/// isBlockOnlyReachableByFallthough - Return true if the basic block has
/// exactly one predecessor and the control transfer mechanism between
/// the predecessor and this block is a fall-through.
///
/// This overrides AsmPrinter's implementation to handle delay slots.
bool SparcAsmPrinter::
isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
// If this is a landing pad, it isn't a fall through. If it has no preds,
// then nothing falls through to it.
if (MBB->isLandingPad() || MBB->pred_empty())
return false;
// If there isn't exactly one predecessor, it can't be a fall through.
MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
++PI2;
if (PI2 != MBB->pred_end())
return false;
// The predecessor has to be immediately before this block.
const MachineBasicBlock *Pred = *PI;
if (!Pred->isLayoutSuccessor(MBB))
return false;
// Check if the last terminator is an unconditional branch.
MachineBasicBlock::const_iterator I = Pred->end();
while (I != Pred->begin() && !(--I)->isTerminator())
; // Noop
return I == Pred->end() || !I->isBarrier();
}
// KLUDGE: HexagonInstrInfo::AnalyzeBranch may be unable to recognize
// that a block can never fall-through.
bool HexagonEarlyIfConversion::hasUncondBranch(const MachineBasicBlock *B)
const {
MachineBasicBlock::const_iterator I = B->getFirstTerminator(), E = B->end();
while (I != E) {
if (I->isBarrier())
return true;
++I;
}
return false;
}
void llvm::guessSuccessors(const MachineBasicBlock &MBB,
SmallVectorImpl<MachineBasicBlock*> &Result,
bool &IsFallthrough) {
SmallPtrSet<MachineBasicBlock*,8> Seen;
for (const MachineInstr &MI : MBB) {
if (MI.isPHI())
continue;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isMBB())
continue;
MachineBasicBlock *Succ = MO.getMBB();
auto RP = Seen.insert(Succ);
if (RP.second)
Result.push_back(Succ);
}
}
MachineBasicBlock::const_iterator I = MBB.getLastNonDebugInstr();
IsFallthrough = I == MBB.end() || !I->isBarrier();
}
bool PatmosAsmPrinter::
isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
// If this is a landing pad, it isn't a fall through. If it has no preds,
// then nothing falls through to it.
if (MBB->isLandingPad() || MBB->pred_empty() || MBB->hasAddressTaken())
return false;
// If there isn't exactly one predecessor, it can't be a fall through.
MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
if (++PI2 != MBB->pred_end())
return false;
// The predecessor has to be immediately before this block.
const MachineBasicBlock *Pred = *PI;
if (!Pred->isLayoutSuccessor(MBB))
return false;
// if the block starts a new cache block, do not fall through (we need to
// insert cache stuff, even if we only reach this block from a jump from the
// previous block, and we need the label).
if (isFStart(MBB))
return false;
// If the block is completely empty, then it definitely does fall through.
if (Pred->empty())
return true;
// Here is the difference to the AsmPrinter method;
// We do not check properties of all terminator instructions
// (delay slot instructions do not have to be terminators),
// but instead check if the *last terminator* is an
// unconditional branch (no barrier)
MachineBasicBlock::const_iterator I = Pred->end();
// find last terminator
while (I != Pred->begin() && !(--I)->isTerminator()) ;
return I == Pred->end() || !I->isBarrier();
}
/// isBlockOnlyReachableByFallthough - Return true if the basic block has
/// exactly one predecessor and the control transfer mechanism between
/// the predecessor and this block is a fall-through.
// FIXME: could the overridden cases be handled in AnalyzeBranch?
bool OR1KAsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock*
MBB) const {
// The predecessor has to be immediately before this block.
const MachineBasicBlock *Pred = *MBB->pred_begin();
// If the predecessor is a switch statement, assume a jump table
// implementation, so it is not a fall through.
if (const BasicBlock *bb = Pred->getBasicBlock())
if (isa<SwitchInst>(bb->getTerminator()))
return false;
// Check default implementation
if (!AsmPrinter::isBlockOnlyReachableByFallthrough(MBB))
return false;
// Otherwise, check the last instruction.
// Check if the last terminator is an unconditional branch.
MachineBasicBlock::const_iterator I = Pred->end();
while (I != Pred->begin() && !(--I)->isTerminator()) ;
return !I->isBarrier();
}
/// isBlockOnlyReachableByFallthough - Return true if the basic block has
/// exactly one predecessor and the control transfer mechanism between
/// the predecessor and this block is a fall-through.
bool MipsAsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock*
MBB) const {
// The predecessor has to be immediately before this block.
const MachineBasicBlock *Pred = *MBB->pred_begin();
// If the predecessor is a switch statement, assume a jump table
// implementation, so it is not a fall through.
if (const BasicBlock *bb = Pred->getBasicBlock())
if (isa<SwitchInst>(bb->getTerminator()))
return false;
// If this is a landing pad, it isn't a fall through. If it has no preds,
// then nothing falls through to it.
if (MBB->isEHPad() || MBB->pred_empty())
return false;
// If there isn't exactly one predecessor, it can't be a fall through.
MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
++PI2;
if (PI2 != MBB->pred_end())
return false;
// The predecessor has to be immediately before this block.
if (!Pred->isLayoutSuccessor(MBB))
return false;
// If the block is completely empty, then it definitely does fall through.
if (Pred->empty())
return true;
// Otherwise, check the last instruction.
// Check if the last terminator is an unconditional branch.
MachineBasicBlock::const_iterator I = Pred->end();
while (I != Pred->begin() && !(--I)->isTerminator()) ;
return !I->isBarrier();
}