C++ BlockBegin::fpu_stack_state方法代码示例

void FpuStackAllocator::allocate() {
  int num_blocks = allocator()->block_count();
  for (int i = 0; i < num_blocks; i++) {
    // Set up to process block
    BlockBegin* block = allocator()->block_at(i);
    intArray* fpu_stack_state = block->fpu_stack_state();

#ifndef PRODUCT
    if (TraceFPUStack) {
      tty->cr();
      tty->print_cr("------- Begin of new Block %d -------", block->block_id());
    }
#endif

    assert(fpu_stack_state != NULL ||
           block->end()->as_Base() != NULL ||
           block->is_set(BlockBegin::exception_entry_flag),
           "FPU stack state must be present due to linear-scan order for FPU stack allocation");
    // note: exception handler entries always start with an empty fpu stack
    //       because stack merging would be too complicated

    if (fpu_stack_state != NULL) {
      sim()->read_state(fpu_stack_state);
    } else {
      sim()->clear();
    }

#ifndef PRODUCT
    if (TraceFPUStack) {
      tty->print("Reading FPU state for block %d:", block->block_id());
      sim()->print();
      tty->cr();
    }
#endif

    allocate_block(block);
    CHECK_BAILOUT();
  }
}

bool FpuStackAllocator::merge_fpu_stack_with_successors(BlockBegin* block) {
#ifndef PRODUCT
  if (TraceFPUStack) {
    tty->print_cr("Propagating FPU stack state for B%d at LIR_Op position %d to successors:",
                  block->block_id(), pos());
    sim()->print();
    tty->cr();
  }
#endif

  bool changed = false;
  int number_of_sux = block->number_of_sux();

  if (number_of_sux == 1 && block->sux_at(0)->number_of_preds() > 1) {
    // The successor has at least two incoming edges, so a stack merge will be necessary
    // If this block is the first predecessor, cleanup the current stack and propagate it
    // If this block is not the first predecessor, a stack merge will be necessary

    BlockBegin* sux = block->sux_at(0);
    intArray* state = sux->fpu_stack_state();
    LIR_List* instrs = new LIR_List(_compilation);

    if (state != NULL) {
      // Merge with a successors that already has a FPU stack state
      // the block must only have one successor because critical edges must been split
      FpuStackSim* cur_sim = sim();
      FpuStackSim* sux_sim = temp_sim();
      sux_sim->read_state(state);

      merge_fpu_stack(instrs, cur_sim, sux_sim);

    } else {
      // propagate current FPU stack state to successor without state
      // clean up stack first so that there are no dead values on the stack
      if (ComputeExactFPURegisterUsage) {
        FpuStackSim* cur_sim = sim();
        ResourceBitMap live_fpu_regs = block->sux_at(0)->fpu_register_usage();
        assert(live_fpu_regs.size() == FrameMap::nof_fpu_regs, "missing register usage");

        merge_cleanup_fpu_stack(instrs, cur_sim, live_fpu_regs);
      }

      intArray* state = sim()->write_state();
      if (TraceFPUStack) {
        tty->print_cr("Setting FPU stack state of B%d (merge path)", sux->block_id());
        sim()->print(); tty->cr();
      }
      sux->set_fpu_stack_state(state);
    }

    if (instrs->instructions_list()->length() > 0) {
      lir()->insert_before(pos(), instrs);
      set_pos(instrs->instructions_list()->length() + pos());
      changed = true;
    }

  } else {
    // Propagate unmodified Stack to successors where a stack merge is not necessary
    intArray* state = sim()->write_state();
    for (int i = 0; i < number_of_sux; i++) {
      BlockBegin* sux = block->sux_at(i);

#ifdef ASSERT
      for (int j = 0; j < sux->number_of_preds(); j++) {
        assert(block == sux->pred_at(j), "all critical edges must be broken");
      }

      // check if new state is same
      if (sux->fpu_stack_state() != NULL) {
        intArray* sux_state = sux->fpu_stack_state();
        assert(state->length() == sux_state->length(), "overwriting existing stack state");
        for (int j = 0; j < state->length(); j++) {
          assert(state->at(j) == sux_state->at(j), "overwriting existing stack state");
        }
      }
#endif
#ifndef PRODUCT
      if (TraceFPUStack) {
        tty->print_cr("Setting FPU stack state of B%d", sux->block_id());
        sim()->print(); tty->cr();
      }
#endif

      sux->set_fpu_stack_state(state);
    }
  }

#ifndef PRODUCT
  // assertions that FPU stack state conforms to all successors' states
  intArray* cur_state = sim()->write_state();
  for (int i = 0; i < number_of_sux; i++) {
    BlockBegin* sux = block->sux_at(i);
    intArray* sux_state = sux->fpu_stack_state();

    assert(sux_state != NULL, "no fpu state");
    assert(cur_state->length() == sux_state->length(), "incorrect length");
    for (int i = 0; i < cur_state->length(); i++) {
      assert(cur_state->at(i) == sux_state->at(i), "element not equal");
    }
  }
//.........这里部分代码省略.........