Move StructurizeCFG out of R600 to generic Transforms.
Register it with PassManager
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184343 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/CMakeLists.txt b/lib/Transforms/Scalar/CMakeLists.txt
index fd55e08..aeddf78 100644
--- a/lib/Transforms/Scalar/CMakeLists.txt
+++ b/lib/Transforms/Scalar/CMakeLists.txt
@@ -30,6 +30,7 @@
SimplifyCFGPass.cpp
SimplifyLibCalls.cpp
Sink.cpp
+ StructurizeCFG.cpp
TailRecursionElimination.cpp
)
diff --git a/lib/Transforms/Scalar/Scalar.cpp b/lib/Transforms/Scalar/Scalar.cpp
index 8a9c7da..5f57f77 100644
--- a/lib/Transforms/Scalar/Scalar.cpp
+++ b/lib/Transforms/Scalar/Scalar.cpp
@@ -58,6 +58,7 @@
initializeSROA_DTPass(Registry);
initializeSROA_SSAUpPass(Registry);
initializeCFGSimplifyPassPass(Registry);
+ initializeStructurizeCFGPass(Registry);
initializeSimplifyLibCallsPass(Registry);
initializeSinkingPass(Registry);
initializeTailCallElimPass(Registry);
diff --git a/lib/Transforms/Scalar/StructurizeCFG.cpp b/lib/Transforms/Scalar/StructurizeCFG.cpp
new file mode 100644
index 0000000..bec066b
--- /dev/null
+++ b/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -0,0 +1,879 @@
+//===-- StructurizeCFG.cpp ------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "structurizecfg"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/Analysis/RegionInfo.h"
+#include "llvm/Analysis/RegionIterator.h"
+#include "llvm/Analysis/RegionPass.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/PatternMatch.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
+
+using namespace llvm;
+using namespace llvm::PatternMatch;
+
+namespace {
+
+// Definition of the complex types used in this pass.
+
+typedef std::pair<BasicBlock *, Value *> BBValuePair;
+
+typedef SmallVector<RegionNode*, 8> RNVector;
+typedef SmallVector<BasicBlock*, 8> BBVector;
+typedef SmallVector<BranchInst*, 8> BranchVector;
+typedef SmallVector<BBValuePair, 2> BBValueVector;
+
+typedef SmallPtrSet<BasicBlock *, 8> BBSet;
+
+typedef MapVector<PHINode *, BBValueVector> PhiMap;
+typedef MapVector<BasicBlock *, BBVector> BB2BBVecMap;
+
+typedef DenseMap<DomTreeNode *, unsigned> DTN2UnsignedMap;
+typedef DenseMap<BasicBlock *, PhiMap> BBPhiMap;
+typedef DenseMap<BasicBlock *, Value *> BBPredicates;
+typedef DenseMap<BasicBlock *, BBPredicates> PredMap;
+typedef DenseMap<BasicBlock *, BasicBlock*> BB2BBMap;
+
+// The name for newly created blocks.
+
+static const char *FlowBlockName = "Flow";
+
+/// @brief Find the nearest common dominator for multiple BasicBlocks
+///
+/// Helper class for StructurizeCFG
+/// TODO: Maybe move into common code
+class NearestCommonDominator {
+ DominatorTree *DT;
+
+ DTN2UnsignedMap IndexMap;
+
+ BasicBlock *Result;
+ unsigned ResultIndex;
+ bool ExplicitMentioned;
+
+public:
+ /// \brief Start a new query
+ NearestCommonDominator(DominatorTree *DomTree) {
+ DT = DomTree;
+ Result = 0;
+ }
+
+ /// \brief Add BB to the resulting dominator
+ void addBlock(BasicBlock *BB, bool Remember = true) {
+ DomTreeNode *Node = DT->getNode(BB);
+
+ if (Result == 0) {
+ unsigned Numbering = 0;
+ for (;Node;Node = Node->getIDom())
+ IndexMap[Node] = ++Numbering;
+ Result = BB;
+ ResultIndex = 1;
+ ExplicitMentioned = Remember;
+ return;
+ }
+
+ for (;Node;Node = Node->getIDom())
+ if (IndexMap.count(Node))
+ break;
+ else
+ IndexMap[Node] = 0;
+
+ assert(Node && "Dominator tree invalid!");
+
+ unsigned Numbering = IndexMap[Node];
+ if (Numbering > ResultIndex) {
+ Result = Node->getBlock();
+ ResultIndex = Numbering;
+ ExplicitMentioned = Remember && (Result == BB);
+ } else if (Numbering == ResultIndex) {
+ ExplicitMentioned |= Remember;
+ }
+ }
+
+ /// \brief Is "Result" one of the BBs added with "Remember" = True?
+ bool wasResultExplicitMentioned() {
+ return ExplicitMentioned;
+ }
+
+ /// \brief Get the query result
+ BasicBlock *getResult() {
+ return Result;
+ }
+};
+
+/// @brief Transforms the control flow graph on one single entry/exit region
+/// at a time.
+///
+/// After the transform all "If"/"Then"/"Else" style control flow looks like
+/// this:
+///
+/// \verbatim
+/// 1
+/// ||
+/// | |
+/// 2 |
+/// | /
+/// |/
+/// 3
+/// || Where:
+/// | | 1 = "If" block, calculates the condition
+/// 4 | 2 = "Then" subregion, runs if the condition is true
+/// | / 3 = "Flow" blocks, newly inserted flow blocks, rejoins the flow
+/// |/ 4 = "Else" optional subregion, runs if the condition is false
+/// 5 5 = "End" block, also rejoins the control flow
+/// \endverbatim
+///
+/// Control flow is expressed as a branch where the true exit goes into the
+/// "Then"/"Else" region, while the false exit skips the region
+/// The condition for the optional "Else" region is expressed as a PHI node.
+/// The incomming values of the PHI node are true for the "If" edge and false
+/// for the "Then" edge.
+///
+/// Additionally to that even complicated loops look like this:
+///
+/// \verbatim
+/// 1
+/// ||
+/// | |
+/// 2 ^ Where:
+/// | / 1 = "Entry" block
+/// |/ 2 = "Loop" optional subregion, with all exits at "Flow" block
+/// 3 3 = "Flow" block, with back edge to entry block
+/// |
+/// \endverbatim
+///
+/// The back edge of the "Flow" block is always on the false side of the branch
+/// while the true side continues the general flow. So the loop condition
+/// consist of a network of PHI nodes where the true incoming values expresses
+/// breaks and the false values expresses continue states.
+class StructurizeCFG : public RegionPass {
+ Type *Boolean;
+ ConstantInt *BoolTrue;
+ ConstantInt *BoolFalse;
+ UndefValue *BoolUndef;
+
+ Function *Func;
+ Region *ParentRegion;
+
+ DominatorTree *DT;
+
+ RNVector Order;
+ BBSet Visited;
+
+ BBPhiMap DeletedPhis;
+ BB2BBVecMap AddedPhis;
+
+ PredMap Predicates;
+ BranchVector Conditions;
+
+ BB2BBMap Loops;
+ PredMap LoopPreds;
+ BranchVector LoopConds;
+
+ RegionNode *PrevNode;
+
+ void orderNodes();
+
+ void analyzeLoops(RegionNode *N);
+
+ Value *invert(Value *Condition);
+
+ Value *buildCondition(BranchInst *Term, unsigned Idx, bool Invert);
+
+ void gatherPredicates(RegionNode *N);
+
+ void collectInfos();
+
+ void insertConditions(bool Loops);
+
+ void delPhiValues(BasicBlock *From, BasicBlock *To);
+
+ void addPhiValues(BasicBlock *From, BasicBlock *To);
+
+ void setPhiValues();
+
+ void killTerminator(BasicBlock *BB);
+
+ void changeExit(RegionNode *Node, BasicBlock *NewExit,
+ bool IncludeDominator);
+
+ BasicBlock *getNextFlow(BasicBlock *Dominator);
+
+ BasicBlock *needPrefix(bool NeedEmpty);
+
+ BasicBlock *needPostfix(BasicBlock *Flow, bool ExitUseAllowed);
+
+ void setPrevNode(BasicBlock *BB);
+
+ bool dominatesPredicates(BasicBlock *BB, RegionNode *Node);
+
+ bool isPredictableTrue(RegionNode *Node);
+
+ void wireFlow(bool ExitUseAllowed, BasicBlock *LoopEnd);
+
+ void handleLoops(bool ExitUseAllowed, BasicBlock *LoopEnd);
+
+ void createFlow();
+
+ void rebuildSSA();
+
+public:
+ static char ID;
+
+ StructurizeCFG() :
+ RegionPass(ID) {
+ initializeRegionInfoPass(*PassRegistry::getPassRegistry());
+ }
+
+ using Pass::doInitialization;
+ virtual bool doInitialization(Region *R, RGPassManager &RGM);
+
+ virtual bool runOnRegion(Region *R, RGPassManager &RGM);
+
+ virtual const char *getPassName() const {
+ return "Structurize control flow";
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<DominatorTree>();
+ AU.addPreserved<DominatorTree>();
+ RegionPass::getAnalysisUsage(AU);
+ }
+};
+
+} // end anonymous namespace
+
+char StructurizeCFG::ID = 0;
+
+INITIALIZE_PASS_BEGIN(StructurizeCFG, "structurizecfg", "Structurize the CFG",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(RegionInfo)
+INITIALIZE_PASS_END(StructurizeCFG, "structurizecfg", "Structurize the CFG",
+ false, false)
+
+/// \brief Initialize the types and constants used in the pass
+bool StructurizeCFG::doInitialization(Region *R, RGPassManager &RGM) {
+ LLVMContext &Context = R->getEntry()->getContext();
+
+ Boolean = Type::getInt1Ty(Context);
+ BoolTrue = ConstantInt::getTrue(Context);
+ BoolFalse = ConstantInt::getFalse(Context);
+ BoolUndef = UndefValue::get(Boolean);
+
+ return false;
+}
+
+/// \brief Build up the general order of nodes
+void StructurizeCFG::orderNodes() {
+ scc_iterator<Region *> I = scc_begin(ParentRegion),
+ E = scc_end(ParentRegion);
+ for (Order.clear(); I != E; ++I) {
+ std::vector<RegionNode *> &Nodes = *I;
+ Order.append(Nodes.begin(), Nodes.end());
+ }
+}
+
+/// \brief Determine the end of the loops
+void StructurizeCFG::analyzeLoops(RegionNode *N) {
+ if (N->isSubRegion()) {
+ // Test for exit as back edge
+ BasicBlock *Exit = N->getNodeAs<Region>()->getExit();
+ if (Visited.count(Exit))
+ Loops[Exit] = N->getEntry();
+
+ } else {
+ // Test for sucessors as back edge
+ BasicBlock *BB = N->getNodeAs<BasicBlock>();
+ BranchInst *Term = cast<BranchInst>(BB->getTerminator());
+
+ for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
+ BasicBlock *Succ = Term->getSuccessor(i);
+
+ if (Visited.count(Succ))
+ Loops[Succ] = BB;
+ }
+ }
+}
+
+/// \brief Invert the given condition
+Value *StructurizeCFG::invert(Value *Condition) {
+ // First: Check if it's a constant
+ if (Condition == BoolTrue)
+ return BoolFalse;
+
+ if (Condition == BoolFalse)
+ return BoolTrue;
+
+ if (Condition == BoolUndef)
+ return BoolUndef;
+
+ // Second: If the condition is already inverted, return the original value
+ if (match(Condition, m_Not(m_Value(Condition))))
+ return Condition;
+
+ // Third: Check all the users for an invert
+ BasicBlock *Parent = cast<Instruction>(Condition)->getParent();
+ for (Value::use_iterator I = Condition->use_begin(),
+ E = Condition->use_end(); I != E; ++I) {
+
+ Instruction *User = dyn_cast<Instruction>(*I);
+ if (!User || User->getParent() != Parent)
+ continue;
+
+ if (match(*I, m_Not(m_Specific(Condition))))
+ return *I;
+ }
+
+ // Last option: Create a new instruction
+ return BinaryOperator::CreateNot(Condition, "", Parent->getTerminator());
+}
+
+/// \brief Build the condition for one edge
+Value *StructurizeCFG::buildCondition(BranchInst *Term, unsigned Idx,
+ bool Invert) {
+ Value *Cond = Invert ? BoolFalse : BoolTrue;
+ if (Term->isConditional()) {
+ Cond = Term->getCondition();
+
+ if (Idx != (unsigned)Invert)
+ Cond = invert(Cond);
+ }
+ return Cond;
+}
+
+/// \brief Analyze the predecessors of each block and build up predicates
+void StructurizeCFG::gatherPredicates(RegionNode *N) {
+ RegionInfo *RI = ParentRegion->getRegionInfo();
+ BasicBlock *BB = N->getEntry();
+ BBPredicates &Pred = Predicates[BB];
+ BBPredicates &LPred = LoopPreds[BB];
+
+ for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
+ PI != PE; ++PI) {
+
+ // Ignore it if it's a branch from outside into our region entry
+ if (!ParentRegion->contains(*PI))
+ continue;
+
+ Region *R = RI->getRegionFor(*PI);
+ if (R == ParentRegion) {
+
+ // It's a top level block in our region
+ BranchInst *Term = cast<BranchInst>((*PI)->getTerminator());
+ for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
+ BasicBlock *Succ = Term->getSuccessor(i);
+ if (Succ != BB)
+ continue;
+
+ if (Visited.count(*PI)) {
+ // Normal forward edge
+ if (Term->isConditional()) {
+ // Try to treat it like an ELSE block
+ BasicBlock *Other = Term->getSuccessor(!i);
+ if (Visited.count(Other) && !Loops.count(Other) &&
+ !Pred.count(Other) && !Pred.count(*PI)) {
+
+ Pred[Other] = BoolFalse;
+ Pred[*PI] = BoolTrue;
+ continue;
+ }
+ }
+ Pred[*PI] = buildCondition(Term, i, false);
+
+ } else {
+ // Back edge
+ LPred[*PI] = buildCondition(Term, i, true);
+ }
+ }
+
+ } else {
+
+ // It's an exit from a sub region
+ while(R->getParent() != ParentRegion)
+ R = R->getParent();
+
+ // Edge from inside a subregion to its entry, ignore it
+ if (R == N)
+ continue;
+
+ BasicBlock *Entry = R->getEntry();
+ if (Visited.count(Entry))
+ Pred[Entry] = BoolTrue;
+ else
+ LPred[Entry] = BoolFalse;
+ }
+ }
+}
+
+/// \brief Collect various loop and predicate infos
+void StructurizeCFG::collectInfos() {
+ // Reset predicate
+ Predicates.clear();
+
+ // and loop infos
+ Loops.clear();
+ LoopPreds.clear();
+
+ // Reset the visited nodes
+ Visited.clear();
+
+ for (RNVector::reverse_iterator OI = Order.rbegin(), OE = Order.rend();
+ OI != OE; ++OI) {
+
+ // Analyze all the conditions leading to a node
+ gatherPredicates(*OI);
+
+ // Remember that we've seen this node
+ Visited.insert((*OI)->getEntry());
+
+ // Find the last back edges
+ analyzeLoops(*OI);
+ }
+}
+
+/// \brief Insert the missing branch conditions
+void StructurizeCFG::insertConditions(bool Loops) {
+ BranchVector &Conds = Loops ? LoopConds : Conditions;
+ Value *Default = Loops ? BoolTrue : BoolFalse;
+ SSAUpdater PhiInserter;
+
+ for (BranchVector::iterator I = Conds.begin(),
+ E = Conds.end(); I != E; ++I) {
+
+ BranchInst *Term = *I;
+ assert(Term->isConditional());
+
+ BasicBlock *Parent = Term->getParent();
+ BasicBlock *SuccTrue = Term->getSuccessor(0);
+ BasicBlock *SuccFalse = Term->getSuccessor(1);
+
+ PhiInserter.Initialize(Boolean, "");
+ PhiInserter.AddAvailableValue(&Func->getEntryBlock(), Default);
+ PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);
+
+ BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];
+
+ NearestCommonDominator Dominator(DT);
+ Dominator.addBlock(Parent, false);
+
+ Value *ParentValue = 0;
+ for (BBPredicates::iterator PI = Preds.begin(), PE = Preds.end();
+ PI != PE; ++PI) {
+
+ if (PI->first == Parent) {
+ ParentValue = PI->second;
+ break;
+ }
+ PhiInserter.AddAvailableValue(PI->first, PI->second);
+ Dominator.addBlock(PI->first);
+ }
+
+ if (ParentValue) {
+ Term->setCondition(ParentValue);
+ } else {
+ if (!Dominator.wasResultExplicitMentioned())
+ PhiInserter.AddAvailableValue(Dominator.getResult(), Default);
+
+ Term->setCondition(PhiInserter.GetValueInMiddleOfBlock(Parent));
+ }
+ }
+}
+
+/// \brief Remove all PHI values coming from "From" into "To" and remember
+/// them in DeletedPhis
+void StructurizeCFG::delPhiValues(BasicBlock *From, BasicBlock *To) {
+ PhiMap &Map = DeletedPhis[To];
+ for (BasicBlock::iterator I = To->begin(), E = To->end();
+ I != E && isa<PHINode>(*I);) {
+
+ PHINode &Phi = cast<PHINode>(*I++);
+ while (Phi.getBasicBlockIndex(From) != -1) {
+ Value *Deleted = Phi.removeIncomingValue(From, false);
+ Map[&Phi].push_back(std::make_pair(From, Deleted));
+ }
+ }
+}
+
+/// \brief Add a dummy PHI value as soon as we knew the new predecessor
+void StructurizeCFG::addPhiValues(BasicBlock *From, BasicBlock *To) {
+ for (BasicBlock::iterator I = To->begin(), E = To->end();
+ I != E && isa<PHINode>(*I);) {
+
+ PHINode &Phi = cast<PHINode>(*I++);
+ Value *Undef = UndefValue::get(Phi.getType());
+ Phi.addIncoming(Undef, From);
+ }
+ AddedPhis[To].push_back(From);
+}
+
+/// \brief Add the real PHI value as soon as everything is set up
+void StructurizeCFG::setPhiValues() {
+ SSAUpdater Updater;
+ for (BB2BBVecMap::iterator AI = AddedPhis.begin(), AE = AddedPhis.end();
+ AI != AE; ++AI) {
+
+ BasicBlock *To = AI->first;
+ BBVector &From = AI->second;
+
+ if (!DeletedPhis.count(To))
+ continue;
+
+ PhiMap &Map = DeletedPhis[To];
+ for (PhiMap::iterator PI = Map.begin(), PE = Map.end();
+ PI != PE; ++PI) {
+
+ PHINode *Phi = PI->first;
+ Value *Undef = UndefValue::get(Phi->getType());
+ Updater.Initialize(Phi->getType(), "");
+ Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
+ Updater.AddAvailableValue(To, Undef);
+
+ NearestCommonDominator Dominator(DT);
+ Dominator.addBlock(To, false);
+ for (BBValueVector::iterator VI = PI->second.begin(),
+ VE = PI->second.end(); VI != VE; ++VI) {
+
+ Updater.AddAvailableValue(VI->first, VI->second);
+ Dominator.addBlock(VI->first);
+ }
+
+ if (!Dominator.wasResultExplicitMentioned())
+ Updater.AddAvailableValue(Dominator.getResult(), Undef);
+
+ for (BBVector::iterator FI = From.begin(), FE = From.end();
+ FI != FE; ++FI) {
+
+ int Idx = Phi->getBasicBlockIndex(*FI);
+ assert(Idx != -1);
+ Phi->setIncomingValue(Idx, Updater.GetValueAtEndOfBlock(*FI));
+ }
+ }
+
+ DeletedPhis.erase(To);
+ }
+ assert(DeletedPhis.empty());
+}
+
+/// \brief Remove phi values from all successors and then remove the terminator.
+void StructurizeCFG::killTerminator(BasicBlock *BB) {
+ TerminatorInst *Term = BB->getTerminator();
+ if (!Term)
+ return;
+
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
+ SI != SE; ++SI) {
+
+ delPhiValues(BB, *SI);
+ }
+
+ Term->eraseFromParent();
+}
+
+/// \brief Let node exit(s) point to NewExit
+void StructurizeCFG::changeExit(RegionNode *Node, BasicBlock *NewExit,
+ bool IncludeDominator) {
+ if (Node->isSubRegion()) {
+ Region *SubRegion = Node->getNodeAs<Region>();
+ BasicBlock *OldExit = SubRegion->getExit();
+ BasicBlock *Dominator = 0;
+
+ // Find all the edges from the sub region to the exit
+ for (pred_iterator I = pred_begin(OldExit), E = pred_end(OldExit);
+ I != E;) {
+
+ BasicBlock *BB = *I++;
+ if (!SubRegion->contains(BB))
+ continue;
+
+ // Modify the edges to point to the new exit
+ delPhiValues(BB, OldExit);
+ BB->getTerminator()->replaceUsesOfWith(OldExit, NewExit);
+ addPhiValues(BB, NewExit);
+
+ // Find the new dominator (if requested)
+ if (IncludeDominator) {
+ if (!Dominator)
+ Dominator = BB;
+ else
+ Dominator = DT->findNearestCommonDominator(Dominator, BB);
+ }
+ }
+
+ // Change the dominator (if requested)
+ if (Dominator)
+ DT->changeImmediateDominator(NewExit, Dominator);
+
+ // Update the region info
+ SubRegion->replaceExit(NewExit);
+
+ } else {
+ BasicBlock *BB = Node->getNodeAs<BasicBlock>();
+ killTerminator(BB);
+ BranchInst::Create(NewExit, BB);
+ addPhiValues(BB, NewExit);
+ if (IncludeDominator)
+ DT->changeImmediateDominator(NewExit, BB);
+ }
+}
+
+/// \brief Create a new flow node and update dominator tree and region info
+BasicBlock *StructurizeCFG::getNextFlow(BasicBlock *Dominator) {
+ LLVMContext &Context = Func->getContext();
+ BasicBlock *Insert = Order.empty() ? ParentRegion->getExit() :
+ Order.back()->getEntry();
+ BasicBlock *Flow = BasicBlock::Create(Context, FlowBlockName,
+ Func, Insert);
+ DT->addNewBlock(Flow, Dominator);
+ ParentRegion->getRegionInfo()->setRegionFor(Flow, ParentRegion);
+ return Flow;
+}
+
+/// \brief Create a new or reuse the previous node as flow node
+BasicBlock *StructurizeCFG::needPrefix(bool NeedEmpty) {
+ BasicBlock *Entry = PrevNode->getEntry();
+
+ if (!PrevNode->isSubRegion()) {
+ killTerminator(Entry);
+ if (!NeedEmpty || Entry->getFirstInsertionPt() == Entry->end())
+ return Entry;
+
+ }
+
+ // create a new flow node
+ BasicBlock *Flow = getNextFlow(Entry);
+
+ // and wire it up
+ changeExit(PrevNode, Flow, true);
+ PrevNode = ParentRegion->getBBNode(Flow);
+ return Flow;
+}
+
+/// \brief Returns the region exit if possible, otherwise just a new flow node
+BasicBlock *StructurizeCFG::needPostfix(BasicBlock *Flow,
+ bool ExitUseAllowed) {
+ if (Order.empty() && ExitUseAllowed) {
+ BasicBlock *Exit = ParentRegion->getExit();
+ DT->changeImmediateDominator(Exit, Flow);
+ addPhiValues(Flow, Exit);
+ return Exit;
+ }
+ return getNextFlow(Flow);
+}
+
+/// \brief Set the previous node
+void StructurizeCFG::setPrevNode(BasicBlock *BB) {
+ PrevNode = ParentRegion->contains(BB) ? ParentRegion->getBBNode(BB) : 0;
+}
+
+/// \brief Does BB dominate all the predicates of Node ?
+bool StructurizeCFG::dominatesPredicates(BasicBlock *BB, RegionNode *Node) {
+ BBPredicates &Preds = Predicates[Node->getEntry()];
+ for (BBPredicates::iterator PI = Preds.begin(), PE = Preds.end();
+ PI != PE; ++PI) {
+
+ if (!DT->dominates(BB, PI->first))
+ return false;
+ }
+ return true;
+}
+
+/// \brief Can we predict that this node will always be called?
+bool StructurizeCFG::isPredictableTrue(RegionNode *Node) {
+ BBPredicates &Preds = Predicates[Node->getEntry()];
+ bool Dominated = false;
+
+ // Regionentry is always true
+ if (PrevNode == 0)
+ return true;
+
+ for (BBPredicates::iterator I = Preds.begin(), E = Preds.end();
+ I != E; ++I) {
+
+ if (I->second != BoolTrue)
+ return false;
+
+ if (!Dominated && DT->dominates(I->first, PrevNode->getEntry()))
+ Dominated = true;
+ }
+
+ // TODO: The dominator check is too strict
+ return Dominated;
+}
+
+/// Take one node from the order vector and wire it up
+void StructurizeCFG::wireFlow(bool ExitUseAllowed,
+ BasicBlock *LoopEnd) {
+ RegionNode *Node = Order.pop_back_val();
+ Visited.insert(Node->getEntry());
+
+ if (isPredictableTrue(Node)) {
+ // Just a linear flow
+ if (PrevNode) {
+ changeExit(PrevNode, Node->getEntry(), true);
+ }
+ PrevNode = Node;
+
+ } else {
+ // Insert extra prefix node (or reuse last one)
+ BasicBlock *Flow = needPrefix(false);
+
+ // Insert extra postfix node (or use exit instead)
+ BasicBlock *Entry = Node->getEntry();
+ BasicBlock *Next = needPostfix(Flow, ExitUseAllowed);
+
+ // let it point to entry and next block
+ Conditions.push_back(BranchInst::Create(Entry, Next, BoolUndef, Flow));
+ addPhiValues(Flow, Entry);
+ DT->changeImmediateDominator(Entry, Flow);
+
+ PrevNode = Node;
+ while (!Order.empty() && !Visited.count(LoopEnd) &&
+ dominatesPredicates(Entry, Order.back())) {
+ handleLoops(false, LoopEnd);
+ }
+
+ changeExit(PrevNode, Next, false);
+ setPrevNode(Next);
+ }
+}
+
+void StructurizeCFG::handleLoops(bool ExitUseAllowed,
+ BasicBlock *LoopEnd) {
+ RegionNode *Node = Order.back();
+ BasicBlock *LoopStart = Node->getEntry();
+
+ if (!Loops.count(LoopStart)) {
+ wireFlow(ExitUseAllowed, LoopEnd);
+ return;
+ }
+
+ if (!isPredictableTrue(Node))
+ LoopStart = needPrefix(true);
+
+ LoopEnd = Loops[Node->getEntry()];
+ wireFlow(false, LoopEnd);
+ while (!Visited.count(LoopEnd)) {
+ handleLoops(false, LoopEnd);
+ }
+
+ // Create an extra loop end node
+ LoopEnd = needPrefix(false);
+ BasicBlock *Next = needPostfix(LoopEnd, ExitUseAllowed);
+ LoopConds.push_back(BranchInst::Create(Next, LoopStart,
+ BoolUndef, LoopEnd));
+ addPhiValues(LoopEnd, LoopStart);
+ setPrevNode(Next);
+}
+
+/// After this function control flow looks like it should be, but
+/// branches and PHI nodes only have undefined conditions.
+void StructurizeCFG::createFlow() {
+ BasicBlock *Exit = ParentRegion->getExit();
+ bool EntryDominatesExit = DT->dominates(ParentRegion->getEntry(), Exit);
+
+ DeletedPhis.clear();
+ AddedPhis.clear();
+ Conditions.clear();
+ LoopConds.clear();
+
+ PrevNode = 0;
+ Visited.clear();
+
+ while (!Order.empty()) {
+ handleLoops(EntryDominatesExit, 0);
+ }
+
+ if (PrevNode)
+ changeExit(PrevNode, Exit, EntryDominatesExit);
+ else
+ assert(EntryDominatesExit);
+}
+
+/// Handle a rare case where the disintegrated nodes instructions
+/// no longer dominate all their uses. Not sure if this is really nessasary
+void StructurizeCFG::rebuildSSA() {
+ SSAUpdater Updater;
+ for (Region::block_iterator I = ParentRegion->block_begin(),
+ E = ParentRegion->block_end();
+ I != E; ++I) {
+
+ BasicBlock *BB = *I;
+ for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
+ II != IE; ++II) {
+
+ bool Initialized = false;
+ for (Use *I = &II->use_begin().getUse(), *Next; I; I = Next) {
+
+ Next = I->getNext();
+
+ Instruction *User = cast<Instruction>(I->getUser());
+ if (User->getParent() == BB) {
+ continue;
+
+ } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+ if (UserPN->getIncomingBlock(*I) == BB)
+ continue;
+ }
+
+ if (DT->dominates(II, User))
+ continue;
+
+ if (!Initialized) {
+ Value *Undef = UndefValue::get(II->getType());
+ Updater.Initialize(II->getType(), "");
+ Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
+ Updater.AddAvailableValue(BB, II);
+ Initialized = true;
+ }
+ Updater.RewriteUseAfterInsertions(*I);
+ }
+ }
+ }
+}
+
+/// \brief Run the transformation for each region found
+bool StructurizeCFG::runOnRegion(Region *R, RGPassManager &RGM) {
+ if (R->isTopLevelRegion())
+ return false;
+
+ Func = R->getEntry()->getParent();
+ ParentRegion = R;
+
+ DT = &getAnalysis<DominatorTree>();
+
+ orderNodes();
+ collectInfos();
+ createFlow();
+ insertConditions(false);
+ insertConditions(true);
+ setPhiValues();
+ rebuildSSA();
+
+ // Cleanup
+ Order.clear();
+ Visited.clear();
+ DeletedPhis.clear();
+ AddedPhis.clear();
+ Predicates.clear();
+ Conditions.clear();
+ Loops.clear();
+ LoopPreds.clear();
+ LoopConds.clear();
+
+ return true;
+}
+
+/// \brief Create the pass
+Pass *llvm::createStructurizeCFGPass() {
+ return new StructurizeCFG();
+}