Callee.h

//===--- Callee.h - Information about a physical callee ---------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file defines the Callee type, which stores all necessary
// information about a physical callee.
//
//===----------------------------------------------------------------------===//

#ifndef SWIFT_IRGEN_CALLEE_H
#define SWIFT_IRGEN_CALLEE_H

#include <type_traits>
#include "swift/AST/IRGenOptions.h"
#include "llvm/IR/DerivedTypes.h"
#include "swift/SIL/SILType.h"
#include "IRGen.h"
#include "Signature.h"

namespace llvm {
  class ConstantInt;
}

namespace swift {

namespace irgen {
  class Callee;
  class IRGenFunction;
  class PointerAuthEntity;

  class CalleeInfo {
  public:
    /// The unsubstituted function type being called.
    CanSILFunctionType OrigFnType;

    /// The substituted result type of the function being called.
    CanSILFunctionType SubstFnType;

    /// The archetype substitutions under which the function is being
    /// called.
    SubstitutionMap Substitutions;

    CalleeInfo(CanSILFunctionType origFnType,
               CanSILFunctionType substFnType,
               SubstitutionMap substitutions)
      : OrigFnType(origFnType), SubstFnType(substFnType),
        Substitutions(substitutions) {
    }
  };

  /// Information necessary for pointer authentication.
  class PointerAuthInfo {
    unsigned Signed : 1;
    unsigned Key : 31;
    llvm::Value *Discriminator;
  public:
    PointerAuthInfo() {
      Signed = false;
    }
    PointerAuthInfo(unsigned key, llvm::Value *discriminator)
        : Discriminator(discriminator) {
      assert(discriminator->getType()->isIntegerTy() ||
             discriminator->getType()->isPointerTy());
      Signed = true;
      Key = key;
    }

    static PointerAuthInfo emit(IRGenFunction &IGF,
                                const PointerAuthSchema &schema,
                                llvm::Value *storageAddress,
                                const PointerAuthEntity &entity);

    static PointerAuthInfo forFunctionPointer(IRGenModule &IGM,
                                              CanSILFunctionType fnType);

    static llvm::ConstantInt *getOtherDiscriminator(IRGenModule &IGM,
                                           const PointerAuthSchema &schema,
                                           const PointerAuthEntity &entity);

    explicit operator bool() const {
      return isSigned();
    }

    bool isSigned() const {
      return Signed;
    }

    bool isConstant() const {
      return (!isSigned() || isa<llvm::Constant>(Discriminator));
    }

    unsigned getKey() const {
      assert(isSigned());
      return Key;
    }
    bool hasCodeKey() const {
      assert(isSigned());
      return (getKey() == (unsigned)PointerAuthSchema::ARM8_3Key::ASIA) ||
             (getKey() == (unsigned)PointerAuthSchema::ARM8_3Key::ASIB);
    }
    bool hasDataKey() const {
      assert(isSigned());
      return (getKey() == (unsigned)PointerAuthSchema::ARM8_3Key::ASDA) ||
             (getKey() == (unsigned)PointerAuthSchema::ARM8_3Key::ASDB);
    }
    bool getCorrespondingCodeKey() const {
      assert(hasDataKey());
      switch (getKey()) {
      case (unsigned)PointerAuthSchema::ARM8_3Key::ASDA:
        return (unsigned)PointerAuthSchema::ARM8_3Key::ASIA;
      case (unsigned)PointerAuthSchema::ARM8_3Key::ASDB:
        return (unsigned)PointerAuthSchema::ARM8_3Key::ASIB;
      }
      llvm_unreachable("unhandled case");
    }
    unsigned getCorrespondingDataKey() const {
      assert(hasCodeKey());
      switch (getKey()) {
      case (unsigned)PointerAuthSchema::ARM8_3Key::ASIA:
        return (unsigned)PointerAuthSchema::ARM8_3Key::ASDA;
      case (unsigned)PointerAuthSchema::ARM8_3Key::ASIB:
        return (unsigned)PointerAuthSchema::ARM8_3Key::ASDB;
      }
      llvm_unreachable("unhandled case");
    }
    llvm::Value *getDiscriminator() const {
      assert(isSigned());
      return Discriminator;
    }
    PointerAuthInfo getCorrespondingCodeAuthInfo() const {
      if (auto authInfo = *this) {
        return PointerAuthInfo(authInfo.getCorrespondingCodeKey(),
                               authInfo.getDiscriminator());
      }
      return *this;
    }

    /// Are the auth infos obviously the same?
    friend bool operator==(const PointerAuthInfo &lhs,
                           const PointerAuthInfo &rhs) {
      if (!lhs.Signed)
        return !rhs.Signed;
      if (!rhs.Signed)
        return false;

      return (lhs.Key == rhs.Key && lhs.Discriminator == rhs.Discriminator);
    }
    friend bool operator!=(const PointerAuthInfo &lhs,
                           const PointerAuthInfo &rhs) {
      return !(lhs == rhs);
    }
  };

  class FunctionPointerKind {
  public:
    enum class BasicKind {
      Function,
      AsyncFunctionPointer
    };

    enum class SpecialKind {
      TaskFutureWait,
      TaskFutureWaitThrowing,
      AsyncLetWait,
      AsyncLetWaitThrowing,
      AsyncLetGet,
      AsyncLetGetThrowing,
      AsyncLetFinish,
      TaskGroupWaitNext,
      DistributedExecuteTarget,
    };

  private:
    static constexpr unsigned SpecialOffset = 2;
    unsigned value;
  public:
    static constexpr BasicKind Function =
      BasicKind::Function;
    static constexpr BasicKind AsyncFunctionPointer =
      BasicKind::AsyncFunctionPointer;

    FunctionPointerKind(BasicKind kind)
      : value(unsigned(kind)) {}
    FunctionPointerKind(SpecialKind kind)
      : value(unsigned(kind) + SpecialOffset) {}
    FunctionPointerKind(CanSILFunctionType fnType)
      : FunctionPointerKind(fnType->isAsync()
                              ? BasicKind::AsyncFunctionPointer
                              : BasicKind::Function) {}

    static FunctionPointerKind defaultSync() {
      return BasicKind::Function;
    }
    static FunctionPointerKind defaultAsync() {
      return BasicKind::AsyncFunctionPointer;
    }

    BasicKind getBasicKind() const {
      return value < SpecialOffset ? BasicKind(value) : BasicKind::Function;
    }
    bool isAsyncFunctionPointer() const {
      return value == unsigned(BasicKind::AsyncFunctionPointer);
    }

    bool isSpecial() const {
      return value >= SpecialOffset;
    }
    SpecialKind getSpecialKind() const {
      assert(isSpecial());
      return SpecialKind(value - SpecialOffset);
    }


    /// Given that this is an async function, does it have a
    /// statically-specified size for its async context?
    ///
    /// Returning a non-None value is necessary for special functions
    /// defined in the runtime.  Without this, we'll attempt to load
    /// the context size from an async FP symbol which the runtime
    /// doesn't actually emit.
    Optional<Size> getStaticAsyncContextSize(IRGenModule &IGM) const;

    /// Given that this is an async function, should we pass the
    /// continuation function pointer and context directly to it
    /// rather than building a frame?
    ///
    /// This is a micro-optimization that is reasonable for functions
    /// that are expected to return immediately in a common fast path.
    /// Other functions should not do this.
    bool shouldPassContinuationDirectly() const {
      if (!isSpecial()) return false;

      switch (getSpecialKind()) {
      case SpecialKind::TaskFutureWaitThrowing:
      case SpecialKind::TaskFutureWait:
      case SpecialKind::AsyncLetWait:
      case SpecialKind::AsyncLetWaitThrowing:
      case SpecialKind::AsyncLetGet:
      case SpecialKind::AsyncLetGetThrowing:
      case SpecialKind::AsyncLetFinish:
      case SpecialKind::TaskGroupWaitNext:
        return true;
      case SpecialKind::DistributedExecuteTarget:
        return false;
      }
      llvm_unreachable("covered switch");
    }

    /// Should we suppress passing arguments associated with the generic
    /// signature from the given function?
    ///
    /// This is a micro-optimization for certain runtime functions that
    /// are known to not need the generic arguments, probably because
    /// they've already been stored elsewhere.
    ///
    /// This may only work for async function types right now.  If so,
    /// that's a totally unnecessary restriction which should be easy
    /// to lift, if you have a sync runtime function that would benefit
    /// from this.
    bool shouldSuppressPolymorphicArguments() const {
      if (!isSpecial()) return false;

      switch (getSpecialKind()) {
      case SpecialKind::TaskFutureWaitThrowing:
      case SpecialKind::TaskFutureWait:
      case SpecialKind::AsyncLetWait:
      case SpecialKind::AsyncLetWaitThrowing:
      case SpecialKind::AsyncLetGet:
      case SpecialKind::AsyncLetGetThrowing:
      case SpecialKind::AsyncLetFinish:
      case SpecialKind::TaskGroupWaitNext:
        return true;
      case SpecialKind::DistributedExecuteTarget:
        return false;
      }
      llvm_unreachable("covered switch");
    }

    friend bool operator==(FunctionPointerKind lhs, FunctionPointerKind rhs) {
      return lhs.value == rhs.value;
    }
    friend bool operator!=(FunctionPointerKind lhs, FunctionPointerKind rhs) {
      return !(lhs == rhs);
    }
  };

  /// A function pointer value.
  class FunctionPointer {
  public:
    using Kind = FunctionPointerKind;
    using BasicKind = Kind::BasicKind;
    using SpecialKind = Kind::SpecialKind;

  private:
    Kind kind;

    /// The actual pointer, either to the function or to its descriptor.
    llvm::Value *Value;

    /// An additional value whose meaning varies by the FunctionPointer's Kind:
    /// - Kind::AsyncFunctionPointer -> pointer to the corresponding function
    ///                                 if the FunctionPointer was created via
    ///                                 forDirect; nullptr otherwise. 
    llvm::Value *SecondaryValue;

    PointerAuthInfo AuthInfo;

    Signature Sig;
    // If this is an await function pointer contains the signature of the await
    // call (without return values).
    llvm::Type *awaitSignature = nullptr;

    explicit FunctionPointer(Kind kind, llvm::Value *value,
                             const Signature &signature)
        : FunctionPointer(kind, value, PointerAuthInfo(), signature) {}

    explicit FunctionPointer(Kind kind, llvm::Value *value,
                             PointerAuthInfo authInfo,
                             const Signature &signature)
        : FunctionPointer(kind, value, nullptr, authInfo, signature){};

    /// Construct a FunctionPointer for an arbitrary pointer value.
    /// We may add more arguments to this; try to use the other
    /// constructors/factories if possible.
    explicit FunctionPointer(Kind kind, llvm::Value *value,
                             llvm::Value *secondaryValue,
                             PointerAuthInfo authInfo,
                             const Signature &signature,
                             llvm::Type *awaitSignature = nullptr)
        : kind(kind), Value(value), SecondaryValue(secondaryValue),
          AuthInfo(authInfo), Sig(signature), awaitSignature(awaitSignature) {
      // The function pointer should have function type.
      assert(!value->getContext().supportsTypedPointers() ||
             value->getType()->getPointerElementType()->isFunctionTy());
      // TODO: maybe assert similarity to signature.getType()?
      if (authInfo) {
        if (kind == Kind::Function) {
          assert(authInfo.hasCodeKey());
        } else {
          assert(authInfo.hasDataKey());
        }
      }
    }

  public:
    FunctionPointer()
        : kind(FunctionPointer::Kind::Function), Value(nullptr),
          SecondaryValue(nullptr) {}

    static FunctionPointer createForAsyncCall(llvm::Value *value,
                                              PointerAuthInfo authInfo,
                                              const Signature &signature,
                                              llvm::Type *awaitCallSignature) {
      return FunctionPointer(FunctionPointer::Kind::Function, value, nullptr,
                             authInfo, signature, awaitCallSignature);
    }

    static FunctionPointer createSigned(Kind kind, llvm::Value *value,
                                        PointerAuthInfo authInfo,
                                        const Signature &signature) {
      return FunctionPointer(kind, value, authInfo, signature);
    }

    static FunctionPointer createUnsigned(Kind kind, llvm::Value *value,
                                          const Signature &signature) {
      return FunctionPointer(kind, value, signature);
    }

    static FunctionPointer forDirect(IRGenModule &IGM, llvm::Constant *value,
                                     llvm::Constant *secondaryValue,
                                     CanSILFunctionType fnType);

    static FunctionPointer forDirect(Kind kind, llvm::Constant *value,
                                     llvm::Constant *secondaryValue,
                                     const Signature &signature) {
      return FunctionPointer(kind, value, secondaryValue, PointerAuthInfo(),
                             signature);
    }

    static FunctionPointer forExplosionValue(IRGenFunction &IGF,
                                             llvm::Value *fnPtr,
                                             CanSILFunctionType fnType);

    /// Is this function pointer completely constant?  That is, can it
    /// be safely moved to a different function context?
    bool isConstant() const {
      return (isa<llvm::Constant>(Value) && AuthInfo.isConstant());
    }

    Kind getKind() const { return kind; }
    BasicKind getBasicKind() const { return kind.getBasicKind(); }

    /// Given that this value is known to have been constructed from a direct
    /// function,  Return the name of that function.
    StringRef getName(IRGenModule &IGM) const;

    /// Return the actual function pointer.
    llvm::Value *getPointer(IRGenFunction &IGF) const;

    /// Return the actual function pointer.
    llvm::Value *getRawPointer() const { return Value; }

    /// Assuming that the receiver is of kind AsyncFunctionPointer, returns the
    /// pointer to the corresponding function if available.
    llvm::Value *getRawAsyncFunction() const {
      assert(kind.isAsyncFunctionPointer());
      return SecondaryValue;
    }

    /// Given that this value is known to have been constructed from
    /// a direct function, return the function pointer.
    llvm::Constant *getDirectPointer() const {
      return cast<llvm::Constant>(Value);
    }

    llvm::FunctionType *getFunctionType() const;

    const PointerAuthInfo &getAuthInfo() const {
      return AuthInfo;
    }

    const Signature &getSignature() const {
      return Sig;
    }

    llvm::CallingConv::ID getCallingConv() const {
      return Sig.getCallingConv();
    }

    llvm::AttributeList getAttributes() const {
      return Sig.getAttributes();
    }
    llvm::AttributeList &getMutableAttributes() & {
      return Sig.getMutableAttributes();
    }

    ForeignFunctionInfo getForeignInfo() const {
      return Sig.getForeignInfo();
    }

    llvm::Value *getExplosionValue(IRGenFunction &IGF,
                                   CanSILFunctionType fnType) const;

    /// Form a FunctionPointer whose Kind is ::Function.
    FunctionPointer getAsFunction(IRGenFunction &IGF) const;

    Optional<Size> getStaticAsyncContextSize(IRGenModule &IGM) const {
      return kind.getStaticAsyncContextSize(IGM);
    }
    bool shouldPassContinuationDirectly() const {
      return kind.shouldPassContinuationDirectly();
    }
    bool shouldSuppressPolymorphicArguments() const {
      return kind.shouldSuppressPolymorphicArguments();
    }
  };

  class Callee {
    CalleeInfo Info;

    /// The actual function pointer to invoke.
    FunctionPointer Fn;

    /// The first data pointer required by the function invocation.
    llvm::Value *FirstData;

    /// The second data pointer required by the function invocation.
    llvm::Value *SecondData;

  public:
    Callee(const Callee &other) = delete;
    Callee &operator=(const Callee &other) = delete;

    Callee(Callee &&other) = default;
    Callee &operator=(Callee &&other) = default;

    Callee(CalleeInfo &&info, const FunctionPointer &fn,
           llvm::Value *firstData = nullptr,
           llvm::Value *secondData = nullptr);

    SILFunctionTypeRepresentation getRepresentation() const {
      return Info.OrigFnType->getRepresentation();
    }

    CanSILFunctionType getOrigFunctionType() const {
      return Info.OrigFnType;
    }
    CanSILFunctionType getSubstFunctionType() const {
      return Info.SubstFnType;
    }

    bool hasSubstitutions() const {
      return Info.Substitutions.hasAnySubstitutableParams();
    }
    
    SubstitutionMap getSubstitutions() const { return Info.Substitutions; }

    const FunctionPointer &getFunctionPointer() const { return Fn; }

    llvm::FunctionType *getLLVMFunctionType() {
      return Fn.getFunctionType();
    }

    llvm::AttributeList getAttributes() const {
      return Fn.getAttributes();
    }
    llvm::AttributeList &getMutableAttributes() & {
      return Fn.getMutableAttributes();
    }

    ForeignFunctionInfo getForeignInfo() const {
      return Fn.getForeignInfo();
    }

    const Signature &getSignature() const {
      return Fn.getSignature();
    }

    Optional<Size> getStaticAsyncContextSize(IRGenModule &IGM) const {
      return Fn.getStaticAsyncContextSize(IGM);
    }
    bool shouldPassContinuationDirectly() const {
      return Fn.shouldPassContinuationDirectly();
    }
    bool shouldSuppressPolymorphicArguments() const {
      return Fn.shouldSuppressPolymorphicArguments();
    }

    /// If this callee has a value for the Swift context slot, return
    /// it; otherwise return non-null.
    llvm::Value *getSwiftContext() const;

    /// Given that this callee is a block, return the block pointer.
    llvm::Value *getBlockObject() const;

    /// Given that this callee is a C++ method, return the self argument.
    llvm::Value *getCXXMethodSelf() const;

    /// Given that this callee is an ObjC method, return the receiver
    /// argument.  This might not be 'self' anymore.
    llvm::Value *getObjCMethodReceiver() const;

    /// Given that this callee is an ObjC method, return the receiver
    /// argument.  This might not be 'self' anymore.
    llvm::Value *getObjCMethodSelector() const;
  };

  FunctionPointer::Kind classifyFunctionPointerKind(SILFunction *fn);
} // end namespace irgen
} // end namespace swift

#endif