[mlir][vector] Create VectorToLLVMDialectInterface (#121440)

Create `VectorToLLVMDialectInterface` which allows automatic conversion
discovery by generic `--convert-to-llvm` pass. This only covers final
dialect conversion step and not any previous preparation steps. Also,
currently there is no way to pass any additional parameters through this
conversion interface, but most users using default parameters anyway.

Author: Hardcode84

mlir/include/mlir/Conversion/VectorToLLVM/ConvertVectorToLLVM.h

@@ -24,6 +24,9 @@ void populateVectorToLLVMConversionPatterns(
     const LLVMTypeConverter &converter, RewritePatternSet &patterns,
     bool reassociateFPReductions = false, bool force32BitVectorIndices = false);
 
+namespace vector {
+void registerConvertVectorToLLVMInterface(DialectRegistry &registry);
+}
 } // namespace mlir
 
 #endif // MLIR_CONVERSION_VECTORTOLLVM_CONVERTVECTORTOLLVM_H_

mlir/include/mlir/InitAllExtensions.h

@@ -26,6 +26,7 @@
 #include "mlir/Conversion/NVVMToLLVM/NVVMToLLVM.h"
 #include "mlir/Conversion/OpenMPToLLVM/ConvertOpenMPToLLVM.h"
 #include "mlir/Conversion/UBToLLVM/UBToLLVM.h"
+#include "mlir/Conversion/VectorToLLVM/ConvertVectorToLLVM.h"
 #include "mlir/Dialect/AMX/Transforms.h"
 #include "mlir/Dialect/Affine/TransformOps/AffineTransformOps.h"
 #include "mlir/Dialect/Bufferization/TransformOps/BufferizationTransformOps.h"
@@ -76,6 +77,7 @@ inline void registerAllExtensions(DialectRegistry &registry) {
   registerConvertAMXToLLVMInterface(registry);
   gpu::registerConvertGpuToLLVMInterface(registry);
   NVVM::registerConvertGpuToNVVMInterface(registry);
+  vector::registerConvertVectorToLLVMInterface(registry);
 
   // Register all transform dialect extensions.
   affine::registerTransformDialectExtension(registry);

mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp

@@ -9,6 +9,7 @@
 #include "mlir/Conversion/VectorToLLVM/ConvertVectorToLLVM.h"
 
 #include "mlir/Conversion/ArithCommon/AttrToLLVMConverter.h"
+#include "mlir/Conversion/ConvertToLLVM/ToLLVMInterface.h"
 #include "mlir/Conversion/LLVMCommon/PrintCallHelper.h"
 #include "mlir/Conversion/LLVMCommon/TypeConverter.h"
 #include "mlir/Conversion/LLVMCommon/VectorPattern.h"
@@ -1942,3 +1943,27 @@ void mlir::populateVectorToLLVMMatrixConversionPatterns(
   patterns.add<VectorMatmulOpConversion>(converter);
   patterns.add<VectorFlatTransposeOpConversion>(converter);
 }
+
+namespace {
+struct VectorToLLVMDialectInterface : public ConvertToLLVMPatternInterface {
+  using ConvertToLLVMPatternInterface::ConvertToLLVMPatternInterface;
+  void loadDependentDialects(MLIRContext *context) const final {
+    context->loadDialect<LLVM::LLVMDialect>();
+  }
+
+  /// Hook for derived dialect interface to provide conversion patterns
+  /// and mark dialect legal for the conversion target.
+  void populateConvertToLLVMConversionPatterns(
+      ConversionTarget &target, LLVMTypeConverter &typeConverter,
+      RewritePatternSet &patterns) const final {
+    populateVectorToLLVMConversionPatterns(typeConverter, patterns);
+  }
+};
+} // namespace
+
+void mlir::vector::registerConvertVectorToLLVMInterface(
+    DialectRegistry &registry) {
+  registry.addExtension(+[](MLIRContext *ctx, vector::VectorDialect *dialect) {
+    dialect->addInterfaces<VectorToLLVMDialectInterface>();
+  });
+}

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -13,6 +13,7 @@
 
 #include "mlir/Dialect/Vector/IR/VectorOps.h"
 
+#include "mlir/Conversion/ConvertToLLVM/ToLLVMInterface.h"
 #include "mlir/Dialect/Affine/IR/ValueBoundsOpInterfaceImpl.h"
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/Arith/Utils/Utils.h"
@@ -428,6 +429,7 @@ void VectorDialect::initialize() {
                             TransferWriteOp>();
   declarePromisedInterface<SubsetExtractionOpInterface, TransferReadOp>();
   declarePromisedInterface<SubsetInsertionOpInterface, TransferWriteOp>();
+  declarePromisedInterface<ConvertToLLVMPatternInterface, VectorDialect>();
 }
 
 /// Materialize a single constant operation from a given attribute value with

mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir

@@ -0,0 +1,14 @@
+// Most of the vector lowering is tested in vector-to-llvm.mlir, this file only for the interface smoke test
+// RUN: mlir-opt --convert-to-llvm="filter-dialects=vector" --split-input-file %s | FileCheck %s
+
+func.func @bitcast_f32_to_i32_vector_0d(%arg0: vector<f32>) -> vector<i32> {
+  %0 = vector.bitcast %arg0 : vector<f32> to vector<i32>
+  return %0 : vector<i32>
+}
+
+// CHECK-LABEL: @bitcast_f32_to_i32_vector_0d
+// CHECK-SAME:  %[[ARG_0:.*]]: vector<f32>
+// CHECK:       %[[VEC_F32_1D:.*]] = builtin.unrealized_conversion_cast %[[ARG_0]] : vector<f32> to vector<1xf32>
+// CHECK:       %[[VEC_I32_1D:.*]] = llvm.bitcast %[[VEC_F32_1D]] : vector<1xf32> to vector<1xi32>
+// CHECK:       %[[VEC_I32_0D:.*]] = builtin.unrealized_conversion_cast %[[VEC_I32_1D]] : vector<1xi32> to vector<i32>
+// CHECK:       return %[[VEC_I32_0D]] : vector<i32>