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/*
* Copyright (C) 2016 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef AirEmitShuffle_h
#define AirEmitShuffle_h
#if ENABLE(B3_JIT)
#include "AirArg.h"
#include "AirInst.h"
#include <wtf/Vector.h>
namespace JSC { namespace B3 {
class Value;
namespace Air {
class ShufflePair {
public:
ShufflePair()
{
}
ShufflePair(const Arg& src, const Arg& dst, Arg::Width width)
: m_src(src)
, m_dst(dst)
, m_width(width)
{
}
const Arg& src() const { return m_src; }
const Arg& dst() const { return m_dst; }
// The width determines the kind of move we do. You can only choose Width32 or Width64 right now.
// For GP, it picks between Move32 and Move. For FP, it picks between MoveFloat and MoveDouble.
Arg::Width width() const { return m_width; }
void dump(PrintStream&) const;
private:
Arg m_src;
Arg m_dst;
Arg::Width m_width { Arg::Width8 };
};
// Create a Shuffle instruction.
Inst createShuffle(Value* origin, const Vector<ShufflePair>&);
// Perform a shuffle of a given type. The scratch argument is mandatory. You should pass it as
// follows: If you know that you have scratch registers or temporaries available - that is, they're
// registers that are not mentioned in the shuffle, have the same type as the shuffle, and are not
// live at the shuffle - then you can pass them. If you don't have scratch registers available or if
// you don't feel like looking for them, you can pass memory locations. It's always safe to pass a
// pair of memory locations, and replacing either memory location with a register can be viewed as an
// optimization. It's a pretty important optimization. Some more notes:
//
// - We define scratch registers as things that are not live before the shuffle and are not one of
// the destinations of the shuffle. Not being live before the shuffle also means that they cannot
// be used for any of the sources of the shuffle.
//
// - A second scratch location is only needed when you have shuffle pairs where memory is used both
// as source and destination.
//
// - You're guaranteed not to need any scratch locations if there is a Swap instruction available for
// the type and you don't have any memory locations that are both the source and the destination of
// some pairs. GP supports Swap on x86 while FP never supports Swap.
//
// - Passing memory locations as scratch if are running emitShuffle() before register allocation is
// silly, since that will cause emitShuffle() to pick some specific registers when it does need
// scratch. One easy way to avoid that predicament is to ensure that you call emitShuffle() after
// register allocation. For this reason we could add a Shuffle instruction so that we can defer
// shufflings until after regalloc.
//
// - Shuffles with memory=>memory pairs are not very well tuned. You should avoid them if you want
// performance. If you need to do them, then making sure that you reserve a temporary is one way to
// get acceptable performance.
//
// NOTE: Use this method (and its friend below) to emit shuffles after register allocation. Before
// register allocation it is much better to simply use the Shuffle instruction.
Vector<Inst> emitShuffle(
Vector<ShufflePair>, std::array<Arg, 2> scratch, Arg::Type, Value* origin);
// Perform a shuffle that involves any number of types. Pass scratch registers or memory locations
// for each type according to the rules above.
Vector<Inst> emitShuffle(
const Vector<ShufflePair>&,
const std::array<Arg, 2>& gpScratch, const std::array<Arg, 2>& fpScratch,
Value* origin);
} } } // namespace JSC::B3::Air
#endif // ENABLE(B3_JIT)
#endif // AirEmitShuffle_h
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