#define DEBUG_TYPE "strongphielim"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/BreakCriticalMachineEdge.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/Statistic.h"
static char ID; // Pass identification, replacement for typeid
StrongPHIElimination() : MachineFunctionPass((intptr_t)&ID) {}
- bool runOnMachineFunction(MachineFunction &Fn) {
- computeDFS(Fn);
-
-
- return false;
- }
-
+ bool runOnMachineFunction(MachineFunction &Fn);
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
AU.addPreservedID(PHIEliminationID);
AU.addRequired<MachineDominatorTree>();
+ AU.addRequired<LiveVariables>();
+ AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual void releaseMemory() {
preorder.clear();
maxpreorder.clear();
+
+ waiting.clear();
}
private:
struct DomForestNode {
private:
std::vector<DomForestNode*> children;
- MachineInstr* instr;
+ unsigned reg;
void addChild(DomForestNode* DFN) { children.push_back(DFN); }
public:
typedef std::vector<DomForestNode*>::iterator iterator;
- DomForestNode(MachineInstr* MI, DomForestNode* parent) : instr(MI) {
+ DomForestNode(unsigned r, DomForestNode* parent) : reg(r) {
if (parent)
parent->addChild(this);
}
- MachineInstr* getInstr() { return instr; }
+ ~DomForestNode() {
+ for (iterator I = begin(), E = end(); I != E; ++I)
+ delete *I;
+ }
+
+ inline unsigned getReg() { return reg; }
- DomForestNode::iterator begin() { return children.begin(); }
- DomForestNode::iterator end() { return children.end(); }
+ inline DomForestNode::iterator begin() { return children.begin(); }
+ inline DomForestNode::iterator end() { return children.end(); }
};
DenseMap<MachineBasicBlock*, unsigned> preorder;
DenseMap<MachineBasicBlock*, unsigned> maxpreorder;
+ DenseMap<MachineBasicBlock*, std::vector<MachineInstr*> > waiting;
+
+
void computeDFS(MachineFunction& MF);
+ void processBlock(MachineBasicBlock* MBB);
- std::vector<DomForestNode*>
- computeDomForest(SmallPtrSet<MachineInstr*, 8>& instrs);
+ std::vector<DomForestNode*> computeDomForest(std::set<unsigned>& instrs);
+ void breakCriticalEdges(MachineFunction &Fn);
};
}
}
+/// PreorderSorter - a helper class that is used to sort registers
+/// according to the preorder number of their defining blocks
class PreorderSorter {
private:
DenseMap<MachineBasicBlock*, unsigned>& preorder;
+ LiveVariables& LV;
public:
- PreorderSorter(DenseMap<MachineBasicBlock*, unsigned>& p) : preorder(p) { }
+ PreorderSorter(DenseMap<MachineBasicBlock*, unsigned>& p,
+ LiveVariables& L) : preorder(p), LV(L) { }
- bool operator()(MachineInstr* A, MachineInstr* B) {
+ bool operator()(unsigned A, unsigned B) {
if (A == B)
return false;
- if (preorder[A->getParent()] < preorder[B->getParent()])
+ MachineBasicBlock* ABlock = LV.getVarInfo(A).DefInst->getParent();
+ MachineBasicBlock* BBlock = LV.getVarInfo(A).DefInst->getParent();
+
+ if (preorder[ABlock] < preorder[BBlock])
return true;
- else if (preorder[A->getParent()] > preorder[B->getParent()])
+ else if (preorder[ABlock] > preorder[BBlock])
return false;
- if (A->getOpcode() == TargetInstrInfo::PHI &&
- B->getOpcode() == TargetInstrInfo::PHI)
- return A < B;
-
- MachineInstr* begin = A->getParent()->begin();
- return std::distance(begin, A) < std::distance(begin, B);
+ assert(0 && "Error sorting by dominance!");
+ return false;
}
};
+/// computeDomForest - compute the subforest of the DomTree corresponding
+/// to the defining blocks of the registers in question
std::vector<StrongPHIElimination::DomForestNode*>
-StrongPHIElimination::computeDomForest(SmallPtrSet<MachineInstr*, 8>& instrs) {
+StrongPHIElimination::computeDomForest(std::set<unsigned>& regs) {
+ LiveVariables& LV = getAnalysis<LiveVariables>();
+
DomForestNode* VirtualRoot = new DomForestNode(0, 0);
maxpreorder.insert(std::make_pair((MachineBasicBlock*)0, ~0UL));
- std::vector<MachineInstr*> worklist;
- worklist.reserve(instrs.size());
- for (SmallPtrSet<MachineInstr*, 8>::iterator I = instrs.begin(),
- E = instrs.end(); I != E; ++I)
+ std::vector<unsigned> worklist;
+ worklist.reserve(regs.size());
+ for (std::set<unsigned>::iterator I = regs.begin(), E = regs.end();
+ I != E; ++I)
worklist.push_back(*I);
- PreorderSorter PS(preorder);
+
+ PreorderSorter PS(preorder, LV);
std::sort(worklist.begin(), worklist.end(), PS);
DomForestNode* CurrentParent = VirtualRoot;
std::vector<DomForestNode*> stack;
stack.push_back(VirtualRoot);
- for (std::vector<MachineInstr*>::iterator I = worklist.begin(),
- E = worklist.end(); I != E; ++I) {
- while (preorder[(*I)->getParent()] >
- maxpreorder[CurrentParent->getInstr()->getParent()]) {
+ for (std::vector<unsigned>::iterator I = worklist.begin(), E = worklist.end();
+ I != E; ++I) {
+ unsigned pre = preorder[LV.getVarInfo(*I).DefInst->getParent()];
+ MachineBasicBlock* parentBlock =
+ LV.getVarInfo(CurrentParent->getReg()).DefInst->getParent();
+
+ while (pre > maxpreorder[parentBlock]) {
stack.pop_back();
CurrentParent = stack.back();
+
+ parentBlock = LV.getVarInfo(CurrentParent->getReg()).DefInst->getParent();
}
DomForestNode* child = new DomForestNode(*I, CurrentParent);
ret.insert(ret.end(), VirtualRoot->begin(), VirtualRoot->end());
return ret;
}
+
+/// isLiveIn - helper method that determines, from a VarInfo, if a register
+/// is live into a block
+bool isLiveIn(LiveVariables::VarInfo& V, MachineBasicBlock* MBB) {
+ if (V.AliveBlocks.test(MBB->getNumber()))
+ return true;
+
+ if (V.DefInst->getParent() != MBB &&
+ V.UsedBlocks.test(MBB->getNumber()))
+ return true;
+
+ return false;
+}
+
+/// isLiveOut - help method that determines, from a VarInfo, if a register is
+/// live out of a block.
+bool isLiveOut(LiveVariables::VarInfo& V, MachineBasicBlock* MBB) {
+ if (MBB == V.DefInst->getParent() ||
+ V.UsedBlocks.test(MBB->getNumber())) {
+ for (std::vector<MachineInstr*>::iterator I = V.Kills.begin(),
+ E = V.Kills.end(); I != E; ++I)
+ if ((*I)->getParent() == MBB)
+ return false;
+
+ return true;
+ }
+
+ return false;
+}
+
+/// processBlock - Eliminate PHIs in the given block
+void StrongPHIElimination::processBlock(MachineBasicBlock* MBB) {
+ LiveVariables& LV = getAnalysis<LiveVariables>();
+
+ // Holds names that have been added to a set in any PHI within this block
+ // before the current one.
+ std::set<unsigned> ProcessedNames;
+
+ MachineBasicBlock::iterator P = MBB->begin();
+ while (P->getOpcode() == TargetInstrInfo::PHI) {
+ LiveVariables::VarInfo& PHIInfo = LV.getVarInfo(P->getOperand(0).getReg());
+
+ // Hold the names that are currently in the candidate set.
+ std::set<unsigned> PHIUnion;
+ std::set<MachineBasicBlock*> UnionedBlocks;
+
+ for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
+ unsigned SrcReg = P->getOperand(i-1).getReg();
+ LiveVariables::VarInfo& SrcInfo = LV.getVarInfo(SrcReg);
+
+ if (isLiveIn(SrcInfo, P->getParent())) {
+ // add a copy from a_i to p in Waiting[From[a_i]]
+ } else if (isLiveOut(PHIInfo, SrcInfo.DefInst->getParent())) {
+ // add a copy to Waiting[From[a_i]]
+ } else if (PHIInfo.DefInst->getOpcode() == TargetInstrInfo::PHI &&
+ isLiveIn(PHIInfo, SrcInfo.DefInst->getParent())) {
+ // add a copy to Waiting[From[a_i]]
+ } else if (ProcessedNames.count(SrcReg)) {
+ // add a copy to Waiting[From[a_i]]
+ } else if (UnionedBlocks.count(SrcInfo.DefInst->getParent())) {
+ // add a copy to Waiting[From[a_i]]
+ } else {
+ PHIUnion.insert(SrcReg);
+ UnionedBlocks.insert(SrcInfo.DefInst->getParent());
+ }
+ }
+
+ std::vector<StrongPHIElimination::DomForestNode*> DF =
+ computeDomForest(PHIUnion);
+
+ // DO STUFF HERE
+
+ ProcessedNames.insert(PHIUnion.begin(), PHIUnion.end());
+ ++P;
+ }
+}
+
+/// breakCriticalEdges - Break critical edges coming into blocks with PHI
+/// nodes, preserving dominator and livevariable info.
+void StrongPHIElimination::breakCriticalEdges(MachineFunction &Fn) {
+ typedef std::pair<MachineBasicBlock*, MachineBasicBlock*> MBB_pair;
+
+ MachineDominatorTree& MDT = getAnalysis<MachineDominatorTree>();
+ LiveVariables& LV = getAnalysis<LiveVariables>();
+
+ // Find critical edges
+ std::vector<MBB_pair> criticals;
+ for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
+ if (!I->empty() &&
+ I->begin()->getOpcode() == TargetInstrInfo::PHI &&
+ I->pred_size() > 1)
+ for (MachineBasicBlock::pred_iterator PI = I->pred_begin(),
+ PE = I->pred_end(); PI != PE; ++PI)
+ if ((*PI)->succ_size() > 1)
+ criticals.push_back(std::make_pair(*PI, I));
+
+ for (std::vector<MBB_pair>::iterator I = criticals.begin(),
+ E = criticals.end(); I != E; ++I) {
+ // Split the edge
+ MachineBasicBlock* new_bb = SplitCriticalMachineEdge(I->first, I->second);
+
+ // Update dominators
+ MDT.splitBlock(I->first);
+
+ // Update livevariables
+ for (unsigned var = 1024; var < Fn.getSSARegMap()->getLastVirtReg(); ++var)
+ if (isLiveOut(LV.getVarInfo(var), I->first))
+ LV.getVarInfo(var).AliveBlocks.set(new_bb->getNumber());
+ }
+}
+
+bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
+ breakCriticalEdges(Fn);
+ computeDFS(Fn);
+
+ for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
+ if (!I->empty() &&
+ I->begin()->getOpcode() == TargetInstrInfo::PHI)
+ processBlock(I);
+
+ return false;
+}
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