/**
 * @file llfasttimer.h
 * @brief Declaration of a fast timer.
 *
 * $LicenseInfo:firstyear=2004&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_FASTTIMER_H
#define LL_FASTTIMER_H

#include "llinstancetracker.h"
#include "lltrace.h"
#include "lltreeiterators.h"

#if LL_WINDOWS
#include <intrin.h>
#endif

#define LL_FAST_TIMER_ON 1
#define LL_FASTTIMER_USE_RDTSC 1

// NOTE: Also see llprofiler.h
#if !defined(LL_PROFILER_CONFIGURATION)
#define LL_RECORD_BLOCK_TIME(timer_stat) const LLTrace::BlockTimer& LL_GLUE_TOKENS(block_time_recorder, __LINE__)(LLTrace::timeThisBlock(timer_stat)); (void)LL_GLUE_TOKENS(block_time_recorder, __LINE__);
#endif // LL_PROFILER_CONFIGURATION

namespace LLTrace
{
// use to create blocktimer rvalue to be captured in a reference so that the BlockTimer lives to the end of the block.
class BlockTimer timeThisBlock(class BlockTimerStatHandle& timer);

class BlockTimer
{
public:
    typedef BlockTimer self_t;
    typedef class BlockTimerStatHandle DeclareTimer;

    ~BlockTimer();

    F64Seconds getElapsedTime();

        //////////////////////////////////////////////////////////////////////////////
    //
    // Important note: These implementations must be FAST!
    //


#if LL_WINDOWS
    //
    // Windows implementation of CPU clock
    //

    //
    // NOTE: put back in when we aren't using platform sdk anymore
    //
    // because MS has different signatures for these functions in winnt.h
    // need to rename them to avoid conflicts
    //#define _interlockedbittestandset _renamed_interlockedbittestandset
    //#define _interlockedbittestandreset _renamed_interlockedbittestandreset
    //#include <intrin.h>
    //#undef _interlockedbittestandset
    //#undef _interlockedbittestandreset

    //inline U32 getCPUClockCount32()
    //{
    //  U64 time_stamp = __rdtsc();
    //  return (U32)(time_stamp >> 8);
    //}
    //
    //// return full timer value, *not* shifted by 8 bits
    //inline U64 getCPUClockCount64()
    //{
    //  return __rdtsc();
    //}



    // shift off lower 8 bits for lower resolution but longer term timing
    // on 1Ghz machine, a 32-bit word will hold ~1000 seconds of timing
#if LL_FASTTIMER_USE_RDTSC
    static U32 getCPUClockCount32()
    {
        unsigned __int64 val = __rdtsc();
        val = val >> 8;
        return static_cast<U32>(val);
    }

    // return full timer value, *not* shifted by 8 bits
    static U64 getCPUClockCount64()
    {
        return static_cast<U64>( __rdtsc() );
    }

#else
    //U64 get_clock_count(); // in lltimer.cpp
    // These use QueryPerformanceCounter, which is arguably fine and also works on AMD architectures.
    static U32 getCPUClockCount32()
    {
        return (U32)(get_clock_count()>>8);
    }

    static U64 getCPUClockCount64()
    {
        return get_clock_count();
    }

#endif

#endif

#if (LL_DARWIN && defined(__arm64__))

    static U32 getCPUClockCount64()
    {
        U64 t = clock_gettime_nsec_np(CLOCK_UPTIME_RAW);
        return t/1000;
    }

    static U64 getCPUClockCount32()
    {
        return (U32) (getCPUClockCount64() >> 8);
    }

#endif

#if (LL_LINUX && !(defined(__i386__) || defined(__amd64__)))
    //
    // Linux implementation of CPU clock - non-x86.
    // This is accurate but SLOW!  Only use out of desperation.
    //
    // Try to use the MONOTONIC clock if available, this is a constant time counter
    // with nanosecond resolution (but not necessarily accuracy) and attempts are
    // made to synchronize this value between cores at kernel start. It should not
    // be affected by CPU frequency. If not available use the REALTIME clock, but
    // this may be affected by NTP adjustments or other user activity affecting
    // the system time.
    static U64 getCPUClockCount64()
    {
        struct timespec tp;

#ifdef CLOCK_MONOTONIC // MONOTONIC supported at build-time?
        if (-1 == clock_gettime(CLOCK_MONOTONIC,&tp)) // if MONOTONIC isn't supported at runtime then ouch, try REALTIME
#endif
            clock_gettime(CLOCK_REALTIME,&tp);

        return (tp.tv_sec*sClockResolution)+tp.tv_nsec;
    }

    static U32 getCPUClockCount32()
    {
        return (U32)(getCPUClockCount64() >> 8);
    }

#endif // (LL_LINUX) && !(defined(__i386__) || defined(__amd64__))


#if (LL_LINUX || LL_DARWIN || __FreeBSD__) && (defined(__i386__) || defined(__amd64__))
    //
    // Mac+Linux FAST x86 implementation of CPU clock
    static U32 getCPUClockCount32()
    {
        U32 low(0),high(0);
        __asm__ volatile (".byte 0x0f, 0x31": "=a"(low), "=d"(high) );
        return (low>>8) | (high<<24);
    }

    static U64 getCPUClockCount64()
    {
        U32 low(0),high(0);
        __asm__ volatile (".byte 0x0f, 0x31": "=a"(low), "=d"(high) );
        return (U64)low | ( ((U64)high) << 32);
    }

#endif

    static BlockTimerStatHandle& getRootTimeBlock();
    static void pushLog(LLSD sd);
    static void setLogLock(class LLMutex* mutex);
    static void writeLog(std::ostream& os);
    static void updateTimes();

    static U64 countsPerSecond();

    // updates cumulative times and hierarchy,
    // can be called multiple times in a frame, at any point
    static void processTimes();

    static void bootstrapTimerTree();
    static void incrementalUpdateTimerTree();

    // call this once a frame to periodically log timers
    static void logStats();

    // dumps current cumulative frame stats to log
    // call nextFrame() to reset timers
    static void dumpCurTimes();

private:
    friend class BlockTimerStatHandle;
    // FIXME: this friendship exists so that each thread can instantiate a root timer,
    // which could be a derived class with a public constructor instead, possibly
    friend class ThreadRecorder;
    friend BlockTimer timeThisBlock(BlockTimerStatHandle&);

    BlockTimer(BlockTimerStatHandle& timer);

    // no-copy
    BlockTimer(const BlockTimer& other);
    BlockTimer& operator=(const BlockTimer& other);

private:
    U64                     mStartTime;
    BlockTimerStackRecord   mParentTimerData{};

public:
    // statics
    static std::string      sLogName;
    static bool             sMetricLog,
                            sLog;
    static U64              sClockResolution;

};

// this dummy function assists in allocating a block timer with stack-based lifetime.
// this is done by capturing the return value in a stack-allocated const reference variable.
// (This is most easily done using the macro LL_RECORD_BLOCK_TIME)
// Otherwise, it would be possible to store a BlockTimer on the heap, resulting in non-nested lifetimes,
// which would break the invariants of the timing hierarchy logic
LL_FORCE_INLINE class BlockTimer timeThisBlock(class BlockTimerStatHandle& timer)
{
    return BlockTimer(timer);
}

// stores a "named" timer instance to be reused via multiple BlockTimer stack instances
class BlockTimerStatHandle
:   public StatType<TimeBlockAccumulator>
{
public:
    BlockTimerStatHandle(const char* name, const char* description = "");

    TimeBlockTreeNode& getTreeNode() const;
    BlockTimerStatHandle* getParent() const { return getTreeNode().getParent(); }
    void setParent(BlockTimerStatHandle* parent) { getTreeNode().setParent(parent); }

    typedef std::vector<BlockTimerStatHandle*>::iterator child_iter;
    typedef std::vector<BlockTimerStatHandle*>::const_iterator child_const_iter;
    child_iter beginChildren();
    child_iter endChildren();
    bool hasChildren();
    std::vector<BlockTimerStatHandle*>& getChildren();

    StatType<TimeBlockAccumulator::CallCountFacet>& callCount()
    {
        return static_cast<StatType<TimeBlockAccumulator::CallCountFacet>&>(*(StatType<TimeBlockAccumulator>*)this);
    }

    StatType<TimeBlockAccumulator::SelfTimeFacet>& selfTime()
    {
        return static_cast<StatType<TimeBlockAccumulator::SelfTimeFacet>&>(*(StatType<TimeBlockAccumulator>*)this);
    }

    bool                        mCollapsed;             // don't show children
};

// iterators and helper functions for walking the call hierarchy of block timers in different ways
typedef LLTreeDFSIter<BlockTimerStatHandle, BlockTimerStatHandle::child_const_iter> block_timer_tree_df_iterator_t;
typedef LLTreeDFSPostIter<BlockTimerStatHandle, BlockTimerStatHandle::child_const_iter> block_timer_tree_df_post_iterator_t;
typedef LLTreeBFSIter<BlockTimerStatHandle, BlockTimerStatHandle::child_const_iter> block_timer_tree_bf_iterator_t;

block_timer_tree_df_iterator_t begin_block_timer_tree_df(BlockTimerStatHandle& id);
block_timer_tree_df_iterator_t end_block_timer_tree_df();
block_timer_tree_df_post_iterator_t begin_block_timer_tree_df_post(BlockTimerStatHandle& id);
block_timer_tree_df_post_iterator_t end_block_timer_tree_df_post();
block_timer_tree_bf_iterator_t begin_block_timer_tree_bf(BlockTimerStatHandle& id);
block_timer_tree_bf_iterator_t end_block_timer_tree_bf();

LL_FORCE_INLINE BlockTimer::BlockTimer(BlockTimerStatHandle& timer)
{
#if LL_FAST_TIMER_ON
    BlockTimerStackRecord* cur_timer_data = LLThreadLocalSingletonPointer<BlockTimerStackRecord>::getInstance();
    if (!cur_timer_data)
    {
        // How likely is it that
        // LLThreadLocalSingletonPointer<T>::getInstance() will return NULL?
        // Even without researching, what we can say is that if we exit
        // without setting mStartTime at all, gcc 4.7 produces (fatal)
        // warnings about a possibly-uninitialized data member.
        mStartTime = 0;
        return;
    }
    TimeBlockAccumulator& accumulator = timer.getCurrentAccumulator();
    accumulator.mActiveCount++;
    // keep current parent as long as it is active when we are
    accumulator.mMoveUpTree |= (accumulator.mParent->getCurrentAccumulator().mActiveCount == 0);

    // store top of stack
    mParentTimerData = *cur_timer_data;
    // push new information
    cur_timer_data->mActiveTimer = this;
    cur_timer_data->mTimeBlock = &timer;
    cur_timer_data->mChildTime = 0;

    mStartTime = getCPUClockCount64();
#endif
}

LL_FORCE_INLINE BlockTimer::~BlockTimer()
{
#if LL_FAST_TIMER_ON
    U64 total_time = getCPUClockCount64() - mStartTime;
    BlockTimerStackRecord* cur_timer_data = LLThreadLocalSingletonPointer<BlockTimerStackRecord>::getInstance();
    if (!cur_timer_data) return;

    TimeBlockAccumulator& accumulator = cur_timer_data->mTimeBlock->getCurrentAccumulator();

    accumulator.mCalls++;
    accumulator.mTotalTimeCounter += total_time;
    accumulator.mSelfTimeCounter += total_time - cur_timer_data->mChildTime;
    accumulator.mActiveCount--;

    // store last caller to bootstrap tree creation
    // do this in the destructor in case of recursion to get topmost caller
    accumulator.mLastCaller = mParentTimerData.mTimeBlock;

    // we are only tracking self time, so subtract our total time delta from parents
    mParentTimerData.mChildTime += total_time;

    //pop stack
    *cur_timer_data = mParentTimerData;
#endif
}

}

typedef LLTrace::BlockTimer LLFastTimer;

#endif // LL_LLFASTTIMER_H