[clang] [CIR] Initial implementation of lowering CIR to MLIR (PR #127835)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,201 @@
+//====- LowerCIRToMLIR.cpp - Lowering from CIR to MLIR --------------------===//
+//
+// 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 file implements lowering of CIR operations to MLIR.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/MemRef/IR/MemRef.h"
+#include "mlir/IR/BuiltinDialect.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Pass/PassManager.h"
+#include "mlir/Transforms/DialectConversion.h"
+#include "clang/CIR/Dialect/IR/CIRDialect.h"
+#include "clang/CIR/Dialect/IR/CIRTypes.h"
+#include "clang/CIR/LowerToLLVM.h"
+#include "clang/CIR/MissingFeatures.h"
+#include "llvm/ADT/TypeSwitch.h"
+#include "llvm/Support/TimeProfiler.h"
+
+using namespace cir;
+using namespace llvm;
+
+namespace cir {
+
+struct ConvertCIRToMLIRPass
+    : public mlir::PassWrapper<ConvertCIRToMLIRPass,
+                               mlir::OperationPass<mlir::ModuleOp>> {
+  void getDependentDialects(mlir::DialectRegistry &registry) const override {
+    registry.insert<mlir::BuiltinDialect, mlir::memref::MemRefDialect>();
+  }
+  void runOnOperation() final;
+
+  StringRef getDescription() const override {
+    return "Convert the CIR dialect module to MLIR standard dialects";
+  }
+
+  StringRef getArgument() const override { return "cir-to-mlir"; }
+};
+
+class CIRGlobalOpLowering : public mlir::OpConversionPattern<cir::GlobalOp> {
+public:
+  using OpConversionPattern<cir::GlobalOp>::OpConversionPattern;
+  mlir::LogicalResult
+  matchAndRewrite(cir::GlobalOp op, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    auto moduleOp = op->getParentOfType<mlir::ModuleOp>();
+    if (!moduleOp)
+      return mlir::failure();
+
+    mlir::OpBuilder b(moduleOp.getContext());
+
+    const auto cirSymType = op.getSymType();
+    assert(!cir::MissingFeatures::convertTypeForMemory());
+    auto convertedType = getTypeConverter()->convertType(cirSymType);
+    if (!convertedType)
+      return mlir::failure();
+    auto memrefType = dyn_cast<mlir::MemRefType>(convertedType);
----------------
AaronBallman wrote:

`auto *`, right?

https://github.com/llvm/llvm-project/pull/127835