[mlir][LLVM] Add the ConvertToLLVMAttrInterface and ConvertToLLVMOpInterface interfaces

This patch adds the `ConvertToLLVMAttrInterface` and `ConvertToLLVMOpInterface` interfaces. It also modifies the `convert-to-llvm` pass to use these interfaces when available.

The `ConvertToLLVMAttrInterface` interfaces allows attributes to configure conversion to LLVM, including the conversion target, LLVM type converter, and populating conversion patterns. See the `NVVMTargetAttr` implementation of this interface for an example of how this interface can be used to configure conversion to LLVM.

The `ConvertToLLVMOpInterface` interface collects all convert to LLVM attributes stored in an operation.

Finally, the `convert-to-llvm` pass was modified to use these interfaces when available. This allows applying `convert-to-llvm` to GPU modules and letting the `NVVMTargetAttr` decide which patterns to populate.

Author: fabianmcg

mlir/include/mlir/Conversion/CMakeLists.txt

@@ -6,3 +6,5 @@ mlir_tablegen(Passes.capi.cpp.inc -gen-pass-capi-impl --prefix Conversion)
 add_public_tablegen_target(MLIRConversionPassIncGen)
 
 add_mlir_doc(Passes ConversionPasses ./ -gen-pass-doc)
+
+add_subdirectory(ConvertToLLVM)

mlir/include/mlir/Conversion/ConvertToLLVM/CMakeLists.txt

@@ -0,0 +1,7 @@
+set(LLVM_TARGET_DEFINITIONS ToLLVMInterface.td)
+mlir_tablegen(ToLLVMAttrInterface.h.inc -gen-attr-interface-decls)
+mlir_tablegen(ToLLVMAttrInterface.cpp.inc -gen-attr-interface-defs)
+mlir_tablegen(ToLLVMOpInterface.h.inc -gen-op-interface-decls)
+mlir_tablegen(ToLLVMOpInterface.cpp.inc -gen-op-interface-defs)
+add_public_tablegen_target(MLIRConvertToLLVMInterfaceIncGen)
+add_dependencies(mlir-generic-headers MLIRConvertToLLVMInterfaceIncGen)

mlir/include/mlir/Conversion/ConvertToLLVM/ToLLVMInterface.h

@@ -11,6 +11,7 @@
 
 #include "mlir/IR/DialectInterface.h"
 #include "mlir/IR/MLIRContext.h"
+#include "mlir/IR/OpDefinition.h"
 
 namespace mlir {
 class ConversionTarget;
@@ -50,6 +51,18 @@ void populateConversionTargetFromOperation(Operation *op,
                                            LLVMTypeConverter &typeConverter,
                                            RewritePatternSet &patterns);
 
+/// Helper function for populating LLVM conversion patterns. If `op` implements
+/// the `ConvertToLLVMOpInterface` interface, then the LLVM conversion pattern
+/// attributes provided by the interface will be used to configure the
+/// conversion target, type converter, and the pattern set.
+void populateOpConvertToLLVMConversionPatterns(Operation *op,
+                                               ConversionTarget &target,
+                                               LLVMTypeConverter &typeConverter,
+                                               RewritePatternSet &patterns);
 } // namespace mlir
 
+#include "mlir/Conversion/ConvertToLLVM/ToLLVMAttrInterface.h.inc"
+
+#include "mlir/Conversion/ConvertToLLVM/ToLLVMOpInterface.h.inc"
+
 #endif // MLIR_CONVERSION_CONVERTTOLLVM_TOLLVMINTERFACE_H

mlir/include/mlir/Conversion/ConvertToLLVM/ToLLVMInterface.td

@@ -0,0 +1,76 @@
+
+//===- ToLLVMInterface.td - Conversion to LLVM interfaces -----*- tablegen -*-===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines interfaces for managing transformations, including populating
+// pattern rewrites.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_CONVERTTOLLVM_TOLLVMINTERFACE_TD
+#define MLIR_CONVERSION_CONVERTTOLLVM_TOLLVMINTERFACE_TD
+
+include "mlir/IR/OpBase.td"
+
+//===----------------------------------------------------------------------===//
+// Attribute interface
+//===----------------------------------------------------------------------===//
+
+def ConvertToLLVMAttrInterface :
+    AttrInterface<"ConvertToLLVMAttrInterface"> {
+  let description = [{
+    The `ConvertToLLVMAttrInterface` attribute interfaces allows using
+    attributes to configure the convert to LLVM infrastructure, this includes:
+     - The conversion target.
+     - The LLVM type converter.
+     - The pattern set.
+
+    This interface permits fined grained configuration of the `convert-to-llvm`
+    process. For example, attributes with target information like
+    `#nvvm.target` or `#rodcl.target` can leverage this interface for populating
+    patterns specific to a particular target.
+  }];
+  let cppNamespace = "::mlir";
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/[{
+        Populate the dialect conversion target, type converter and pattern set.
+      }],
+      /*retTy=*/"void",
+      /*methodName=*/"populateConvertToLLVMConversionPatterns",
+      /*args=*/(ins "::mlir::ConversionTarget&":$target,
+                    "::mlir::LLVMTypeConverter&":$typeConverter,
+                    "::mlir::RewritePatternSet&":$patternSet)>
+  ];
+}
+
+//===----------------------------------------------------------------------===//
+// Op interface
+//===----------------------------------------------------------------------===//
+
+def ConvertToLLVMOpInterface : OpInterface<"ConvertToLLVMOpInterface"> {
+  let description = [{
+    Interface for collecting all convert to LLVM attributes stored in an
+    operation. See `ConvertToLLVMAttrInterface` for more information on these
+    attributes.
+  }];
+  let cppNamespace = "::mlir";
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/[{
+        Populate the provided vector with a list of convert to LLVM attributes
+        to apply.
+      }],
+      /*retTy=*/"void",
+      /*methodName=*/"getConvertToLLVMConversionAttrs",
+      /*args=*/(ins
+        "::llvm::SmallVectorImpl<::mlir::ConvertToLLVMAttrInterface>&":$attrs)
+    >
+  ];
+}
+
+#endif // MLIR_CONVERSION_CONVERTTOLLVM_TOLLVMINTERFACE_TD

mlir/include/mlir/Conversion/GPUCommon/GPUToLLVM.h

@@ -0,0 +1,25 @@
+//===- GPUToLLVM.h - Convert GPU to LLVM dialect ----------------*- 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 files declares registration functions for converting GPU to LLVM.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_GPUCOMMON_GPUTOLLVM_H
+#define MLIR_CONVERSION_GPUCOMMON_GPUTOLLVM_H
+
+namespace mlir {
+class DialectRegistry;
+namespace gpu {
+/// Registers the `ConvertToLLVMOpInterface` interface on the `gpu::GPUModuleOP`
+/// operation.
+void registerConvertGpuToLLVMInterface(DialectRegistry &registry);
+} // namespace gpu
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_GPUCOMMON_GPUTOLLVM_H

mlir/include/mlir/Conversion/GPUToNVVM/GPUToNVVM.h

@@ -0,0 +1,27 @@
+//===- GPUToNVVM.h - Convert GPU to NVVM dialect ----------------*- 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 files declares registration functions for converting GPU to NVVM.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_GPUTONVVM_GPUTONVVM_H
+#define MLIR_CONVERSION_GPUTONVVM_GPUTONVVM_H
+
+namespace mlir {
+class DialectRegistry;
+namespace NVVM {
+/// Registers the `ConvertToLLVMAttrInterface` interface on the
+/// `NVVM::NVVMTargetAttr` attribute. This interface populates the conversion
+/// target, LLVM type converter, and pattern set for converting GPU operations
+/// to NVVM.
+void registerConvertGpuToNVVMInterface(DialectRegistry &registry);
+} // namespace NVVM
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_GPUTONVVM_GPUTONVVM_H

mlir/include/mlir/Conversion/GPUToNVVM/GPUToNVVMPass.h

@@ -31,6 +31,10 @@ LLVM::LLVMStructType convertMMAToLLVMType(gpu::MMAMatrixType type);
 /// Configure target to convert from the GPU dialect to NVVM.
 void configureGpuToNVVMConversionLegality(ConversionTarget &target);
 
+/// Configure the LLVM type convert to convert types and address spaces from the
+/// GPU dialect to NVVM.
+void configureGpuToNVVMTypeConverter(LLVMTypeConverter &converter);
+
 /// Collect a set of patterns to convert from the GPU dialect to NVVM.
 void populateGpuToNVVMConversionPatterns(const LLVMTypeConverter &converter,
                                          RewritePatternSet &patterns);

mlir/include/mlir/InitAllExtensions.h

@@ -18,6 +18,8 @@
 #include "mlir/Conversion/ComplexToLLVM/ComplexToLLVM.h"
 #include "mlir/Conversion/ControlFlowToLLVM/ControlFlowToLLVM.h"
 #include "mlir/Conversion/FuncToLLVM/ConvertFuncToLLVM.h"
+#include "mlir/Conversion/GPUCommon/GPUToLLVM.h"
+#include "mlir/Conversion/GPUToNVVM/GPUToNVVM.h"
 #include "mlir/Conversion/IndexToLLVM/IndexToLLVM.h"
 #include "mlir/Conversion/MathToLLVM/MathToLLVM.h"
 #include "mlir/Conversion/MemRefToLLVM/MemRefToLLVM.h"
@@ -72,6 +74,8 @@ inline void registerAllExtensions(DialectRegistry &registry) {
   registerConvertOpenMPToLLVMInterface(registry);
   ub::registerConvertUBToLLVMInterface(registry);
   registerConvertAMXToLLVMInterface(registry);
+  gpu::registerConvertGpuToLLVMInterface(registry);
+  NVVM::registerConvertGpuToNVVMInterface(registry);
 
   // Register all transform dialect extensions.
   affine::registerTransformDialectExtension(registry);

mlir/lib/Conversion/ConvertToLLVM/CMakeLists.txt

@@ -7,6 +7,7 @@ add_mlir_conversion_library(MLIRConvertToLLVMInterface
   ToLLVMInterface.cpp
 
   DEPENDS
+  MLIRConvertToLLVMInterfaceIncGen
 
   LINK_LIBS PUBLIC
   MLIRIR

mlir/lib/Conversion/ConvertToLLVM/ConvertToLLVMPass.cpp

@@ -63,9 +63,8 @@ class LoadDependentDialectExtension : public DialectExtensionBase {
 /// the injection of conversion patterns.
 class ConvertToLLVMPass
     : public impl::ConvertToLLVMPassBase<ConvertToLLVMPass> {
-  std::shared_ptr<const FrozenRewritePatternSet> patterns;
-  std::shared_ptr<const ConversionTarget> target;
-  std::shared_ptr<const LLVMTypeConverter> typeConverter;
+  std::shared_ptr<const SmallVector<ConvertToLLVMPatternInterface *>>
+      interfaces;
 
 public:
   using impl::ConvertToLLVMPassBase<ConvertToLLVMPass>::ConvertToLLVMPassBase;
@@ -75,11 +74,8 @@ class ConvertToLLVMPass
   }
 
   LogicalResult initialize(MLIRContext *context) final {
-    RewritePatternSet tempPatterns(context);
-    auto target = std::make_shared<ConversionTarget>(*context);
-    target->addLegalDialect<LLVM::LLVMDialect>();
-    auto typeConverter = std::make_shared<LLVMTypeConverter>(context);
-
+    auto interfaces =
+        std::make_shared<SmallVector<ConvertToLLVMPatternInterface *>>();
     if (!filterDialects.empty()) {
       // Test mode: Populate only patterns from the specified dialects. Produce
       // an error if the dialect is not loaded or does not implement the
@@ -94,8 +90,7 @@ class ConvertToLLVMPass
           return emitError(UnknownLoc::get(context))
                  << "dialect does not implement ConvertToLLVMPatternInterface: "
                  << dialectName << "\n";
-        iface->populateConvertToLLVMConversionPatterns(*target, *typeConverter,
-                                                       tempPatterns);
+        interfaces->push_back(iface);
       }
     } else {
       // Normal mode: Populate all patterns from all dialects that implement the
@@ -106,20 +101,33 @@ class ConvertToLLVMPass
         auto *iface = dyn_cast<ConvertToLLVMPatternInterface>(dialect);
         if (!iface)
           continue;
-        iface->populateConvertToLLVMConversionPatterns(*target, *typeConverter,
-                                                       tempPatterns);
+        interfaces->push_back(iface);
       }
     }
 
-    this->patterns =
-        std::make_unique<FrozenRewritePatternSet>(std::move(tempPatterns));
-    this->target = target;
-    this->typeConverter = typeConverter;
+    this->interfaces = interfaces;
     return success();
   }
 
   void runOnOperation() final {
-    if (failed(applyPartialConversion(getOperation(), *target, *patterns)))
+    MLIRContext *context = &getContext();
+    RewritePatternSet patterns(context);
+    ConversionTarget target(*context);
+    target.addLegalDialect<LLVM::LLVMDialect>();
+    LLVMTypeConverter typeConverter(context);
+
+    // Configure the conversion with dialect level interfaces.
+    for (ConvertToLLVMPatternInterface *iface : *interfaces)
+      iface->populateConvertToLLVMConversionPatterns(target, typeConverter,
+                                                     patterns);
+
+    // Configure the conversion attribute interfaces.
+    populateOpConvertToLLVMConversionPatterns(getOperation(), target,
+                                              typeConverter, patterns);
+
+    // Apply the conversion.
+    if (failed(applyPartialConversion(getOperation(), target,
+                                      std::move(patterns))))
       signalPassFailure();
   }
 };