+#define DEBUG_TYPE "phielim"
+
+static cl::opt<bool>
+DisableEdgeSplitting("disable-phi-elim-edge-splitting", cl::init(false),
+ cl::Hidden, cl::desc("Disable critical edge splitting "
+ "during PHI elimination"));
+
+static cl::opt<bool>
+SplitAllCriticalEdges("phi-elim-split-all-critical-edges", cl::init(false),
+ cl::Hidden, cl::desc("Split all critical edges during "
+ "PHI elimination"));
+
+static cl::opt<bool> NoPhiElimLiveOutEarlyExit(
+ "no-phi-elim-live-out-early-exit", cl::init(false), cl::Hidden,
+ cl::desc("Do not use an early exit if isLiveOutPastPHIs returns true."));
+
+namespace {
+ class PHIElimination : public MachineFunctionPass {
+ MachineRegisterInfo *MRI; // Machine register information
+ LiveVariables *LV;
+ LiveIntervals *LIS;
+
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ PHIElimination() : MachineFunctionPass(ID) {
+ initializePHIEliminationPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnMachineFunction(MachineFunction &Fn) override;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+ private:
+ /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
+ /// in predecessor basic blocks.
+ ///
+ bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
+ void LowerPHINode(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator LastPHIIt);
+
+ /// analyzePHINodes - Gather information about the PHI nodes in
+ /// here. In particular, we want to map the number of uses of a virtual
+ /// register which is used in a PHI node. We map that to the BB the
+ /// vreg is coming from. This is used later to determine when the vreg
+ /// is killed in the BB.
+ ///
+ void analyzePHINodes(const MachineFunction& Fn);
+
+ /// Split critical edges where necessary for good coalescer performance.
+ bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
+ MachineLoopInfo *MLI);
+
+ // These functions are temporary abstractions around LiveVariables and
+ // LiveIntervals, so they can go away when LiveVariables does.
+ bool isLiveIn(unsigned Reg, const MachineBasicBlock *MBB);
+ bool isLiveOutPastPHIs(unsigned Reg, const MachineBasicBlock *MBB);
+
+ typedef std::pair<unsigned, unsigned> BBVRegPair;
+ typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse;
+
+ VRegPHIUse VRegPHIUseCount;
+
+ // Defs of PHI sources which are implicit_def.
+ SmallPtrSet<MachineInstr*, 4> ImpDefs;
+
+ // Map reusable lowered PHI node -> incoming join register.
+ typedef DenseMap<MachineInstr*, unsigned,
+ MachineInstrExpressionTrait> LoweredPHIMap;
+ LoweredPHIMap LoweredPHIs;
+ };
+}
+
+STATISTIC(NumLowered, "Number of phis lowered");
+STATISTIC(NumCriticalEdgesSplit, "Number of critical edges split");