors.h

@@ -374,9 +374,8 @@ class pure_subclass {
     static_assert(!std::is_member_function_pointer<Func>::value,
                   "def_staticmethod(...) called with a non-static member "
                   "function pointer");
-    py::cpp_function cf(
-        std::forward<Func>(f), py::name(name), py::scope(thisClass),
-        py::sibling(py::getattr(thisClass, name, py::none())), extra...);
+    py::cpp_function cf(std::forward<Func>(f), py::name(name),
+                        py::scope(thisClass), extra...);
     thisClass.attr(cf.name()) = py::staticmethod(cf);
     return *this;
   }
@@ -387,9 +386,8 @@ class pure_subclass {
     static_assert(!std::is_member_function_pointer<Func>::value,
                   "def_classmethod(...) called with a non-static member "
                   "function pointer");
-    py::cpp_function cf(
-        std::forward<Func>(f), py::name(name), py::scope(thisClass),
-        py::sibling(py::getattr(thisClass, name, py::none())), extra...);
+    py::cpp_function cf(std::forward<Func>(f), py::name(name),
+                        py::scope(thisClass), extra...);
     thisClass.attr(cf.name()) =
         py::reinterpret_borrow<py::object>(PyClassMethod_New(cf.ptr()));
     return *this;

mlir/lib/Bindings/Python/Globals.h

@@ -9,17 +9,16 @@
 #ifndef MLIR_BINDINGS_PYTHON_GLOBALS_H
 #define MLIR_BINDINGS_PYTHON_GLOBALS_H
 
-#include "PybindUtils.h"
+#include <optional>
+#include <string>
+#include <vector>
 
-#include "mlir-c/IR.h"
-#include "mlir/CAPI/Support.h"
+#include "NanobindUtils.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
-
-#include <optional>
-#include <string>
-#include <vector>
+#include "mlir-c/IR.h"
+#include "mlir/CAPI/Support.h"
 
 namespace mlir {
 namespace python {
@@ -57,71 +56,71 @@ class PyGlobals {
   /// Raises an exception if the mapping already exists and replace == false.
   /// This is intended to be called by implementation code.
   void registerAttributeBuilder(const std::string &attributeKind,
-                                pybind11::function pyFunc,
+                                nanobind::callable pyFunc,
                                 bool replace = false);
 
   /// Adds a user-friendly type caster. Raises an exception if the mapping
   /// already exists and replace == false. This is intended to be called by
   /// implementation code.
-  void registerTypeCaster(MlirTypeID mlirTypeID, pybind11::function typeCaster,
+  void registerTypeCaster(MlirTypeID mlirTypeID, nanobind::callable typeCaster,
                           bool replace = false);
 
   /// Adds a user-friendly value caster. Raises an exception if the mapping
   /// already exists and replace == false. This is intended to be called by
   /// implementation code.
   void registerValueCaster(MlirTypeID mlirTypeID,
-                           pybind11::function valueCaster,
+                           nanobind::callable valueCaster,
                            bool replace = false);
 
   /// Adds a concrete implementation dialect class.
   /// Raises an exception if the mapping already exists.
   /// This is intended to be called by implementation code.
   void registerDialectImpl(const std::string &dialectNamespace,
-                           pybind11::object pyClass);
+                           nanobind::object pyClass);
 
   /// Adds a concrete implementation operation class.
   /// Raises an exception if the mapping already exists and replace == false.
   /// This is intended to be called by implementation code.
   void registerOperationImpl(const std::string &operationName,
-                             pybind11::object pyClass, bool replace = false);
+                             nanobind::object pyClass, bool replace = false);
 
   /// Returns the custom Attribute builder for Attribute kind.
-  std::optional<pybind11::function>
-  lookupAttributeBuilder(const std::string &attributeKind);
+  std::optional<nanobind::callable> lookupAttributeBuilder(
+      const std::string &attributeKind);
 
   /// Returns the custom type caster for MlirTypeID mlirTypeID.
-  std::optional<pybind11::function> lookupTypeCaster(MlirTypeID mlirTypeID,
+  std::optional<nanobind::callable> lookupTypeCaster(MlirTypeID mlirTypeID,
                                                      MlirDialect dialect);
 
   /// Returns the custom value caster for MlirTypeID mlirTypeID.
-  std::optional<pybind11::function> lookupValueCaster(MlirTypeID mlirTypeID,
+  std::optional<nanobind::callable> lookupValueCaster(MlirTypeID mlirTypeID,
                                                       MlirDialect dialect);
 
   /// Looks up a registered dialect class by namespace. Note that this may
   /// trigger loading of the defining module and can arbitrarily re-enter.
-  std::optional<pybind11::object>
-  lookupDialectClass(const std::string &dialectNamespace);
+  std::optional<nanobind::object> lookupDialectClass(
+      const std::string &dialectNamespace);
 
   /// Looks up a registered operation class (deriving from OpView) by operation
   /// name. Note that this may trigger a load of the dialect, which can
   /// arbitrarily re-enter.
-  std::optional<pybind11::object>
-  lookupOperationClass(llvm::StringRef operationName);
+  std::optional<nanobind::object> lookupOperationClass(
+      llvm::StringRef operationName);
 
-private:
+ private:
   static PyGlobals *instance;
   /// Module name prefixes to search under for dialect implementation modules.
   std::vector<std::string> dialectSearchPrefixes;
   /// Map of dialect namespace to external dialect class object.
-  llvm::StringMap<pybind11::object> dialectClassMap;
+  llvm::StringMap<nanobind::object> dialectClassMap;
   /// Map of full operation name to external operation class object.
-  llvm::StringMap<pybind11::object> operationClassMap;
+  llvm::StringMap<nanobind::object> operationClassMap;
   /// Map of attribute ODS name to custom builder.
-  llvm::StringMap<pybind11::object> attributeBuilderMap;
+  llvm::StringMap<nanobind::callable> attributeBuilderMap;
   /// Map of MlirTypeID to custom type caster.
-  llvm::DenseMap<MlirTypeID, pybind11::object> typeCasterMap;
+  llvm::DenseMap<MlirTypeID, nanobind::callable> typeCasterMap;
   /// Map of MlirTypeID to custom value caster.
-  llvm::DenseMap<MlirTypeID, pybind11::object> valueCasterMap;
+  llvm::DenseMap<MlirTypeID, nanobind::callable> valueCasterMap;
   /// Set of dialect namespaces that we have attempted to import implementation
   /// modules for.
   llvm::StringSet<> loadedDialectModules;