//===--- SILOpenedArchetypesTracker.cpp - Track opened archetypes ---------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "swift/SIL/SILOpenedArchetypesTracker.h"

using namespace swift;

void SILOpenedArchetypesTracker::addOpenedArchetypeDef(Type archetype,
                                                       SILValue Def) {
  archetype = archetype->getDesugaredType();
  assert(archetype->is<ArchetypeType>() && "The type should be an archetype");
  auto OldDef = getOpenedArchetypeDef(archetype);
  if (OldDef && isa<GlobalAddrInst>(OldDef)) {
    // It is a forward definition created during deserialization.
    // Replace it with the real definition now.
    OldDef->replaceAllUsesWith(Def);
    OldDef = SILValue();
  }
  assert(!OldDef &&
         "There can be only one definition of an opened archetype");
  OpenedArchetypeDefs[archetype] = Def;
}

/// Check if there are any unresolved forward definitions of opened
/// archetypes.
bool SILOpenedArchetypesTracker::hasUnresolvedOpenedArchetypeDefinitions() {
  for (auto &KV : getOpenedArchetypeDefs()) {
    assert(KV.getFirst()->is<ArchetypeType>() && "The type should be an archetype");
    if (!KV.getSecond() || isa<GlobalAddrInst>(KV.getSecond()))
      return true;
  }
  return false;
}

void SILOpenedArchetypesTracker::registerUsedOpenedArchetypes(Type Ty) {
  // Nothing else to be done if the type does not contain an opened archetype.
  if (!Ty || !Ty->hasOpenedExistential())
    return;

  // Find all opened existentials used by this type and check if their
  // definitions are known.
  Ty.visit([&](Type ty) {
    if (!ty->isOpenedExistential())
      return;

    ty = ty->getDesugaredType();

    // Nothing to do if a definition was seen already.
    if (getOpenedArchetypeDef(ty))
      return;

    auto &SILMod = this->getFunction().getModule();
    // Create a placeholder representing a forward definition.
    auto Placeholder = new (SILMod)
        GlobalAddrInst(SILDebugLocation(), SILMod.Types.getLoweredType(ty));
    // Make it available to SILBuilder, so that instructions using this
    // archetype can be constructed.
    addOpenedArchetypeDef(ty, Placeholder);
  });
}

// Register archetypes opened by a given instruction.
// Can be used to incrementally populate the mapping, e.g.
// if it is done when performing a scan of all instructions
// inside a function.
void SILOpenedArchetypesTracker::registerOpenedArchetypes(
    const SILInstruction *I) {
  assert((!I->getParent() || I->getFunction() == &F) &&
         "Instruction does not belong to a proper SILFunction");
  auto Archetype = getOpenedArchetypeOf(I);
  if (Archetype)
    addOpenedArchetypeDef(Archetype, I);
}

// Register opened archetypes whose definitions are referenced by
// the typedef operands of this instruction.
void SILOpenedArchetypesTracker::registerUsedOpenedArchetypes(
    const SILInstruction *I) {
  assert((!I->getParent() || I->getFunction() == &F) &&
         "Instruction does not belong to a proper SILFunction");
  for (auto &Op : I->getOpenedArchetypeOperands()) {
    auto OpenedArchetypeDef = Op.get();
    assert(isa<SILInstruction>(OpenedArchetypeDef) &&
           "typedef operand should refer to a SILInstruction");
    addOpenedArchetypeDef(
        getOpenedArchetypeOf(cast<SILInstruction>(OpenedArchetypeDef)),
        OpenedArchetypeDef);
  }
}

// Unregister archetypes opened by a given instruction.
// Should be only called when this instruction is to be removed.
void SILOpenedArchetypesTracker::unregisterOpenedArchetypes(
    const SILInstruction *I) {
  assert(I->getFunction() == &F &&
         "Instruction does not belong to a proper SILFunction");
  auto Archetype = getOpenedArchetypeOf(I);
  if (Archetype)
    removeOpenedArchetypeDef(Archetype, I);
}

void SILOpenedArchetypesTracker::handleDeleteNotification(
    swift::ValueBase *Value) {
  if (auto I = dyn_cast<SILInstruction>(Value))
    if (I->getFunction() == &F)
      unregisterOpenedArchetypes(I);
}

/// Find an opened archetype defined by an instruction.
/// \returns The found archetype or empty type otherwise.
CanType swift::getOpenedArchetypeOf(const SILInstruction *I) {
  if (isa<OpenExistentialAddrInst>(I) || isa<OpenExistentialRefInst>(I) ||
      isa<OpenExistentialBoxInst>(I) || isa<OpenExistentialMetatypeInst>(I)) {
    auto Ty = getOpenedArchetypeOf(I->getType().getSwiftRValueType());
    assert(Ty->isOpenedExistential() && "Type should be an opened archetype");
    return Ty;
  }

  return CanType();
}


bool hasAtMostOneOpenedArchetype(CanType Ty) {
  int NumOpenedArchetypes = 0;
  Ty.visit([&](Type t) {
    if (t->isOpenedExistential()) {
      NumOpenedArchetypes++;
    }
    return;
  });
  return NumOpenedArchetypes <= 1;
}

/// Find an opened archetype represented by this type.
/// It is assumed by this method that the type contains
/// at most one opened archetype.
/// Typically, it would be called from a type visitor.
/// It checks only the type itself, but does not try to
/// recursively check any children of this type, because
/// this is the task of the type visitor invoking it.
/// \returns The found archetype or empty type otherwise.
CanType swift::getOpenedArchetypeOf(CanType Ty) {
  if (!Ty)
    return CanType();
  assert(hasAtMostOneOpenedArchetype(Ty) &&
         "Type should contain at most one opened archetype");
  while (auto MetaTy = dyn_cast<AnyMetatypeType>(Ty)) {
    Ty = MetaTy->getInstanceType().getCanonicalTypeOrNull();
  }
  if (Ty->isOpenedExistential())
    return Ty;
  return CanType();
}

SILValue SILOpenedArchetypesState::getOpenedArchetypeDef(Type Ty) const {
  if (!Ty)
    return SILValue();
  auto CanTy = Ty.getCanonicalTypeOrNull();
  // First perform a quick check.
  for (auto &Op : OpenedArchetypeOperands) {
    auto Def = Op.get();
    if (getOpenedArchetypeOf(cast<SILInstruction>(Def)) == CanTy)
      return Def;
  }
  // Then use a regular lookup.
  if (OpenedArchetypesTracker)
    return OpenedArchetypesTracker->getOpenedArchetypeDef(Ty);
  return SILValue();
}