B3EnsureLoopPreHeaders.cpp [plain text]
#include "config.h"
#include "B3EnsureLoopPreHeaders.h"
#if ENABLE(B3_JIT)
#include "B3BasicBlockInlines.h"
#include "B3BlockInsertionSet.h"
#include "B3NaturalLoops.h"
#include "B3ValueInlines.h"
namespace JSC { namespace B3 {
bool ensureLoopPreHeaders(Procedure& proc)
{
NaturalLoops& loops = proc.naturalLoops();
BlockInsertionSet insertionSet(proc);
for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
const NaturalLoop& loop = loops.loop(loopIndex);
Vector<BasicBlock*, 4> outOfBodyPredecessors;
double totalFrequency = 0;
for (BasicBlock* predecessor : loop.header()->predecessors()) {
if (loops.belongsTo(predecessor, loop))
continue;
outOfBodyPredecessors.append(predecessor);
totalFrequency += predecessor->frequency();
}
if (outOfBodyPredecessors.size() <= 1)
continue;
BasicBlock* preHeader = insertionSet.insertBefore(loop.header(), totalFrequency);
preHeader->appendNew<Value>(proc, Jump, loop.header()->at(0)->origin());
preHeader->setSuccessors(FrequentedBlock(loop.header()));
for (BasicBlock* predecessor : outOfBodyPredecessors) {
predecessor->replaceSuccessor(loop.header(), preHeader);
preHeader->addPredecessor(predecessor);
loop.header()->removePredecessor(predecessor);
}
loop.header()->addPredecessor(preHeader);
}
if (insertionSet.execute()) {
proc.invalidateCFG();
return true;
}
return false;
}
} }
#endif // ENABLE(B3_JIT)