- /// LoopDependencies - This class analyzes loop-oriented register
- /// dependencies, which are used to guide scheduling decisions.
- /// For example, loop induction variable increments should be
- /// scheduled as soon as possible after the variable's last use.
- ///
- class LoopDependencies {
- const MachineLoopInfo &MLI;
- const MachineDominatorTree &MDT;
-
- public:
- typedef std::map<unsigned, std::pair<const MachineOperand *, unsigned> >
- LoopDeps;
- LoopDeps Deps;
-
- LoopDependencies(const MachineLoopInfo &mli,
- const MachineDominatorTree &mdt) :
- MLI(mli), MDT(mdt) {}
-
- /// VisitLoop - Clear out any previous state and analyze the given loop.
- ///
- void VisitLoop(const MachineLoop *Loop) {
- assert(Deps.empty() && "stale loop dependencies");
-
- MachineBasicBlock *Header = Loop->getHeader();
- SmallSet<unsigned, 8> LoopLiveIns;
- for (MachineBasicBlock::livein_iterator LI = Header->livein_begin(),
- LE = Header->livein_end(); LI != LE; ++LI)
- LoopLiveIns.insert(*LI);
-
- const MachineDomTreeNode *Node = MDT.getNode(Header);
- const MachineBasicBlock *MBB = Node->getBlock();
- assert(Loop->contains(MBB) &&
- "Loop does not contain header!");
- VisitRegion(Node, MBB, Loop, LoopLiveIns);
- }
-
- private:
- void VisitRegion(const MachineDomTreeNode *Node,
- const MachineBasicBlock *MBB,
- const MachineLoop *Loop,
- const SmallSet<unsigned, 8> &LoopLiveIns) {
- unsigned Count = 0;
- for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end();
- I != E; ++I) {
- const MachineInstr *MI = I;
- if (MI->isDebugValue())
- continue;
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || !MO.isUse())
- continue;
- unsigned MOReg = MO.getReg();
- if (LoopLiveIns.count(MOReg))
- Deps.insert(std::make_pair(MOReg, std::make_pair(&MO, Count)));
- }
- ++Count; // Not every iteration due to dbg_value above.
- }
-
- const std::vector<MachineDomTreeNode*> &Children = Node->getChildren();
- for (std::vector<MachineDomTreeNode*>::const_iterator I =
- Children.begin(), E = Children.end(); I != E; ++I) {
- const MachineDomTreeNode *ChildNode = *I;
- MachineBasicBlock *ChildBlock = ChildNode->getBlock();
- if (Loop->contains(ChildBlock))
- VisitRegion(ChildNode, ChildBlock, Loop, LoopLiveIns);
- }
- }
- };
-