[Clang Interpreter] Initial patch for the constexpr interpreter

Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370476

1 files changed, 45 insertions, 0 deletions

diff --git a/clang/lib/AST/Interp/Frame.h b/clang/lib/AST/Interp/Frame.h
new file mode 100644
index 00000000000..b9a0ea9412f
--- /dev/null
+++ b/clang/lib/AST/Interp/Frame.h
@@ -0,0 +1,45 @@
+//===--- Frame.h - Call frame for the VM and AST Walker ---------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines the base class of interpreter and evaluator stack frames.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_INTERP_FRAME_H
+#define LLVM_CLANG_AST_INTERP_FRAME_H
+
+#include "clang/Basic/SourceLocation.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace clang {
+class FunctionDecl;
+
+namespace interp {
+
+/// Base class for stack frames, shared between VM and walker.
+class Frame {
+public:
+  virtual ~Frame();
+
+  /// Generates a human-readable description of the call site.
+  virtual void describe(llvm::raw_ostream &OS) = 0;
+
+  /// Returns a pointer to the caller frame.
+  virtual Frame *getCaller() const = 0;
+
+  /// Returns the location of the call site.
+  virtual SourceLocation getCallLocation() const = 0;
+
+  /// Returns the called function's declaration.
+  virtual const FunctionDecl *getCallee() const = 0;
+};
+
+} // namespace interp
+} // namespace clang
+
+#endif