[llvm] [SandboxIR] Boilerplate code (PR #95814)

[Arthur Eubanks via llvm-commits]

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@@ -0,0 +1,154 @@
+//===- SandboxIR.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
+//
+//===----------------------------------------------------------------------===//
+//
+// Sandbox IR is a lightweight overlay transactional IR on top of LLVM IR.
+// Features:
+// - You can save/rollback the state of the IR at any time.
+// - Any changes made to Sandbox IR will automatically update the underlying
+//   LLVM IR so both IRs are always in sync.
+// - Feels like LLVM IR, similar API.
+//
+// SandboxIR forms a class hierarcy that resembles that of LLVM IR
+// but is in the `sandboxir` namespace:
+//
+// namespace sandboxir {
+//
+//        +- Argument                   +- BinaryOperator
+//        |                             |
+// Value -+- BasicBlock                 +- BranchInst
+//        |                             |
+//        +- Function   +- Constant     +- CastInst
+//        |             |               |
+//        +- User ------+- Instruction -+- CallInst
+//                                      |
+//                                      +- CmpInst
+//                                      |
+//                                      +- ExtractElementInst
+//                                      |
+//                                      +- GetElementPtrInst
+//                                      |
+//                                      +- InsertElementInst
+//                                      |
+//                                      +- LoadInst
+//                                      |
+//                                      +- OpaqueInst
+//                                      |
+//                                      +- PHINode
+//                                      |
+//                                      +- RetInst
+//                                      |
+//                                      +- SelectInst
+//                                      |
+//                                      +- ShuffleVectorInst
+//                                      |
+//                                      +- StoreInst
+//                                      |
+//                                      +- UnaryOperator
+//
+// Use
+//
+// } // namespace sandboxir
+//
+
+#ifndef LLVM_TRANSFORMS_SANDBOXIR_SANDBOXIR_H
+#define LLVM_TRANSFORMS_SANDBOXIR_SANDBOXIR_H
+
+#include "llvm/IR/User.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+
+namespace sandboxir {
+
+class Context;
+
+/// A SandboxIR Value has users. This is the base class.
+class Value {
+public:
+  enum class ClassID : unsigned {
+#define DEF_VALUE(ID, CLASS) ID,
+#define DEF_USER(ID, CLASS) ID,
+#define DEF_INSTR(ID, OPC, CLASS) ID,
+#include "llvm/Transforms/SandboxIR/SandboxIRValues.def"
+  };
+
+protected:
+  static const char *getSubclassIDStr(ClassID ID) {
+    switch (ID) {
+      // clang-format off
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aeubanks wrote:

is `clang-format off` just for one space? doesn't seem worth it

https://github.com/llvm/llvm-project/pull/95814