src/compiler/instruction-selector-impl.h

// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
#define V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_

#include "src/compiler/instruction.h"
#include "src/compiler/instruction-selector.h"
#include "src/compiler/linkage.h"
#include "src/compiler/schedule.h"
#include "src/macro-assembler.h"

namespace v8 {
namespace internal {
namespace compiler {

// Helper struct containing data about a table or lookup switch.
struct SwitchInfo {
  int32_t min_value;           // minimum value of {case_values}
  int32_t max_value;           // maximum value of {case_values}
  size_t value_range;          // |max_value - min_value| + 1
  size_t case_count;           // number of cases
  int32_t* case_values;        // actual case values, unsorted
  BasicBlock** case_branches;  // basic blocks corresponding to case values
  BasicBlock* default_branch;  // default branch target
};

// A helper class for the instruction selector that simplifies construction of
// Operands. This class implements a base for architecture-specific helpers.
class OperandGenerator {
 public:
  explicit OperandGenerator(InstructionSelector* selector)
      : selector_(selector) {}

  InstructionOperand NoOutput() {
    return InstructionOperand();  // Generates an invalid operand.
  }

  InstructionOperand DefineAsRegister(Node* node) {
    return Define(node,
                  UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                                     GetVReg(node)));
  }

  InstructionOperand DefineSameAsFirst(Node* node) {
    return Define(node,
                  UnallocatedOperand(UnallocatedOperand::SAME_AS_FIRST_INPUT,
                                     GetVReg(node)));
  }

  InstructionOperand DefineAsFixed(Node* node, Register reg) {
    return Define(node, UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
                                           reg.code(), GetVReg(node)));
  }

  InstructionOperand DefineAsFixed(Node* node, DoubleRegister reg) {
    return Define(node,
                  UnallocatedOperand(UnallocatedOperand::FIXED_DOUBLE_REGISTER,
                                     reg.code(), GetVReg(node)));
  }

  InstructionOperand DefineAsConstant(Node* node) {
    selector()->MarkAsDefined(node);
    int virtual_register = GetVReg(node);
    sequence()->AddConstant(virtual_register, ToConstant(node));
    return ConstantOperand(virtual_register);
  }

  InstructionOperand DefineAsLocation(Node* node, LinkageLocation location,
                                      MachineRepresentation rep) {
    return Define(node, ToUnallocatedOperand(location, rep, GetVReg(node)));
  }

  InstructionOperand DefineAsDualLocation(Node* node,
                                          LinkageLocation primary_location,
                                          LinkageLocation secondary_location) {
    return Define(node,
                  ToDualLocationUnallocatedOperand(
                      primary_location, secondary_location, GetVReg(node)));
  }

  InstructionOperand Use(Node* node) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::NONE,
                                        UnallocatedOperand::USED_AT_START,
                                        GetVReg(node)));
  }

  InstructionOperand UseAny(Node* node) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::ANY,
                                        UnallocatedOperand::USED_AT_START,
                                        GetVReg(node)));
  }

  InstructionOperand UseRegister(Node* node) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                                        UnallocatedOperand::USED_AT_START,
                                        GetVReg(node)));
  }

  InstructionOperand UseUniqueSlot(Node* node) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::MUST_HAVE_SLOT,
                                        GetVReg(node)));
  }

  // Use register or operand for the node. If a register is chosen, it won't
  // alias any temporary or output registers.
  InstructionOperand UseUnique(Node* node) {
    return Use(node,
               UnallocatedOperand(UnallocatedOperand::NONE, GetVReg(node)));
  }

  // Use a unique register for the node that does not alias any temporary or
  // output registers.
  InstructionOperand UseUniqueRegister(Node* node) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                                        GetVReg(node)));
  }

  InstructionOperand UseFixed(Node* node, Register reg) {
    return Use(node, UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
                                        reg.code(), GetVReg(node)));
  }

  InstructionOperand UseFixed(Node* node, DoubleRegister reg) {
    return Use(node,
               UnallocatedOperand(UnallocatedOperand::FIXED_DOUBLE_REGISTER,
                                  reg.code(), GetVReg(node)));
  }

  InstructionOperand UseExplicit(LinkageLocation location) {
    MachineRepresentation rep = InstructionSequence::DefaultRepresentation();
    if (location.IsRegister()) {
      return ExplicitOperand(LocationOperand::REGISTER, rep,
                             location.AsRegister());
    } else {
      return ExplicitOperand(LocationOperand::STACK_SLOT, rep,
                             location.GetLocation());
    }
  }

  InstructionOperand UseImmediate(Node* node) {
    return sequence()->AddImmediate(ToConstant(node));
  }

  InstructionOperand UseLocation(Node* node, LinkageLocation location,
                                 MachineRepresentation rep) {
    return Use(node, ToUnallocatedOperand(location, rep, GetVReg(node)));
  }

  // Used to force gap moves from the from_location to the to_location
  // immediately before an instruction.
  InstructionOperand UsePointerLocation(LinkageLocation to_location,
                                        LinkageLocation from_location) {
    MachineRepresentation rep = MachineType::PointerRepresentation();
    UnallocatedOperand casted_from_operand =
        UnallocatedOperand::cast(TempLocation(from_location, rep));
    selector_->Emit(kArchNop, casted_from_operand);
    return ToUnallocatedOperand(to_location, rep,
                                casted_from_operand.virtual_register());
  }

  InstructionOperand TempRegister() {
    return UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                              UnallocatedOperand::USED_AT_START,
                              sequence()->NextVirtualRegister());
  }

  InstructionOperand TempDoubleRegister() {
    UnallocatedOperand op = UnallocatedOperand(
        UnallocatedOperand::MUST_HAVE_REGISTER,
        UnallocatedOperand::USED_AT_START, sequence()->NextVirtualRegister());
    sequence()->MarkAsRepresentation(MachineRepresentation::kFloat64,
                                     op.virtual_register());
    return op;
  }

  InstructionOperand TempRegister(Register reg) {
    return UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER, reg.code(),
                              InstructionOperand::kInvalidVirtualRegister);
  }

  InstructionOperand TempImmediate(int32_t imm) {
    return sequence()->AddImmediate(Constant(imm));
  }

  InstructionOperand TempLocation(LinkageLocation location,
                                  MachineRepresentation rep) {
    return ToUnallocatedOperand(location, rep,
                                sequence()->NextVirtualRegister());
  }

  InstructionOperand Label(BasicBlock* block) {
    return sequence()->AddImmediate(
        Constant(RpoNumber::FromInt(block->rpo_number())));
  }

 protected:
  InstructionSelector* selector() const { return selector_; }
  InstructionSequence* sequence() const { return selector()->sequence(); }
  Zone* zone() const { return selector()->instruction_zone(); }

 private:
  int GetVReg(Node* node) const { return selector_->GetVirtualRegister(node); }

  static Constant ToConstant(const Node* node) {
    switch (node->opcode()) {
      case IrOpcode::kInt32Constant:
        return Constant(OpParameter<int32_t>(node));
      case IrOpcode::kInt64Constant:
        return Constant(OpParameter<int64_t>(node));
      case IrOpcode::kFloat32Constant:
        return Constant(OpParameter<float>(node));
      case IrOpcode::kFloat64Constant:
      case IrOpcode::kNumberConstant:
        return Constant(OpParameter<double>(node));
      case IrOpcode::kExternalConstant:
        return Constant(OpParameter<ExternalReference>(node));
      case IrOpcode::kHeapConstant:
        return Constant(OpParameter<Handle<HeapObject>>(node));
      default:
        break;
    }
    UNREACHABLE();
    return Constant(static_cast<int32_t>(0));
  }

  UnallocatedOperand Define(Node* node, UnallocatedOperand operand) {
    DCHECK_NOT_NULL(node);
    DCHECK_EQ(operand.virtual_register(), GetVReg(node));
    selector()->MarkAsDefined(node);
    return operand;
  }

  UnallocatedOperand Use(Node* node, UnallocatedOperand operand) {
    DCHECK_NOT_NULL(node);
    DCHECK_EQ(operand.virtual_register(), GetVReg(node));
    selector()->MarkAsUsed(node);
    return operand;
  }

  UnallocatedOperand ToDualLocationUnallocatedOperand(
      LinkageLocation primary_location, LinkageLocation secondary_location,
      int virtual_register) {
    // We only support the primary location being a register and the secondary
    // one a slot.
    DCHECK(primary_location.IsRegister() &&
           secondary_location.IsCalleeFrameSlot());
    int reg_id = primary_location.AsRegister();
    int slot_id = secondary_location.AsCalleeFrameSlot();
    return UnallocatedOperand(reg_id, slot_id, virtual_register);
  }

  UnallocatedOperand ToUnallocatedOperand(LinkageLocation location,
                                          MachineRepresentation rep,
                                          int virtual_register) {
    if (location.IsAnyRegister()) {
      // any machine register.
      return UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                                virtual_register);
    }
    if (location.IsCallerFrameSlot()) {
      // a location on the caller frame.
      return UnallocatedOperand(UnallocatedOperand::FIXED_SLOT,
                                location.AsCallerFrameSlot(), virtual_register);
    }
    if (location.IsCalleeFrameSlot()) {
      // a spill location on this (callee) frame.
      return UnallocatedOperand(UnallocatedOperand::FIXED_SLOT,
                                location.AsCalleeFrameSlot(), virtual_register);
    }
    // a fixed register.
    if (IsFloatingPoint(rep)) {
      return UnallocatedOperand(UnallocatedOperand::FIXED_DOUBLE_REGISTER,
                                location.AsRegister(), virtual_register);
    }
    return UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
                              location.AsRegister(), virtual_register);
  }

  InstructionSelector* selector_;
};


// The flags continuation is a way to combine a branch or a materialization
// of a boolean value with an instruction that sets the flags register.
// The whole instruction is treated as a unit by the register allocator, and
// thus no spills or moves can be introduced between the flags-setting
// instruction and the branch or set it should be combined with.
class FlagsContinuation final {
 public:
  FlagsContinuation() : mode_(kFlags_none) {}

  // Creates a new flags continuation from the given condition and true/false
  // blocks.
  FlagsContinuation(FlagsCondition condition, BasicBlock* true_block,
                    BasicBlock* false_block)
      : mode_(kFlags_branch),
        condition_(condition),
        true_block_(true_block),
        false_block_(false_block) {
    DCHECK_NOT_NULL(true_block);
    DCHECK_NOT_NULL(false_block);
  }

  // Creates a new flags continuation for an eager deoptimization exit.
  static FlagsContinuation ForDeoptimize(FlagsCondition condition,
                                         Node* frame_state) {
    return FlagsContinuation(kFlags_deoptimize, condition, frame_state);
  }

  // Creates a new flags continuation for a boolean value.
  static FlagsContinuation ForSet(FlagsCondition condition, Node* result) {
    return FlagsContinuation(kFlags_set, condition, result);
  }

  bool IsNone() const { return mode_ == kFlags_none; }
  bool IsBranch() const { return mode_ == kFlags_branch; }
  bool IsDeoptimize() const { return mode_ == kFlags_deoptimize; }
  bool IsSet() const { return mode_ == kFlags_set; }
  FlagsCondition condition() const {
    DCHECK(!IsNone());
    return condition_;
  }
  Node* frame_state() const {
    DCHECK(IsDeoptimize());
    return frame_state_or_result_;
  }
  Node* result() const {
    DCHECK(IsSet());
    return frame_state_or_result_;
  }
  BasicBlock* true_block() const {
    DCHECK(IsBranch());
    return true_block_;
  }
  BasicBlock* false_block() const {
    DCHECK(IsBranch());
    return false_block_;
  }

  void Negate() {
    DCHECK(!IsNone());
    condition_ = NegateFlagsCondition(condition_);
  }

  void Commute() {
    DCHECK(!IsNone());
    condition_ = CommuteFlagsCondition(condition_);
  }

  void OverwriteAndNegateIfEqual(FlagsCondition condition) {
    bool negate = condition_ == kEqual;
    condition_ = condition;
    if (negate) Negate();
  }

  // Encodes this flags continuation into the given opcode.
  InstructionCode Encode(InstructionCode opcode) {
    opcode |= FlagsModeField::encode(mode_);
    if (mode_ != kFlags_none) {
      opcode |= FlagsConditionField::encode(condition_);
    }
    return opcode;
  }

 private:
  FlagsContinuation(FlagsMode mode, FlagsCondition condition,
                    Node* frame_state_or_result)
      : mode_(mode),
        condition_(condition),
        frame_state_or_result_(frame_state_or_result) {
    DCHECK_NOT_NULL(frame_state_or_result);
  }

  FlagsMode const mode_;
  FlagsCondition condition_;
  Node* frame_state_or_result_;  // Only valid if mode_ == kFlags_deoptimize
                                 // or mode_ == kFlags_set.
  BasicBlock* true_block_;       // Only valid if mode_ == kFlags_branch.
  BasicBlock* false_block_;      // Only valid if mode_ == kFlags_branch.
};

}  // namespace compiler
}  // namespace internal
}  // namespace v8

#endif  // V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_