/// \brief Check if this instruction corresponds to user-written code.
static bool isUserCode(const SILInstruction *I) {
  SILLocation Loc = I->getLoc();
  if (Loc.isAutoGenerated())
    return false;
  
  // Branch instructions are not user code. These could belong to the control
  // flow statement we are folding (ex: while loop).
  // Also, unreachable instructions are not user code, they are "expected" in
  // unreachable blocks.
  if ((isa<BranchInst>(I) || isa<UnreachableInst>(I)) &&
      Loc.is<RegularLocation>())
    return false;
  
  // If the instruction corresponds to user-written return or some other
  // statement, we know it corresponds to user code.
  if (Loc.is<RegularLocation>() || Loc.is<ReturnLocation>()) {
    if (auto *E = Loc.getAsASTNode<Expr>())
      return !E->isImplicit();
    if (auto *D = Loc.getAsASTNode<Decl>())
      return !D->isImplicit();
    if (auto *S = Loc.getAsASTNode<Decl>())
      return !S->isImplicit();
    if (auto *P = Loc.getAsASTNode<Decl>())
      return !P->isImplicit();
    return true;
  }
  return false;
}

static void diagnoseMissingReturn(const UnreachableInst *UI,
                                  ASTContext &Context) {
  const SILBasicBlock *BB = UI->getParent();
  const SILFunction *F = BB->getParent();
  SILLocation FLoc = F->getLocation();

  Type ResTy;

  if (auto *FD = FLoc.getAsASTNode<FuncDecl>()) {
    ResTy = FD->getResultType();
  } else if (auto *CE = FLoc.getAsASTNode<ClosureExpr>()) {
    ResTy = CE->getResultType();
  } else {
    llvm_unreachable("unhandled case in MissingReturn");
  }

  bool isNoReturn = F->getLoweredFunctionType()->isNoReturn();

  // No action required if the function returns 'Void' or that the
  // function is marked 'noreturn'.
  if (ResTy->isVoid() || isNoReturn)
    return;

  SILLocation L = UI->getLoc();
  assert(L && ResTy);
  diagnose(Context,
           L.getEndSourceLoc(),
           diag::missing_return, ResTy,
           FLoc.isASTNode<ClosureExpr>() ? 1 : 0);
}

SILFunction *MaterializeForSetEmitter::createCallback(SILFunction &F,
                                                      GeneratorFn generator) {
  auto callbackType =
      SGM.Types.getMaterializeForSetCallbackType(WitnessStorage,
                                                 GenericSig,
                                                 SelfInterfaceType,
                                                 CallbackRepresentation);

  auto *genericEnv = GenericEnv;
  if (GenericEnv && GenericEnv->getGenericSignature()->areAllParamsConcrete())
    genericEnv = nullptr;

  auto callback =
    SGM.M.createFunction(Linkage, CallbackName, callbackType,
                         genericEnv, SILLocation(Witness),
                         IsBare, F.isTransparent(), F.isFragile(),
                         IsNotThunk,
                         /*ClassVisibility=*/SILFunction::NotRelevant,
                         /*InlineStrategy=*/InlineDefault,
                         /*EffectsKind=*/EffectsKind::Unspecified,
                         /*InsertBefore=*/&F);

  callback->setDebugScope(new (SGM.M) SILDebugScope(Witness, callback));

  PrettyStackTraceSILFunction X("silgen materializeForSet callback", callback);
  {
    SILGenFunction gen(SGM, *callback);

    auto makeParam = [&](unsigned index) -> SILArgument * {
      SILType type = gen.F.mapTypeIntoContext(
          gen.getSILType(callbackType->getParameters()[index]));
      return gen.F.begin()->createFunctionArgument(type);
    };

    // Add arguments for all the parameters.
    auto valueBuffer = makeParam(0);
    auto storageBuffer = makeParam(1);
    auto self = makeParam(2);
    (void) makeParam(3);

    SILLocation loc = Witness;
    loc.markAutoGenerated();

    // Call the generator function we were provided.
    {
      LexicalScope scope(gen.Cleanups, gen, CleanupLocation::get(loc));
      generator(gen, loc, valueBuffer, storageBuffer, self);
    }

    // Return void.
    auto result = gen.emitEmptyTuple(loc);
    gen.B.createReturn(loc, result);
  }

  callback->verify();
  return callback;
}

SILFunction *MaterializeForSetEmitter::createCallback(SILFunction &F,
                                                      GeneratorFn generator) {
  auto callbackType =
      SGM.Types.getMaterializeForSetCallbackType(WitnessStorage,
                                                 GenericSig,
                                                 SelfInterfaceType);
  auto callback =
      SGM.M.getOrCreateFunction(Witness, CallbackName, Linkage,
                                callbackType, IsBare,
                                F.isTransparent(),
                                F.isFragile());

  callback->setGenericEnvironment(GenericEnv);
  callback->setDebugScope(new (SGM.M) SILDebugScope(Witness, callback));

  PrettyStackTraceSILFunction X("silgen materializeForSet callback", callback);
  {
    SILGenFunction gen(SGM, *callback);

    auto makeParam = [&](unsigned index) -> SILArgument* {
      SILType type = gen.F.mapTypeIntoContext(
          callbackType->getParameters()[index].getSILType());
      return new (SGM.M) SILArgument(gen.F.begin(), type);
    };

    // Add arguments for all the parameters.
    auto valueBuffer = makeParam(0);
    auto storageBuffer = makeParam(1);
    auto self = makeParam(2);
    (void) makeParam(3);

    SILLocation loc = Witness;
    loc.markAutoGenerated();

    // Call the generator function we were provided.
    {
      LexicalScope scope(gen.Cleanups, gen, CleanupLocation::get(loc));
      generator(gen, loc, valueBuffer, storageBuffer, self);
    }

    // Return void.
    auto result = gen.emitEmptyTuple(loc);
    gen.B.createReturn(loc, result);
  }

  callback->verify();
  return callback;
}

/// Given that this is an 'Unknown' value, emit diagnostic notes providing
/// context about what the problem is.
void SymbolicValue::emitUnknownDiagnosticNotes(SILLocation fallbackLoc) {
  auto badInst = dyn_cast<SILInstruction>(getUnknownNode());
  if (!badInst)
    return;

  bool emittedFirstNote = emitNoteDiagnostic(badInst, getUnknownReason(),
                                             fallbackLoc);

  auto sourceLoc = fallbackLoc.getSourceLoc();
  auto &module = badInst->getModule();
  if (sourceLoc.isInvalid()) {
    diagnose(module.getASTContext(), sourceLoc, diag::constexpr_not_evaluable);
    return;
  }
  for (auto &sourceLoc : llvm::reverse(getUnknownCallStack())) {
    // Skip unknown sources.
    if (!sourceLoc.isValid())
      continue;

    auto diag = emittedFirstNote ? diag::constexpr_called_from
                                 : diag::constexpr_not_evaluable;
    diagnose(module.getASTContext(), sourceLoc, diag);
    emittedFirstNote = true;
  }
}

CleanupLocation CleanupLocation::get(SILLocation L) {
  if (Expr *E = L.getAsASTNode<Expr>())
    return CleanupLocation(E, L.getSpecialFlags());
  if (Stmt *S = L.getAsASTNode<Stmt>())
    return CleanupLocation(S, L.getSpecialFlags());
  if (Pattern *P = L.getAsASTNode<Pattern>())
    return CleanupLocation(P, L.getSpecialFlags());
  if (Decl *D = L.getAsASTNode<Decl>())
    return CleanupLocation(D, L.getSpecialFlags());
  if (L.isNull())
    return CleanupLocation();
  if (L.getAs<SILFileLocation>())
    return CleanupLocation();
  llvm_unreachable("Cannot construct Cleanup loc from the "
                   "given location.");
}

SILValue SILGenFunction::emitGlobalFunctionRef(SILLocation loc,
                                               SILDeclRef constant,
                                               SILConstantInfo constantInfo) {
  assert(constantInfo == getConstantInfo(constant));

  // Builtins must be fully applied at the point of reference.
  if (constant.hasDecl() &&
      isa<BuiltinUnit>(constant.getDecl()->getDeclContext())) {
    SGM.diagnose(loc.getSourceLoc(), diag::not_implemented,
                 "delayed application of builtin");
    return SILUndef::get(constantInfo.getSILType(), SGM.M);
  }
  
  // If the constant is a thunk we haven't emitted yet, emit it.
  if (!SGM.hasFunction(constant)) {
    if (constant.isCurried) {
      SGM.emitCurryThunk(constant);
    } else if (constant.isForeignToNativeThunk()) {
      SGM.emitForeignToNativeThunk(constant);
    } else if (constant.isNativeToForeignThunk()) {
      SGM.emitNativeToForeignThunk(constant);
    } else if (constant.kind == SILDeclRef::Kind::EnumElement) {
      SGM.emitEnumConstructor(cast<EnumElementDecl>(constant.getDecl()));
    }
  }

  auto f = SGM.getFunction(constant, NotForDefinition);
  assert(f->getLoweredFunctionType() == constantInfo.SILFnType);
  return B.createFunctionRef(loc, f);
}

void swift::printSILLocationDescription(llvm::raw_ostream &out,
                                        SILLocation loc,
                                        ASTContext &Context) {
  if (loc.isNull()) {
    out << "<<invalid location>>";
  } else if (loc.isSILFile()) {
    printSourceLocDescription(out, loc.getSourceLoc(), Context);
  } else if (auto decl = loc.getAsASTNode<Decl>()) {
    printDeclDescription(out, decl, Context);
  } else if (auto expr = loc.getAsASTNode<Expr>()) {
    printExprDescription(out, expr, Context);
  } else if (auto stmt = loc.getAsASTNode<Stmt>()) {
    printStmtDescription(out, stmt, Context);
  } else if (auto pattern = loc.castToASTNode<Pattern>()) {
    printPatternDescription(out, pattern, Context);
  }
}

static void diagnoseReturn(const SILInstruction *I, ASTContext &Context) {
  auto *TI = dyn_cast<TermInst>(I);
  if (!TI || !(isa<BranchInst>(TI) || isa<ReturnInst>(TI)))
    return;

  const SILBasicBlock *BB = TI->getParent();
  const SILFunction *F = BB->getParent();

  // Warn if we reach a return inside a noreturn function.
  if (F->getLoweredFunctionType()->isNoReturn()) {
    SILLocation L = TI->getLoc();
    if (L.is<ReturnLocation>())
      diagnose(Context, L.getSourceLoc(), diag::return_from_noreturn);
    if (L.is<ImplicitReturnLocation>())
      diagnose(Context, L.getSourceLoc(), diag::return_from_noreturn);
  }
}

static void diagnoseMissingReturn(const UnreachableInst *UI,
                                  ASTContext &Context) {
  const SILBasicBlock *BB = UI->getParent();
  const SILFunction *F = BB->getParent();
  SILLocation FLoc = F->getLocation();

  Type ResTy;
  BraceStmt *BS;

  if (auto *FD = FLoc.getAsASTNode<FuncDecl>()) {
    ResTy = FD->getResultInterfaceType();
    BS = FD->getBody(/*canSynthesize=*/false);
  } else if (auto *CD = FLoc.getAsASTNode<ConstructorDecl>()) {
    ResTy = CD->getResultInterfaceType();
    BS = FD->getBody();
  } else if (auto *CE = FLoc.getAsASTNode<ClosureExpr>()) {
    ResTy = CE->getResultType();
    BS = CE->getBody();
  } else {
    llvm_unreachable("unhandled case in MissingReturn");
  }

  SILLocation L = UI->getLoc();
  assert(L && ResTy);
  auto numElements = BS->getNumElements();
  if (numElements > 0) {
    auto element = BS->getElement(numElements - 1);
    if (auto expr = element.dyn_cast<Expr *>()) {
      if (expr->getType()->getCanonicalType() == ResTy->getCanonicalType()) {
        Context.Diags.diagnose(
          expr->getStartLoc(),
          diag::missing_return_last_expr, ResTy,
          FLoc.isASTNode<ClosureExpr>() ? 1 : 0)
        .fixItInsert(expr->getStartLoc(), "return ");
        return;
      }
    }
  }
  auto diagID = F->isNoReturnFunction() ? diag::missing_never_call
                                        : diag::missing_return;
  diagnose(Context,
           L.getEndSourceLoc(),
           diagID, ResTy,
           FLoc.isASTNode<ClosureExpr>() ? 1 : 0);
}

InlinedLocation InlinedLocation::getInlinedLocation(SILLocation L) {
  if (Expr *E = L.getAsASTNode<Expr>())
    return InlinedLocation(E, L.getSpecialFlags());
  if (Stmt *S = L.getAsASTNode<Stmt>())
    return InlinedLocation(S, L.getSpecialFlags());
  if (Pattern *P = L.getAsASTNode<Pattern>())
    return InlinedLocation(P, L.getSpecialFlags());
  if (Decl *D = L.getAsASTNode<Decl>())
    return InlinedLocation(D, L.getSpecialFlags());

  if (L.hasSILFileSourceLoc())
    return InlinedLocation(L.getSILFileSourceLoc(), L.getSpecialFlags());

  if (L.isInTopLevel())
    return InlinedLocation::getModuleLocation(L.getSpecialFlags());

  if (L.isAutoGenerated()) {
    InlinedLocation IL;
    IL.markAutoGenerated();
    return IL;
  }
  llvm_unreachable("Cannot construct Inlined loc from the given location.");
}

static void diagnoseUnreachable(const SILInstruction *I,
                                ASTContext &Context) {
  if (auto *UI = dyn_cast<UnreachableInst>(I)){
    SILLocation L = UI->getLoc();

    // Invalid location means that the instruction has been generated by SIL
    // passes, such as DCE. FIXME: we might want to just introduce a separate
    // instruction kind, instead of keeping this invariant.
    //
    // We also do not want to emit diagnostics for code that was
    // transparently inlined. We should have already emitted these
    // diagnostics when we process the callee function prior to
    // inlining it.
    if (!L.hasASTLocation() || L.is<MandatoryInlinedLocation>())
      return;

    // The most common case of getting an unreachable instruction is a
    // missing return statement. In this case, we know that the instruction
    // location will be the enclosing function.
    if (L.isASTNode<AbstractFunctionDecl>() || L.isASTNode<ClosureExpr>()) {
      diagnoseMissingReturn(UI, Context);
      return;
    }

    // A non-exhaustive switch would also produce an unreachable instruction.
    if (L.isASTNode<SwitchStmt>()) {
      diagnose(Context, L.getEndSourceLoc(), diag::non_exhaustive_switch);
      return;
    }

    if (auto *Guard = L.getAsASTNode<GuardStmt>()) {
      diagnose(Context, Guard->getBody()->getEndLoc(),
               diag::guard_body_must_not_fallthrough);
      return;
    }
  }
}

SILValue SILGenFunction::emitGlobalFunctionRef(SILLocation loc,
                                               SILDeclRef constant,
                                               SILConstantInfo constantInfo) {
  assert(constantInfo == getConstantInfo(constant));

  // Builtins must be fully applied at the point of reference.
  if (constant.hasDecl() &&
      isa<BuiltinUnit>(constant.getDecl()->getDeclContext())) {
    SGM.diagnose(loc.getSourceLoc(), diag::not_implemented,
                 "delayed application of builtin");
    return SILUndef::get(constantInfo.getSILType(), SGM.M);
  }
  
  // If the constant is a thunk we haven't emitted yet, emit it.
  if (!SGM.hasFunction(constant)) {
    if (constant.isCurried) {
      auto vd = constant.getDecl();
      // Reference the next uncurrying level of the function.
      SILDeclRef next = SILDeclRef(vd, constant.kind,
                                 SILDeclRef::ConstructAtBestResilienceExpansion,
                                 constant.uncurryLevel + 1);
      // If the function is fully uncurried and natively foreign, reference its
      // foreign entry point.
      if (!next.isCurried) {
        if (requiresForeignToNativeThunk(vd))
          next = next.asForeign();
      }
      
      // Preserve whether the curry thunks lead to a direct reference to the
      // method implementation.
      next = next.asDirectReference(constant.isDirectReference);

      SGM.emitCurryThunk(vd, constant, next);
    }
    // Otherwise, if this is a calling convention thunk we haven't emitted yet,
    // emit it.
    else if (constant.isForeignToNativeThunk()) {
      SGM.emitForeignToNativeThunk(constant);
    } else if (constant.isNativeToForeignThunk()) {
      SGM.emitNativeToForeignThunk(constant);
    } else if (constant.kind == SILDeclRef::Kind::EnumElement) {
      SGM.emitEnumConstructor(cast<EnumElementDecl>(constant.getDecl()));
    }
  }

  auto f = SGM.getFunction(constant, NotForDefinition);
  assert(f->getLoweredFunctionType() == constantInfo.SILFnType);
  return B.createFunctionRef(loc, f);
}

MandatoryInlinedLocation
MandatoryInlinedLocation::getMandatoryInlinedLocation(SILLocation L) {
  if (Expr *E = L.getAsASTNode<Expr>())
    return MandatoryInlinedLocation(E, L.getSpecialFlags());
  if (Stmt *S = L.getAsASTNode<Stmt>())
    return MandatoryInlinedLocation(S, L.getSpecialFlags());
  if (Pattern *P = L.getAsASTNode<Pattern>())
    return MandatoryInlinedLocation(P, L.getSpecialFlags());
  if (Decl *D = L.getAsASTNode<Decl>())
    return MandatoryInlinedLocation(D, L.getSpecialFlags());

  if (L.isSILFile())
    return MandatoryInlinedLocation(L.Loc.SILFileLoc, L.getSpecialFlags());

  if (L.isInTopLevel())
    return MandatoryInlinedLocation::getModuleLocation(L.getSpecialFlags());

  llvm_unreachable("Cannot construct Inlined loc from the given location.");
}

/// Emit a check for whether a non-native function call produced an
/// error.
///
/// \c results should be left with only values that match the formal
/// direct results of the function.
void
SILGenFunction::emitForeignErrorCheck(SILLocation loc,
                                      SmallVectorImpl<ManagedValue> &results,
                                      ManagedValue errorSlot,
                                      bool suppressErrorCheck,
                                const ForeignErrorConvention &foreignError) {
  // All of this is autogenerated.
  loc.markAutoGenerated();

  switch (foreignError.getKind()) {
  case ForeignErrorConvention::ZeroPreservedResult:
    assert(results.size() == 1);
    emitResultIsZeroErrorCheck(*this, loc, results[0], errorSlot,
                               suppressErrorCheck,
                               /*zeroIsError*/ true);
    return;
  case ForeignErrorConvention::ZeroResult:
    assert(results.size() == 1);
    emitResultIsZeroErrorCheck(*this, loc, results.pop_back_val(),
                               errorSlot, suppressErrorCheck,
                               /*zeroIsError*/ true);
    return;
  case ForeignErrorConvention::NonZeroResult:
    assert(results.size() == 1);
    emitResultIsZeroErrorCheck(*this, loc, results.pop_back_val(),
                               errorSlot, suppressErrorCheck,
                               /*zeroIsError*/ false);
    return;
  case ForeignErrorConvention::NilResult:
    assert(results.size() == 1);
    results[0] = emitResultIsNilErrorCheck(*this, loc, results[0], errorSlot,
                                           suppressErrorCheck);
    return;
  case ForeignErrorConvention::NonNilError:
    // Leave the direct results alone.
    emitErrorIsNonNilErrorCheck(*this, loc, errorSlot, suppressErrorCheck);
    return;
  }
  llvm_unreachable("bad foreign error convention kind");
}

static void emitSourceLocationArgs(SILGenFunction &gen,
                                   SILLocation loc,
                                   ManagedValue (&args)[4]) {
  auto &ctx = gen.getASTContext();
  auto sourceLoc = loc.getSourceLoc();
  
  StringRef filename = "";
  unsigned line = 0;
  if (sourceLoc.isValid()) {
    unsigned bufferID = ctx.SourceMgr.findBufferContainingLoc(sourceLoc);
    filename = ctx.SourceMgr.getIdentifierForBuffer(bufferID);
    line = ctx.SourceMgr.getLineAndColumn(sourceLoc).first;
  }
  
  bool isASCII = true;
  for (unsigned char c : filename) {
    if (c > 127) {
      isASCII = false;
      break;
    }
  }
  
  auto wordTy = SILType::getBuiltinWordType(ctx);
  auto i1Ty = SILType::getBuiltinIntegerType(1, ctx);
  
  // File
  SILValue literal = gen.B.createStringLiteral(loc, filename,
                                             StringLiteralInst::Encoding::UTF8);
  args[0] = ManagedValue::forUnmanaged(literal);
  // File length
  literal = gen.B.createIntegerLiteral(loc, wordTy, filename.size());
  args[1] = ManagedValue::forUnmanaged(literal);
  // File is ascii
  literal = gen.B.createIntegerLiteral(loc, i1Ty, isASCII);
  args[2] = ManagedValue::forUnmanaged(literal);
  // Line
  literal = gen.B.createIntegerLiteral(loc, wordTy, line);
  args[3] = ManagedValue::forUnmanaged(literal);
}

/// Emits an explanatory note if there is useful information to note or if there
/// is an interesting SourceLoc to point at.
/// Returns true if a diagnostic was emitted.
static bool emitNoteDiagnostic(SILInstruction *badInst, UnknownReason reason,
                               SILLocation fallbackLoc) {
  auto loc = skipInternalLocations(badInst->getDebugLocation()).getLocation();
  if (loc.isNull()) {
    // If we have important clarifying information, make sure to emit it.
    if (reason == UnknownReason::Default || fallbackLoc.isNull())
      return false;
    loc = fallbackLoc;
  }

  auto &ctx = badInst->getModule().getASTContext();
  auto sourceLoc = loc.getSourceLoc();
  switch (reason) {
  case UnknownReason::Default:
    diagnose(ctx, sourceLoc, diag::constexpr_unknown_reason_default)
        .highlight(loc.getSourceRange());
    break;
  case UnknownReason::TooManyInstructions:
    // TODO: Should pop up a level of the stack trace.
    diagnose(ctx, sourceLoc, diag::constexpr_too_many_instructions,
             ConstExprLimit)
        .highlight(loc.getSourceRange());
    break;
  case UnknownReason::Loop:
    diagnose(ctx, sourceLoc, diag::constexpr_loop)
        .highlight(loc.getSourceRange());
    break;
  case UnknownReason::Overflow:
    diagnose(ctx, sourceLoc, diag::constexpr_overflow)
        .highlight(loc.getSourceRange());
    break;
  case UnknownReason::Trap:
    diagnose(ctx, sourceLoc, diag::constexpr_trap)
        .highlight(loc.getSourceRange());
    break;
  }
  return true;
}

/// \brief Issue an "unreachable code" diagnostic if the blocks contains or
/// leads to another block that contains user code.
///
/// Note, we rely on SILLocation information to determine if SILInstructions
/// correspond to user code.
static bool diagnoseUnreachableBlock(const SILBasicBlock &B,
                                     SILModule &M,
                                     const SILBasicBlockSet &Reachable,
                                     UnreachableUserCodeReportingState *State,
                                     const SILBasicBlock *TopLevelB,
                         llvm::SmallPtrSetImpl<const SILBasicBlock*> &Visited){
  if (Visited.count(&B))
    return false;
  Visited.insert(&B);
  
  assert(State);
  for (auto I = B.begin(), E = B.end(); I != E; ++I) {
    SILLocation Loc = I->getLoc();
    // If we've reached an implicit return, we have not found any user code and
    // can stop searching for it.
    if (Loc.is<ImplicitReturnLocation>() || Loc.isAutoGenerated())
      return false;

    // Check if the instruction corresponds to user-written code, also make
    // sure we don't report an error twice for the same instruction.
    if (isUserCode(&*I) && !State->BlocksWithErrors.count(&B)) {

      // Emit the diagnostic.
      auto BrInfoIter = State->MetaMap.find(TopLevelB);
      assert(BrInfoIter != State->MetaMap.end());
      auto BrInfo = BrInfoIter->second;

      switch (BrInfo.Kind) {
      case (UnreachableKind::FoldedBranch):
        // Emit the diagnostic on the unreachable block and emit the
        // note on the branch responsible for the unreachable code.
        diagnose(M.getASTContext(), Loc.getSourceLoc(), diag::unreachable_code);
        diagnose(M.getASTContext(), BrInfo.Loc.getSourceLoc(),
                 diag::unreachable_code_branch, BrInfo.CondIsAlwaysTrue);
        break;

      case (UnreachableKind::FoldedSwitchEnum): {
        // If we are warning about a switch condition being a constant, the main
        // emphasis should be on the condition (to ensure we have a single
        // message per switch).
        const SwitchStmt *SS = BrInfo.Loc.getAsASTNode<SwitchStmt>();
        if (!SS)
          break;
        assert(SS);
        const Expr *SE = SS->getSubjectExpr();
        diagnose(M.getASTContext(), SE->getLoc(), diag::switch_on_a_constant);
        diagnose(M.getASTContext(), Loc.getSourceLoc(),
                 diag::unreachable_code_note);
        break;
      }

      case (UnreachableKind::NoreturnCall): {
        // Specialcase when we are warning about unreachable code after a call
        // to a noreturn function.
        if (!BrInfo.Loc.isASTNode<ExplicitCastExpr>()) {
          assert(BrInfo.Loc.isASTNode<ApplyExpr>());
          diagnose(M.getASTContext(), Loc.getSourceLoc(),
                   diag::unreachable_code);
          diagnose(M.getASTContext(), BrInfo.Loc.getSourceLoc(),
                   diag::call_to_noreturn_note);
        }
        break;
      }
      }

      // Record that we've reported this unreachable block to avoid duplicates
      // in the future.
      State->BlocksWithErrors.insert(&B);
      return true;
    }
  }

  // This block could be empty if it's terminator has been folded.
  if (B.empty())
    return false;

  // If we have not found user code in this block, inspect it's successors.
  // Check if at least one of the successors contains user code.
  for (auto I = B.succ_begin(), E = B.succ_end(); I != E; ++I) {
    SILBasicBlock *SB = *I;
    bool HasReachablePred = false;
    for (auto PI = SB->pred_begin(), PE = SB->pred_end(); PI != PE; ++PI) {
      if (Reachable.count(*PI))
        HasReachablePred = true;
    }

    // If all of the predecessors of this successor are unreachable, check if
    // it contains user code.
    if (!HasReachablePred && diagnoseUnreachableBlock(*SB, M, Reachable,
                                                    State, TopLevelB, Visited))
      return true;
  }
  
  return false;
}

/// \brief Inlines all mandatory inlined functions into the body of a function,
/// first recursively inlining all mandatory apply instructions in those
/// functions into their bodies if necessary.
///
/// \param F the function to be processed
/// \param AI nullptr if this is being called from the top level; the relevant
///   ApplyInst requiring the recursive call when non-null
/// \param FullyInlinedSet the set of all functions already known to be fully
///   processed, to avoid processing them over again
/// \param SetFactory an instance of ImmutableFunctionSet::Factory
/// \param CurrentInliningSet the set of functions currently being inlined in
///   the current call stack of recursive calls
///
/// \returns true if successful, false if failed due to circular inlining.
static bool
runOnFunctionRecursively(SILFunction *F, FullApplySite AI,
                         SILModule::LinkingMode Mode,
                         DenseFunctionSet &FullyInlinedSet,
                         ImmutableFunctionSet::Factory &SetFactory,
                         ImmutableFunctionSet CurrentInliningSet,
                         ClassHierarchyAnalysis *CHA) {
  // Avoid reprocessing functions needlessly.
  if (FullyInlinedSet.count(F))
    return true;

  // Prevent attempt to circularly inline.
  if (CurrentInliningSet.contains(F)) {
    // This cannot happen on a top-level call, so AI should be non-null.
    assert(AI && "Cannot have circular inline without apply");
    SILLocation L = AI.getLoc();
    assert(L && "Must have location for transparent inline apply");
    diagnose(F->getModule().getASTContext(), L.getStartSourceLoc(),
             diag::circular_transparent);
    return false;
  }

  // Add to the current inlining set (immutably, so we only affect the set
  // during this call and recursive subcalls).
  CurrentInliningSet = SetFactory.add(CurrentInliningSet, F);

  SmallVector<SILValue, 16> CaptureArgs;
  SmallVector<SILValue, 32> FullArgs;

  for (auto FI = F->begin(), FE = F->end(); FI != FE; ++FI) {
    for (auto I = FI->begin(), E = FI->end(); I != E; ++I) {
      FullApplySite InnerAI = FullApplySite::isa(&*I);

      if (!InnerAI)
        continue;

      auto *ApplyBlock = InnerAI.getParent();

      auto NewInstPair = tryDevirtualizeApply(InnerAI, CHA);
      if (auto *NewInst = NewInstPair.first) {
        replaceDeadApply(InnerAI, NewInst);
        if (auto *II = dyn_cast<SILInstruction>(NewInst))
          I = II->getIterator();
        else
          I = NewInst->getParentBlock()->begin();
        auto NewAI = FullApplySite::isa(NewInstPair.second.getInstruction());
        if (!NewAI)
          continue;

        InnerAI = NewAI;
      }

      SILLocation Loc = InnerAI.getLoc();
      SILValue CalleeValue = InnerAI.getCallee();
      bool IsThick;
      PartialApplyInst *PAI;
      SILFunction *CalleeFunction = getCalleeFunction(InnerAI, IsThick,
                                                      CaptureArgs, FullArgs,
                                                      PAI,
                                                      Mode);
      if (!CalleeFunction ||
          CalleeFunction->isTransparent() == IsNotTransparent)
        continue;

      if (F->isFragile() &&
          !CalleeFunction->hasValidLinkageForFragileRef()) {
        if (!CalleeFunction->hasValidLinkageForFragileInline()) {
          llvm::errs() << "caller: " << F->getName() << "\n";
          llvm::errs() << "callee: " << CalleeFunction->getName() << "\n";
          llvm_unreachable("Should never be inlining a resilient function into "
                           "a fragile function");
        }
        continue;
      }

      // Then recursively process it first before trying to inline it.
      if (!runOnFunctionRecursively(CalleeFunction, InnerAI, Mode,
                                    FullyInlinedSet, SetFactory,
                                    CurrentInliningSet, CHA)) {
        // If we failed due to circular inlining, then emit some notes to
        // trace back the failure if we have more information.
        // FIXME: possibly it could be worth recovering and attempting other
        // inlines within this same recursive call rather than simply
        // propagating the failure.
        if (AI) {
          SILLocation L = AI.getLoc();
//.........这里部分代码省略.........

void SILGenFunction::emitClassConstructorInitializer(ConstructorDecl *ctor) {
  MagicFunctionName = SILGenModule::getMagicFunctionName(ctor);

  assert(ctor->getBody() && "Class constructor without a body?");

  // True if this constructor delegates to a peer constructor with self.init().
  bool isDelegating = false;
  if (!ctor->hasStubImplementation()) {
    isDelegating = ctor->getDelegatingOrChainedInitKind(nullptr) ==
      ConstructorDecl::BodyInitKind::Delegating;
  }

  // Set up the 'self' argument.  If this class has a superclass, we set up
  // self as a box.  This allows "self reassignment" to happen in super init
  // method chains, which is important for interoperating with Objective-C
  // classes.  We also use a box for delegating constructors, since the
  // delegated-to initializer may also replace self.
  //
  // TODO: If we could require Objective-C classes to have an attribute to get
  // this behavior, we could avoid runtime overhead here.
  VarDecl *selfDecl = ctor->getImplicitSelfDecl();
  auto *dc = ctor->getDeclContext();
  auto selfClassDecl = dc->getAsClassOrClassExtensionContext();
  bool NeedsBoxForSelf = isDelegating ||
    (selfClassDecl->hasSuperclass() && !ctor->hasStubImplementation());
  bool usesObjCAllocator = Lowering::usesObjCAllocator(selfClassDecl);

  // If needed, mark 'self' as uninitialized so that DI knows to
  // enforce its DI properties on stored properties.
  MarkUninitializedInst::Kind MUKind;

  if (isDelegating)
    MUKind = MarkUninitializedInst::DelegatingSelf;
  else if (selfClassDecl->requiresStoredPropertyInits() &&
           usesObjCAllocator) {
    // Stored properties will be initialized in a separate
    // .cxx_construct method called by the Objective-C runtime.
    assert(selfClassDecl->hasSuperclass() &&
           "Cannot use ObjC allocation without a superclass");
    MUKind = MarkUninitializedInst::DerivedSelfOnly;
  } else if (selfClassDecl->hasSuperclass())
    MUKind = MarkUninitializedInst::DerivedSelf;
  else
    MUKind = MarkUninitializedInst::RootSelf;

  if (NeedsBoxForSelf) {
    // Allocate the local variable for 'self'.
    emitLocalVariableWithCleanup(selfDecl, false)->finishInitialization(*this);

    auto &SelfVarLoc = VarLocs[selfDecl];
    SelfVarLoc.value = B.createMarkUninitialized(selfDecl,
                                                 SelfVarLoc.value, MUKind);
  }

  // Emit the prolog for the non-self arguments.
  // FIXME: Handle self along with the other body patterns.
  emitProlog(ctor->getParameterList(1),
             TupleType::getEmpty(F.getASTContext()), ctor, ctor->hasThrows());

  SILType selfTy = getLoweredLoadableType(selfDecl->getType());
  SILValue selfArg = new (SGM.M) SILArgument(F.begin(), selfTy, selfDecl);

  if (!NeedsBoxForSelf) {
    SILLocation PrologueLoc(selfDecl);
    PrologueLoc.markAsPrologue();
    B.createDebugValue(PrologueLoc, selfArg);
  }

  if (!ctor->hasStubImplementation()) {
    assert(selfTy.hasReferenceSemantics() &&
           "can't emit a value type ctor here");
    if (NeedsBoxForSelf) {
      SILLocation prologueLoc = RegularLocation(ctor);
      prologueLoc.markAsPrologue();
      B.createStore(prologueLoc, selfArg, VarLocs[selfDecl].value,
                    StoreOwnershipQualifier::Unqualified);
    } else {
      selfArg = B.createMarkUninitialized(selfDecl, selfArg, MUKind);
      VarLocs[selfDecl] = VarLoc::get(selfArg);
      enterDestroyCleanup(VarLocs[selfDecl].value);
    }
  }

  // Prepare the end of initializer location.
  SILLocation endOfInitLoc = RegularLocation(ctor);
  endOfInitLoc.pointToEnd();

  // Create a basic block to jump to for the implicit 'self' return.
  // We won't emit the block until after we've emitted the body.
  prepareEpilog(Type(), ctor->hasThrows(),
                CleanupLocation::get(endOfInitLoc));

  // If the constructor can fail, set up an alternative epilog for constructor
  // failure.
  SILBasicBlock *failureExitBB = nullptr;
  SILArgument *failureExitArg = nullptr;
  auto &resultLowering = getTypeLowering(ctor->getResultType());

  if (ctor->getFailability() != OTK_None) {
    SILBasicBlock *failureBB = createBasicBlock(FunctionSection::Postmatter);
//.........这里部分代码省略.........