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https://github.com/c64scene-ar/llvm-6502.git
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08e1b756df
If the beginning of the loop was also the entry block of the function, branches were inserted to the entry block which isn't allowed. If this occurs, create a new dummy function entry block that branches to the start of the loop. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195493 91177308-0d34-0410-b5e6-96231b3b80d8
907 lines
25 KiB
C++
907 lines
25 KiB
C++
//===-- StructurizeCFG.cpp ------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "structurizecfg"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/MapVector.h"
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#include "llvm/ADT/SCCIterator.h"
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#include "llvm/Analysis/RegionInfo.h"
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#include "llvm/Analysis/RegionIterator.h"
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#include "llvm/Analysis/RegionPass.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/PatternMatch.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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namespace {
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// Definition of the complex types used in this pass.
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typedef std::pair<BasicBlock *, Value *> BBValuePair;
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typedef SmallVector<RegionNode*, 8> RNVector;
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typedef SmallVector<BasicBlock*, 8> BBVector;
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typedef SmallVector<BranchInst*, 8> BranchVector;
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typedef SmallVector<BBValuePair, 2> BBValueVector;
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typedef SmallPtrSet<BasicBlock *, 8> BBSet;
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typedef MapVector<PHINode *, BBValueVector> PhiMap;
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typedef MapVector<BasicBlock *, BBVector> BB2BBVecMap;
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typedef DenseMap<DomTreeNode *, unsigned> DTN2UnsignedMap;
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typedef DenseMap<BasicBlock *, PhiMap> BBPhiMap;
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typedef DenseMap<BasicBlock *, Value *> BBPredicates;
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typedef DenseMap<BasicBlock *, BBPredicates> PredMap;
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typedef DenseMap<BasicBlock *, BasicBlock*> BB2BBMap;
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// The name for newly created blocks.
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static const char *const FlowBlockName = "Flow";
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/// @brief Find the nearest common dominator for multiple BasicBlocks
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///
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/// Helper class for StructurizeCFG
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/// TODO: Maybe move into common code
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class NearestCommonDominator {
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DominatorTree *DT;
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DTN2UnsignedMap IndexMap;
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BasicBlock *Result;
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unsigned ResultIndex;
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bool ExplicitMentioned;
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public:
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/// \brief Start a new query
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NearestCommonDominator(DominatorTree *DomTree) {
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DT = DomTree;
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Result = 0;
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}
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/// \brief Add BB to the resulting dominator
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void addBlock(BasicBlock *BB, bool Remember = true) {
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DomTreeNode *Node = DT->getNode(BB);
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if (Result == 0) {
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unsigned Numbering = 0;
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for (;Node;Node = Node->getIDom())
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IndexMap[Node] = ++Numbering;
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Result = BB;
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ResultIndex = 1;
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ExplicitMentioned = Remember;
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return;
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}
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for (;Node;Node = Node->getIDom())
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if (IndexMap.count(Node))
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break;
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else
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IndexMap[Node] = 0;
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assert(Node && "Dominator tree invalid!");
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unsigned Numbering = IndexMap[Node];
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if (Numbering > ResultIndex) {
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Result = Node->getBlock();
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ResultIndex = Numbering;
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ExplicitMentioned = Remember && (Result == BB);
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} else if (Numbering == ResultIndex) {
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ExplicitMentioned |= Remember;
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}
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}
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/// \brief Is "Result" one of the BBs added with "Remember" = True?
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bool wasResultExplicitMentioned() {
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return ExplicitMentioned;
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}
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/// \brief Get the query result
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BasicBlock *getResult() {
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return Result;
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}
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};
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/// @brief Transforms the control flow graph on one single entry/exit region
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/// at a time.
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///
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/// After the transform all "If"/"Then"/"Else" style control flow looks like
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/// this:
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///
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/// \verbatim
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/// 1
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/// ||
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/// | |
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/// 2 |
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/// | /
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/// |/
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/// 3
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/// || Where:
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/// | | 1 = "If" block, calculates the condition
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/// 4 | 2 = "Then" subregion, runs if the condition is true
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/// | / 3 = "Flow" blocks, newly inserted flow blocks, rejoins the flow
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/// |/ 4 = "Else" optional subregion, runs if the condition is false
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/// 5 5 = "End" block, also rejoins the control flow
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/// \endverbatim
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///
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/// Control flow is expressed as a branch where the true exit goes into the
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/// "Then"/"Else" region, while the false exit skips the region
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/// The condition for the optional "Else" region is expressed as a PHI node.
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/// The incomming values of the PHI node are true for the "If" edge and false
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/// for the "Then" edge.
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///
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/// Additionally to that even complicated loops look like this:
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///
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/// \verbatim
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/// 1
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/// ||
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/// | |
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/// 2 ^ Where:
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/// | / 1 = "Entry" block
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/// |/ 2 = "Loop" optional subregion, with all exits at "Flow" block
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/// 3 3 = "Flow" block, with back edge to entry block
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/// |
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/// \endverbatim
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///
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/// The back edge of the "Flow" block is always on the false side of the branch
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/// while the true side continues the general flow. So the loop condition
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/// consist of a network of PHI nodes where the true incoming values expresses
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/// breaks and the false values expresses continue states.
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class StructurizeCFG : public RegionPass {
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Type *Boolean;
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ConstantInt *BoolTrue;
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ConstantInt *BoolFalse;
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UndefValue *BoolUndef;
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Function *Func;
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Region *ParentRegion;
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DominatorTree *DT;
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RNVector Order;
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BBSet Visited;
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BBPhiMap DeletedPhis;
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BB2BBVecMap AddedPhis;
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PredMap Predicates;
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BranchVector Conditions;
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BB2BBMap Loops;
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PredMap LoopPreds;
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BranchVector LoopConds;
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RegionNode *PrevNode;
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void orderNodes();
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void analyzeLoops(RegionNode *N);
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Value *invert(Value *Condition);
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Value *buildCondition(BranchInst *Term, unsigned Idx, bool Invert);
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void gatherPredicates(RegionNode *N);
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void collectInfos();
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void insertConditions(bool Loops);
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void delPhiValues(BasicBlock *From, BasicBlock *To);
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void addPhiValues(BasicBlock *From, BasicBlock *To);
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void setPhiValues();
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void killTerminator(BasicBlock *BB);
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void changeExit(RegionNode *Node, BasicBlock *NewExit,
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bool IncludeDominator);
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BasicBlock *getNextFlow(BasicBlock *Dominator);
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BasicBlock *needPrefix(bool NeedEmpty);
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BasicBlock *needPostfix(BasicBlock *Flow, bool ExitUseAllowed);
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void setPrevNode(BasicBlock *BB);
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bool dominatesPredicates(BasicBlock *BB, RegionNode *Node);
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bool isPredictableTrue(RegionNode *Node);
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void wireFlow(bool ExitUseAllowed, BasicBlock *LoopEnd);
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void handleLoops(bool ExitUseAllowed, BasicBlock *LoopEnd);
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void createFlow();
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void rebuildSSA();
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public:
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static char ID;
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StructurizeCFG() :
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RegionPass(ID) {
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initializeStructurizeCFGPass(*PassRegistry::getPassRegistry());
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}
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using Pass::doInitialization;
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virtual bool doInitialization(Region *R, RGPassManager &RGM);
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virtual bool runOnRegion(Region *R, RGPassManager &RGM);
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virtual const char *getPassName() const {
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return "Structurize control flow";
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}
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void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequiredID(LowerSwitchID);
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AU.addRequired<DominatorTree>();
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AU.addPreserved<DominatorTree>();
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RegionPass::getAnalysisUsage(AU);
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}
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};
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} // end anonymous namespace
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char StructurizeCFG::ID = 0;
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INITIALIZE_PASS_BEGIN(StructurizeCFG, "structurizecfg", "Structurize the CFG",
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false, false)
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INITIALIZE_PASS_DEPENDENCY(LowerSwitch)
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INITIALIZE_PASS_DEPENDENCY(DominatorTree)
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INITIALIZE_PASS_DEPENDENCY(RegionInfo)
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INITIALIZE_PASS_END(StructurizeCFG, "structurizecfg", "Structurize the CFG",
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false, false)
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/// \brief Initialize the types and constants used in the pass
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bool StructurizeCFG::doInitialization(Region *R, RGPassManager &RGM) {
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LLVMContext &Context = R->getEntry()->getContext();
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Boolean = Type::getInt1Ty(Context);
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BoolTrue = ConstantInt::getTrue(Context);
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BoolFalse = ConstantInt::getFalse(Context);
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BoolUndef = UndefValue::get(Boolean);
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return false;
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}
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/// \brief Build up the general order of nodes
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void StructurizeCFG::orderNodes() {
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scc_iterator<Region *> I = scc_begin(ParentRegion),
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E = scc_end(ParentRegion);
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for (Order.clear(); I != E; ++I) {
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std::vector<RegionNode *> &Nodes = *I;
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Order.append(Nodes.begin(), Nodes.end());
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}
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}
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/// \brief Determine the end of the loops
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void StructurizeCFG::analyzeLoops(RegionNode *N) {
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if (N->isSubRegion()) {
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// Test for exit as back edge
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BasicBlock *Exit = N->getNodeAs<Region>()->getExit();
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if (Visited.count(Exit))
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Loops[Exit] = N->getEntry();
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} else {
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// Test for sucessors as back edge
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BasicBlock *BB = N->getNodeAs<BasicBlock>();
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BranchInst *Term = cast<BranchInst>(BB->getTerminator());
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for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
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BasicBlock *Succ = Term->getSuccessor(i);
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if (Visited.count(Succ))
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Loops[Succ] = BB;
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}
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}
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}
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/// \brief Invert the given condition
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Value *StructurizeCFG::invert(Value *Condition) {
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// First: Check if it's a constant
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if (Condition == BoolTrue)
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return BoolFalse;
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if (Condition == BoolFalse)
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return BoolTrue;
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if (Condition == BoolUndef)
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return BoolUndef;
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// Second: If the condition is already inverted, return the original value
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if (match(Condition, m_Not(m_Value(Condition))))
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return Condition;
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if (Instruction *Inst = dyn_cast<Instruction>(Condition)) {
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// Third: Check all the users for an invert
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BasicBlock *Parent = Inst->getParent();
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for (Value::use_iterator I = Condition->use_begin(),
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E = Condition->use_end(); I != E; ++I) {
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Instruction *User = dyn_cast<Instruction>(*I);
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if (!User || User->getParent() != Parent)
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continue;
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if (match(*I, m_Not(m_Specific(Condition))))
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return *I;
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}
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// Last option: Create a new instruction
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return BinaryOperator::CreateNot(Condition, "", Parent->getTerminator());
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}
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if (Argument *Arg = dyn_cast<Argument>(Condition)) {
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BasicBlock &EntryBlock = Arg->getParent()->getEntryBlock();
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return BinaryOperator::CreateNot(Condition,
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Arg->getName() + ".inv",
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EntryBlock.getTerminator());
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}
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llvm_unreachable("Unhandled condition to invert");
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}
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/// \brief Build the condition for one edge
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Value *StructurizeCFG::buildCondition(BranchInst *Term, unsigned Idx,
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bool Invert) {
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Value *Cond = Invert ? BoolFalse : BoolTrue;
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if (Term->isConditional()) {
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Cond = Term->getCondition();
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if (Idx != (unsigned)Invert)
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Cond = invert(Cond);
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}
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return Cond;
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}
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/// \brief Analyze the predecessors of each block and build up predicates
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void StructurizeCFG::gatherPredicates(RegionNode *N) {
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RegionInfo *RI = ParentRegion->getRegionInfo();
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BasicBlock *BB = N->getEntry();
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BBPredicates &Pred = Predicates[BB];
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BBPredicates &LPred = LoopPreds[BB];
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for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
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PI != PE; ++PI) {
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// Ignore it if it's a branch from outside into our region entry
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if (!ParentRegion->contains(*PI))
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continue;
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Region *R = RI->getRegionFor(*PI);
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if (R == ParentRegion) {
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// It's a top level block in our region
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BranchInst *Term = cast<BranchInst>((*PI)->getTerminator());
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for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
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BasicBlock *Succ = Term->getSuccessor(i);
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if (Succ != BB)
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continue;
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if (Visited.count(*PI)) {
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// Normal forward edge
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if (Term->isConditional()) {
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// Try to treat it like an ELSE block
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BasicBlock *Other = Term->getSuccessor(!i);
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if (Visited.count(Other) && !Loops.count(Other) &&
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!Pred.count(Other) && !Pred.count(*PI)) {
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Pred[Other] = BoolFalse;
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Pred[*PI] = BoolTrue;
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continue;
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}
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}
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Pred[*PI] = buildCondition(Term, i, false);
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} else {
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// Back edge
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LPred[*PI] = buildCondition(Term, i, true);
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}
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}
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} else {
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// It's an exit from a sub region
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while(R->getParent() != ParentRegion)
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R = R->getParent();
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// Edge from inside a subregion to its entry, ignore it
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if (R == N)
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continue;
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BasicBlock *Entry = R->getEntry();
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if (Visited.count(Entry))
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Pred[Entry] = BoolTrue;
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else
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LPred[Entry] = BoolFalse;
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}
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}
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}
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/// \brief Collect various loop and predicate infos
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void StructurizeCFG::collectInfos() {
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// Reset predicate
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Predicates.clear();
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// and loop infos
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Loops.clear();
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LoopPreds.clear();
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// Reset the visited nodes
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Visited.clear();
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for (RNVector::reverse_iterator OI = Order.rbegin(), OE = Order.rend();
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OI != OE; ++OI) {
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// Analyze all the conditions leading to a node
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gatherPredicates(*OI);
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// Remember that we've seen this node
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Visited.insert((*OI)->getEntry());
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// Find the last back edges
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analyzeLoops(*OI);
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}
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}
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/// \brief Insert the missing branch conditions
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void StructurizeCFG::insertConditions(bool Loops) {
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BranchVector &Conds = Loops ? LoopConds : Conditions;
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Value *Default = Loops ? BoolTrue : BoolFalse;
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SSAUpdater PhiInserter;
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for (BranchVector::iterator I = Conds.begin(),
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E = Conds.end(); I != E; ++I) {
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BranchInst *Term = *I;
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assert(Term->isConditional());
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BasicBlock *Parent = Term->getParent();
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BasicBlock *SuccTrue = Term->getSuccessor(0);
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BasicBlock *SuccFalse = Term->getSuccessor(1);
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PhiInserter.Initialize(Boolean, "");
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PhiInserter.AddAvailableValue(&Func->getEntryBlock(), Default);
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PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);
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BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];
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NearestCommonDominator Dominator(DT);
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Dominator.addBlock(Parent, false);
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Value *ParentValue = 0;
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for (BBPredicates::iterator PI = Preds.begin(), PE = Preds.end();
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PI != PE; ++PI) {
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if (PI->first == Parent) {
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ParentValue = PI->second;
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break;
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}
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PhiInserter.AddAvailableValue(PI->first, PI->second);
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Dominator.addBlock(PI->first);
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}
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if (ParentValue) {
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Term->setCondition(ParentValue);
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} else {
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if (!Dominator.wasResultExplicitMentioned())
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PhiInserter.AddAvailableValue(Dominator.getResult(), Default);
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Term->setCondition(PhiInserter.GetValueInMiddleOfBlock(Parent));
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}
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}
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}
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/// \brief Remove all PHI values coming from "From" into "To" and remember
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/// them in DeletedPhis
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void StructurizeCFG::delPhiValues(BasicBlock *From, BasicBlock *To) {
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PhiMap &Map = DeletedPhis[To];
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for (BasicBlock::iterator I = To->begin(), E = To->end();
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I != E && isa<PHINode>(*I);) {
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PHINode &Phi = cast<PHINode>(*I++);
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while (Phi.getBasicBlockIndex(From) != -1) {
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Value *Deleted = Phi.removeIncomingValue(From, false);
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Map[&Phi].push_back(std::make_pair(From, Deleted));
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}
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}
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}
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/// \brief Add a dummy PHI value as soon as we knew the new predecessor
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void StructurizeCFG::addPhiValues(BasicBlock *From, BasicBlock *To) {
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for (BasicBlock::iterator I = To->begin(), E = To->end();
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I != E && isa<PHINode>(*I);) {
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PHINode &Phi = cast<PHINode>(*I++);
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Value *Undef = UndefValue::get(Phi.getType());
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Phi.addIncoming(Undef, From);
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}
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AddedPhis[To].push_back(From);
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}
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/// \brief Add the real PHI value as soon as everything is set up
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void StructurizeCFG::setPhiValues() {
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SSAUpdater Updater;
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for (BB2BBVecMap::iterator AI = AddedPhis.begin(), AE = AddedPhis.end();
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AI != AE; ++AI) {
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BasicBlock *To = AI->first;
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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);
|
|
}
|
|
|
|
// If the start of the loop is the entry block, we can't branch to it so
|
|
// insert a new dummy entry block.
|
|
Function *LoopFunc = LoopStart->getParent();
|
|
if (LoopStart == &LoopFunc->getEntryBlock()) {
|
|
LoopStart->setName("entry.orig");
|
|
|
|
BasicBlock *NewEntry =
|
|
BasicBlock::Create(LoopStart->getContext(),
|
|
"entry",
|
|
LoopFunc,
|
|
LoopStart);
|
|
BranchInst::Create(LoopStart, NewEntry);
|
|
}
|
|
|
|
// 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();
|
|
}
|