path: root/chromium/v8/src/codegen/riscv/assembler-riscv.h

// Copyright (c) 1994-2006 Sun Microsystems Inc.
// All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// - Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// - Redistribution in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// - Neither the name of Sun Microsystems or the names of contributors may
// be used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// The original source code covered by the above license above has been
// modified significantly by Google Inc.
// Copyright 2021 the V8 project authors. All rights reserved.

#ifndef V8_CODEGEN_RISCV_ASSEMBLER_RISCV_H_
#define V8_CODEGEN_RISCV_ASSEMBLER_RISCV_H_

#include <stdio.h>

#include <memory>
#include <set>

#include "src/codegen/assembler.h"
#include "src/codegen/constant-pool.h"
#include "src/codegen/constants-arch.h"
#include "src/codegen/external-reference.h"
#include "src/codegen/flush-instruction-cache.h"
#include "src/codegen/label.h"
#include "src/codegen/riscv/base-assembler-riscv.h"
#include "src/codegen/riscv/base-riscv-i.h"
#include "src/codegen/riscv/extension-riscv-a.h"
#include "src/codegen/riscv/extension-riscv-c.h"
#include "src/codegen/riscv/extension-riscv-d.h"
#include "src/codegen/riscv/extension-riscv-f.h"
#include "src/codegen/riscv/extension-riscv-m.h"
#include "src/codegen/riscv/extension-riscv-v.h"
#include "src/codegen/riscv/extension-riscv-zicsr.h"
#include "src/codegen/riscv/extension-riscv-zifencei.h"
#include "src/codegen/riscv/register-riscv.h"
#include "src/objects/contexts.h"
#include "src/objects/smi.h"

namespace v8 {
namespace internal {

#define DEBUG_PRINTF(...)     \
  if (v8_flags.riscv_debug) { \
    printf(__VA_ARGS__);      \
  }

class SafepointTableBuilder;

// -----------------------------------------------------------------------------
// Machine instruction Operands.
constexpr int kSmiShift = kSmiTagSize + kSmiShiftSize;
constexpr uintptr_t kSmiShiftMask = (1UL << kSmiShift) - 1;
// Class Operand represents a shifter operand in data processing instructions.
class Operand {
 public:
  // Immediate.
  V8_INLINE explicit Operand(intptr_t immediate,
                             RelocInfo::Mode rmode = RelocInfo::NO_INFO)
      : rm_(no_reg), rmode_(rmode) {
    value_.immediate = immediate;
  }
  V8_INLINE explicit Operand(const ExternalReference& f)
      : rm_(no_reg), rmode_(RelocInfo::EXTERNAL_REFERENCE) {
    value_.immediate = static_cast<intptr_t>(f.address());
  }

  explicit Operand(Handle<HeapObject> handle);
  V8_INLINE explicit Operand(Smi value)
      : rm_(no_reg), rmode_(RelocInfo::NO_INFO) {
    value_.immediate = static_cast<intptr_t>(value.ptr());
  }

  static Operand EmbeddedNumber(double number);  // Smi or HeapNumber.

  // Register.
  V8_INLINE explicit Operand(Register rm) : rm_(rm) {}

  // Return true if this is a register operand.
  V8_INLINE bool is_reg() const { return rm_.is_valid(); }
  inline intptr_t immediate() const {
    DCHECK(!is_reg());
    DCHECK(!IsHeapNumberRequest());
    return value_.immediate;
  }

  bool IsImmediate() const { return !rm_.is_valid(); }

  HeapNumberRequest heap_number_request() const {
    DCHECK(IsHeapNumberRequest());
    return value_.heap_number_request;
  }

  bool IsHeapNumberRequest() const {
    DCHECK_IMPLIES(is_heap_number_request_, IsImmediate());
    DCHECK_IMPLIES(is_heap_number_request_,
                   rmode_ == RelocInfo::FULL_EMBEDDED_OBJECT ||
                       rmode_ == RelocInfo::CODE_TARGET);
    return is_heap_number_request_;
  }

  Register rm() const { return rm_; }

  RelocInfo::Mode rmode() const { return rmode_; }

 private:
  Register rm_;
  union Value {
    Value() {}
    HeapNumberRequest heap_number_request;  // if is_heap_number_request_
    intptr_t immediate;                     // otherwise
  } value_;                                 // valid if rm_ == no_reg
  bool is_heap_number_request_ = false;
  RelocInfo::Mode rmode_;

  friend class Assembler;
  friend class MacroAssembler;
};

// On RISC-V we have only one addressing mode with base_reg + offset.
// Class MemOperand represents a memory operand in load and store instructions.
class V8_EXPORT_PRIVATE MemOperand : public Operand {
 public:
  // Immediate value attached to offset.
  enum OffsetAddend { offset_minus_one = -1, offset_zero = 0 };

  explicit MemOperand(Register rn, int32_t offset = 0);
  explicit MemOperand(Register rn, int32_t unit, int32_t multiplier,
                      OffsetAddend offset_addend = offset_zero);
  int32_t offset() const { return offset_; }

  void set_offset(int32_t offset) { offset_ = offset; }

  bool OffsetIsInt12Encodable() const { return is_int12(offset_); }

 private:
  int32_t offset_;

  friend class Assembler;
};

class V8_EXPORT_PRIVATE Assembler : public AssemblerBase,
                                    public AssemblerRISCVI,
                                    public AssemblerRISCVA,
                                    public AssemblerRISCVF,
                                    public AssemblerRISCVD,
                                    public AssemblerRISCVM,
                                    public AssemblerRISCVC,
                                    public AssemblerRISCVZifencei,
                                    public AssemblerRISCVZicsr,
                                    public AssemblerRISCVV {
 public:
  // Create an assembler. Instructions and relocation information are emitted
  // into a buffer, with the instructions starting from the beginning and the
  // relocation information starting from the end of the buffer. See CodeDesc
  // for a detailed comment on the layout (globals.h).
  //
  // If the provided buffer is nullptr, the assembler allocates and grows its
  // own buffer. Otherwise it takes ownership of the provided buffer.
  explicit Assembler(const AssemblerOptions&,
                     std::unique_ptr<AssemblerBuffer> = {});

  virtual ~Assembler();
  void AbortedCodeGeneration();
  // GetCode emits any pending (non-emitted) code and fills the descriptor desc.
  static constexpr int kNoHandlerTable = 0;
  static constexpr SafepointTableBuilder* kNoSafepointTable = nullptr;
  void GetCode(Isolate* isolate, CodeDesc* desc,
               SafepointTableBuilder* safepoint_table_builder,
               int handler_table_offset);

  // Convenience wrapper for code without safepoint or handler tables.
  void GetCode(Isolate* isolate, CodeDesc* desc) {
    GetCode(isolate, desc, kNoSafepointTable, kNoHandlerTable);
  }

  // Unused on this architecture.
  void MaybeEmitOutOfLineConstantPool() {}

  // Label operations & relative jumps (PPUM Appendix D).
  //
  // Takes a branch opcode (cc) and a label (L) and generates
  // either a backward branch or a forward branch and links it
  // to the label fixup chain. Usage:
  //
  // Label L;    // unbound label
  // j(cc, &L);  // forward branch to unbound label
  // bind(&L);   // bind label to the current pc
  // j(cc, &L);  // backward branch to bound label
  // bind(&L);   // illegal: a label may be bound only once
  //
  // Note: The same Label can be used for forward and backward branches
  // but it may be bound only once.
  void bind(Label* L);  // Binds an unbound label L to current code position.

  // Determines if Label is bound and near enough so that branch instruction
  // can be used to reach it, instead of jump instruction.
  bool is_near(Label* L);
  bool is_near(Label* L, OffsetSize bits);
  bool is_near_branch(Label* L);

  // Get offset from instr.
  int BranchOffset(Instr instr);
  static int BrachlongOffset(Instr auipc, Instr jalr);
  static int PatchBranchlongOffset(Address pc, Instr auipc, Instr instr_I,
                                   int32_t offset);

  // Returns the branch offset to the given label from the current code
  // position. Links the label to the current position if it is still unbound.
  // Manages the jump elimination optimization if the second parameter is true.
  virtual int32_t branch_offset_helper(Label* L, OffsetSize bits);
  uintptr_t jump_address(Label* L);
  int32_t branch_long_offset(Label* L);

  // Puts a labels target address at the given position.
  // The high 8 bits are set to zero.
  void label_at_put(Label* L, int at_offset);

  // Read/Modify the code target address in the branch/call instruction at pc.
  // The isolate argument is unused (and may be nullptr) when skipping flushing.
  static Address target_address_at(Address pc);
  V8_INLINE static void set_target_address_at(
      Address pc, Address target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED) {
    set_target_value_at(pc, target, icache_flush_mode);
  }

  static Address target_address_at(Address pc, Address constant_pool);

  static void set_target_address_at(
      Address pc, Address constant_pool, Address target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED);

  // Read/Modify the code target address in the branch/call instruction at pc.
  inline static Tagged_t target_compressed_address_at(Address pc,
                                                      Address constant_pool);
  inline static void set_target_compressed_address_at(
      Address pc, Address constant_pool, Tagged_t target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED);

  inline Handle<Object> code_target_object_handle_at(Address pc,
                                                     Address constant_pool);
  inline Handle<HeapObject> compressed_embedded_object_handle_at(
      Address pc, Address constant_pool);

  static bool IsConstantPoolAt(Instruction* instr);
  static int ConstantPoolSizeAt(Instruction* instr);
  // See Assembler::CheckConstPool for more info.
  void EmitPoolGuard();

  static void set_target_value_at(
      Address pc, uintptr_t target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED);

  static void JumpLabelToJumpRegister(Address pc);

  // This sets the branch destination (which gets loaded at the call address).
  // This is for calls and branches within generated code.  The serializer
  // has already deserialized the lui/ori instructions etc.
  inline static void deserialization_set_special_target_at(
      Address instruction_payload, Code code, Address target);

  // Get the size of the special target encoded at 'instruction_payload'.
  inline static int deserialization_special_target_size(
      Address instruction_payload);

  // This sets the internal reference at the pc.
  inline static void deserialization_set_target_internal_reference_at(
      Address pc, Address target,
      RelocInfo::Mode mode = RelocInfo::INTERNAL_REFERENCE);

  // Here we are patching the address in the LUI/ADDI instruction pair.
  // These values are used in the serialization process and must be zero for
  // RISC-V platform, as Code, Embedded Object or External-reference pointers
  // are split across two consecutive instructions and don't exist separately
  // in the code, so the serializer should not step forwards in memory after
  // a target is resolved and written.
  static constexpr int kSpecialTargetSize = 0;

  // Number of consecutive instructions used to store 32bit/64bit constant.
  // This constant was used in RelocInfo::target_address_address() function
  // to tell serializer address of the instruction that follows
  // LUI/ADDI instruction pair.
  static constexpr int kInstructionsFor32BitConstant = 2;
  static constexpr int kInstructionsFor64BitConstant = 8;

  // Difference between address of current opcode and value read from pc
  // register.
  static constexpr int kPcLoadDelta = 4;

  // Bits available for offset field in branches
  static constexpr int kBranchOffsetBits = 13;

  // Bits available for offset field in jump
  static constexpr int kJumpOffsetBits = 21;

  // Bits available for offset field in compresed jump
  static constexpr int kCJalOffsetBits = 12;

  // Bits available for offset field in compressed branch
  static constexpr int kCBranchOffsetBits = 9;

  // Max offset for b instructions with 12-bit offset field (multiple of 2)
  static constexpr int kMaxBranchOffset = (1 << (13 - 1)) - 1;

  // Max offset for jal instruction with 20-bit offset field (multiple of 2)
  static constexpr int kMaxJumpOffset = (1 << (21 - 1)) - 1;

  static constexpr int kTrampolineSlotsSize = 2 * kInstrSize;

  RegList* GetScratchRegisterList() { return &scratch_register_list_; }

  // ---------------------------------------------------------------------------
  // Code generation.

  // Insert the smallest number of nop instructions
  // possible to align the pc offset to a multiple
  // of m. m must be a power of 2 (>= 4).
  void Align(int m);
  // Insert the smallest number of zero bytes possible to align the pc offset
  // to a mulitple of m. m must be a power of 2 (>= 2).
  void DataAlign(int m);
  // Aligns code to something that's optimal for a jump target for the platform.
  void CodeTargetAlign();
  void LoopHeaderAlign() { CodeTargetAlign(); }

  // Different nop operations are used by the code generator to detect certain
  // states of the generated code.
  enum NopMarkerTypes {
    NON_MARKING_NOP = 0,
    DEBUG_BREAK_NOP,
    // IC markers.
    PROPERTY_ACCESS_INLINED,
    PROPERTY_ACCESS_INLINED_CONTEXT,
    PROPERTY_ACCESS_INLINED_CONTEXT_DONT_DELETE,
    // Helper values.
    LAST_CODE_MARKER,
    FIRST_IC_MARKER = PROPERTY_ACCESS_INLINED,
  };

  void NOP();
  void EBREAK();

  // Assembler Pseudo Instructions (Tables 25.2, 25.3, RISC-V Unprivileged ISA)
  void nop();
  void RV_li(Register rd, intptr_t imm);
  // Returns the number of instructions required to load the immediate
  static int li_estimate(intptr_t imm, bool is_get_temp_reg = false);
  // Loads an immediate, always using 8 instructions, regardless of the value,
  // so that it can be modified later.
  void li_constant(Register rd, intptr_t imm);
  void li_ptr(Register rd, intptr_t imm);

  void break_(uint32_t code, bool break_as_stop = false);
  void stop(uint32_t code = kMaxStopCode);

  // Check the code size generated from label to here.
  int SizeOfCodeGeneratedSince(Label* label) {
    return pc_offset() - label->pos();
  }

  // Check the number of instructions generated from label to here.
  int InstructionsGeneratedSince(Label* label) {
    return SizeOfCodeGeneratedSince(label) / kInstrSize;
  }

  using BlockConstPoolScope = ConstantPool::BlockScope;
  // Class for scoping postponing the trampoline pool generation.
  class BlockTrampolinePoolScope {
   public:
    explicit BlockTrampolinePoolScope(Assembler* assem, int margin = 0)
        : assem_(assem) {
      assem_->StartBlockTrampolinePool();
    }

    explicit BlockTrampolinePoolScope(Assembler* assem, PoolEmissionCheck check)
        : assem_(assem) {
      assem_->StartBlockTrampolinePool();
    }
    ~BlockTrampolinePoolScope() { assem_->EndBlockTrampolinePool(); }

   private:
    Assembler* assem_;
    DISALLOW_IMPLICIT_CONSTRUCTORS(BlockTrampolinePoolScope);
  };

  // Class for postponing the assembly buffer growth. Typically used for
  // sequences of instructions that must be emitted as a unit, before
  // buffer growth (and relocation) can occur.
  // This blocking scope is not nestable.
  class BlockGrowBufferScope {
   public:
    explicit BlockGrowBufferScope(Assembler* assem) : assem_(assem) {
      assem_->StartBlockGrowBuffer();
    }
    ~BlockGrowBufferScope() { assem_->EndBlockGrowBuffer(); }

   private:
    Assembler* assem_;

    DISALLOW_IMPLICIT_CONSTRUCTORS(BlockGrowBufferScope);
  };

  // Record a deoptimization reason that can be used by a log or cpu profiler.
  // Use --trace-deopt to enable.
  void RecordDeoptReason(DeoptimizeReason reason, uint32_t node_id,
                         SourcePosition position, int id);

  static int RelocateInternalReference(RelocInfo::Mode rmode, Address pc,
                                       intptr_t pc_delta);
  static void RelocateRelativeReference(RelocInfo::Mode rmode, Address pc,
                                        intptr_t pc_delta);

  // Writes a single byte or word of data in the code stream.  Used for
  // inline tables, e.g., jump-tables.
  void db(uint8_t data);
  void dd(uint32_t data, RelocInfo::Mode rmode = RelocInfo::NO_INFO);
  void dq(uint64_t data, RelocInfo::Mode rmode = RelocInfo::NO_INFO);
  void dp(uintptr_t data, RelocInfo::Mode rmode = RelocInfo::NO_INFO) {
    dq(data, rmode);
  }
  void dd(Label* label);

  Instruction* pc() const { return reinterpret_cast<Instruction*>(pc_); }

  // Postpone the generation of the trampoline pool for the specified number of
  // instructions.
  void BlockTrampolinePoolFor(int instructions);

  // Check if there is less than kGap bytes available in the buffer.
  // If this is the case, we need to grow the buffer before emitting
  // an instruction or relocation information.
  inline bool overflow() const { return pc_ >= reloc_info_writer.pos() - kGap; }

  // Get the number of bytes available in the buffer.
  inline intptr_t available_space() const {
    return reloc_info_writer.pos() - pc_;
  }

  // Read/patch instructions.
  static Instr instr_at(Address pc) { return *reinterpret_cast<Instr*>(pc); }
  static void instr_at_put(Address pc, Instr instr) {
    *reinterpret_cast<Instr*>(pc) = instr;
  }
  Instr instr_at(int pos) {
    return *reinterpret_cast<Instr*>(buffer_start_ + pos);
  }
  void instr_at_put(int pos, Instr instr) {
    *reinterpret_cast<Instr*>(buffer_start_ + pos) = instr;
  }

  void instr_at_put(int pos, ShortInstr instr) {
    *reinterpret_cast<ShortInstr*>(buffer_start_ + pos) = instr;
  }

  Address toAddress(int pos) {
    return reinterpret_cast<Address>(buffer_start_ + pos);
  }

  void CheckTrampolinePool();

  // Get the code target object for a pc-relative call or jump.
  V8_INLINE Handle<Code> relative_code_target_object_handle_at(
      Address pc_) const;

  inline int UnboundLabelsCount() { return unbound_labels_count_; }

  using BlockPoolsScope = BlockTrampolinePoolScope;

  void RecordConstPool(int size);

  void ForceConstantPoolEmissionWithoutJump() {
    constpool_.Check(Emission::kForced, Jump::kOmitted);
  }
  void ForceConstantPoolEmissionWithJump() {
    constpool_.Check(Emission::kForced, Jump::kRequired);
  }
  // Check if the const pool needs to be emitted while pretending that {margin}
  // more bytes of instructions have already been emitted.
  void EmitConstPoolWithJumpIfNeeded(size_t margin = 0) {
    constpool_.Check(Emission::kIfNeeded, Jump::kRequired, margin);
  }

  void EmitConstPoolWithoutJumpIfNeeded(size_t margin = 0) {
    constpool_.Check(Emission::kIfNeeded, Jump::kOmitted, margin);
  }

  void RecordEntry(uint32_t data, RelocInfo::Mode rmode) {
    constpool_.RecordEntry(data, rmode);
  }

  void RecordEntry(uint64_t data, RelocInfo::Mode rmode) {
    constpool_.RecordEntry(data, rmode);
  }

  void CheckTrampolinePoolQuick(int extra_instructions = 0) {
    DEBUG_PRINTF("\tpc_offset:%d %d\n", pc_offset(),
                 next_buffer_check_ - extra_instructions * kInstrSize);
    if (pc_offset() >= next_buffer_check_ - extra_instructions * kInstrSize) {
      CheckTrampolinePool();
    }
  }

  friend class VectorUnit;
  class VectorUnit {
   public:
    inline int32_t sew() const { return 2 ^ (sew_ + 3); }

    inline int32_t vlmax() const {
      if ((lmul_ & 0b100) != 0) {
        return (kRvvVLEN / sew()) >> (lmul_ & 0b11);
      } else {
        return ((kRvvVLEN << lmul_) / sew());
      }
    }

    explicit VectorUnit(Assembler* assm) : assm_(assm) {}

    void set(Register rd, VSew sew, Vlmul lmul) {
      if (sew != sew_ || lmul != lmul_ || vl != vlmax()) {
        sew_ = sew;
        lmul_ = lmul;
        vl = vlmax();
        assm_->vsetvlmax(rd, sew_, lmul_);
      }
    }

    void set(Register rd, int8_t sew, int8_t lmul) {
      DCHECK_GE(sew, E8);
      DCHECK_LE(sew, E64);
      DCHECK_GE(lmul, m1);
      DCHECK_LE(lmul, mf2);
      set(rd, VSew(sew), Vlmul(lmul));
    }

    void set(FPURoundingMode mode) {
      if (mode_ != mode) {
        assm_->addi(kScratchReg, zero_reg, mode << kFcsrFrmShift);
        assm_->fscsr(kScratchReg);
        mode_ = mode;
      }
    }
    void set(Register rd, Register rs1, VSew sew, Vlmul lmul) {
      if (sew != sew_ || lmul != lmul_) {
        sew_ = sew;
        lmul_ = lmul;
        vl = 0;
        assm_->vsetvli(rd, rs1, sew_, lmul_);
      }
    }

    void set(VSew sew, Vlmul lmul) {
      if (sew != sew_ || lmul != lmul_) {
        sew_ = sew;
        lmul_ = lmul;
        assm_->vsetvl(sew_, lmul_);
      }
    }

    void clear() {
      sew_ = kVsInvalid;
      lmul_ = kVlInvalid;
    }

   private:
    VSew sew_ = kVsInvalid;
    Vlmul lmul_ = kVlInvalid;
    int32_t vl = 0;
    Assembler* assm_;
    FPURoundingMode mode_ = RNE;
  };

  VectorUnit VU;

 protected:
  // Readable constants for base and offset adjustment helper, these indicate if
  // aside from offset, another value like offset + 4 should fit into int16.
  enum class OffsetAccessType : bool {
    SINGLE_ACCESS = false,
    TWO_ACCESSES = true
  };

  // Determine whether need to adjust base and offset of memroy load/store
  bool NeedAdjustBaseAndOffset(
      const MemOperand& src, OffsetAccessType = OffsetAccessType::SINGLE_ACCESS,
      int second_Access_add_to_offset = 4);

  // Helper function for memory load/store using base register and offset.
  void AdjustBaseAndOffset(
      MemOperand* src, Register scratch,
      OffsetAccessType access_type = OffsetAccessType::SINGLE_ACCESS,
      int second_access_add_to_offset = 4);

  inline static void set_target_internal_reference_encoded_at(Address pc,
                                                              Address target);

  intptr_t buffer_space() const { return reloc_info_writer.pos() - pc_; }

  // Decode branch instruction at pos and return branch target pos.
  int target_at(int pos, bool is_internal);

  // Patch branch instruction at pos to branch to given branch target pos.
  void target_at_put(int pos, int target_pos, bool is_internal,
                     bool trampoline = false);

  // Say if we need to relocate with this mode.
  bool MustUseReg(RelocInfo::Mode rmode);

  // Record reloc info for current pc_.
  void RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data = 0);

  // Block the emission of the trampoline pool before pc_offset.
  void BlockTrampolinePoolBefore(int pc_offset) {
    if (no_trampoline_pool_before_ < pc_offset)
      no_trampoline_pool_before_ = pc_offset;
  }

  void StartBlockTrampolinePool() {
    DEBUG_PRINTF("\tStartBlockTrampolinePool\n");
    trampoline_pool_blocked_nesting_++;
  }

  void EndBlockTrampolinePool() {
    trampoline_pool_blocked_nesting_--;
    DEBUG_PRINTF("\ttrampoline_pool_blocked_nesting:%d\n",
                 trampoline_pool_blocked_nesting_);
    if (trampoline_pool_blocked_nesting_ == 0) {
      CheckTrampolinePoolQuick(1);
    }
  }

  bool is_trampoline_pool_blocked() const {
    return trampoline_pool_blocked_nesting_ > 0;
  }

  bool has_exception() const { return internal_trampoline_exception_; }

  bool is_trampoline_emitted() const { return trampoline_emitted_; }

  // Temporarily block automatic assembly buffer growth.
  void StartBlockGrowBuffer() {
    DCHECK(!block_buffer_growth_);
    block_buffer_growth_ = true;
  }

  void EndBlockGrowBuffer() {
    DCHECK(block_buffer_growth_);
    block_buffer_growth_ = false;
  }

  bool is_buffer_growth_blocked() const { return block_buffer_growth_; }

 private:
  // Avoid overflows for displacements etc.
  static const int kMaximalBufferSize = 512 * MB;

  // Buffer size and constant pool distance are checked together at regular
  // intervals of kBufferCheckInterval emitted bytes.
  static constexpr int kBufferCheckInterval = 1 * KB / 2;

  // Code generation.
  // The relocation writer's position is at least kGap bytes below the end of
  // the generated instructions. This is so that multi-instruction sequences do
  // not have to check for overflow. The same is true for writes of large
  // relocation info entries.
  static constexpr int kGap = 64;
  static_assert(AssemblerBase::kMinimalBufferSize >= 2 * kGap);

  // Repeated checking whether the trampoline pool should be emitted is rather
  // expensive. By default we only check again once a number of instructions
  // has been generated.
  static constexpr int kCheckConstIntervalInst = 32;
  static constexpr int kCheckConstInterval =
      kCheckConstIntervalInst * kInstrSize;

  int next_buffer_check_;  // pc offset of next buffer check.

  // Emission of the trampoline pool may be blocked in some code sequences.
  int trampoline_pool_blocked_nesting_;  // Block emission if this is not zero.
  int no_trampoline_pool_before_;  // Block emission before this pc offset.

  // Keep track of the last emitted pool to guarantee a maximal distance.
  int last_trampoline_pool_end_;  // pc offset of the end of the last pool.

  // Automatic growth of the assembly buffer may be blocked for some sequences.
  bool block_buffer_growth_;  // Block growth when true.

  // Relocation information generation.
  // Each relocation is encoded as a variable size value.
  static constexpr int kMaxRelocSize = RelocInfoWriter::kMaxSize;
  RelocInfoWriter reloc_info_writer;

  // The bound position, before this we cannot do instruction elimination.
  int last_bound_pos_;

  // Code emission.
  inline void CheckBuffer();
  void GrowBuffer();
  void emit(Instr x);
  void emit(ShortInstr x);
  void emit(uint64_t x);
  template <typename T>
  inline void EmitHelper(T x);

  static void disassembleInstr(Instr instr);

  // Labels.
  void print(const Label* L);
  void bind_to(Label* L, int pos);
  void next(Label* L, bool is_internal);

  // One trampoline consists of:
  // - space for trampoline slots,
  // - space for labels.
  //
  // Space for trampoline slots is equal to slot_count * 2 * kInstrSize.
  // Space for trampoline slots precedes space for labels. Each label is of one
  // instruction size, so total amount for labels is equal to
  // label_count *  kInstrSize.
  class Trampoline {
   public:
    Trampoline() {
      start_ = 0;
      next_slot_ = 0;
      free_slot_count_ = 0;
      end_ = 0;
    }
    Trampoline(int start, int slot_count) {
      start_ = start;
      next_slot_ = start;
      free_slot_count_ = slot_count;
      end_ = start + slot_count * kTrampolineSlotsSize;
    }
    int start() { return start_; }
    int end() { return end_; }
    int take_slot() {
      int trampoline_slot = kInvalidSlotPos;
      if (free_slot_count_ <= 0) {
        // We have run out of space on trampolines.
        // Make sure we fail in debug mode, so we become aware of each case
        // when this happens.
        DCHECK(0);
        // Internal exception will be caught.
      } else {
        trampoline_slot = next_slot_;
        free_slot_count_--;
        next_slot_ += kTrampolineSlotsSize;
      }
      return trampoline_slot;
    }

   private:
    int start_;
    int end_;
    int next_slot_;
    int free_slot_count_;
  };

  int32_t get_trampoline_entry(int32_t pos);
  int unbound_labels_count_;
  // After trampoline is emitted, long branches are used in generated code for
  // the forward branches whose target offsets could be beyond reach of branch
  // instruction. We use this information to trigger different mode of
  // branch instruction generation, where we use jump instructions rather
  // than regular branch instructions.
  bool trampoline_emitted_ = false;
  static constexpr int kInvalidSlotPos = -1;

  // Internal reference positions, required for unbounded internal reference
  // labels.
  std::set<intptr_t> internal_reference_positions_;
  bool is_internal_reference(Label* L) {
    return internal_reference_positions_.find(L->pos()) !=
           internal_reference_positions_.end();
  }

  Trampoline trampoline_;
  bool internal_trampoline_exception_;

  RegList scratch_register_list_;

 private:
  ConstantPool constpool_;

  void AllocateAndInstallRequestedHeapNumbers(Isolate* isolate);

  int WriteCodeComments();

  friend class RegExpMacroAssemblerRISCV;
  friend class RelocInfo;
  friend class BlockTrampolinePoolScope;
  friend class EnsureSpace;
  friend class ConstantPool;
};

class EnsureSpace {
 public:
  explicit inline EnsureSpace(Assembler* assembler);
};

class V8_EXPORT_PRIVATE UseScratchRegisterScope {
 public:
  explicit UseScratchRegisterScope(Assembler* assembler);
  ~UseScratchRegisterScope();

  Register Acquire();
  bool hasAvailable() const;
  void Include(const RegList& list) { *available_ |= list; }
  void Exclude(const RegList& list) {
    *available_ &= RegList::FromBits(~list.bits());
  }
  void Include(const Register& reg1, const Register& reg2 = no_reg) {
    RegList list({reg1, reg2});
    Include(list);
  }
  void Exclude(const Register& reg1, const Register& reg2 = no_reg) {
    RegList list({reg1, reg2});
    Exclude(list);
  }

 private:
  RegList* available_;
  RegList old_available_;
};

}  // namespace internal
}  // namespace v8

#endif  // V8_CODEGEN_RISCV_ASSEMBLER_RISCV_H_