[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.

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>();
+  });
+}