Add MissingFeatures tracker

Author: andykaylor

clang/include/clang/CIR/MissingFeatures.h

@@ -0,0 +1,40 @@
+//===---- MissingFeatures.h - Checks for unimplemented features -*- 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 file introduces some helper classes to guard against features that
+// CIR dialect supports that we do not have and also do not have great ways to
+// assert against.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CLANG_CIR_MISSINGFEATURES_H
+#define CLANG_CIR_MISSINGFEATURES_H
+
+namespace cir {
+
+// As a way to track features that haven't yet been implemented this class
+// explicitly contains a list of static fns that will return false that you
+// can guard against. If and when a feature becomes implemented simply changing
+// this return to true will cause compilation to fail at all the points in which
+// we noted that we needed to address. This is a much more explicit way to
+// handle "TODO"s.
+struct MissingFeatures {
+  // Address space related
+  static bool addressSpace() { return false; }
+
+  // Unhandled global/linkage information.
+  static bool opGlobalDSOLocal() { return false; }
+  static bool opGlobalThreadLocal() { return false; }
+  static bool opGlobalConstant() { return false; }
+  static bool opGlobalAlignment() { return false; }
+  static bool opGlobalLinkage() { return false; }
+};
+
+} // namespace cir
+
+#endif // CLANG_CIR_MISSINGFEATURES_H

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -25,6 +25,7 @@
 #include "mlir/Target/LLVMIR/Export.h"
 #include "mlir/Transforms/DialectConversion.h"
 #include "clang/CIR/Dialect/IR/CIRDialect.h"
+#include "clang/CIR/MissingFeatures.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/TimeProfiler.h"
 
@@ -62,12 +63,18 @@ mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
   // This is the LLVM dialect type.
   const mlir::Type llvmType = getTypeConverter()->convertType(cirSymType);
   // FIXME: These default values are placeholders until the the equivalent
-  //        attributes are available on cir.global ops.  
+  //        attributes are available on cir.global ops.
+  assert(!cir::MissingFeatures::opGlobalConstant());
   const bool isConst = false;
+  assert(!cir::MissingFeatures::addressSpace());
   const unsigned addrSpace = 0;
+  assert(!cir::MissingFeatures::opGlobalDSOLocal());
   const bool isDsoLocal = true;
+  assert(!cir::MissingFeatures::opGlobalThreadLocal());
   const bool isThreadLocal = false;
+  assert(!cir::MissingFeatures::opGlobalAlignment());
   const uint64_t alignment = 0;
+  assert(!cir::MissingFeatures::opGlobalLinkage());
   const mlir::LLVM::Linkage linkage = mlir::LLVM::Linkage::External;
   const StringRef symbol = op.getSymName();
   std::optional<mlir::Attribute> init = op.getInitialValue();