// 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;
// print - Output information about this region...
void print(std::ostream &OS) const;
+ void dump() const;
// Allow external access.
typedef ValueMapTy::iterator iterator;
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
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,
// 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
// 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;
}
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
//
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)));
}
}
-// 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
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); }
projects / oota-llvm.git / commitdiff