diff options
| -rw-r--r-- | lib/Transforms/Scalar/CorrelatedExprs.cpp | 447 |
1 files changed, 394 insertions, 53 deletions
diff --git a/lib/Transforms/Scalar/CorrelatedExprs.cpp b/lib/Transforms/Scalar/CorrelatedExprs.cpp index 2ff504de6c..f8934f3033 100644 --- a/lib/Transforms/Scalar/CorrelatedExprs.cpp +++ b/lib/Transforms/Scalar/CorrelatedExprs.cpp @@ -167,6 +167,9 @@ namespace { // this region. BasicBlock *getEntryBlock() const { return BB; } + // empty - return true if this region has no information known about it. + bool empty() const { return ValueMap.empty(); } + const RegionInfo &operator=(const RegionInfo &RI) { ValueMap = RI.ValueMap; return *this; @@ -174,6 +177,7 @@ namespace { // print - Output information about this region... void print(std::ostream &OS) const; + void dump() const; // Allow external access. typedef ValueMapTy::iterator iterator; @@ -191,6 +195,13 @@ namespace { if (I != ValueMap.end()) return &I->second; return 0; } + + /// removeValueInfo - Remove anything known about V from our records. This + /// works whether or not we know anything about V. + /// + void removeValueInfo(Value *V) { + ValueMap.erase(V); + } }; /// CEE - Correlated Expression Elimination @@ -231,7 +242,18 @@ namespace { bool TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks); - BasicBlock *isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI); + bool ForwardCorrelatedEdgeDestination(TerminatorInst *TI, unsigned SuccNo, + RegionInfo &RI); + + void ForwardSuccessorTo(TerminatorInst *TI, unsigned Succ, BasicBlock *D, + RegionInfo &RI); + void ReplaceUsesOfValueInRegion(Value *Orig, Value *New, + BasicBlock *RegionDominator); + void CalculateRegionExitBlocks(BasicBlock *BB, BasicBlock *OldSucc, + std::vector<BasicBlock*> &RegionExitBlocks); + void InsertRegionExitMerges(PHINode *NewPHI, Instruction *OldVal, + const std::vector<BasicBlock*> &RegionExitBlocks); + void PropogateBranchInfo(BranchInst *BI); void PropogateEquality(Value *Op0, Value *Op1, RegionInfo &RI); void PropogateRelation(Instruction::BinaryOps Opcode, Value *Op0, @@ -313,12 +335,13 @@ bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){ // information down now. // DominatorTree::Node *BBN = (*DT)[BB]; - for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i) { - BasicBlock *Dominated = BBN->getChildren()[i]->getNode(); - assert(RegionInfoMap.find(Dominated) == RegionInfoMap.end() && - "RegionInfo should be calculated in dominanace order!"); - getRegionInfo(Dominated) = RI; - } + if (!RI.empty()) // Time opt: only propogate if we can change something + for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i) { + BasicBlock *Dominated = BBN->getChildren()[i]->getNode(); + assert(RegionInfoMap.find(Dominated) == RegionInfoMap.end() && + "RegionInfo should be calculated in dominanace order!"); + getRegionInfo(Dominated) = RI; + } // Now that all of our successors have information if they deserve it, // propogate any information our terminator instruction finds to our @@ -332,25 +355,7 @@ bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){ // region, then vector this outgoing edge directly to the known destination. // for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) - while (BasicBlock *Dest = isCorrelatedBranchBlock(TI->getSuccessor(i), RI)){ - // If there are any PHI nodes in the Dest BB, we must duplicate the entry - // in the PHI node for the old successor to now include an entry from the - // current basic block. - // - BasicBlock *OldSucc = TI->getSuccessor(i); - - // Loop over all of the PHI nodes... - for (BasicBlock::iterator I = Dest->begin(); - PHINode *PN = dyn_cast<PHINode>(&*I); ++I) { - // Find the entry in the PHI node for OldSucc, create a duplicate entry - // for BB now. - int BlockIndex = PN->getBasicBlockIndex(OldSucc); - assert(BlockIndex != -1 && "Block should have entry in PHI!"); - PN->addIncoming(PN->getIncomingValue(BlockIndex), BB); - } - - // Actually revector the branch now... - TI->setSuccessor(i, Dest); + while (ForwardCorrelatedEdgeDestination(TI, i, RI)) { ++BranchRevectors; Changed = true; } @@ -362,37 +367,374 @@ bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){ return Changed; } -// If this block is a simple block not in the current region, which contains -// only a conditional branch, we determine if the outcome of the branch can be -// determined from information inside of the region. Instead of going to this -// block, we can instead go to the destination we know is the right target. +// isBlockSimpleEnoughForCheck to see if the block is simple enough for us to +// revector the conditional branch in the bottom of the block, do so now. // -BasicBlock *CEE::isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI) { +static bool isBlockSimpleEnough(BasicBlock *BB) { + assert(isa<BranchInst>(BB->getTerminator())); + BranchInst *BI = cast<BranchInst>(BB->getTerminator()); + assert(BI->isConditional()); + + // Check the common case first: empty block, or block with just a setcc. + if (BB->size() == 1 || + (BB->size() == 2 && &BB->front() == BI->getCondition() && + BI->getCondition()->use_size() == 1)) + return true; + + // Check the more complex case now... + BasicBlock::iterator I = BB->begin(); + + // FIXME: This should be reenabled once the regression with SIM is fixed! +#if 0 + // PHI Nodes are ok, just skip over them... + while (isa<PHINode>(*I)) ++I; +#endif + + // Accept the setcc instruction... + if (&*I == BI->getCondition()) + ++I; + + // Nothing else is acceptable here yet. We must not revector... unless we are + // at the terminator instruction. + if (&*I == BI) + return true; + + return false; +} + + +bool CEE::ForwardCorrelatedEdgeDestination(TerminatorInst *TI, unsigned SuccNo, + RegionInfo &RI) { + // If this successor is a simple block not in the current region, which + // contains only a conditional branch, we decide if the outcome of the branch + // can be determined from information inside of the region. Instead of going + // to this block, we can instead go to the destination we know is the right + // target. + // + // Check to see if we dominate the block. If so, this block will get the // condition turned to a constant anyway. // //if (DS->dominates(RI.getEntryBlock(), BB)) // return 0; - // Check to see if this is a conditional branch... - if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) - if (BI->isConditional()) { - // Make sure that the block is either empty, or only contains a setcc. - if (BB->size() == 1 || - (BB->size() == 2 && &BB->front() == BI->getCondition() && - BI->getCondition()->use_size() == 1)) - if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition())) { - Relation::KnownResult Result = getSetCCResult(SCI, RI); - - if (Result == Relation::KnownTrue) - return BI->getSuccessor(0); - else if (Result == Relation::KnownFalse) - return BI->getSuccessor(1); - } + BasicBlock *BB = TI->getParent(); + + // Get the destination block of this edge... + BasicBlock *OldSucc = TI->getSuccessor(SuccNo); + + // Make sure that the block ends with a conditional branch and is simple + // enough for use to be able to revector over. + BranchInst *BI = dyn_cast<BranchInst>(OldSucc->getTerminator()); + if (BI == 0 || !BI->isConditional() || !isBlockSimpleEnough(OldSucc)) + return false; + + // We can only forward the branch over the block if the block ends with a + // setcc we can determine the outcome for. + // + // FIXME: we can make this more generic. Code below already handles more + // generic case. + SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition()); + if (SCI == 0) return false; + + // Make a new RegionInfo structure so that we can simulate the effect of the + // PHI nodes in the block we are skipping over... + // + RegionInfo NewRI(RI); + + // Remove value information for all of the values we are simulating... to make + // sure we don't have any stale information. + for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); I!=E; ++I) + if (I->getType() != Type::VoidTy) + NewRI.removeValueInfo(I); + + // Put the newly discovered information into the RegionInfo... + for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); I!=E; ++I) + if (PHINode *PN = dyn_cast<PHINode>(&*I)) { + int OpNum = PN->getBasicBlockIndex(BB); + assert(OpNum != -1 && "PHI doesn't have incoming edge for predecessor!?"); + PropogateEquality(PN, PN->getIncomingValue(OpNum), NewRI); + } else if (SetCondInst *SCI = dyn_cast<SetCondInst>(&*I)) { + Relation::KnownResult Res = getSetCCResult(SCI, NewRI); + if (Res == Relation::Unknown) return false; + PropogateEquality(SCI, ConstantBool::get(Res), NewRI); + } else { + assert(isa<BranchInst>(*I) && "Unexpected instruction type!"); + } + + // Compute the facts implied by what we have discovered... + ComputeReplacements(NewRI); + + ValueInfo &PredicateVI = NewRI.getValueInfo(BI->getCondition()); + if (PredicateVI.getReplacement() && + isa<Constant>(PredicateVI.getReplacement())) { + ConstantBool *CB = cast<ConstantBool>(PredicateVI.getReplacement()); + + // Forward to the successor that corresponds to the branch we will take. + ForwardSuccessorTo(TI, SuccNo, BI->getSuccessor(!CB->getValue()), NewRI); + return true; + } + + return false; +} + +static Value *getReplacementOrValue(Value *V, RegionInfo &RI) { + if (const ValueInfo *VI = RI.requestValueInfo(V)) + if (Value *Repl = VI->getReplacement()) + return Repl; + return V; +} + +/// ForwardSuccessorTo - We have found that we can forward successor # 'SuccNo' +/// of Terminator 'TI' to the 'Dest' BasicBlock. This method performs the +/// mechanics of updating SSA information and revectoring the branch. +/// +void CEE::ForwardSuccessorTo(TerminatorInst *TI, unsigned SuccNo, + BasicBlock *Dest, RegionInfo &RI) { + // If there are any PHI nodes in the Dest BB, we must duplicate the entry + // in the PHI node for the old successor to now include an entry from the + // current basic block. + // + BasicBlock *OldSucc = TI->getSuccessor(SuccNo); + BasicBlock *BB = TI->getParent(); + + DEBUG(std::cerr << "Forwarding branch in basic block %" << BB->getName() + << " from block %" << OldSucc->getName() << " to block %" + << Dest->getName() << "\n"); + + DEBUG(std::cerr << "Before forwarding: " << *BB->getParent()); + + // Because we know that there cannot be critical edges in the flow graph, and + // that OldSucc has multiple outgoing edges, this means that Dest cannot have + // multiple incoming edges. + // +#ifndef NDEBUG + pred_iterator DPI = pred_begin(Dest); ++DPI; + assert(DPI == pred_end(Dest) && "Critical edge found!!"); +#endif + + // Loop over any PHI nodes in the destination, eliminating them, because they + // may only have one input. + // + while (PHINode *PN = dyn_cast<PHINode>(&Dest->front())) { + assert(PN->getNumIncomingValues() == 1 && "Crit edge found!"); + // Eliminate the PHI node + PN->replaceAllUsesWith(PN->getIncomingValue(0)); + Dest->getInstList().erase(PN); + } + + // If there are values defined in the "OldSucc" basic block, we need to insert + // PHI nodes in the regions we are dealing with to emulate them. This can + // insert dead phi nodes, but it is more trouble to see if they are used than + // to just blindly insert them. + // + if (DS->dominates(OldSucc, Dest)) { + // RegionExitBlocks - Find all of the blocks that are not dominated by Dest, + // but have predecessors that are. Additionally, prune down the set to only + // include blocks that are dominated by OldSucc as well. + // + std::vector<BasicBlock*> RegionExitBlocks; + CalculateRegionExitBlocks(Dest, OldSucc, RegionExitBlocks); + + for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); + I != E; ++I) + if (I->getType() != Type::VoidTy) { + // Create and insert the PHI node into the top of Dest. + PHINode *NewPN = new PHINode(I->getType(), I->getName()+".fw_merge", + Dest->begin()); + // There is definately an edge from OldSucc... add the edge now + NewPN->addIncoming(I, OldSucc); + + // There is also an edge from BB now, add the edge with the calculated + // value from the RI. + NewPN->addIncoming(getReplacementOrValue(I, RI), BB); + + // Make everything in the Dest region use the new PHI node now... + ReplaceUsesOfValueInRegion(I, NewPN, Dest); + + // Make sure that exits out of the region dominated by NewPN get PHI + // nodes that merge the values as appropriate. + InsertRegionExitMerges(NewPN, I, RegionExitBlocks); + } + } + + // If there were PHI nodes in OldSucc, we need to remove the entry for this + // edge from the PHI node, and we need to replace any references to the PHI + // node with a new value. + // + for (BasicBlock::iterator I = OldSucc->begin(); + PHINode *PN = dyn_cast<PHINode>(&*I); ) { + + // Get the value flowing across the old edge and remove the PHI node entry + // for this edge: we are about to remove the edge! Don't remove the PHI + // node yet though if this is the last edge into it. + Value *EdgeValue = PN->removeIncomingValue(BB, false); + + // Make sure that anything that used to use PN now refers to EdgeValue + ReplaceUsesOfValueInRegion(PN, EdgeValue, Dest); + + // If there is only one value left coming into the PHI node, replace the PHI + // node itself with the one incoming value left. + // + if (PN->getNumIncomingValues() == 1) { + assert(PN->getNumIncomingValues() == 1); + PN->replaceAllUsesWith(PN->getIncomingValue(0)); + PN->getParent()->getInstList().erase(PN); + I = OldSucc->begin(); + } else if (PN->getNumIncomingValues() == 0) { // Nuke the PHI + // If we removed the last incoming value to this PHI, nuke the PHI node + // now. + PN->replaceAllUsesWith(Constant::getNullValue(PN->getType())); + PN->getParent()->getInstList().erase(PN); + I = OldSucc->begin(); + } else { + ++I; // Otherwise, move on to the next PHI node + } + } + + // Actually revector the branch now... + TI->setSuccessor(SuccNo, Dest); + + // If we just introduced a critical edge in the flow graph, make sure to break + // it right away... + if (isCriticalEdge(TI, SuccNo)) + SplitCriticalEdge(TI, SuccNo, this); + + // Make sure that we don't introduce critical edges from oldsucc now! + for (unsigned i = 0, e = OldSucc->getTerminator()->getNumSuccessors(); + i != e; ++i) + if (isCriticalEdge(OldSucc->getTerminator(), i)) + SplitCriticalEdge(OldSucc->getTerminator(), i, this); + + // Since we invalidated the CFG, recalculate the dominator set so that it is + // useful for later processing! + // FIXME: This is much worse than it really should be! + //DS->recalculate(); + + DEBUG(std::cerr << "After forwarding: " << *BB->getParent()); +} + +/// ReplaceUsesOfValueInRegion - This method replaces all uses of Orig with uses +/// of New. It only affects instructions that are defined in basic blocks that +/// are dominated by Head. +/// +void CEE::ReplaceUsesOfValueInRegion(Value *Orig, Value *New, + BasicBlock *RegionDominator) { + assert(Orig != New && "Cannot replace value with itself"); + std::vector<Instruction*> InstsToChange; + std::vector<PHINode*> PHIsToChange; + InstsToChange.reserve(Orig->use_size()); + + // Loop over instructions adding them to InstsToChange vector, this allows us + // an easy way to avoid invalidating the use_iterator at a bad time. + for (Value::use_iterator I = Orig->use_begin(), E = Orig->use_end(); + I != E; ++I) + if (Instruction *User = dyn_cast<Instruction>(*I)) + if (DS->dominates(RegionDominator, User->getParent())) + InstsToChange.push_back(User); + else if (PHINode *PN = dyn_cast<PHINode>(User)) { + PHIsToChange.push_back(PN); + } + + // PHIsToChange contains PHI nodes that use Orig that do not live in blocks + // dominated by orig. If the block the value flows in from is dominated by + // RegionDominator, then we rewrite the PHI + for (unsigned i = 0, e = PHIsToChange.size(); i != e; ++i) { + PHINode *PN = PHIsToChange[i]; + for (unsigned j = 0, e = PN->getNumIncomingValues(); j != e; ++j) + if (PN->getIncomingValue(j) == Orig && + DS->dominates(RegionDominator, PN->getIncomingBlock(j))) + PN->setIncomingValue(j, New); + } + + // Loop over the InstsToChange list, replacing all uses of Orig with uses of + // New. This list contains all of the instructions in our region that use + // Orig. + for (unsigned i = 0, e = InstsToChange.size(); i != e; ++i) + if (PHINode *PN = dyn_cast<PHINode>(InstsToChange[i])) { + // PHINodes must be handled carefully. If the PHI node itself is in the + // region, we have to make sure to only do the replacement for incoming + // values that correspond to basic blocks in the region. + for (unsigned j = 0, e = PN->getNumIncomingValues(); j != e; ++j) + if (PN->getIncomingValue(j) == Orig && + DS->dominates(RegionDominator, PN->getIncomingBlock(j))) + PN->setIncomingValue(j, New); + + } else { + InstsToChange[i]->replaceUsesOfWith(Orig, New); + } +} + +static void CalcRegionExitBlocks(BasicBlock *Header, BasicBlock *BB, + std::set<BasicBlock*> &Visited, + DominatorSet &DS, + std::vector<BasicBlock*> &RegionExitBlocks) { + if (Visited.count(BB)) return; + Visited.insert(BB); + + if (DS.dominates(Header, BB)) { // Block in the region, recursively traverse + for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) + CalcRegionExitBlocks(Header, *I, Visited, DS, RegionExitBlocks); + } else { + // Header does not dominate this block, but we have a predecessor that does + // dominate us. Add ourself to the list. + RegionExitBlocks.push_back(BB); + } +} + +/// CalculateRegionExitBlocks - Find all of the blocks that are not dominated by +/// BB, but have predecessors that are. Additionally, prune down the set to +/// only include blocks that are dominated by OldSucc as well. +/// +void CEE::CalculateRegionExitBlocks(BasicBlock *BB, BasicBlock *OldSucc, + std::vector<BasicBlock*> &RegionExitBlocks){ + std::set<BasicBlock*> Visited; // Don't infinite loop + + // Recursively calculate blocks we are interested in... + CalcRegionExitBlocks(BB, BB, Visited, *DS, RegionExitBlocks); + + // Filter out blocks that are not dominated by OldSucc... + for (unsigned i = 0; i != RegionExitBlocks.size(); ) { + if (DS->dominates(OldSucc, RegionExitBlocks[i])) + ++i; // Block is ok, keep it. + else { + // Move to end of list... + std::swap(RegionExitBlocks[i], RegionExitBlocks.back()); + RegionExitBlocks.pop_back(); // Nuke the end + } + } +} + +void CEE::InsertRegionExitMerges(PHINode *BBVal, Instruction *OldVal, + const std::vector<BasicBlock*> &RegionExitBlocks) { + assert(BBVal->getType() == OldVal->getType() && "Should be derived values!"); + BasicBlock *BB = BBVal->getParent(); + BasicBlock *OldSucc = OldVal->getParent(); + + // Loop over all of the blocks we have to place PHIs in, doing it. + for (unsigned i = 0, e = RegionExitBlocks.size(); i != e; ++i) { + BasicBlock *FBlock = RegionExitBlocks[i]; // Block on the frontier + + // Create the new PHI node + PHINode *NewPN = new PHINode(BBVal->getType(), + OldVal->getName()+".fw_frontier", + FBlock->begin()); + + // Add an incoming value for every predecessor of the block... + for (pred_iterator PI = pred_begin(FBlock), PE = pred_end(FBlock); + PI != PE; ++PI) { + // If the incoming edge is from the region dominated by BB, use BBVal, + // otherwise use OldVal. + NewPN->addIncoming(DS->dominates(BB, *PI) ? BBVal : OldVal, *PI); } - return 0; + + // Now make everyone dominated by this block use this new value! + ReplaceUsesOfValueInRegion(OldVal, NewPN, FBlock); + } } + + // BuildRankMap - This method builds the rank map data structure which gives // each instruction/value in the function a value based on how early it appears // in the function. We give constants and globals rank 0, arguments are @@ -425,19 +767,16 @@ void CEE::BuildRankMap(Function &F) { // void CEE::PropogateBranchInfo(BranchInst *BI) { assert(BI->isConditional() && "Must be a conditional branch!"); - BasicBlock *BB = BI->getParent(); - BasicBlock *TrueBB = BI->getSuccessor(0); - BasicBlock *FalseBB = BI->getSuccessor(1); // Propogate information into the true block... // PropogateEquality(BI->getCondition(), ConstantBool::True, - getRegionInfo(TrueBB)); + getRegionInfo(BI->getSuccessor(0))); // Propogate information into the false block... // PropogateEquality(BI->getCondition(), ConstantBool::False, - getRegionInfo(FalseBB)); + getRegionInfo(BI->getSuccessor(1))); } @@ -702,7 +1041,7 @@ bool CEE::SimplifyInstruction(Instruction *I, const RegionInfo &RI) { } -// SimplifySetCC - Try to simplify a setcc instruction based on information +// getSetCCResult - Try to simplify a setcc instruction based on information // inherited from a dominating setcc instruction. V is one of the operands to // the setcc instruction, and VI is the set of information known about it. We // take two cases into consideration here. If the comparison is against a @@ -965,5 +1304,7 @@ void Relation::print(std::ostream &OS) const { OS << "\n"; } +// Don't inline these methods or else we won't be able to call them from GDB! void Relation::dump() const { print(std::cerr); } void ValueInfo::dump() const { print(std::cerr, 0); } +void RegionInfo::dump() const { print(std::cerr); } |