Add ISsaContext: Type-erased wrapper for SsaContext

[nhaehnle]

Summary

Virtual method dispatch is used to provide the functionality of
SsaContext to algorithms that are written to be generic without
the use of templates.

Change-Id: Id8fdc249baf34cb4e215738344fa418d067257a1

llvm/include/llvm/Support/SsaContext.h

 //===- SsaContext.h ---------------------------------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 /// \file
 ///
 /// This file defines a set of classes around the SsaContext concept that allows
 /// code to abstract over some of the differences between SSA-form IRs beyond
 /// what is possible from templates via context-free functions like
 /// \ref llvm::GraphTraits<T>::child_begin()/child_end().
 ///
+/// Additionally, this file defines the \ref ISsaContext interface class and
+/// its implementation that provides a superset of the SsaContext functionality
+/// to code that wants to abstract over different IRs without being written as
+/// templates.
+///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_SSACONTEXT_H
 #define LLVM_SUPPORT_SSACONTEXT_H
 
+#include "llvm/Support/Handle.h"
 #include "llvm/Support/Printable.h"
 
 namespace llvm {
 
 class Printable;
 
 /// Users of SsaContext should use \ref SsaContextFor instead.
 ///

 ///     Printable printableName(BlockRef ref) const;
 ///     Printable printable(InstructionRef ref) const;
 ///     Printable printable(ValueRef ref) const;
 ///   };
 ///
 template <typename RefType>
 using SsaContextFor = typename SsaContextForImpl<RefType>::Context;
 
+/// \brief Interface class for type-erased wrapping of SsaContext
+///
+/// Do not provide manual implementations of this class. Instead, specialize
+/// \ref SsaContextForImpl and rely on \ref ISsaContextImpl.
+class ISsaContext {
+  virtual void anchor();
+
+public:
+  virtual BlockHandle getDefBlock(SsaValueHandle value) const = 0;
+
+  virtual Printable printableName(BlockHandle ref) const = 0;
+  virtual Printable printable(InstructionHandle ref) const = 0;
+  virtual Printable printable(SsaValueHandle ref) const = 0;
+};
+
+/// \brief Implementation of \ref ISsaContext for a context-type
+///
+/// Analysis classes that desire a broader interface can have that interface
+/// inherit from ISsaContext, with implementations instantiating this template
+/// with a custom Base parameter that refers to the broader interface.
+template <typename SsaContextT, typename Base = ISsaContext>
+class ISsaContextImpl : public Base, SsaContextT {
+public:
+  using SsaContext = SsaContextT;
+  using BlockRef = typename SsaContext::BlockRef;
+  using InstructionRef = typename SsaContext::InstructionRef;
+  using ValueRef = typename SsaContext::ValueRef;
+  using Wrapper = typename SsaContext::Wrapper;
+
+  ISsaContextImpl(BlockRef ref) : SsaContext(ref) {}
+  ISsaContextImpl(InstructionRef ref) : SsaContext(ref) {}
+
+  const SsaContext &getSsaContext() const { return *this; }
+
+  BlockHandle getDefBlock(SsaValueHandle value) const final {
+    return Wrapper::wrapRef(SsaContext::getDefBlock(Wrapper::unwrapRef(value)));
+  }
+
+  Printable printableName(BlockHandle ref) const final {
+    return SsaContext::printableName(Wrapper::unwrapRef(ref));
+  }
+
+  Printable printable(InstructionHandle ref) const final {
+    return SsaContext::printable(Wrapper::unwrapRef(ref));
+  }
+
+  Printable printable(SsaValueHandle ref) const final {
+    return SsaContext::printable(Wrapper::unwrapRef(ref));
+  }
+};
+
+template <typename RefTypeT>
+using ISsaContextFor = ISsaContextImpl<SsaContextFor<RefTypeT>>;
+
 } // namespace llvm
 
 #endif // LLVM_SUPPORT_SSACONTEXT_H

llvm/lib/Support/CMakeLists.txt

add_llvm_component_library(LLVMSupport
   ScaledNumber.cpp
   ScopedPrinter.cpp
   SHA1.cpp
   Signposts.cpp
   SmallPtrSet.cpp
   SmallVector.cpp
   SourceMgr.cpp
   SpecialCaseList.cpp
+  SsaContext.cpp
   Statistic.cpp
   StringExtras.cpp
   StringMap.cpp
   StringSaver.cpp
   StringRef.cpp
   SuffixTree.cpp
   SymbolRemappingReader.cpp
   SystemUtils.cpp

llvm/lib/Support/SsaContext.cpp

+//===- SsaContext.cpp -------------------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/SsaContext.h"
+
+using namespace llvm;
+
+void ISsaContext::anchor() {}