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/*
* Copyright (C) 2015-2016 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 AirTmpWidth_h
#define AirTmpWidth_h
#if ENABLE(B3_JIT)
#include "AirArg.h"
#include <wtf/HashSet.h>
namespace JSC { namespace B3 { namespace Air {
class Code;
class TmpWidth {
public:
TmpWidth();
TmpWidth(Code&);
~TmpWidth();
void recompute(Code&);
// The width of a Tmp is the number of bits that you need to be able to track without some trivial
// recovery. A Tmp may have a "subwidth" (say, Width32 on a 64-bit system) if either of the following
// is true:
//
// - The high bits are never read.
// - The high bits are always zero.
//
// This doesn't tell you which of those properties holds, but you can query that using the other
// methods.
Arg::Width width(Tmp tmp) const
{
auto iter = m_width.find(tmp);
if (iter == m_width.end())
return Arg::minimumWidth(Arg(tmp).type());
return std::min(iter->value.use, iter->value.def);
}
// This indirectly tells you how much of the tmp's high bits are guaranteed to be zero. The number of
// high bits that are zero are:
//
// TotalBits - defWidth(tmp)
//
// Where TotalBits are the total number of bits in the register, so 64 on a 64-bit system.
Arg::Width defWidth(Tmp tmp) const
{
auto iter = m_width.find(tmp);
if (iter == m_width.end())
return Arg::minimumWidth(Arg(tmp).type());
return iter->value.def;
}
// This tells you how much of Tmp is going to be read.
Arg::Width useWidth(Tmp tmp) const
{
auto iter = m_width.find(tmp);
if (iter == m_width.end())
return Arg::minimumWidth(Arg(tmp).type());
return iter->value.use;
}
private:
struct Widths {
Widths() { }
Widths(Arg::Type type)
{
use = Arg::minimumWidth(type);
def = Arg::minimumWidth(type);
}
void dump(PrintStream& out) const;
Arg::Width use;
Arg::Width def;
};
HashMap<Tmp, Widths> m_width;
};
} } } // namespace JSC::B3::Air
#endif // ENABLE(B3_JIT)
#endif // AirTmpWidth_h
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