runtime/vm/compiler/frontend/prologue_builder.cc

// Copyright (c) 2017, 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.

#include "vm/compiler/frontend/prologue_builder.h"

#include "vm/compiler/backend/il.h"
#include "vm/compiler/backend/il_printer.h"
#include "vm/compiler/frontend/base_flow_graph_builder.h"
#include "vm/compiler/jit/compiler.h"
#include "vm/kernel_loader.h"
#include "vm/longjump.h"
#include "vm/object_store.h"
#include "vm/report.h"
#include "vm/resolver.h"
#include "vm/stack_frame.h"

namespace dart {
namespace kernel {

#define Z (zone_)

// Returns static type of the parameter if it can be trusted (was type checked
// by caller) and dynamic otherwise.
static CompileType ParameterType(LocalVariable* param,
                                 Representation representation = kTagged) {
  return param->was_type_checked_by_caller()
             ? CompileType::FromAbstractType(param->type(),
                                             representation == kTagged)
             : ((representation == kTagged)
                    ? CompileType::Dynamic()
                    : CompileType::FromCid(kDynamicCid).CopyNonNullable());
}

bool PrologueBuilder::PrologueSkippableOnUncheckedEntry(
    const Function& function) {
  return !function.HasOptionalParameters() &&
         !function.IsNonImplicitClosureFunction() && !function.IsGeneric();
}

bool PrologueBuilder::HasEmptyPrologue(const Function& function) {
  return !function.HasOptionalParameters() && !function.IsGeneric() &&
         !function.CanReceiveDynamicInvocation() &&
         !function.IsClosureFunction();
}

BlockEntryInstr* PrologueBuilder::BuildPrologue(BlockEntryInstr* entry,
                                                PrologueInfo* prologue_info,
                                                JoinEntryInstr* provided_nsm) {
  // We always have to build the graph, but we only link it sometimes.
  const bool link = !is_inlining_ && !compiling_for_osr_;

  const intptr_t previous_block_id = last_used_block_id_;

  const bool load_optional_arguments = function_.HasOptionalParameters();
  const bool expect_type_args = function_.IsGeneric();
  const bool check_shapes = function_.CanReceiveDynamicInvocation();

  Fragment prologue = Fragment(entry);

  // We only check for bad argument shapes and throw NSM in functions that
  // can receive dynamic invocation. Otherwise, the NSM block is never used
  // and so there's no need to create it. The helper methods can only throw
  // NSM in appropriate spots if one was created.
  JoinEntryInstr* nsm = nullptr;
  if (check_shapes) {
    // If no block for throwing NSM was provided, create a new one.
    nsm = provided_nsm != nullptr ? provided_nsm : BuildThrowNoSuchMethod();
    Fragment f = BuildTypeArgumentsLengthCheck(nsm, expect_type_args);
    if (link) prologue += f;
  }
  if (load_optional_arguments) {
    Fragment f = BuildOptionalParameterHandling(
        nsm, parsed_function_->expression_temp_var());
    if (link) prologue += f;
  } else if (check_shapes) {
    Fragment f = BuildFixedParameterLengthChecks(nsm);
    if (link) prologue += f;
  }
  if (function_.IsClosureFunction()) {
    Fragment f = BuildClosureContextHandling();
    if (!compiling_for_osr_) prologue += f;
  }
  if (expect_type_args) {
    Fragment f = BuildTypeArgumentsHandling(nsm);
    if (link) prologue += f;
  }

  const bool is_empty_prologue = prologue.entry == prologue.current;
  // Double-check we create empty prologues when HasEmptyPrologue returns true.
  ASSERT(!HasEmptyPrologue(function_) || is_empty_prologue);

  // Always do this to preserve deoptid numbering.
  JoinEntryInstr* normal_code = BuildJoinEntry();
  Fragment jump_to_normal_code = Goto(normal_code);

  if (is_empty_prologue) {
    *prologue_info = PrologueInfo(-1, -1);
    return entry;
  } else {
    prologue += jump_to_normal_code;
    *prologue_info =
        PrologueInfo(previous_block_id, normal_code->block_id() - 1);
    return normal_code;
  }
}

Fragment PrologueBuilder::BuildTypeArgumentsLengthCheck(JoinEntryInstr* nsm,
                                                        bool expect_type_args) {
  ASSERT(nsm != nullptr);
  Fragment check_type_args;
  JoinEntryInstr* done = BuildJoinEntry();

  // Type args are always optional, so length can always be zero.
  // If expect_type_args, a non-zero length must match the declaration length.
  TargetEntryInstr *then, *fail;
  check_type_args += LoadArgDescriptor();
  check_type_args += LoadNativeField(Slot::ArgumentsDescriptor_type_args_len());
  if (expect_type_args) {
    JoinEntryInstr* join2 = BuildJoinEntry();

    LocalVariable* len = MakeTemporary();

    TargetEntryInstr* otherwise;
    check_type_args += LoadLocal(len);
    check_type_args += IntConstant(0);
    check_type_args += BranchIfEqual(&then, &otherwise);

    TargetEntryInstr* then2;
    Fragment check_len(otherwise);
    check_len += LoadLocal(len);
    check_len += IntConstant(function_.NumTypeParameters());
    check_len += BranchIfEqual(&then2, &fail);

    Fragment(then) + Goto(join2);
    Fragment(then2) + Goto(join2);

    Fragment(join2) + Drop() + Goto(done);
    Fragment(fail) + Goto(nsm);
  } else {
    check_type_args += IntConstant(0);
    check_type_args += BranchIfEqual(&then, &fail);
    Fragment(then) + Goto(done);
    Fragment(fail) + Goto(nsm);
  }

  return Fragment(check_type_args.entry, done);
}

Fragment PrologueBuilder::BuildOptionalParameterHandling(
    JoinEntryInstr* nsm,
    LocalVariable* temp_var) {
  // We only need to check the shape of the arguments (correct parameter count
  // and correct names/provided required arguments) when the function can be
  // invoked dynamically. The caller only provides a non-nullptr nsm block if
  // dynamic invocation is possible.
  const bool check_arguments_shape = nsm != nullptr;

  Fragment copy_args_prologue;
  const int num_fixed_params = function_.num_fixed_parameters();
  const int num_opt_pos_params = function_.NumOptionalPositionalParameters();
  const int num_opt_named_params = function_.NumOptionalNamedParameters();
  const int num_params =
      num_fixed_params + num_opt_pos_params + num_opt_named_params;
  ASSERT(function_.NumParameters() == num_params);
  const intptr_t fixed_params_size =
      FlowGraph::ParameterOffsetAt(function_, num_params, /*last_slot=*/false) -
      num_opt_named_params - num_opt_pos_params;

  // Check that min_num_pos_args <= num_pos_args <= max_num_pos_args,
  // where num_pos_args is the number of positional arguments passed in.
  const int min_num_pos_args = num_fixed_params;
  const int max_num_pos_args = num_fixed_params + num_opt_pos_params;

  copy_args_prologue += LoadArgDescriptor();
  copy_args_prologue +=
      LoadNativeField(Slot::ArgumentsDescriptor_positional_count());
  LocalVariable* positional_count_var = MakeTemporary();

  copy_args_prologue += LoadArgDescriptor();
  copy_args_prologue += LoadNativeField(Slot::ArgumentsDescriptor_count());
  LocalVariable* count_var = MakeTemporary();

  if (check_arguments_shape) {
    // Ensure the caller provided at least [min_num_pos_args] arguments.
    copy_args_prologue += IntConstant(min_num_pos_args);
    copy_args_prologue += LoadLocal(positional_count_var);
    copy_args_prologue += SmiRelationalOp(Token::kLTE);
    TargetEntryInstr *success1, *fail1;
    copy_args_prologue += BranchIfTrue(&success1, &fail1);
    copy_args_prologue = Fragment(copy_args_prologue.entry, success1);

    // Ensure the caller provided at most [max_num_pos_args] arguments.
    copy_args_prologue += LoadLocal(positional_count_var);
    copy_args_prologue += IntConstant(max_num_pos_args);
    copy_args_prologue += SmiRelationalOp(Token::kLTE);
    TargetEntryInstr *success2, *fail2;
    copy_args_prologue += BranchIfTrue(&success2, &fail2);
    copy_args_prologue = Fragment(copy_args_prologue.entry, success2);

    // Link up the argument check failing code.
    Fragment(fail1) + Goto(nsm);
    Fragment(fail2) + Goto(nsm);
  }

  copy_args_prologue += LoadLocal(count_var);
  copy_args_prologue += IntConstant(min_num_pos_args);
  copy_args_prologue += SmiBinaryOp(Token::kSUB, /* truncate= */ true);
  LocalVariable* optional_count_var = MakeTemporary();

  // Copy mandatory parameters down.
  intptr_t param = 0;
  intptr_t param_offset = -1;

  const auto update_param_offset = [&param_offset](const Function& function,
                                                   intptr_t param_id) {
    if (param_id < 0) {
      // Type arguments of Factory constructor is processed with parameters
      param_offset++;
      return;
    }

    // update parameter offset
    if (function.is_unboxed_integer_parameter_at(param_id)) {
      param_offset += compiler::target::kIntSpillFactor;
    } else if (function.is_unboxed_double_parameter_at(param_id)) {
      param_offset += compiler::target::kDoubleSpillFactor;
    } else {
      ASSERT(!function.is_unboxed_parameter_at(param_id));
      // Tagged parameters always occupy one word
      param_offset++;
    }
  };

  for (; param < num_fixed_params; ++param) {
    const intptr_t param_index = param - (function_.IsFactory() ? 1 : 0);
    update_param_offset(function_, param_index);

    const auto representation =
        ((param_index >= 0)
             ? FlowGraph::ParameterRepresentationAt(function_, param_index)
             : kTagged);

    copy_args_prologue += LoadLocal(optional_count_var);
    copy_args_prologue += LoadFpRelativeSlot(
        compiler::target::kWordSize *
            (compiler::target::frame_layout.param_end_from_fp +
             fixed_params_size - param_offset),
        ParameterType(ParameterVariable(param), representation),
        representation);
    copy_args_prologue +=
        StoreLocalRaw(TokenPosition::kNoSource, ParameterVariable(param));
    copy_args_prologue += Drop();
  }

  // Copy optional parameters down.
  if (num_opt_pos_params > 0) {
    JoinEntryInstr* next_missing = NULL;
    for (intptr_t opt_param = 1; param < num_params; ++param, ++opt_param) {
      const intptr_t param_index = param - (function_.IsFactory() ? 1 : 0);
      update_param_offset(function_, param_index);

      TargetEntryInstr *supplied, *missing;
      copy_args_prologue += IntConstant(opt_param);
      copy_args_prologue += LoadLocal(optional_count_var);
      copy_args_prologue += SmiRelationalOp(Token::kLTE);
      copy_args_prologue += BranchIfTrue(&supplied, &missing);

      Fragment good(supplied);
      good += LoadLocal(optional_count_var);
      good += LoadFpRelativeSlot(
          compiler::target::kWordSize *
              (compiler::target::frame_layout.param_end_from_fp +
               fixed_params_size - param_offset),
          ParameterType(ParameterVariable(param)));
      good += StoreLocalRaw(TokenPosition::kNoSource, ParameterVariable(param));
      good += Drop();

      Fragment not_good(missing);
      if (next_missing != NULL) {
        not_good += Goto(next_missing);
        not_good.current = next_missing;
      }
      next_missing = BuildJoinEntry();
      not_good += Constant(DefaultParameterValueAt(opt_param - 1));
      not_good +=
          StoreLocalRaw(TokenPosition::kNoSource, ParameterVariable(param));
      not_good += Drop();
      not_good += Goto(next_missing);

      copy_args_prologue.current = good.current;
    }
    copy_args_prologue += Goto(next_missing /* join good/not_good flows */);
    copy_args_prologue.current = next_missing;

    if (check_arguments_shape) {
      // Check for unprocessed arguments and throw NSM if there are any.
      TargetEntryInstr *done, *unknown_named_arg_passed;
      copy_args_prologue += LoadLocal(positional_count_var);
      copy_args_prologue += LoadLocal(count_var);
      copy_args_prologue += BranchIfEqual(&done, &unknown_named_arg_passed);
      copy_args_prologue.current = done;
      {
        Fragment f(unknown_named_arg_passed);
        f += Goto(nsm);
      }
    }
  } else {
    ASSERT(num_opt_named_params > 0);

    bool null_safety = Isolate::Current()->null_safety();
    const intptr_t first_name_offset =
        compiler::target::ArgumentsDescriptor::first_named_entry_offset() -
        compiler::target::Array::data_offset();

    // Start by alphabetically sorting the names of the optional parameters.
    int* opt_param_position = Z->Alloc<int>(num_opt_named_params);
    SortOptionalNamedParametersInto(opt_param_position, num_fixed_params,
                                    num_params);

    ASSERT(temp_var != nullptr);
    LocalVariable* optional_count_vars_processed = temp_var;
    copy_args_prologue += IntConstant(0);
    copy_args_prologue +=
        StoreLocalRaw(TokenPosition::kNoSource, optional_count_vars_processed);
    copy_args_prologue += Drop();

    for (intptr_t i = 0; param < num_params; ++param, ++i) {
      copy_args_prologue += IntConstant(
          compiler::target::ArgumentsDescriptor::named_entry_size() /
          compiler::target::kWordSize);
      copy_args_prologue += LoadLocal(optional_count_vars_processed);
      copy_args_prologue += SmiBinaryOp(Token::kMUL, /* truncate= */ true);
      LocalVariable* tuple_diff = MakeTemporary();

      // Let's load position from arg descriptor (to see which parameter is the
      // name) and move kEntrySize forward in ArgDescriptopr names array.
      //
      // Later we'll either add this fragment directly to the copy_args_prologue
      // if no check is needed or add an appropriate check.
      Fragment good;
      {
        // fp[target::frame_layout.param_end_from_fp + (count_var - pos)]
        good += LoadLocal(count_var);
        {
          // pos = arg_desc[names_offset + arg_desc_name_index + positionOffset]
          good += LoadArgDescriptor();
          good += IntConstant(
              (first_name_offset +
               compiler::target::ArgumentsDescriptor::position_offset()) /
              compiler::target::kWordSize);
          good += LoadLocal(tuple_diff);
          good += SmiBinaryOp(Token::kADD, /* truncate= */ true);
          good += LoadIndexed(/* index_scale = */ compiler::target::kWordSize);
        }
        good += SmiBinaryOp(Token::kSUB, /* truncate= */ true);
        good += LoadFpRelativeSlot(
            compiler::target::kWordSize *
                compiler::target::frame_layout.param_end_from_fp,
            ParameterType(ParameterVariable(opt_param_position[i])));

        // Copy down.
        good += StoreLocalRaw(TokenPosition::kNoSource,
                              ParameterVariable(opt_param_position[i]));
        good += Drop();

        // Increase processed optional variable count.
        good += LoadLocal(optional_count_vars_processed);
        good += IntConstant(1);
        good += SmiBinaryOp(Token::kADD, /* truncate= */ true);
        good += StoreLocalRaw(TokenPosition::kNoSource,
                              optional_count_vars_processed);
        good += Drop();
      }

      const bool required =
          null_safety && function_.IsRequiredAt(opt_param_position[i]);

      // If this function cannot be invoked dynamically and this is a required
      // named argument, then we can just add this fragment directly without
      // checking the name to ensure it was provided.
      if (required && !check_arguments_shape) {
        copy_args_prologue += good;
      } else {
        // name = arg_desc[names_offset + arg_desc_name_index + nameOffset]
        copy_args_prologue += LoadArgDescriptor();
        copy_args_prologue +=
            IntConstant((first_name_offset +
                         compiler::target::ArgumentsDescriptor::name_offset()) /
                        compiler::target::kWordSize);
        copy_args_prologue += LoadLocal(tuple_diff);
        copy_args_prologue += SmiBinaryOp(Token::kADD, /* truncate= */ true);
        copy_args_prologue +=
            LoadIndexed(/* index_scale = */ compiler::target::kWordSize);

        // first name in sorted list of all names
        const String& param_name = String::ZoneHandle(
            Z, function_.ParameterNameAt(opt_param_position[i]));
        ASSERT(param_name.IsSymbol());
        copy_args_prologue += Constant(param_name);

        // Compare the two names: Note that the ArgumentDescriptor array always
        // terminates with a "null" name (i.e. kNullCid), which will prevent us
        // from running out-of-bounds.
        TargetEntryInstr *supplied, *missing;
        copy_args_prologue += BranchIfStrictEqual(&supplied, &missing);

        // Join good/not_good.
        JoinEntryInstr* join = BuildJoinEntry();

        // Put good in the flowgraph as a separate basic block.
        good.Prepend(supplied);
        good += Goto(join);

        // We had no match. If the param is required, throw a NoSuchMethod
        // error. Otherwise just load the default constant.
        Fragment not_good(missing);
        if (required) {
          ASSERT(nsm != nullptr);
          not_good += Goto(nsm);
        } else {
          not_good += Constant(DefaultParameterValueAt(opt_param_position[i] -
                                                       num_fixed_params));

          // Copy down with default value.
          not_good += StoreLocalRaw(TokenPosition::kNoSource,
                                    ParameterVariable(opt_param_position[i]));
          not_good += Drop();
          not_good += Goto(join);
        }

        copy_args_prologue.current = join;
      }

      copy_args_prologue += Drop();  // tuple_diff
    }

    if (check_arguments_shape) {
      // Check for unprocessed arguments and throw NSM if there are any.
      TargetEntryInstr *done, *unknown_named_arg_passed;
      copy_args_prologue += LoadLocal(optional_count_var);
      copy_args_prologue += LoadLocal(optional_count_vars_processed);
      copy_args_prologue += BranchIfEqual(&done, &unknown_named_arg_passed);
      copy_args_prologue.current = done;

      {
        Fragment f(unknown_named_arg_passed);
        f += Goto(nsm);
      }
    }
  }

  copy_args_prologue += Drop();  // optional_count_var
  copy_args_prologue += Drop();  // count_var
  copy_args_prologue += Drop();  // positional_count_var

  return copy_args_prologue;
}

Fragment PrologueBuilder::BuildFixedParameterLengthChecks(JoinEntryInstr* nsm) {
  Fragment check_args;
  JoinEntryInstr* done = BuildJoinEntry();

  check_args += LoadArgDescriptor();
  check_args += LoadNativeField(Slot::ArgumentsDescriptor_count());
  LocalVariable* count = MakeTemporary();

  TargetEntryInstr *then, *fail;
  check_args += LoadLocal(count);
  check_args += IntConstant(function_.num_fixed_parameters());
  check_args += BranchIfEqual(&then, &fail);

  TargetEntryInstr *then2, *fail2;
  Fragment check_len(then);
  check_len += LoadArgDescriptor();
  check_len += LoadNativeField(Slot::ArgumentsDescriptor_positional_count());
  check_len += BranchIfEqual(&then2, &fail2);

  Fragment(fail) + Goto(nsm);
  Fragment(fail2) + Goto(nsm);
  Fragment(then2) + Goto(done);

  return Fragment(check_args.entry, done);
}

Fragment PrologueBuilder::BuildClosureContextHandling() {
  LocalVariable* closure_parameter = parsed_function_->ParameterVariable(0);
  LocalVariable* context = parsed_function_->current_context_var();

  // Load closure.context & store it into the context variable.
  // (both load/store happen on the copyied-down places).
  Fragment populate_context;
  populate_context += LoadLocal(closure_parameter);
  populate_context += LoadNativeField(Slot::Closure_context());
  populate_context += StoreLocal(TokenPosition::kNoSource, context);
  populate_context += Drop();
  return populate_context;
}

Fragment PrologueBuilder::BuildTypeArgumentsHandling(JoinEntryInstr* nsm) {
  // We only need to check the shape of the arguments (correct parameter count
  // and correct names/provided required arguments) when the function can be
  // invoked dynamically. The caller only provides a non-nullptr nsm block if
  // dynamic invocation is possible.
  const bool check_argument_shapes = nsm != nullptr;

  LocalVariable* type_args_var = parsed_function_->RawTypeArgumentsVariable();
  ASSERT(type_args_var != nullptr);

  Fragment handling;

  Fragment store_type_args;
  store_type_args += LoadArgDescriptor();
  store_type_args += LoadNativeField(Slot::ArgumentsDescriptor_size());
  store_type_args += LoadFpRelativeSlot(
      compiler::target::kWordSize *
          (1 + compiler::target::frame_layout.param_end_from_fp),
      CompileType::CreateNullable(/*is_nullable=*/true, kTypeArgumentsCid));
  store_type_args += StoreLocal(TokenPosition::kNoSource, type_args_var);
  store_type_args += Drop();

  Fragment store_null;
  store_null += NullConstant();
  store_null += StoreLocal(TokenPosition::kNoSource, type_args_var);
  store_null += Drop();

  handling += TestTypeArgsLen(store_null, store_type_args, 0);

  const auto& function = parsed_function_->function();
  if (function.IsClosureFunction() ||
      function.IsDynamicClosureCallDispatcher(thread_)) {
    LocalVariable* closure = parsed_function_->ParameterVariable(0);

    // Currently, delayed type arguments can only be introduced through type
    // inference in the FE. So if they are present, we can assume they are
    // correct in number and bound.
    Fragment use_delayed_type_args;
    use_delayed_type_args += LoadLocal(closure);
    use_delayed_type_args +=
        LoadNativeField(Slot::Closure_delayed_type_arguments());
    use_delayed_type_args +=
        StoreLocal(TokenPosition::kNoSource, type_args_var);
    use_delayed_type_args += Drop();

    handling += TestDelayedTypeArgs(
        closure,
        /*present=*/
        // No need to check the type arguments length if this function cannot
        // be invoked dynamically, and thus we are not checking argument shapes.
        check_argument_shapes
            ? TestTypeArgsLen(use_delayed_type_args, Goto(nsm), 0)
            : use_delayed_type_args,
        /*absent=*/Fragment());
  }

  return handling;
}

void PrologueBuilder::SortOptionalNamedParametersInto(int* opt_param_position,
                                                      int num_fixed_params,
                                                      int num_params) {
  String& name = String::Handle(Z);
  String& name_i = String::Handle(Z);
  for (int pos = num_fixed_params; pos < num_params; pos++) {
    name = function_.ParameterNameAt(pos);
    int i = pos - num_fixed_params;
    while (--i >= 0) {
      name_i = function_.ParameterNameAt(opt_param_position[i]);
      const intptr_t result = name.CompareTo(name_i);
      ASSERT(result != 0);
      if (result > 0) break;
      opt_param_position[i + 1] = opt_param_position[i];
    }
    opt_param_position[i + 1] = pos;
  }
}

}  // namespace kernel
}  // namespace dart