/*

 * Copyright (C) 2012 David Anderson

 *

 * This file is part of JITCraft.

 *

 * JITCraft is free software: you can redistribute it and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option)

 * any later version.

 * 

 * Foobar is distributed in the hope that it will be useful, but WITHOUT ANY

 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * JITCraft. If not, see http://www.gnu.org/licenses/.

 */

#include <new>

#include <stdlib.h>

#include "Stack.h"

#include "Zone.h"

#include "Heap-inl.h"

using namespace jc;

Stack::Stack()

  : buffer_(NULL),

    top_(NULL),

    end_(NULL)

{

}

Stack::~Stack()

{

    free(buffer_);

}

bool

Stack::initialize()

{

    buffer_ = (char *)malloc(STACK_SIZE);

    if (!buffer_)

        return false;

    top_ = NULL;

    end_ = buffer_ + STACK_SIZE;

    return true;

}

static inline size_t

SizeForCodeFrame(Code *code)

{

    return sizeof(Frame) + sizeof(LocalSlot) * (code->nlocals() + code->maxStackDepth());

}

Frame *

Stack::pushFrame(Frame *prev, Function *fun)

{

    Code *code = fun->code();

    size_t nbytes = SizeForCodeFrame(code);

    if (reinterpret_cast<char *>(top_->sp) + nbytes >= end_)

        return NULL;

    Frame *frame = reinterpret_cast<Frame *>(top_->sp);

    new (frame) Frame(prev, top_->pc, fun, code, ZONE()->heap().lifoPosition());

    memset(frame->locals(), 0, sizeof(LocalSlot) * code->nlocals());

    top_->pc = frame->code()->start();

    top_->sp = frame->stackBase();

    return frame;

}

Frame *

Stack::popFrame(Frame *frame)

{

    Frame *prev = frame->prev();

    Function *fun = frame->maybeFun();

    Code *code = frame->code();

    size_t nbytes = sizeof(LocalSlot) * code->nlocals() +

                    sizeof(Frame) +

                    sizeof(LocalSlot) * (fun ? fun->nargs() : 0);

    top_->pc = frame->prevpc();

    top_->sp = reinterpret_cast<LocalSlot *>(reinterpret_cast<char *>(top_->sp) - nbytes);

    ZONE()->heap().unwindLifo(frame->lifoPosition());

    return prev;

}