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/*
* Copyright (C) 2017 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 "B3HoistLoopInvariantValues.h"
#if ENABLE(B3_JIT)
#include "B3BackwardsDominators.h"
#include "B3Dominators.h"
#include "B3EnsureLoopPreHeaders.h"
#include "B3NaturalLoops.h"
#include "B3PhaseScope.h"
#include "B3ProcedureInlines.h"
#include "B3ValueInlines.h"
#include <wtf/RangeSet.h>
namespace JSC { namespace B3 {
bool hoistLoopInvariantValues(Procedure& proc)
{
PhaseScope phaseScope(proc, "hoistLoopInvariantValues"_s);
ensureLoopPreHeaders(proc);
NaturalLoops& loops = proc.naturalLoops();
if (!loops.numLoops())
return false;
proc.resetValueOwners();
Dominators& dominators = proc.dominators();
BackwardsDominators& backwardsDominators = proc.backwardsDominators();
// FIXME: We should have a reusable B3::EffectsSet data structure.
// https://bugs.webkit.org/show_bug.cgi?id=174762
struct LoopData {
RangeSet<HeapRange> writes;
bool writesLocalState { false };
bool writesPinned { false };
bool sideExits { false };
BasicBlock* preHeader { nullptr };
};
IndexMap<NaturalLoop, LoopData> data(loops.numLoops());
for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
const NaturalLoop& loop = loops.loop(loopIndex);
for (BasicBlock* predecessor : loop.header()->predecessors()) {
if (loops.belongsTo(predecessor, loop))
continue;
RELEASE_ASSERT(!data[loop].preHeader);
data[loop].preHeader = predecessor;
}
}
for (BasicBlock* block : proc) {
const NaturalLoop* loop = loops.innerMostLoopOf(block);
if (!loop)
continue;
for (Value* value : *block) {
Effects effects = value->effects();
data[*loop].writes.add(effects.writes);
data[*loop].writesLocalState |= effects.writesLocalState;
data[*loop].writesPinned |= effects.writesPinned;
data[*loop].sideExits |= effects.exitsSideways;
}
}
for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
const NaturalLoop& loop = loops.loop(loopIndex);
for (const NaturalLoop* current = loops.innerMostOuterLoop(loop); current; current = loops.innerMostOuterLoop(*current)) {
data[*current].writes.addAll(data[loop].writes);
data[*current].writesLocalState |= data[loop].writesLocalState;
data[*current].writesPinned |= data[loop].writesPinned;
data[*current].sideExits |= data[loop].sideExits;
}
}
bool changed = false;
// Pre-order ensures that we visit our dominators before we visit ourselves. Otherwise we'd miss some
// hoisting opportunities in complex CFGs.
for (BasicBlock* block : proc.blocksInPreOrder()) {
Vector<const NaturalLoop*> blockLoops = loops.loopsOf(block);
if (blockLoops.isEmpty())
continue;
for (Value*& value : *block) {
Effects effects = value->effects();
// We never hoist write effects or control constructs.
if (effects.mustExecute())
continue;
// Try outermost loop first.
for (unsigned i = blockLoops.size(); i--;) {
const NaturalLoop& loop = *blockLoops[i];
bool ok = true;
for (Value* child : value->children()) {
if (!dominators.dominates(child->owner, data[loop].preHeader)) {
ok = false;
break;
}
}
if (!ok)
continue;
if (effects.controlDependent) {
if (!backwardsDominators.dominates(block, data[loop].preHeader))
continue;
// FIXME: This is super conservative. In reality, we just need to make sure that there
// aren't any side exits between here and the pre-header according to backwards search.
// https://bugs.webkit.org/show_bug.cgi?id=174763
if (data[loop].sideExits)
continue;
}
if (effects.readsPinned && data[loop].writesPinned)
continue;
if (effects.readsLocalState && data[loop].writesLocalState)
continue;
if (data[loop].writes.overlaps(effects.reads))
continue;
data[loop].preHeader->appendNonTerminal(value);
value = proc.add<Value>(Nop, Void, value->origin());
changed = true;
}
}
}
return changed;
}
} } // namespace JSC::B3
#endif // ENABLE(B3_JIT)
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