[clang] [CIR] Add framework for CIR to LLVM IR lowering (PR #124650)

[Andy Kaylor via cfe-commits]

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@@ -0,0 +1,41 @@
+//====- LowerToLLVM.cpp - Lowering from CIR to LLVMIR ---------------------===//
+//
+// 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 LLVMIR.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/CIR/LowerToLLVM.h"
+
+#include "mlir/IR/BuiltinOps.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Pass/PassManager.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/TimeProfiler.h"
+
+using namespace cir;
+using namespace llvm;
+
+namespace cir {
+namespace direct {
+
+std::unique_ptr<llvm::Module>
+lowerDirectlyFromCIRToLLVMIR(mlir::ModuleOp MOp, LLVMContext &LLVMCtx) {
+  llvm::TimeTraceScope scope("lower from CIR to LLVM directly");
+
+  std::optional<StringRef> ModuleName = MOp.getName();
+  auto M = std::make_unique<llvm::Module>(
+      ModuleName ? *ModuleName : "CIRToLLVMModule", LLVMCtx);
+
+  if (!M)
+    report_fatal_error("Lowering from LLVMIR dialect to llvm IR failed!");
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andykaylor wrote:

The incubator implementation uses report_fatal_error in several situations similar to this. I don't know if it was intended as a temporary measure or not. Is the right way to handle this passing in a reference to a DiagnosticsEngine?

https://github.com/llvm/llvm-project/pull/124650