/// Set successor probability of a given iterator.
void MachineBasicBlock::setSuccProbability(succ_iterator I,
BranchProbability Prob) {
assert(!Prob.isUnknown());
if (Probs.empty() || Weights.empty())
return;
*getProbabilityIterator(I) = Prob;
// FIXME: Temporarily use the numerator of the probability to represent edge
// weight. This will be removed once all weight-version interfaces in MBB
// are replaces with probability-version interfaces.
*getWeightIterator(I) = Prob.getNumerator();
}
/// Set successor probability of a given iterator.
void MachineBasicBlock::setSuccProbability(succ_iterator I,
BranchProbability Prob) {
assert(!Prob.isUnknown());
if (Probs.empty())
return;
*getProbabilityIterator(I) = Prob;
}
void MachineBasicBlock::addSuccessor(MachineBasicBlock *Succ,
BranchProbability Prob) {
// Probability list is either empty (if successor list isn't empty, this means
// disabled optimization) or has the same size as successor list.
if (!(Probs.empty() && !Successors.empty())) {
Probs.push_back(Prob);
// FIXME: Temporarily use the numerator of the probability to represent edge
// weight. This will be removed once all weight-version interfaces in MBB
// are replaced with probability-version interfaces.
Weights.push_back(Prob.getNumerator());
}
Successors.push_back(Succ);
Succ->addPredecessor(this);
}
/// Splits a MachineBasicBlock to branch before \p SplitBefore. The original
/// branch is \p OrigBranch. The target of the new branch can either be the same
/// as the target of the original branch or the fallthrough successor of the
/// original block as determined by \p BranchToFallThrough. The branch
/// conditions will be inverted according to \p InvertNewBranch and
/// \p InvertOrigBranch. If an instruction that previously fed the branch is to
/// be deleted, it is provided in \p MIToDelete and \p NewCond will be used as
/// the branch condition. The branch probabilities will be set if the
/// MachineBranchProbabilityInfo isn't null.
static bool splitMBB(BlockSplitInfo &BSI) {
assert(BSI.allInstrsInSameMBB() &&
"All instructions must be in the same block.");
MachineBasicBlock *ThisMBB = BSI.OrigBranch->getParent();
MachineFunction *MF = ThisMBB->getParent();
MachineRegisterInfo *MRI = &MF->getRegInfo();
assert(MRI->isSSA() && "Can only do this while the function is in SSA form.");
if (ThisMBB->succ_size() != 2) {
LLVM_DEBUG(
dbgs() << "Don't know how to handle blocks that don't have exactly"
<< " two successors.\n");
return false;
}
const PPCInstrInfo *TII = MF->getSubtarget<PPCSubtarget>().getInstrInfo();
unsigned OrigBROpcode = BSI.OrigBranch->getOpcode();
unsigned InvertedOpcode =
OrigBROpcode == PPC::BC
? PPC::BCn
: OrigBROpcode == PPC::BCn
? PPC::BC
: OrigBROpcode == PPC::BCLR ? PPC::BCLRn : PPC::BCLR;
unsigned NewBROpcode = BSI.InvertNewBranch ? InvertedOpcode : OrigBROpcode;
MachineBasicBlock *OrigTarget = BSI.OrigBranch->getOperand(1).getMBB();
MachineBasicBlock *OrigFallThrough = OrigTarget == *ThisMBB->succ_begin()
? *ThisMBB->succ_rbegin()
: *ThisMBB->succ_begin();
MachineBasicBlock *NewBRTarget =
BSI.BranchToFallThrough ? OrigFallThrough : OrigTarget;
BranchProbability ProbToNewTarget =
!BSI.MBPI ? BranchProbability::getUnknown()
: BSI.MBPI->getEdgeProbability(ThisMBB, NewBRTarget);
// Create a new basic block.
MachineBasicBlock::iterator InsertPoint = BSI.SplitBefore;
const BasicBlock *LLVM_BB = ThisMBB->getBasicBlock();
MachineFunction::iterator It = ThisMBB->getIterator();
MachineBasicBlock *NewMBB = MF->CreateMachineBasicBlock(LLVM_BB);
MF->insert(++It, NewMBB);
// Move everything after SplitBefore into the new block.
NewMBB->splice(NewMBB->end(), ThisMBB, InsertPoint, ThisMBB->end());
NewMBB->transferSuccessors(ThisMBB);
// Add the two successors to ThisMBB. The probabilities come from the
// existing blocks if available.
ThisMBB->addSuccessor(NewBRTarget, ProbToNewTarget);
ThisMBB->addSuccessor(NewMBB, ProbToNewTarget.getCompl());
// Add the branches to ThisMBB.
BuildMI(*ThisMBB, ThisMBB->end(), BSI.SplitBefore->getDebugLoc(),
TII->get(NewBROpcode))
.addReg(BSI.SplitCond->getOperand(0).getReg())
.addMBB(NewBRTarget);
BuildMI(*ThisMBB, ThisMBB->end(), BSI.SplitBefore->getDebugLoc(),
TII->get(PPC::B))
.addMBB(NewMBB);
if (BSI.MIToDelete)
BSI.MIToDelete->eraseFromParent();
// Change the condition on the original branch and invert it if requested.
auto FirstTerminator = NewMBB->getFirstTerminator();
if (BSI.NewCond) {
assert(FirstTerminator->getOperand(0).isReg() &&
"Can't update condition of unconditional branch.");
FirstTerminator->getOperand(0).setReg(BSI.NewCond->getOperand(0).getReg());
}
if (BSI.InvertOrigBranch)
FirstTerminator->setDesc(TII->get(InvertedOpcode));
// If any of the PHIs in the successors of NewMBB reference values that
// now come from NewMBB, they need to be updated.
for (auto *Succ : NewMBB->successors()) {
updatePHIs(Succ, ThisMBB, NewMBB, MRI);
}
addIncomingValuesToPHIs(NewBRTarget, ThisMBB, NewMBB, MRI);
LLVM_DEBUG(dbgs() << "After splitting, ThisMBB:\n"; ThisMBB->dump());
LLVM_DEBUG(dbgs() << "NewMBB:\n"; NewMBB->dump());
LLVM_DEBUG(dbgs() << "New branch-to block:\n"; NewBRTarget->dump());
return true;
}
void PrintTo(BranchProbability P, ::std::ostream *os) {
*os << P.getNumerator() << "/" << P.getDenominator();
}
