runtime/vm/compiler/backend/il_deserializer.h

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#ifndef RUNTIME_VM_COMPILER_BACKEND_IL_DESERIALIZER_H_
#define RUNTIME_VM_COMPILER_BACKEND_IL_DESERIALIZER_H_

#if defined(DART_PRECOMPILED_RUNTIME)
#error "AOT runtime should not use compiler sources (including header files)"
#endif  // defined(DART_PRECOMPILED_RUNTIME)

#include "platform/assert.h"

#include "vm/allocation.h"
#include "vm/compiler/backend/flow_graph.h"
#include "vm/compiler/backend/il.h"
#include "vm/compiler/backend/sexpression.h"
#include "vm/compiler/compiler_pass.h"
#include "vm/object.h"
#include "vm/parser.h"
#include "vm/thread.h"
#include "vm/zone.h"

namespace dart {

// Deserializes FlowGraphs from S-expressions.
class FlowGraphDeserializer : ValueObject {
 public:
  // Adds to the given array all the instructions in the flow graph that are
  // guaranteed not to be handled by the current implementation of the
  // FlowGraphDeserializer. This way, we can filter out graphs that are
  // guaranteed not to be deserializable before going through the round-trip
  // serialization process.
  //
  // Note that there may be other reasons that the deserializer may fail on
  // a given flow graph, so no new members of the array is necessary, but not
  // sufficient, for a successful round-trip pass.
  static void AllUnhandledInstructions(const FlowGraph* graph,
                                       GrowableArray<Instruction*>* out);

  // Takes the FlowGraph from [state] and runs it through the serializer
  // and deserializer. If the deserializer successfully deserializes the
  // graph, then the FlowGraph in [state] is replaced with the new one.
  static void RoundTripSerialization(CompilerPassState* state);

  FlowGraphDeserializer(Thread* thread,
                        Zone* zone,
                        SExpression* root,
                        const ParsedFunction* pf = nullptr)
      : thread_(ASSERT_NOTNULL(thread)),
        zone_(ASSERT_NOTNULL(zone)),
        root_sexp_(ASSERT_NOTNULL(root)),
        parsed_function_(pf),
        block_map_(zone),
        definition_map_(zone),
        values_map_(zone),
        recursive_types_map_(zone),
        pending_typeref_map_(zone),
        array_type_args_(TypeArguments::Handle(zone)),
        instance_class_(Class::Handle(zone)),
        instance_field_(Field::Handle(zone)),
        instance_fields_array_(Array::Handle(zone)),
        instance_type_args_(TypeArguments::Handle(zone)),
        name_class_(Class::Handle(zone)),
        name_field_(Field::Handle(zone)),
        name_function_(Function::Handle(zone)),
        name_library_(Library::Handle(zone)),
        type_class_(Class::Handle(zone)),
        type_param_class_(Class::Handle(zone)),
        type_param_function_(Function::Handle(zone)),
        tmp_string_(String::Handle(zone)) {
    // See canonicalization comment in ParseDartValue as to why this is
    // currently necessary.
    ASSERT(thread->zone() == zone);
  }

  // Walks [root_sexp_] and constructs a new FlowGraph.
  FlowGraph* ParseFlowGraph();

  const char* error_message() const { return error_message_; }
  SExpression* error_sexp() const { return error_sexp_; }

  // Prints the current error information to stderr and aborts.
  DART_NORETURN void ReportError() const;

 private:
#define FOR_EACH_HANDLED_BLOCK_TYPE_IN_DESERIALIZER(M)                         \
  M(FunctionEntry)                                                             \
  M(GraphEntry)                                                                \
  M(JoinEntry)                                                                 \
  M(TargetEntry)

#define FOR_EACH_HANDLED_INSTRUCTION_IN_DESERIALIZER(M)                        \
  M(AllocateObject)                                                            \
  M(AssertAssignable)                                                          \
  M(AssertBoolean)                                                             \
  M(BooleanNegate)                                                             \
  M(Branch)                                                                    \
  M(CheckNull)                                                                 \
  M(CheckStackOverflow)                                                        \
  M(Constant)                                                                  \
  M(DebugStepCheck)                                                            \
  M(Goto)                                                                      \
  M(InstanceCall)                                                              \
  M(LoadClassId)                                                               \
  M(LoadField)                                                                 \
  M(NativeCall)                                                                \
  M(Parameter)                                                                 \
  M(Return)                                                                    \
  M(SpecialParameter)                                                          \
  M(StaticCall)                                                                \
  M(StoreInstanceField)                                                        \
  M(StrictCompare)                                                             \
  M(Throw)

  // Helper methods for AllUnhandledInstructions.
  static bool IsHandledInstruction(Instruction* inst);
  static bool IsHandledConstant(const Object& obj);

  // **GENERAL DESIGN NOTES FOR PARSING METHODS**
  //
  // For functions that take an SExpression or a subclass, they should return
  // an error signal (false, nullptr, etc.) without changing the error state if
  // passed in nullptr. This way, methods can be chained without intermediate
  // checking.
  //
  // Also, for parsing methods for expressions that are known to be of a certain
  // form, they will take the appropriate subclass of SExpression and assume
  // that the form was already pre-checked by the caller. For forms that are
  // tagged lists, this includes the fact that there is at least one element
  // and the first element is a symbol. If the form can only have one possible
  // tag, they also assume the tag has already been checked.

  // Helper functions that do length/key exists checking and also check that
  // the retrieved element is not nullptr. Notably, do not use these if the
  // retrieved element is optional, to avoid changing the error state
  // unnecessarily.
  SExpression* Retrieve(SExpList* list, intptr_t index);
  SExpression* Retrieve(SExpList* list, const char* key);

  bool ParseConstantPool(SExpList* pool);
  bool ParseEntries(SExpList* list);

  using BlockWorklist = GrowableArray<intptr_t>;

  // Starts parsing the contents of [list], where the blocks begin at position
  // [pos] and [worklist] contains the blocks whose body instructions should
  // be parsed first.
  bool ParseBlocks(SExpList* list, intptr_t pos, BlockWorklist* worklist);

  // Block parsing is split into two passes. This pass adds function entries
  // to the flow graph and also parses initial definitions found in the Entries
  // list. The block is added to the [block_map_] before returning.
  BlockEntryInstr* ParseBlockHeader(SExpList* list,
                                    intptr_t block_id,
                                    SExpSymbol* tag);

  // Expects [current_block_] to be set before calling.
  bool ParseInitialDefinitions(SExpList* list);

  // Expects [current_block_] to be set before calling.
  // Takes the tagged list to parse and the index where parsing should start.
  // Attempts to parse Phi definitions until the first non-Phi instruction.
  bool ParsePhis(SExpList* list);

  // Expects [current_block_] to be set before calling.
  // Returns the position of the first non-Phi instruction in a block.
  intptr_t SkipPhis(SExpList* list);

  // Parses the deopt environment, Phi definitions for JoinEntrys, and the
  // instructions in the body of the block. Adds the IDs of the block successors
  // to the worklist, if any. [current_block_] and [pushed_stack_] must be set
  // before calling.
  bool ParseBlockContents(SExpList* list, BlockWorklist* worklist);

  // Helper function used by ParseConstantPool, ParsePhis, and ParseDefinition.
  // This handles all the extra information stored in (def ...) expressions,
  // and also ensures the index of the definition is appropriately adjusted to
  // match those found in the serialized form.
  bool ParseDefinitionWithParsedBody(SExpList* list, Definition* def);

  Definition* ParseDefinition(SExpList* list);
  Instruction* ParseInstruction(SExpList* list);

  struct EntryInfo {
    intptr_t block_id;
    intptr_t try_index;
    intptr_t deopt_id;
  };

#define HANDLER_DECL(name)                                                     \
  name##Instr* Deserialize##name(SExpList* list, const EntryInfo& info);

  FOR_EACH_HANDLED_BLOCK_TYPE_IN_DESERIALIZER(HANDLER_DECL);

#undef HANDLER_DECL

  struct InstrInfo {
    intptr_t deopt_id;
    TokenPosition token_pos;
  };

  enum HandledInstruction {
#define HANDLED_INST_DECL(name) kHandled##name,
    FOR_EACH_HANDLED_INSTRUCTION_IN_DESERIALIZER(HANDLED_INST_DECL)
#undef HANDLED_INST_DECL
    // clang-format off
    kHandledInvalid = -1,
    // clang-format on
  };

#define HANDLE_CASE(name)                                                      \
  if (strcmp(tag->value(), #name) == 0) return kHandled##name;
  HandledInstruction HandledInstructionForTag(SExpSymbol* tag) {
    ASSERT(tag != nullptr);
    FOR_EACH_HANDLED_INSTRUCTION_IN_DESERIALIZER(HANDLE_CASE)
    return kHandledInvalid;
  }
#undef HANDLE_CASE

#define HANDLER_DECL(name)                                                     \
  name##Instr* Deserialize##name(SExpList* list, const InstrInfo& info);

  FOR_EACH_HANDLED_INSTRUCTION_IN_DESERIALIZER(HANDLER_DECL);

#undef HANDLER_DECL

  // Common information parsed from call instruction S-expressions.
  struct CallInfo : public ValueObject {
    explicit CallInfo(Zone* zone) : argument_names(Array::ZoneHandle(zone)) {}

    Array& argument_names;
    intptr_t type_args_len = 0;
    intptr_t args_len = 0;
    InputsArray* inputs = nullptr;
    CompileType* result_type = nullptr;
    Code::EntryKind entry_kind = Code::EntryKind::kNormal;
  };

  // Helper function for parsing call instructions that returns a structure
  // of information common to all calls.
  bool ParseCallInfo(SExpList* call,
                     CallInfo* out,
                     intptr_t num_extra_inputs = 0);

  // Parses [sexp] as a value form, that is, either the binding name for
  // a definition as a symbol or the form (value <name> { ... }).
  // If [allow_pending], then values for definitions not already in the
  // [definition_map_] will be added to the [values_map_], otherwise,
  // values for definitions not yet seen cause an error to be stored and
  // nullptr to be returned.
  Value* ParseValue(SExpression* sexp, bool allow_pending = true);
  CompileType* ParseCompileType(SExpList* list);

  // Parses [list] as an environment form: a list containing either binding
  // names for definitions or a# for pushed arguments (where # is the depth
  // of the argument from the top of the stack). Requires [pushed_stack_] to
  // be set if any references to pushed arguments are found.
  Environment* ParseEnvironment(SExpList* list);

  // Parsing functions for which there are no good distinguished error
  // values, so use out parameters and a boolean return instead.

  // Parses a Dart value and returns a canonicalized result.
  bool ParseDartValue(SExpression* sexp, Object* out);

  // Canonicalizes and replaces the original contents of the handle pointed to
  // by [inst] if [inst] is an Instance (if not, it trivially succeeds). The
  // replacement happens whether successful or not. [sexp] is the SExpression
  // to be used for error reporting.
  bool CanonicalizeInstance(SExpression* sexp, Object* inst);

  // Helper functions for ParseDartValue for parsing particular type of values.
  // If necessary, they canonicalize the returned value, and so may be used
  // directly by other code as well. Helpers that take SExpression* take either
  // serialized constants or references to constant definitions.
  //
  // Due to particulars of operator=() on non-Object values, for a given X,
  // ParseX takes Object* instead of X* for the out parameter.
  bool ParseAbstractType(SExpression* sexp, Object* out);
  bool ParseClass(SExpList* list, Object* out);
  bool ParseClosure(SExpList* list, Object* out);
  bool ParseField(SExpList* list, Object* out);
  bool ParseFunction(SExpList* list, Object* out);
  bool ParseImmutableList(SExpList* list, Object* out);
  bool ParseInstance(SExpList* list, Object* out);
  bool ParseType(SExpression* sexp, Object* out);
  bool ParseTypeParameter(SExpList* list, Object* out);
  bool ParseTypeArguments(SExpression* sexp, Object* out);
  bool ParseTypeRef(SExpList* list, Object* out);

  bool ParseCanonicalName(SExpSymbol* sym, Object* out);

  const Field& MayCloneField(const Field& field) const;
  bool ParseSlot(SExpList* list, const Slot** out);
  bool ParseRange(SExpList* list, Range* out);
  bool ParseRangeBoundary(SExpression* sexp, RangeBoundary* out);

  bool ParseBlockId(SExpSymbol* sym, intptr_t* out);
  bool ParseSSATemp(SExpSymbol* sym, intptr_t* out);
  bool ParseUse(SExpSymbol* sym, intptr_t* out);
  bool ParseSymbolAsPrefixedInt(SExpSymbol* sym, char prefix, intptr_t* out);

  bool ArePendingTypeRefs() const;

  // Allocates a new ICData structure. [list] is the ICData S-expression, while
  // [inst] is the Instruction generated from the instruction S-expression
  // containing [list].
  bool CreateICData(SExpList* list, Instruction* inst);

  // Helper function for creating a placeholder value when the definition
  // with index [i] has not yet been seen. If [inherit_type], then the type of
  // the definition should be used as the reaching type for the use. [s] is used
  // for any errors that occur when resolving the pending value.
  Value* AddNewPendingValue(SExpression* s, intptr_t i, bool inherit_type);

  // Helper function for rebinding values pending on this definition.
  bool FixPendingValues(intptr_t index, Definition* def);

  // Retrieves the block corresponding to the given block ID symbol from
  // [block_map_]. Assumes all blocks have had their header parsed.
  BlockEntryInstr* FetchBlock(SExpSymbol* sym);

  // Utility functions for checking the shape of an S-expression.
  // If these functions return nullptr for a non-null argument, they have the
  // side effect of setting the stored error message.
#define BASE_CHECK_DECL(name, type) SExp##name* Check##name(SExpression* sexp);
  FOR_EACH_S_EXPRESSION(BASE_CHECK_DECL)
#undef BASE_CHECK_DECL

  // Checks whether [sexp] is a symbol with the given label.
  bool IsTag(SExpression* sexp, const char* label);

  // A version of CheckList that also checks that the list has at least one
  // element and that the first element is a symbol. If [label] is non-null,
  // then the initial symbol element is checked against it.
  SExpList* CheckTaggedList(SExpression* sexp, const char* label = nullptr);

  // Stores appropriate error information using the SExpression as the location
  // and the rest of the arguments as an error message for the user.
  void StoreError(SExpression* s, const char* fmt, ...) PRINTF_ATTRIBUTE(3, 4);

  Thread* thread() const { return thread_; }
  Zone* zone() const { return zone_; }

  Thread* const thread_;
  Zone* const zone_;
  SExpression* const root_sexp_;
  const ParsedFunction* parsed_function_;

  FlowGraph* flow_graph_ = nullptr;
  BlockEntryInstr* current_block_ = nullptr;
  intptr_t max_block_id_ = -1;
  intptr_t max_ssa_index_ = -1;

  // Map from block IDs to blocks. Does not contain an entry for block 0
  // (the graph entry), since it is only used at known points and is already
  // available via [flow_graph_].
  IntMap<BlockEntryInstr*> block_map_;

  // Map from variable indexes to definitions.
  IntMap<Definition*> definition_map_;

  // Information needed to handle uses seen prior to their definitions.
  struct PendingValue {
    // SExpression used for error reporting.
    SExpression* sexp;
    // Value to be rebound once the right definition is found.
    Value* value;
    // Whether the type should inherit the type of the found definition.
    bool inherit_type;
  };

  // Map from variable indices to lists of values. The list of values are
  // values that were parsed prior to the corresponding definition being found.
  IntMap<ZoneGrowableArray<PendingValue>*> values_map_;

  // Map from hash values to SExpLists. This is used by ParseTypeRef to
  // determine whether or not the recursive type it refers to is being currently
  // built. The SExpList can be used to report hash collisions.
  IntMap<SExpList*> recursive_types_map_;

  // Map from hash values to arrays of TypeRefs. This is used by ParseType and
  // ParseTypeRef to store and later fill in TypeRefs pending on the type being
  // constructed. Since entries are added at the start of parsing recursive
  // Type S-exps and removed before the resulting Type is successfully returned,
  // this map should be empty outside of parsing recursive types.
  IntMap<ZoneGrowableArray<TypeRef*>*> pending_typeref_map_;

  // Temporary handles used by functions that are not re-entrant or where the
  // handle is not live after the re-entrant call. Comments show which handles
  // are expected to only be used within a single method.
  TypeArguments& array_type_args_;     // ParseImmutableList
  Class& instance_class_;              // ParseInstance
  Field& instance_field_;              // ParseInstance
  Array& instance_fields_array_;       // ParseInstance
  TypeArguments& instance_type_args_;  // ParseInstance
  Class& name_class_;                  // ParseCanonicalName
  Field& name_field_;                  // ParseCanonicalName
  Function& name_function_;            // ParseCanonicalName
  Library& name_library_;              // ParseCanonicalName
  Class& type_class_;                  // ParseType
  Class& type_param_class_;            // ParseTypeParameter
  Function& type_param_function_;      // ParseTypeParameter
  // Uses of string handles tend to be immediate, so we only need one.
  String& tmp_string_;

  // Stores a message appropriate to surfacing to the user when an error
  // occurs.
  const char* error_message_ = nullptr;
  // Stores the location of the deserialization error by containing the
  // S-expression which caused the failure.
  SExpression* error_sexp_ = nullptr;

  DISALLOW_COPY_AND_ASSIGN(FlowGraphDeserializer);
};

}  // namespace dart

#endif  // RUNTIME_VM_COMPILER_BACKEND_IL_DESERIALIZER_H_