C++ IRGenFunction::emitTypeMetadataRef方法代码示例

/// Emit a checked cast of a metatype.
void irgen::emitMetatypeDowncast(IRGenFunction &IGF,
                                 llvm::Value *metatype,
                                 CanMetatypeType toMetatype,
                                 CheckedCastMode mode,
                                 Explosion &ex) {
  // Pick a runtime entry point and target metadata based on what kind of
  // representation we're casting.
  llvm::Value *castFn;
  llvm::Value *toMetadata;

  switch (toMetatype->getRepresentation()) {
  case MetatypeRepresentation::Thick: {
    // Get the Swift metadata for the type we're checking.
    toMetadata = IGF.emitTypeMetadataRef(toMetatype.getInstanceType());
    switch (mode) {
    case CheckedCastMode::Unconditional:
      castFn = IGF.IGM.getDynamicCastMetatypeUnconditionalFn();
      break;
    case CheckedCastMode::Conditional:
      castFn = IGF.IGM.getDynamicCastMetatypeFn();
      break;
    }
    break;
  }

  case MetatypeRepresentation::ObjC: {
    assert(IGF.IGM.ObjCInterop && "should have objc runtime");

    // Get the ObjC metadata for the type we're checking.
    toMetadata = emitClassHeapMetadataRef(IGF, toMetatype.getInstanceType(),
                                          MetadataValueType::ObjCClass);
    switch (mode) {
    case CheckedCastMode::Unconditional:
      castFn = IGF.IGM.getDynamicCastObjCClassMetatypeUnconditionalFn();
      break;
    case CheckedCastMode::Conditional:
      castFn = IGF.IGM.getDynamicCastObjCClassMetatypeFn();
      break;
    }
    break;
  }

  case MetatypeRepresentation::Thin:
    llvm_unreachable("not implemented");
  }

  auto cc = IGF.IGM.DefaultCC;
  if (auto fun = dyn_cast<llvm::Function>(castFn))
    cc = fun->getCallingConv();

  auto call = IGF.Builder.CreateCall(castFn, {metatype, toMetadata});
  call->setCallingConv(cc);
  call->setDoesNotThrow();
  ex.add(call);
}

void
irgen::emitTypeLayoutVerifier(IRGenFunction &IGF,
                              ArrayRef<CanType> formalTypes) {
  llvm::Type *verifierArgTys[] = {
    IGF.IGM.TypeMetadataPtrTy,
    IGF.IGM.Int8PtrTy,
    IGF.IGM.Int8PtrTy,
    IGF.IGM.SizeTy,
    IGF.IGM.Int8PtrTy,
  };
  auto verifierFnTy = llvm::FunctionType::get(IGF.IGM.VoidTy,
                                              verifierArgTys,
                                              /*var arg*/ false);
  auto verifierFn = IGF.IGM.Module.getOrInsertFunction(
                                       "_swift_debug_verifyTypeLayoutAttribute",
                                       verifierFnTy);
  struct VerifierArgumentBuffers {
    Address runtimeBuf, staticBuf;
  };
  llvm::DenseMap<llvm::Type *, VerifierArgumentBuffers>
    verifierArgBufs;
  
  auto getSizeConstant = [&](Size sz) -> llvm::Constant * {
    return llvm::ConstantInt::get(IGF.IGM.SizeTy, sz.getValue());
  };
  auto getAlignmentMaskConstant = [&](Alignment a) -> llvm::Constant * {
    return llvm::ConstantInt::get(IGF.IGM.SizeTy, a.getValue() - 1);
  };
  auto getBoolConstant = [&](bool b) -> llvm::Constant * {
    return llvm::ConstantInt::get(IGF.IGM.Int1Ty, b);
  };

  SmallString<20> numberBuf;

  for (auto formalType : formalTypes) {
    // Runtime type metadata always represents the maximal abstraction level of
    // the type.
    auto anyTy = ProtocolCompositionType::get(IGF.IGM.Context, {});
    auto openedAnyTy = ArchetypeType::getOpened(anyTy);
    auto maxAbstraction = AbstractionPattern(openedAnyTy);
    auto &ti = IGF.getTypeInfoForUnlowered(maxAbstraction, formalType);
    
    // If there's no fixed type info, we rely on the runtime anyway, so there's
    // nothing to verify.
    // TODO: There are some traits of partially-fixed layouts we could check too.
    auto *fixedTI = dyn_cast<FixedTypeInfo>(&ti);
    if (!fixedTI)
      return;
    
    auto metadata = IGF.emitTypeMetadataRef(formalType);
    
    auto verify = [&](llvm::Value *runtimeVal,
                      llvm::Value *staticVal,
                      const llvm::Twine &description) {
      assert(runtimeVal->getType() == staticVal->getType());
      // Get or create buffers for the arguments.
      VerifierArgumentBuffers bufs;
      auto foundBufs = verifierArgBufs.find(runtimeVal->getType());
      if (foundBufs != verifierArgBufs.end()) {
        bufs = foundBufs->second;
      } else {
        Address runtimeBuf = IGF.createAlloca(runtimeVal->getType(),
                                              IGF.IGM.getPointerAlignment(),
                                              "runtime");
        Address staticBuf = IGF.createAlloca(staticVal->getType(),
                                             IGF.IGM.getPointerAlignment(),
                                             "static");
        bufs = {runtimeBuf, staticBuf};
        verifierArgBufs[runtimeVal->getType()] = bufs;
      }
      
      IGF.Builder.CreateStore(runtimeVal, bufs.runtimeBuf);
      IGF.Builder.CreateStore(staticVal, bufs.staticBuf);
      
      auto runtimePtr = IGF.Builder.CreateBitCast(bufs.runtimeBuf.getAddress(),
                                                  IGF.IGM.Int8PtrTy);
      auto staticPtr = IGF.Builder.CreateBitCast(bufs.staticBuf.getAddress(),
                                                 IGF.IGM.Int8PtrTy);
      auto count = llvm::ConstantInt::get(IGF.IGM.SizeTy,
                    IGF.IGM.DataLayout.getTypeStoreSize(runtimeVal->getType()));
      auto msg
        = IGF.IGM.getAddrOfGlobalString(description.str());
      
      IGF.Builder.CreateCall(
          verifierFn, {metadata, runtimePtr, staticPtr, count, msg});
    };

    // Check that the fixed layout matches the runtime layout.
    SILType layoutType = SILType::getPrimitiveObjectType(formalType);
    verify(emitLoadOfSize(IGF, layoutType),
           getSizeConstant(fixedTI->getFixedSize()),
           "size");
    verify(emitLoadOfAlignmentMask(IGF, layoutType),
           getAlignmentMaskConstant(fixedTI->getFixedAlignment()),
           "alignment mask");
    verify(emitLoadOfStride(IGF, layoutType),
           getSizeConstant(fixedTI->getFixedStride()),
           "stride");
    verify(emitLoadOfIsInline(IGF, layoutType),
           getBoolConstant(fixedTI->getFixedPacking(IGF.IGM)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
  // If we don't need to look up any witness tables, we're done.
  if (witnessTableProtos.empty() && !checkClassConstraint) {
    ex.add(resultValue);
    return;
  }

  // If we're doing a conditional cast, and the ObjC protocol checks failed,
  // then the cast is done.
  Optional<ConditionalDominanceScope> condition;
  llvm::BasicBlock *origBB = nullptr, *successBB = nullptr, *contBB = nullptr;
  if (!objcProtos.empty()) {
    switch (mode) {
    case CheckedCastMode::Unconditional:
      break;
    case CheckedCastMode::Conditional: {
      origBB = IGF.Builder.GetInsertBlock();
      successBB = IGF.createBasicBlock("success");
      contBB = IGF.createBasicBlock("cont");
      auto isNull = IGF.Builder.CreateICmpEQ(objcCast,
                               llvm::ConstantPointerNull::get(
                                 cast<llvm::PointerType>(objcCast->getType())));
      IGF.Builder.CreateCondBr(isNull, contBB, successBB);
      IGF.Builder.emitBlock(successBB);
      condition.emplace(IGF);
    }
    }
  }

  // Get the Swift type metadata for the type.
  llvm::Value *metadataValue;
  if (metatypeKind) {
    switch (*metatypeKind) {
    case MetatypeRepresentation::Thin:
      llvm_unreachable("can't cast to thin metatype");
    case MetatypeRepresentation::Thick:
      // The value is already a native metatype.
      metadataValue = value;
      break;
    case MetatypeRepresentation::ObjC:
      // Get the type metadata from the ObjC class, which may be a wrapper.
      metadataValue = emitObjCMetadataRefForMetadata(IGF, value);
    }
  } else {
    // Get the type metadata for the instance.
    metadataValue = emitDynamicTypeOfHeapObject(IGF, value, srcType);
  }

  // Look up witness tables for the protocols that need them.
  auto fn = emitExistentialScalarCastFn(IGF.IGM,
                                        witnessTableProtos.size(),
                                        mode,
                                        checkClassConstraint,
                                        checkSuperclassConstraint);

  llvm::SmallVector<llvm::Value *, 4> args;

  if (resultValue->getType() != IGF.IGM.Int8PtrTy)
    resultValue = IGF.Builder.CreateBitCast(resultValue, IGF.IGM.Int8PtrTy);
  args.push_back(resultValue);

  args.push_back(metadataValue);

  if (checkSuperclassConstraint)
    args.push_back(IGF.emitTypeMetadataRef(CanType(layout.superclass)));

  for (auto proto : witnessTableProtos)
    args.push_back(proto);

  auto valueAndWitnessTables = IGF.Builder.CreateCall(fn, args);

  resultValue = IGF.Builder.CreateExtractValue(valueAndWitnessTables, 0);
  if (resultValue->getType() != resultType)
    resultValue = IGF.Builder.CreateBitCast(resultValue, resultType);
  ex.add(resultValue);

  for (unsigned i = 0, e = witnessTableProtos.size(); i < e; ++i) {
    auto wt = IGF.Builder.CreateExtractValue(valueAndWitnessTables, i + 1);
    ex.add(wt);
  }

  // If we had conditional ObjC checks, join the failure paths.
  if (contBB) {
    condition.reset();
    IGF.Builder.CreateBr(contBB);
    IGF.Builder.emitBlock(contBB);
    
    // Return null on the failure path.
    Explosion successEx = std::move(ex);
    ex.reset();
    
    while (!successEx.empty()) {
      auto successVal = successEx.claimNext();
      auto failureVal = llvm::Constant::getNullValue(successVal->getType());
      auto phi = IGF.Builder.CreatePHI(successVal->getType(), 2);
      phi->addIncoming(successVal, successBB);
      phi->addIncoming(failureVal, origBB);
      ex.add(phi);
    }
  }
}