class RubyVM::RJIT::Compiler

# File lib/ruby_vm/rjit/compiler.rb, line 38
def self.decode_insn(encoded)
  INSNS.fetch(C.rb_vm_insn_decode(encoded))
end

# File lib/ruby_vm/rjit/compiler.rb, line 42
def initialize
  mem_size = C.rjit_opts.exec_mem_size * 1024 * 1024
  mem_block = C.mmap(mem_size)
  @cb = CodeBlock.new(mem_block: mem_block, mem_size: mem_size / 2)
  @ocb = CodeBlock.new(mem_block: mem_block + mem_size / 2, mem_size: mem_size / 2, outlined: true)
  @exit_compiler = ExitCompiler.new
  @insn_compiler = InsnCompiler.new(@cb, @ocb, @exit_compiler)
  Invariants.initialize(@cb, @ocb, self, @exit_compiler)
end

# File lib/ruby_vm/rjit/compiler.rb, line 75
def branch_stub_hit(branch_stub, cfp, target0_p)
  # Update cfp->pc for `jit.at_current_insn?`
  target = target0_p ? branch_stub.target0 : branch_stub.target1
  cfp.pc = target.pc

  # Reuse an existing block if it already exists
  block = find_block(branch_stub.iseq, target.pc, target.ctx)

  # If the branch stub's jump is the last code, allow overwriting part of
  # the old branch code with the new block code.
  fallthrough = block.nil? && @cb.write_addr == branch_stub.end_addr
  if fallthrough
    # If the branch stub's jump is the last code, allow overwriting part of
    # the old branch code with the new block code.
    @cb.set_write_addr(branch_stub.start_addr)
    branch_stub.shape = target0_p ? Next0 : Next1
    Assembler.new.tap do |branch_asm|
      branch_stub.compile.call(branch_asm)
      @cb.write(branch_asm)
    end
  end

  # Reuse or generate a block
  if block
    target.address = block.start_addr
  else
    jit = JITState.new(iseq: branch_stub.iseq, cfp:)
    target.address = Assembler.new.then do |asm|
      compile_block(asm, jit:, pc: target.pc, ctx: target.ctx.dup)
      @cb.write(asm)
    end
    block = jit.block
  end
  block.incoming << branch_stub # prepare for invalidate_block

  # Re-generate the branch code for non-fallthrough cases
  unless fallthrough
    @cb.with_write_addr(branch_stub.start_addr) do
      branch_asm = Assembler.new
      branch_stub.compile.call(branch_asm)
      @cb.write(branch_asm)
    end
  end

  return target.address
rescue Exception => e
  $stderr.puts e.full_message
  exit 1
end

# File lib/ruby_vm/rjit/compiler.rb, line 55
def compile(iseq, cfp)
  # TODO: Support has_opt
  return if iseq.body.param.flags.has_opt

  jit = JITState.new(iseq:, cfp:)
  asm = Assembler.new
  asm.comment("Block: #{iseq.body.location.label}@#{C.rb_iseq_path(iseq)}:#{iseq.body.location.first_lineno}")
  compile_prologue(asm)
  compile_block(asm, jit:)
  iseq.body.jit_func = @cb.write(asm)
rescue Exception => e
  $stderr.puts e.full_message
  exit 1
end

# File lib/ruby_vm/rjit/compiler.rb, line 139
def invalidate_block(block)
  iseq = block.iseq
  # Avoid touching GCed ISEQs. We assume it won't be re-entered.
  return unless C.imemo_type_p(iseq, C.imemo_iseq)

  # Remove this block from the version array
  remove_block(iseq, block)

  # Invalidate the block with entry exit
  unless block.invalidated
    @cb.with_write_addr(block.start_addr) do
      asm = Assembler.new
      asm.comment('invalidate_block')
      asm.jmp(block.entry_exit)
      @cb.write(asm)
    end
    block.invalidated = true
  end

  # Re-stub incoming branches
  block.incoming.each do |branch_stub|
    target = [branch_stub.target0, branch_stub.target1].compact.find do |target|
      target.pc == block.pc && target.ctx == block.ctx
    end
    next if target.nil?
    # TODO: Could target.address be a stub address? Is invalidation not needed in that case?

    # If the target being re-generated is currently a fallthrough block,
    # the fallthrough code must be rewritten with a jump to the stub.
    if target.address == branch_stub.end_addr
      branch_stub.shape = Default
    end

    target.address = Assembler.new.then do |ocb_asm|
      @exit_compiler.compile_branch_stub(block.ctx, ocb_asm, branch_stub, target == branch_stub.target0)
      @ocb.write(ocb_asm)
    end
    @cb.with_write_addr(branch_stub.start_addr) do
      branch_asm = Assembler.new
      branch_stub.compile.call(branch_asm)
      @cb.write(branch_asm)
    end
  end
end

# File lib/ruby_vm/rjit/compiler.rb, line 127
def invalidate_blocks(iseq, pc)
  list_blocks(iseq, pc).each do |block|
    invalidate_block(block)
  end

  # If they were the ISEQ's first blocks, re-compile RJIT entry as well
  if iseq.body.iseq_encoded.to_i == pc
    iseq.body.jit_func = 0
    iseq.body.total_calls = 0
  end
end

# File lib/ruby_vm/rjit/compiler.rb, line 305
def add_block(iseq, block)
  rjit_blocks(iseq)[block.pc] << block
end

# File lib/ruby_vm/rjit/compiler.rb, line 211
def compile_block(asm, jit:, pc: jit.iseq.body.iseq_encoded.to_i, ctx: Context.new)
  # Mark the block start address and prepare an exit code storage
  block = Block.new(iseq: jit.iseq, pc:, ctx: ctx.dup)
  jit.block = block
  asm.block(block)

  # Compile each insn
  iseq = jit.iseq
  index = (pc - iseq.body.iseq_encoded.to_i) / C.VALUE.size
  while index < iseq.body.iseq_size
    insn = self.class.decode_insn(iseq.body.iseq_encoded[index])
    jit.pc = (iseq.body.iseq_encoded + index).to_i

    # If previous instruction requested to record the boundary
    if jit.record_boundary_patch_point
      # Generate an exit to this instruction and record it
      exit_pos = Assembler.new.then do |ocb_asm|
        @exit_compiler.compile_side_exit(jit.pc, ctx, ocb_asm)
        @ocb.write(ocb_asm)
      end
      Invariants.record_global_inval_patch(asm, exit_pos)
      jit.record_boundary_patch_point = false
    end

    case status = @insn_compiler.compile(jit, ctx, asm, insn)
    when KeepCompiling
      # For now, reset the chain depth after each instruction as only the
      # first instruction in the block can concern itself with the depth.
      ctx.chain_depth = 0

      index += insn.len
    when EndBlock
      # TODO: pad nops if entry exit exists (not needed for x86_64?)
      break
    when CantCompile
      @exit_compiler.compile_side_exit(jit.pc, ctx, asm)

      # If this is the first instruction, this block never needs to be invalidated.
      if block.pc == iseq.body.iseq_encoded.to_i + index * C.VALUE.size
        block.invalidated = true
      end

      break
    else
      raise "compiling #{insn.name} returned unexpected status: #{status.inspect}"
    end
  end

  incr_counter(:compiled_block_count)
  add_block(iseq, block)
end

# File lib/ruby_vm/rjit/compiler.rb, line 190
def compile_prologue(asm)
  asm.comment('RJIT entry point')

  # Save callee-saved registers used by JITed code
  asm.push(CFP)
  asm.push(EC)
  asm.push(SP)

  # Move arguments EC and CFP to dedicated registers
  asm.mov(EC, :rdi)
  asm.mov(CFP, :rsi)

  # Load sp to a dedicated register
  asm.mov(SP, [CFP, C.rb_control_frame_t.offsetof(:sp)]) # rbx = cfp->sp

  # Setup cfp->jit_return
  asm.mov(:rax, leave_exit)
  asm.mov([CFP, C.rb_control_frame_t.offsetof(:jit_return)], :rax)
end

# File lib/ruby_vm/rjit/compiler.rb, line 283
def find_block(iseq, pc, ctx)
  src = ctx
  rjit_blocks(iseq)[pc].find do |block|
    dst = block.ctx

    # Can only lookup the first version in the chain
    if dst.chain_depth != 0
      next false
    end

    # Blocks with depth > 0 always produce new versions
    # Sidechains cannot overlap
    if src.chain_depth != 0
      next false
    end

    src.stack_size == dst.stack_size &&
      src.sp_offset == dst.sp_offset
  end
end

# File lib/ruby_vm/rjit/compiler.rb, line 270
def incr_counter(name)
  if C.rjit_opts.stats
    C.rb_rjit_counters[name][0] += 1
  end
end

# File lib/ruby_vm/rjit/compiler.rb, line 263
def leave_exit
  @leave_exit ||= Assembler.new.then do |asm|
    @exit_compiler.compile_leave_exit(asm)
    @ocb.write(asm)
  end
end

# File lib/ruby_vm/rjit/compiler.rb, line 276
def list_blocks(iseq, pc)
  rjit_blocks(iseq)[pc]
end

# File lib/ruby_vm/rjit/compiler.rb, line 310
def remove_block(iseq, block)
  rjit_blocks(iseq)[block.pc].delete(block)
end

# File lib/ruby_vm/rjit/compiler.rb, line 314
def rjit_blocks(iseq)
  # Guard against ISEQ GC at random moments

  unless C.imemo_type_p(iseq, C.imemo_iseq)
    return Hash.new { |h, k| h[k] = [] }
  end

  unless iseq.body.rjit_blocks
    iseq.body.rjit_blocks = Hash.new { |blocks, pc| blocks[pc] = [] }
    # For some reason, rb_rjit_iseq_mark didn't protect this Hash
    # from being freed. So we rely on GC_REFS to keep the Hash.
    GC_REFS << iseq.body.rjit_blocks
  end
  iseq.body.rjit_blocks
end