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//===- llvm/IR/Statepoint.h - gc.statepoint utilities -----------*- 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 contains utility functions and a wrapper class analogous to

// CallBase for accessing the fields of gc.statepoint, gc.relocate,

// gc.result intrinsics; and some general utilities helpful when dealing with

// gc.statepoint.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_STATEPOINT_H

#define LLVM_IR_STATEPOINT_H

#include "llvm/ADT/iterator_range.h"

#include "llvm/IR/Attributes.h"

#include "llvm/IR/Constants.h"

#include "llvm/IR/Function.h"

#include "llvm/IR/InstrTypes.h"

#include "llvm/IR/Instructions.h"

#include "llvm/IR/IntrinsicInst.h"

#include "llvm/IR/Intrinsics.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/MathExtras.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <optional>

#include <vector>

namespace llvm {

/// The statepoint intrinsic accepts a set of flags as its third argument.

/// Valid values come out of this set.

enum class StatepointFlags {

  None = 0,

  GCTransition = 1, ///< Indicates that this statepoint is a transition from

                    ///< GC-aware code to code that is not GC-aware.

  /// Mark the deopt arguments associated with the statepoint as only being

  /// "live-in". By default, deopt arguments are "live-through".  "live-through"

  /// requires that they the value be live on entry, on exit, and at any point

  /// during the call.  "live-in" only requires the value be available at the

  /// start of the call.  In particular, "live-in" values can be placed in

  /// unused argument registers or other non-callee saved registers.

  DeoptLiveIn = 2,

  MaskAll = 3 ///< A bitmask that includes all valid flags.

};

// These two are defined in IntrinsicInst since they're part of the

// IntrinsicInst class hierarchy.

class GCRelocateInst;

/// Represents a gc.statepoint intrinsic call.  This extends directly from

/// CallBase as the IntrinsicInst only supports calls and gc.statepoint is

/// invokable.

class GCStatepointInst : public CallBase {

public:

  GCStatepointInst() = delete;

  GCStatepointInst(const GCStatepointInst &) = delete;

  GCStatepointInst &operator=(const GCStatepointInst &) = delete;

  static bool classof(const CallBase *I) {

    if (const Function *CF = I->getCalledFunction())

      return CF->getIntrinsicID() == Intrinsic::experimental_gc_statepoint;

    return false;

  }

  static bool classof(const Value *V) {

    return isa<CallBase>(V) && classof(cast<CallBase>(V));

  }

  enum {

    IDPos = 0,

    NumPatchBytesPos = 1,

    CalledFunctionPos = 2,

    NumCallArgsPos = 3,

    FlagsPos = 4,

    CallArgsBeginPos = 5,

  };

  /// Return the ID associated with this statepoint.

  uint64_t getID() const {

    return cast<ConstantInt>(getArgOperand(IDPos))->getZExtValue();

  }

  /// Return the number of patchable bytes associated with this statepoint.

  uint32_t getNumPatchBytes() const {

    const Value *NumPatchBytesVal = getArgOperand(NumPatchBytesPos);

    uint64_t NumPatchBytes =

      cast<ConstantInt>(NumPatchBytesVal)->getZExtValue();

    assert(isInt<32>(NumPatchBytes) && "should fit in 32 bits!");

    return NumPatchBytes;

  }

  /// Number of arguments to be passed to the actual callee.

  int getNumCallArgs() const {

    return cast<ConstantInt>(getArgOperand(NumCallArgsPos))->getZExtValue();

  }

  uint64_t getFlags() const {

    return cast<ConstantInt>(getArgOperand(FlagsPos))->getZExtValue();

  }

  /// Return the value actually being called or invoked.

  Value *getActualCalledOperand() const {

    return getArgOperand(CalledFunctionPos);

  }

  /// Returns the function called if this is a wrapping a direct call, and null

  /// otherwise.

  Function *getActualCalledFunction() const {

    return dyn_cast_or_null<Function>(getActualCalledOperand());

  }

  /// Return the type of the value returned by the call underlying the

  /// statepoint.

  Type *getActualReturnType() const {

    auto *FT = cast<FunctionType>(getParamElementType(CalledFunctionPos));

    return FT->getReturnType();

  }

  /// Return the number of arguments to the underlying call.

  size_t actual_arg_size() const { return getNumCallArgs(); }

  /// Return an iterator to the begining of the arguments to the underlying call

  const_op_iterator actual_arg_begin() const {

    assert(CallArgsBeginPos <= (int)arg_size());

    return arg_begin() + CallArgsBeginPos;

  }

  /// Return an end iterator of the arguments to the underlying call

  const_op_iterator actual_arg_end() const {

    auto I = actual_arg_begin() + actual_arg_size();

    assert((arg_end() - I) == 2);

    return I;

  }

  /// range adapter for actual call arguments

  iterator_range<const_op_iterator> actual_args() const {

    return make_range(actual_arg_begin(), actual_arg_end());

  }

  const_op_iterator gc_transition_args_begin() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_gc_transition))

      return Opt->Inputs.begin();

    return arg_end();

  }

  const_op_iterator gc_transition_args_end() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_gc_transition))

      return Opt->Inputs.end();

    return arg_end();

  }

  /// range adapter for GC transition arguments

  iterator_range<const_op_iterator> gc_transition_args() const {

    return make_range(gc_transition_args_begin(), gc_transition_args_end());

  }

  const_op_iterator deopt_begin() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_deopt))

      return Opt->Inputs.begin();

    return arg_end();

  }

  const_op_iterator deopt_end() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_deopt))

      return Opt->Inputs.end();

    return arg_end();

  }

  /// range adapter for vm state arguments

  iterator_range<const_op_iterator> deopt_operands() const {

    return make_range(deopt_begin(), deopt_end());

  }

  /// Returns an iterator to the begining of the argument range describing gc

  /// values for the statepoint.

  const_op_iterator gc_args_begin() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_gc_live))

      return Opt->Inputs.begin();

    return arg_end();

  }

  /// Return an end iterator for the gc argument range

  const_op_iterator gc_args_end() const {

    if (auto Opt = getOperandBundle(LLVMContext::OB_gc_live))

      return Opt->Inputs.end();

    return arg_end();

  }

  /// range adapter for gc arguments

  iterator_range<const_op_iterator> gc_args() const {

    return make_range(gc_args_begin(), gc_args_end());

  }

  /// Get list of all gc reloactes linked to this statepoint

  /// May contain several relocations for the same base/derived pair.

  /// For example this could happen due to relocations on unwinding

  /// path of invoke.

  inline std::vector<const GCRelocateInst *> getGCRelocates() const;

};

std::vector<const GCRelocateInst *> GCStatepointInst::getGCRelocates() const {

  std::vector<const GCRelocateInst *> Result;

  // Search for relocated pointers.  Note that working backwards from the

  // gc_relocates ensures that we only get pairs which are actually relocated

  // and used after the statepoint.

  for (const User *U : users())

    if (auto *Relocate = dyn_cast<GCRelocateInst>(U))

      Result.push_back(Relocate);

  auto *StatepointInvoke = dyn_cast<InvokeInst>(this);

  if (!StatepointInvoke)

    return Result;

  // We need to scan thorough exceptional relocations if it is invoke statepoint

  LandingPadInst *LandingPad = StatepointInvoke->getLandingPadInst();

  // Search for gc relocates that are attached to this landingpad.

  for (const User *LandingPadUser : LandingPad->users()) {

    if (auto *Relocate = dyn_cast<GCRelocateInst>(LandingPadUser))

      Result.push_back(Relocate);

  }

  return Result;

}

/// Call sites that get wrapped by a gc.statepoint (currently only in

/// RewriteStatepointsForGC and potentially in other passes in the future) can

/// have attributes that describe properties of gc.statepoint call they will be

/// eventually be wrapped in.  This struct is used represent such directives.

struct StatepointDirectives {

  std::optional<uint32_t> NumPatchBytes;

  std::optional<uint64_t> StatepointID;

  static const uint64_t DefaultStatepointID = 0xABCDEF00;

  static const uint64_t DeoptBundleStatepointID = 0xABCDEF0F;

};

/// Parse out statepoint directives from the function attributes present in \p

/// AS.

StatepointDirectives parseStatepointDirectivesFromAttrs(AttributeList AS);

/// Return \c true if the \p Attr is an attribute that is a statepoint

/// directive.

bool isStatepointDirectiveAttr(Attribute Attr);

} // end namespace llvm

#endif // LLVM_IR_STATEPOINT_H