// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#if !V8_ENABLE_WEBASSEMBLY
#error This header should only be included if WebAssembly is enabled.
#endif  // !V8_ENABLE_WEBASSEMBLY

#ifndef V8_WASM_WASM_INIT_EXPR_H_
#define V8_WASM_WASM_INIT_EXPR_H_

#include <memory>

#include "src/wasm/value-type.h"

namespace v8 {
namespace internal {
namespace wasm {

// Representation of an initializer expression.
class WasmInitExpr {
 public:
  enum Operator {
    kNone,
    kGlobalGet,
    kI32Const,
    kI64Const,
    kF32Const,
    kF64Const,
    kS128Const,
    kRefNullConst,
    kRefFuncConst,
    kRttCanon,
    kRttSub,
    kRttFreshSub,
  };

  union Immediate {
    int32_t i32_const;
    int64_t i64_const;
    float f32_const;
    double f64_const;
    std::array<uint8_t, kSimd128Size> s128_const;
    uint32_t index;
    HeapType::Representation heap_type;
  };

  WasmInitExpr() : kind_(kNone) { immediate_.i32_const = 0; }
  explicit WasmInitExpr(int32_t v) : kind_(kI32Const) {
    immediate_.i32_const = v;
  }
  explicit WasmInitExpr(int64_t v) : kind_(kI64Const) {
    immediate_.i64_const = v;
  }
  explicit WasmInitExpr(float v) : kind_(kF32Const) {
    immediate_.f32_const = v;
  }
  explicit WasmInitExpr(double v) : kind_(kF64Const) {
    immediate_.f64_const = v;
  }
  explicit WasmInitExpr(uint8_t v[kSimd128Size]) : kind_(kS128Const) {
    base::Memcpy(immediate_.s128_const.data(), v, kSimd128Size);
  }

  MOVE_ONLY_NO_DEFAULT_CONSTRUCTOR(WasmInitExpr);

  static WasmInitExpr GlobalGet(uint32_t index) {
    WasmInitExpr expr;
    expr.kind_ = kGlobalGet;
    expr.immediate_.index = index;
    return expr;
  }

  static WasmInitExpr RefFuncConst(uint32_t index) {
    WasmInitExpr expr;
    expr.kind_ = kRefFuncConst;
    expr.immediate_.index = index;
    return expr;
  }

  static WasmInitExpr RefNullConst(HeapType::Representation heap_type) {
    WasmInitExpr expr;
    expr.kind_ = kRefNullConst;
    expr.immediate_.heap_type = heap_type;
    return expr;
  }

  static WasmInitExpr RttCanon(uint32_t index) {
    WasmInitExpr expr;
    expr.kind_ = kRttCanon;
    expr.immediate_.index = index;
    return expr;
  }

  static WasmInitExpr RttSub(uint32_t index, WasmInitExpr supertype) {
    WasmInitExpr expr;
    expr.kind_ = kRttSub;
    expr.immediate_.index = index;
    expr.operand_ = std::make_unique<WasmInitExpr>(std::move(supertype));
    return expr;
  }

  static WasmInitExpr RttFreshSub(uint32_t index, WasmInitExpr supertype) {
    WasmInitExpr expr;
    expr.kind_ = kRttFreshSub;
    expr.immediate_.index = index;
    expr.operand_ = std::make_unique<WasmInitExpr>(std::move(supertype));
    return expr;
  }

  Immediate immediate() const { return immediate_; }
  Operator kind() const { return kind_; }
  WasmInitExpr* operand() const { return operand_.get(); }

  bool operator==(const WasmInitExpr& other) const {
    if (kind() != other.kind()) return false;
    switch (kind()) {
      case kNone:
        return true;
      case kGlobalGet:
      case kRefFuncConst:
      case kRttCanon:
        return immediate().index == other.immediate().index;
      case kI32Const:
        return immediate().i32_const == other.immediate().i32_const;
      case kI64Const:
        return immediate().i64_const == other.immediate().i64_const;
      case kF32Const:
        return immediate().f32_const == other.immediate().f32_const;
      case kF64Const:
        return immediate().f64_const == other.immediate().f64_const;
      case kS128Const:
        return immediate().s128_const == other.immediate().s128_const;
      case kRefNullConst:
        return immediate().heap_type == other.immediate().heap_type;
      case kRttSub:
      case kRttFreshSub:
        return immediate().index == other.immediate().index &&
               *operand() == *other.operand();
    }
  }

  V8_INLINE bool operator!=(const WasmInitExpr& other) {
    return !(*this == other);
  }

 private:
  Immediate immediate_;
  Operator kind_;
  std::unique_ptr<WasmInitExpr> operand_ = nullptr;
};

}  // namespace wasm
}  // namespace internal
}  // namespace v8

#endif  // V8_WASM_WASM_INIT_EXPR_H_
