WebKit/Source/JavaScriptCore/b3/B3DuplicateTails.cpp at main · WebKit/WebKit · GitHub

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* 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 "B3DuplicateTails.h"

#if ENABLE(B3_JIT)

#include "B3BasicBlock.h"

#include "B3BreakCriticalEdges.h"

#include "B3FixSSA.h"

#include "B3InsertionSet.h"

#include "B3PhaseScope.h"

#include "B3Procedure.h"

#include "B3ValueInlines.h"

#include <wtf/IndexSet.h>

namespace JSC { namespace B3 {

namespace {

namespace B3DuplicateTailsInternal {

static constexpr bool verbose = false;

}

class DuplicateTails {

public:

DuplicateTails(Procedure& proc)

: m_proc(proc)

, m_insertionSet(proc)

, m_maxSize(Options::maxB3TailDupBlockSize())

, m_maxSuccessors(Options::maxB3TailDupBlockSuccessors())

{

}

void run()

{

// Breaking critical edges introduces blocks that jump to things. Those Jumps' successors

// become candidates for tail duplication. Prior to critical edge breaking, some of those

// Jumps would have been Branches, and so no tail duplication would have happened.

breakCriticalEdges(m_proc);

// Find blocks that would be candidates for tail duplication. They must be small enough

// and they much not have too many successors.

m_proc.resetValueOwners();

IndexSet<BasicBlock*> candidates;

for (BasicBlock* block : m_proc) {

if (block->size() > m_maxSize)

continue;

if (block->numSuccessors() > m_maxSuccessors)

continue;

if (block->last()->type() != Void) // Demoting doesn't handle terminals with values.

continue;

bool canCopyBlock = true;

for (Value* value : *block) {

if (value->kind().isCloningForbidden()) {

canCopyBlock = false;

break;

}

if (canCopyBlock)

candidates.add(block);

}

// Collect the set of values that must be de-SSA'd.

IndexSet<Value*> valuesToDemote;

for (BasicBlock* block : m_proc) {

for (Value* value : *block) {

if (value->opcode() == Phi && candidates.contains(block))

valuesToDemote.add(value);

for (Value* child : value->children()) {

if (child->owner != block && candidates.contains(child->owner))

valuesToDemote.add(child);

}

demoteValues(m_proc, valuesToDemote);

if (B3DuplicateTailsInternal::verbose) {

dataLog("Procedure after value demotion:\n");

dataLog(m_proc);

}

for (BasicBlock* block : m_proc) {

if (block->last()->opcode() != Jump)

continue;

BasicBlock* tail = block->successorBlock(0);

if (!candidates.contains(tail))

continue;

// Don't tail duplicate a trivial self-loop, because the code below can't handle block and

// tail being the same block.

if (block == tail)

continue;

// We're about to change 'block'. Make sure that nobody duplicates block after this

// point.

candidates.remove(block);

if (B3DuplicateTailsInternal::verbose)

dataLog("Duplicating ", *tail, " into ", *block, "\n");

block->removeLast(m_proc);

UncheckedKeyHashMap<Value*, Value*> map;

for (Value* value : *tail) {

Value* clone = m_proc.clone(value);

for (Value*& child : clone->children()) {

if (Value* replacement = map.get(child))

child = replacement;

}

if (value->type() != Void)

map.add(value, clone);

block->append(clone);

}

block->successors() = tail->successors();

}

m_proc.resetReachability();

m_proc.invalidateCFG();

}

private:

Procedure& m_proc;

InsertionSet m_insertionSet;

unsigned m_maxSize;

unsigned m_maxSuccessors;

};

} // anonymous namespace

void duplicateTails(Procedure& proc)

{

PhaseScope phaseScope(proc, "duplicateTails"_s);

DuplicateTails duplicateTails(proc);

duplicateTails.run();

}

} } // namespace JSC::B3

#endif // ENABLE(B3_JIT)

WebKit/Source/JavaScriptCore/b3/B3DuplicateTails.cpp at main · WebKit/WebKit · GitHub

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