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//===-- PhiCleaner.cpp ----------------------------------------------------===//
//
// The KLEE Symbolic Virtual Machine
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Passes.h"
#include <set>
using namespace llvm;
char klee::PhiCleanerPass::ID = 0;
bool klee::PhiCleanerPass::runOnFunction(Function &f) {
bool changed = false;
for (Function::iterator b = f.begin(), be = f.end(); b != be; ++b) {
BasicBlock::iterator it = b->begin();
if (it->getOpcode() == Instruction::PHI) {
PHINode *reference = cast<PHINode>(it);
std::set<Value*> phis;
phis.insert(reference);
unsigned numBlocks = reference->getNumIncomingValues();
for (++it; isa<PHINode>(*it); ++it) {
PHINode *pi = cast<PHINode>(it);
assert(numBlocks == pi->getNumIncomingValues());
// see if it is out of order
unsigned i;
for (i=0; i<numBlocks; i++)
if (pi->getIncomingBlock(i) != reference->getIncomingBlock(i))
break;
if (i!=numBlocks) {
std::vector<Value*> values;
values.reserve(numBlocks);
for (unsigned i=0; i<numBlocks; i++)
values[i] = pi->getIncomingValueForBlock(reference->getIncomingBlock(i));
for (unsigned i=0; i<numBlocks; i++) {
pi->setIncomingBlock(i, reference->getIncomingBlock(i));
pi->setIncomingValue(i, values[i]);
}
changed = true;
}
// see if it uses any previously defined phi nodes
for (i=0; i<numBlocks; i++) {
Value *value = pi->getIncomingValue(i);
if (phis.find(value) != phis.end()) {
// fix by making a "move" at the end of the incoming block
// to a new temporary, which is thus known not to be a phi
// result. we could be somewhat more efficient about this
// by sharing temps and by reordering phi instructions so
// this isn't completely necessary, but in the end this is
// just a pathological case which does not occur very
// often.
Instruction *tmp =
new BitCastInst(value,
value->getType(),
value->getName() + ".phiclean",
pi->getIncomingBlock(i)->getTerminator());
pi->setIncomingValue(i, tmp);
}
changed = true;
}
phis.insert(pi);
}
}
}
return changed;
}
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