/*
 * Copyright (c) 2009, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.lir;

import static com.oracle.graal.api.code.ValueUtil.*;

import java.util.*;

import com.oracle.graal.api.code.*;
import com.oracle.graal.api.meta.*;
import com.oracle.graal.asm.*;

/**
 * This class is used to build the stack frame layout for a compiled method. A {@link StackSlot} is
 * used to index slots of the frame relative to the stack pointer. The frame size is only fixed
 * after register allocation when all spill slots have been allocated. Both the outgoing argument
 * area and the spill are can grow until then. Therefore, outgoing arguments are indexed from the
 * stack pointer, while spill slots are indexed from the beginning of the frame (and the total frame
 * size has to be added to get the actual offset from the stack pointer).
 * <p>
 * This is the format of a stack frame:
 * 
 * <pre>
 *   Base       Contents
 * 
 *            :                                :  -----
 *   caller   | incoming overflow argument n   |    ^
 *   frame    :     ...                        :    | positive
 *            | incoming overflow argument 0   |    | offsets
 *   ---------+--------------------------------+---------------------
 *            | return address                 |    |            ^
 *   current  +--------------------------------+    |            |    -----
 *   frame    |                                |    |            |      ^
 *            : callee save area               :    |            |      |
 *            |                                |    |            |      |
 *            +--------------------------------+    |            |      |
 *            | spill slot 0                   |    | negative   |      |
 *            :     ...                        :    v offsets    |      |
 *            | spill slot n                   |  -----        total  frame
 *            +--------------------------------+               frame  size
 *            | alignment padding              |               size     |
 *            +--------------------------------+  -----          |      |
 *            | outgoing overflow argument n   |    ^            |      |
 *            :     ...                        :    | positive   |      |
 *            | outgoing overflow argument 0   |    | offsets    v      v
 *    %sp-->  +--------------------------------+---------------------------
 * 
 * </pre>
 * 
 * The spill slot area also includes stack allocated memory blocks (ALLOCA blocks). The size of such
 * a block may be greater than the size of a normal spill slot or the word size.
 * <p>
 * A runtime has two ways to reserve space in the stack frame for its own use:
 * <ul>
 * <li>A memory block somewhere in the frame of size
 * {@link CodeCacheProvider#getCustomStackAreaSize()}. The offset to this block is returned in
 * {@link CompilationResult#getCustomStackAreaOffset()}.
 * <li>At the beginning of the overflow argument area: The calling convention can specify that the
 * first overflow stack argument is not at offset 0, but at a specified offset o. Use
 * {@link CodeCacheProvider#getMinimumOutgoingSize()} to make sure that call-free methods also have
 * this space reserved. Then the VM can use memory the memory at offset 0 relative to the stack
 * pointer.
 * </ul>
 */
public final class FrameMap {

    public final CodeCacheProvider runtime;
    public final TargetDescription target;
    public final RegisterConfig registerConfig;

    /**
     * The initial frame size, not including the size of the return address. This is the constant
     * space reserved by the runtime for all compiled methods.
     */
    public final int initialFrameSize;

    /**
     * The final frame size, not including the size of the return address. The value is only set
     * after register allocation is complete, i.e., after all spill slots have been allocated.
     */
    private int frameSize;

    /**
     * Size of the area occupied by spill slots and other stack-allocated memory blocks.
     */
    private int spillSize;

    /**
     * Size of the area occupied by outgoing overflow arguments. This value is adjusted as calling
     * conventions for outgoing calls are retrieved.
     */
    private int outgoingSize;

    /**
     * The list of stack areas allocated in this frame that are present in every reference map.
     */
    private final List<StackSlot> objectStackBlocks;

    /**
     * The stack area reserved for use by the VM, or {@code null} if the VM does not request stack
     * space.
     */
    private final StackSlot customArea;

    /**
     * Records whether an offset to an incoming stack argument was ever returned by
     * {@link #offsetForStackSlot(StackSlot)}.
     */
    private boolean accessesCallerFrame;

    /**
     * Creates a new frame map for the specified method.
     */
    public FrameMap(CodeCacheProvider runtime, TargetDescription target, RegisterConfig registerConfig) {
        this.runtime = runtime;
        this.target = target;
        this.registerConfig = registerConfig;
        this.frameSize = -1;
        this.spillSize = returnAddressSize() + calleeSaveAreaSize();
        this.outgoingSize = runtime.getMinimumOutgoingSize();
        this.objectStackBlocks = new ArrayList<>();
        this.customArea = allocateStackBlock(runtime.getCustomStackAreaSize(), false);
        this.initialFrameSize = currentFrameSize();
    }

    private int returnAddressSize() {
        return target.arch.getReturnAddressSize();
    }

    private int calleeSaveAreaSize() {
        CalleeSaveLayout csl = registerConfig.getCalleeSaveLayout();
        return csl != null ? csl.size : 0;
    }

    /**
     * Determines if an offset to an incoming stack argument was ever returned by
     * {@link #offsetForStackSlot(StackSlot)}.
     */
    public boolean accessesCallerFrame() {
        return accessesCallerFrame;
    }

    /**
     * Gets the frame size of the compiled frame, not including the size of the return address.
     * 
     * @return The size of the frame (in bytes).
     */
    public int frameSize() {
        assert frameSize != -1 : "frame size not computed yet";
        return frameSize;
    }

    /**
     * Gets the total frame size of the compiled frame, including the size of the return address.
     * 
     * @return The total size of the frame (in bytes).
     */
    public int totalFrameSize() {
        return frameSize() + returnAddressSize();
    }

    /**
     * Gets the current size of this frame. This is the size that would be returned by
     * {@link #frameSize()} if {@link #finish()} were called now.
     */
    public int currentFrameSize() {
        return target.alignFrameSize(outgoingSize + spillSize - returnAddressSize());
    }

    /**
     * Computes the final size of this frame. After this method has been called, methods that change
     * the frame size cannot be called anymore, e.g., no more spill slots or outgoing arguments can
     * be requested.
     */
    public void finish() {
        assert this.frameSize == -1 : "must only be set once";
        frameSize = currentFrameSize();
    }

    /**
     * Computes the offset of a stack slot relative to the frame register. This is also the bit
     * index of stack slots in the reference map.
     * 
     * @param slot a stack slot
     * @return the offset of the stack slot
     */
    public int offsetForStackSlot(StackSlot slot) {
        assert (!slot.getRawAddFrameSize() && slot.getRawOffset() < outgoingSize) || (slot.getRawAddFrameSize() && slot.getRawOffset() < 0 && -slot.getRawOffset() <= spillSize) ||
                        (slot.getRawAddFrameSize() && slot.getRawOffset() >= 0);
        if (slot.isInCallerFrame()) {
            accessesCallerFrame = true;
        }
        return slot.getOffset(totalFrameSize());
    }

    /**
     * Gets the offset to the stack area where callee-saved registers are stored.
     * 
     * @return The offset to the callee save area (in bytes).
     */
    public int offsetToCalleeSaveArea() {
        return frameSize() - calleeSaveAreaSize();
    }

    /**
     * Gets the offset of the stack area stack block reserved for use by the VM, or -1 if the VM
     * does not request stack space.
     * 
     * @return The offset to the custom area (in bytes).
     */
    public int offsetToCustomArea() {
        return customArea == null ? -1 : offsetForStackSlot(customArea);
    }

    /**
     * Informs the frame map that the compiled code calls a particular method, which may need stack
     * space for outgoing arguments.
     * 
     * @param cc The calling convention for the called method.
     */
    public void callsMethod(CallingConvention cc) {
        reserveOutgoing(cc.getStackSize());
    }

    /**
     * Reserves space for stack-based outgoing arguments.
     * 
     * @param argsSize The amount of space (in bytes) to reserve for stack-based outgoing arguments.
     */
    public void reserveOutgoing(int argsSize) {
        assert frameSize == -1 : "frame size must not yet be fixed";
        outgoingSize = Math.max(outgoingSize, argsSize);
    }

    private StackSlot getSlot(Kind kind, int additionalOffset) {
        return StackSlot.get(kind, -spillSize + additionalOffset, true);
    }

    /**
     * Reserves a spill slot in the frame of the method being compiled. The returned slot is aligned
     * on its natural alignment, i.e., an 8-byte spill slot is aligned at an 8-byte boundary.
     * 
     * @param kind The kind of the spill slot to be reserved.
     * @return A spill slot denoting the reserved memory area.
     */
    public StackSlot allocateSpillSlot(Kind kind) {
        assert frameSize == -1 : "frame size must not yet be fixed";
        int size = target.sizeInBytes(kind);
        spillSize = NumUtil.roundUp(spillSize + size, size);
        return getSlot(kind, 0);
    }

    /**
     * Reserves a block of memory in the frame of the method being compiled. The returned block is
     * aligned on a word boundary. If the requested size is 0, the method returns {@code null}.
     * 
     * @param size The size to reserve (in bytes).
     * @param refs Specifies if the block is all references. If true, the block will be in all
     *            reference maps for this method. The caller is responsible to initialize the memory
     *            block before the first instruction that uses a reference map.
     * @return A stack slot describing the begin of the memory block.
     */
    public StackSlot allocateStackBlock(int size, boolean refs) {
        assert frameSize == -1 : "frame size must not yet be fixed";
        if (size == 0) {
            return null;
        }
        spillSize = NumUtil.roundUp(spillSize + size, target.wordSize);

        if (refs) {
            assert size % target.wordSize == 0;
            StackSlot result = getSlot(Kind.Object, 0);
            objectStackBlocks.add(result);
            for (int i = target.wordSize; i < size; i += target.wordSize) {
                objectStackBlocks.add(getSlot(Kind.Object, i));
            }
            return result;

        } else {
            return getSlot(target.wordKind, 0);
        }
    }

    private int frameRefMapIndex(StackSlot slot) {
        assert offsetForStackSlot(slot) % target.wordSize == 0;
        return offsetForStackSlot(slot) / target.wordSize;
    }

    /**
     * Initializes a reference map that covers all registers of the target architecture.
     */
    public BitSet initRegisterRefMap() {
        return new BitSet(target.arch.getRegisterReferenceMapBitCount());
    }

    /**
     * Initializes a reference map. Initially, the size is large enough to cover all the slots in
     * the frame. If the method has incoming reference arguments on the stack, the reference map
     * might grow later when such a reference is set.
     */
    public BitSet initFrameRefMap() {
        BitSet frameRefMap = new BitSet(frameSize() / target.wordSize);
        for (StackSlot slot : objectStackBlocks) {
            setReference(slot, null, frameRefMap);
        }
        return frameRefMap;
    }

    /**
     * Marks the specified location as a reference in the reference map of the debug information.
     * The tracked location can be a {@link RegisterValue} or a {@link StackSlot}. Note that a
     * {@link Constant} is automatically tracked.
     * 
     * @param location The location to be added to the reference map.
     * @param registerRefMap A register reference map, as created by {@link #initRegisterRefMap()}.
     * @param frameRefMap A frame reference map, as created by {@link #initFrameRefMap()}.
     */
    public void setReference(Value location, BitSet registerRefMap, BitSet frameRefMap) {
        if (location.getKind() == Kind.Object) {
            if (isRegister(location)) {
                registerRefMap.set(asRegister(location).number);
            } else if (isStackSlot(location)) {
                int index = frameRefMapIndex(asStackSlot(location));
                frameRefMap.set(index);
            } else {
                assert isConstant(location);
            }
        }
    }

    /**
     * Clears the specified location as a reference in the reference map of the debug information.
     * The tracked location can be a {@link RegisterValue} or a {@link StackSlot}. Note that a
     * {@link Constant} is automatically tracked.
     * 
     * @param location The location to be removed from the reference map.
     * @param registerRefMap A register reference map, as created by {@link #initRegisterRefMap()}.
     * @param frameRefMap A frame reference map, as created by {@link #initFrameRefMap()}.
     */
    public void clearReference(Value location, BitSet registerRefMap, BitSet frameRefMap) {
        if (location.getKind() == Kind.Object) {
            if (location instanceof RegisterValue) {
                registerRefMap.clear(asRegister(location).number);
            } else if (isStackSlot(location)) {
                int index = frameRefMapIndex(asStackSlot(location));
                if (index < frameRefMap.size()) {
                    frameRefMap.clear(index);
                }
            } else {
                assert isConstant(location);
            }
        }
    }
}