[Mlir-commits] [mlir] [mlir][NFC] Move LLVM::ModuleTranslation::SaveStack to a shared header (PR #144897)

[Tom Eccles]

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@@ -0,0 +1,116 @@
+//===- StateStack.h - Utility for storing a stack of state ------*- 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 defines utilities for storing a stack of generic context.
+// The context can be arbitrary data, possibly including file-scoped types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_SUPPORT_STACKFRAME_H
+#define MLIR_SUPPORT_STACKFRAME_H
+
+#include "mlir/IR/Visitors.h"
+#include "mlir/Support/TypeID.h"
+#include <memory>
+
+namespace mlir {
+
+/// Common CRTP base class for StateStack frames.
+class StateStackFrame {
+public:
+  virtual ~StateStackFrame() = default;
+  TypeID getTypeID() const { return typeID; }
+
+protected:
+  explicit StateStackFrame(TypeID typeID) : typeID(typeID) {}
+
+private:
+  const TypeID typeID;
+  virtual void anchor() {};
+};
+
+/// Concrete CRTP base class for StateStack frames. This is used for keeping a
+/// stack of common state useful for recursive IR conversions. For example, when
+/// translating operations with regions, users of StateStack can store state on
+/// StateStack before entering the region and inspect it when converting
+/// operations nested within that region. Users are expected to derive this
+/// class and put any relevant information into fields of the derived class. The
+/// usual isa/dyn_cast functionality is available for instances of derived
+/// classes.
+template <typename Derived>
+class StateStackFrameBase : public StateStackFrame {
+public:
+  explicit StateStackFrameBase() : StateStackFrame(TypeID::get<Derived>()) {}
+};
+
+class StateStack {
+public:
+  /// Creates a stack frame of type `T` on StateStack. `T` must
+  /// be derived from `StackFrameBase<T>` and constructible from the provided
+  /// arguments. Doing this before entering the region of the op being
+  /// translated makes the frame available when translating ops within that
+  /// region.
+  template <typename T, typename... Args>
+  void stackPush(Args &&...args) {
+    static_assert(std::is_base_of<StateStackFrame, T>::value,
+                  "can only push instances of StackFrame on StateStack");
+    stack.push_back(std::make_unique<T>(std::forward<Args>(args)...));
+  }
+
+  /// Pops the last element from the StateStack.
+  void stackPop() { stack.pop_back(); }
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tblah wrote:

Probably yes. My aim here was to keep the interface the same instead of attempting to improving it at the same time as moving, especially while there are no users for a return value from `stackPop`.

https://github.com/llvm/llvm-project/pull/144897