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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.
*/
#include "config.h"
#include "AirTmpWidth.h"
#if ENABLE(B3_JIT)
#include "AirCode.h"
#include "AirInstInlines.h"
#include <wtf/ListDump.h>
namespace JSC { namespace B3 { namespace Air {
TmpWidth::TmpWidth()
{
}
TmpWidth::TmpWidth(Code& code)
{
recompute(code);
}
TmpWidth::~TmpWidth()
{
}
void TmpWidth::recompute(Code& code)
{
// Set this to true to cause this analysis to always return pessimistic results.
const bool beCareful = false;
const bool verbose = false;
if (verbose) {
dataLog("Code before TmpWidth:\n");
dataLog(code);
}
m_width.clear();
auto assumeTheWorst = [&] (Tmp tmp) {
Widths& widths = m_width.add(tmp, Widths()).iterator->value;
Arg::Type type = Arg(tmp).type();
widths.use = Arg::conservativeWidth(type);
widths.def = Arg::conservativeWidth(type);
};
// Assume the worst for registers.
RegisterSet::allRegisters().forEach(
[&] (Reg reg) {
assumeTheWorst(Tmp(reg));
});
if (beCareful) {
code.forAllTmps(assumeTheWorst);
// We fall through because the fixpoint that follows can only make things even more
// conservative. This mode isn't meant to be fast, just safe.
}
// Now really analyze everything but Move's over Tmp's, but set aside those Move's so we can find
// them quickly during the fixpoint below. Note that we can make this analysis stronger by
// recognizing more kinds of Move's or anything that has Move-like behavior, though it's probably not
// worth it.
Vector<Inst*> moves;
for (BasicBlock* block : code) {
for (Inst& inst : *block) {
if (inst.opcode == Move && inst.args[1].isTmp()) {
if (inst.args[0].isTmp()) {
// Make sure that both sides of the Move have a width already initialized. The
// fixpoint below assumes that it never has to add things to the HashMap.
m_width.add(inst.args[0].tmp(), Widths(Arg::GP));
m_width.add(inst.args[1].tmp(), Widths(Arg::GP));
moves.append(&inst);
continue;
}
if (inst.args[0].isImm()
&& inst.args[0].value() >= 0) {
Tmp tmp = inst.args[1].tmp();
Widths& widths = m_width.add(tmp, Widths(Arg::GP)).iterator->value;
if (inst.args[0].value() <= std::numeric_limits<int8_t>::max())
widths.def = std::max(widths.def, Arg::Width8);
else if (inst.args[0].value() <= std::numeric_limits<int16_t>::max())
widths.def = std::max(widths.def, Arg::Width16);
else if (inst.args[0].value() <= std::numeric_limits<int32_t>::max())
widths.def = std::max(widths.def, Arg::Width32);
else
widths.def = std::max(widths.def, Arg::Width64);
continue;
}
}
inst.forEachTmp(
[&] (Tmp& tmp, Arg::Role role, Arg::Type type, Arg::Width width) {
Widths& widths = m_width.add(tmp, Widths(type)).iterator->value;
if (Arg::isAnyUse(role))
widths.use = std::max(widths.use, width);
if (Arg::isZDef(role))
widths.def = std::max(widths.def, width);
else if (Arg::isAnyDef(role))
widths.def = Arg::conservativeWidth(type);
});
}
}
// Finally, fixpoint over the Move's.
bool changed = true;
while (changed) {
changed = false;
for (Inst* move : moves) {
ASSERT(move->opcode == Move);
ASSERT(move->args[0].isTmp());
ASSERT(move->args[1].isTmp());
// We already ensure that both tmps are added to the width map. That's important
// because you cannot add both tmps here while simultaneously getting a reference to
// their values, since the second add would invalidate the reference returned by the
// first one.
Widths& srcWidths = m_width.find(move->args[0].tmp())->value;
Widths& dstWidths = m_width.find(move->args[1].tmp())->value;
// Legend:
//
// Move %src, %dst
// defWidth(%dst) is a promise about how many high bits are zero. The smaller the width, the
// stronger the promise. This Move may weaken that promise if we know that %src is making a
// weaker promise. Such forward flow is the only thing that determines defWidth().
if (dstWidths.def < srcWidths.def) {
dstWidths.def = srcWidths.def;
changed = true;
}
// srcWidth(%src) is a promise about how many high bits are ignored. The smaller the width,
// the stronger the promise. This Move may weaken that promise if we know that %dst is making
// a weaker promise. Such backward flow is the only thing that determines srcWidth().
if (srcWidths.use < dstWidths.use) {
srcWidths.use = dstWidths.use;
changed = true;
}
}
}
if (verbose)
dataLog("width: ", mapDump(m_width), "\n");
}
void TmpWidth::Widths::dump(PrintStream& out) const
{
out.print("{use = ", use, ", def = ", def, "}");
}
} } } // namespace JSC::B3::Air
#endif // ENABLE(B3_JIT)
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