// moveExitCondition - Move exit condition EC into split condition block CondBB.
void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
BasicBlock *ExitBB, ICmpInst *EC,
ICmpInst *SC, PHINode *IV,
Instruction *IVAdd, Loop *LP,
unsigned ExitValueNum) {
BasicBlock *ExitingBB = EC->getParent();
Instruction *CurrentBR = CondBB->getTerminator();
// Move exit condition into split condition block.
EC->moveBefore(CurrentBR);
EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV);
// Move exiting block's branch into split condition block. Update its branch
// destination.
BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
ExitingBR->moveBefore(CurrentBR);
BasicBlock *OrigDestBB = NULL;
if (ExitingBR->getSuccessor(0) == ExitBB) {
OrigDestBB = ExitingBR->getSuccessor(1);
ExitingBR->setSuccessor(1, ActiveBB);
}
else {
OrigDestBB = ExitingBR->getSuccessor(0);
ExitingBR->setSuccessor(0, ActiveBB);
}
// Remove split condition and current split condition branch.
SC->eraseFromParent();
CurrentBR->eraseFromParent();
// Connect exiting block to original destination.
BranchInst::Create(OrigDestBB, ExitingBB);
// Update PHINodes
updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
// Fix dominator info.
// ExitBB is now dominated by CondBB
DT->changeImmediateDominator(ExitBB, CondBB);
DF->changeImmediateDominator(ExitBB, CondBB, DT);
// Blocks outside the loop may have been in the dominance frontier of blocks
// inside the condition; this is now impossible because the blocks inside the
// condition no loger dominate the exit. Remove the relevant blocks from
// the dominance frontiers.
for (Loop::block_iterator I = LP->block_begin(), E = LP->block_end();
I != E; ++I) {
if (*I == CondBB || !DT->dominates(CondBB, *I)) continue;
DominanceFrontier::iterator BBDF = DF->find(*I);
DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
while (DomSetI != DomSetE) {
DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
++DomSetI;
BasicBlock *DFBB = *CurrentItr;
if (!LP->contains(DFBB))
BBDF->second.erase(DFBB);
}
}
}
bool LoopBogusCF::runOnLoop(Loop *loop, LPPassManager &LPM) {
if (disableLoopBcf)
return false;
++NumLoops;
DEBUG(errs() << "LoopBogusCF: Dumping loop info\n");
// DEBUG(loop->dump());
BasicBlock *header = loop->getHeader();
BranchInst *branch = dyn_cast<BranchInst>(header->getTerminator());
if (!branch || !branch->isConditional()) {
DEBUG(errs() << "\t Not trivial loop -- skipping\n");
return false;
}
if (!loop->isLoopSimplifyForm()) {
DEBUG(errs() << "\t Not simplified loop -- skipping\n");
return false;
}
BasicBlock *exitBlock = loop->getUniqueExitBlock();
if (!exitBlock) {
DEBUG(errs() << "\t No unique exit block -- skipping\n");
return false;
}
if (branch->getSuccessor(0) != exitBlock &&
branch->getSuccessor(1) != exitBlock) {
DEBUG(errs() << "\t Not trivial loop -- skipping\n");
return false;
}
++NumLoopsObf;
// DEBUG(header->getParent()->viewCFG());
DEBUG(errs() << "\tCreating dummy block\n");
LoopInfo &info = getAnalysis<LoopInfo>();
// Split header block
BasicBlock *dummy = header->splitBasicBlock(header->getTerminator());
loop->addBasicBlockToLoop(dummy, info.getBase());
BasicBlock *trueBlock, *falseBlock = exitBlock;
if (branch->getSuccessor(0) == exitBlock) {
trueBlock = branch->getSuccessor(1);
branch->setSuccessor(1, dummy);
} else {
trueBlock = branch->getSuccessor(0);
branch->setSuccessor(0, dummy);
}
branch->moveBefore(header->getTerminator());
header->getTerminator()->eraseFromParent();
OpaquePredicate::createStub(dummy, trueBlock, falseBlock,
OpaquePredicate::PredicateTrue, false);
// DEBUG(header->getParent()->viewCFG());
return true;
}
