/* vim: set ts=4 sw=4 tw=99 et:

 *

 * 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 ke;

Stack::Stack()

  : buffer_(NULL),

    end_(NULL),

    top_(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(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(top_->fp, top_->pc, fun, code, ZONE()->heap().lifoPosition());

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

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

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

    top_->fp = frame;

    return frame;

}

Frame *

Stack::popFrame()

{

    ZONE()->heap().unwindLifo(top_->fp->lifoPosition());

    Frame *prev = top_->fp->prev();

    Function *fun = top_->fp->maybeFun();

    Code *code = top_->fp->code();

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

                    sizeof(Frame) +

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

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

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

    top_->fp = prev;

    return prev;

}

void

Frame::accept(VirtualObjectVisitor *visitor)

{

    visitor->visit(reinterpret_cast<Object **>(&fun_));

    visitor->visit(reinterpret_cast<Object **>(&code_));

}

static void

TraceFrame(VirtualObjectVisitor *visitor, Frame *fp, LocalSlot *sp, bytecode *pc)

{

    Code *code = fp->code();

    LocalSlot *slots = fp->locals();

    // Trace local variables.

    for (unsigned i = 0; i < code->nlocals(); i++) {

        Type *type = code->localType(i);

        if (type->isTraceable())

            visitor->visit(&slots[i].obj);

    }

    // Trace arguments, if a function call.

    if (Function *fun = fp->maybeFun()) {

        for (unsigned i = 0; i < fun->nargs(); i++) {

            Type *type = fun->argType(i);

            if (type->isTraceable())

                visitor->visit(&fp->arg(i).obj);

        }

    }

    // Finally, trace stack slots. Not every gc-point in the bytecode will

    // have a safepoint; since they are actually uncommon, we don't emit

    // them unless at least one stack slot would be marked.

    if (uint8 *safepoint = code->safepointAt(code->pcToOffset(pc))) {

        LocalSlot *base = fp->stackBase();

        unsigned stackDepth = unsigned(sp - fp->stackBase());

        assert(stackDepth <= code->maxStackDepth());

        for (unsigned i = 0; i < stackDepth; i++) {

            if (safepoint[i / 8] & (1 << (i % 8)))

                visitor->visit(&base[i].obj);

        }

    }

}

void

Stack::accept(VirtualObjectVisitor *visitor)

{

    if (!top_)

        return;

    LocalSlot *sp = top_->sp;

    bytecode *pc = top_->pc;

    for (Frame *frame = top_->fp; frame; frame = frame->prev()) {

        TraceFrame(visitor, frame, sp, pc);

        sp = reinterpret_cast<LocalSlot *>(frame);

        pc = frame->prevpc();

    }

}

bool

Stack::isInCallStack(Handle<Module> module)

{

    if (!top_)

        return false;

    for (Frame *frame = top_->fp; frame; frame = frame->prev()) {

        if (frame->code()->module() == module)

            return true;

    }

    return false;

}