C++ LIR_Opr::is_last_use方法代码示例

void FpuStackAllocator::pop_if_last_use(LIR_Op* op, LIR_Opr opr) {
  assert(op->fpu_pop_count() == 0, "fpu_pop_count alredy set");
  assert(tos_offset(opr) == 0, "can only pop stack top");

  if (opr->is_last_use()) {
    op->set_fpu_pop_count(1);
    sim()->pop();
  }
}

void FpuStackAllocator::handle_op2(LIR_Op2* op2) {
  LIR_Opr left  = op2->in_opr1();
  if (!left->is_float_kind()) {
    return;
  }
  if (left->is_xmm_register()) {
    return;
  }

  LIR_Opr right = op2->in_opr2();
  LIR_Opr res   = op2->result_opr();
  LIR_Opr new_left  = left;  // new operands relative to the actual fpu stack top
  LIR_Opr new_right = right;
  LIR_Opr new_res   = res;

  assert(!left->is_xmm_register() && !right->is_xmm_register() && !res->is_xmm_register(), "not for xmm registers");

  switch (op2->code()) {
    case lir_cmp:
    case lir_cmp_fd2i:
    case lir_ucmp_fd2i:
    case lir_assert: {
      assert(left->is_fpu_register(), "invalid LIR");
      assert(right->is_fpu_register(), "invalid LIR");

      // the left-hand side must be on top of stack.
      // the right-hand side is never popped, even if is_last_use is set
      insert_exchange(left);
      new_left = to_fpu_stack_top(left);
      new_right = to_fpu_stack(right);
      pop_if_last_use(op2, left);
      break;
    }

    case lir_mul_strictfp:
    case lir_div_strictfp: {
      assert(op2->tmp1_opr()->is_fpu_register(), "strict operations need temporary fpu stack slot");
      insert_free_if_dead(op2->tmp1_opr());
      assert(sim()->stack_size() <= 7, "at least one stack slot must be free");
      // fall-through: continue with the normal handling of lir_mul and lir_div
    }
    case lir_add:
    case lir_sub:
    case lir_mul:
    case lir_div: {
      assert(left->is_fpu_register(), "must be");
      assert(res->is_fpu_register(), "must be");
      assert(left->is_equal(res), "must be");

      // either the left-hand or the right-hand side must be on top of stack
      // (if right is not a register, left must be on top)
      if (!right->is_fpu_register()) {
        insert_exchange(left);
        new_left = to_fpu_stack_top(left);
      } else {
        // no exchange necessary if right is alredy on top of stack
        if (tos_offset(right) == 0) {
          new_left = to_fpu_stack(left);
          new_right = to_fpu_stack_top(right);
        } else {
          insert_exchange(left);
          new_left = to_fpu_stack_top(left);
          new_right = to_fpu_stack(right);
        }

        if (right->is_last_use()) {
          op2->set_fpu_pop_count(1);

          if (tos_offset(right) == 0) {
            sim()->pop();
          } else {
            // if left is on top of stack, the result is placed in the stack
            // slot of right, so a renaming from right to res is necessary
            assert(tos_offset(left) == 0, "must be");
            sim()->pop();
            do_rename(right, res);
          }
        }
      }
      new_res = to_fpu_stack(res);

      break;
    }

    case lir_rem: {
      assert(left->is_fpu_register(), "must be");
      assert(right->is_fpu_register(), "must be");
      assert(res->is_fpu_register(), "must be");
      assert(left->is_equal(res), "must be");

      // Must bring both operands to top of stack with following operand ordering:
      // * fpu stack before rem: ... right left
      // * fpu stack after rem:  ... left
      if (tos_offset(right) != 1) {
        insert_exchange(right);
        insert_exchange(1);
      }
      insert_exchange(left);
      assert(tos_offset(right) == 1, "check");
      assert(tos_offset(left) == 0, "check");
//.........这里部分代码省略.........

void FpuStackAllocator::handle_op1(LIR_Op1* op1) {
  LIR_Opr in  = op1->in_opr();
  LIR_Opr res = op1->result_opr();

  LIR_Opr new_in  = in;  // new operands relative to the actual fpu stack top
  LIR_Opr new_res = res;

  // Note: this switch is processed for all LIR_Op1, regardless if they have FPU-arguments,
  //       so checks for is_float_kind() are necessary inside the cases
  switch (op1->code()) {

    case lir_return: {
      // FPU-Stack must only contain the (optional) fpu return value.
      // All remaining dead values are popped from the stack
      // If the input operand is a fpu-register, it is exchanged to the bottom of the stack

      clear_fpu_stack(in);
      if (in->is_fpu_register() && !in->is_xmm_register()) {
        new_in = to_fpu_stack_top(in);
      }

      break;
    }

    case lir_move: {
      if (in->is_fpu_register() && !in->is_xmm_register()) {
        if (res->is_xmm_register()) {
          // move from fpu register to xmm register (necessary for operations that
          // are not available in the SSE instruction set)
          insert_exchange(in);
          new_in = to_fpu_stack_top(in);
          pop_always(op1, in);

        } else if (res->is_fpu_register() && !res->is_xmm_register()) {
          // move from fpu-register to fpu-register:
          // * input and result register equal:
          //   nothing to do
          // * input register is last use:
          //   rename the input register to result register -> input register
          //   not present on fpu-stack afterwards
          // * input register not last use:
          //   duplicate input register to result register to preserve input
          //
          // Note: The LIR-Assembler does not produce any code for fpu register moves,
          //       so input and result stack index must be equal

          if (fpu_num(in) == fpu_num(res)) {
            // nothing to do
          } else if (in->is_last_use()) {
            insert_free_if_dead(res);//, in);
            do_rename(in, res);
          } else {
            insert_free_if_dead(res);
            insert_copy(in, res);
          }
          new_in = to_fpu_stack(res);
          new_res = new_in;

        } else {
          // move from fpu-register to memory
          // input operand must be on top of stack

          insert_exchange(in);

          // create debug information here because afterwards the register may have been popped
          compute_debug_information(op1);

          new_in = to_fpu_stack_top(in);
          pop_if_last_use(op1, in);
        }

      } else if (res->is_fpu_register() && !res->is_xmm_register()) {
        // move from memory/constant to fpu register
        // result is pushed on the stack

        insert_free_if_dead(res);

        // create debug information before register is pushed
        compute_debug_information(op1);

        do_push(res);
        new_res = to_fpu_stack_top(res);
      }
      break;
    }

    case lir_neg: {
      if (in->is_fpu_register() && !in->is_xmm_register()) {
        assert(res->is_fpu_register() && !res->is_xmm_register(), "must be");
        assert(in->is_last_use(), "old value gets destroyed");

        insert_free_if_dead(res, in);
        insert_exchange(in);
        new_in = to_fpu_stack_top(in);

        do_rename(in, res);
        new_res = to_fpu_stack_top(res);
      }
      break;
    }
//.........这里部分代码省略.........