Enhance the memdep interface so that users can tell the difference between a dependency which cannot be calculated and a path reaching the entry point of the function. This patch introduces isNonFuncLocal, which replaces isUnknown in some cases.

Patch by Xiaoyi Guo.

llvm-svn: 141896

docs/ReleaseNotes.html

@@ -707,6 +707,10 @@ merged with other structures, even if their layout is identical.
 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
 <code>INITIALIZE_PASS{BEGIN,END,}</code> and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
 
+<li>The interface for MemDepResult in MemoryDependenceAnalysis has been enhanced
+    with new return types Unknown and NonFuncLocal, in addition to the existing
+    types Clobber, Def, and NonLocal.</li>
+
 </ul>
 </div>
 

include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -52,9 +52,6 @@ namespace llvm {
       ///   1. Loads are clobbered by may-alias stores.
       ///   2. Loads are considered clobbered by partially-aliased loads.  The
       ///      client may choose to analyze deeper into these cases.
-      ///
-      /// A dependence query on the first instruction of the entry block will
-      /// return a clobber(self) result.
       Clobber,
 
       /// Def - This is a dependence on the specified instruction which
@@ -76,11 +73,27 @@ namespace llvm {
       ///      operands to the calls are the same.
       Def,
       
+      /// Other - This marker indicates that the query has no known dependency
+      /// in the specified block.  More detailed state info is encoded in the
+      /// upper part of the pair (i.e. the Instruction*)
+      Other
+    };
+    /// If DepType is "Other", the upper part of the pair
+    /// (i.e. the Instruction* part) is instead used to encode more detailed
+    /// type information as follows
+    enum OtherType {
       /// NonLocal - This marker indicates that the query has no dependency in
       /// the specified block.  To find out more, the client should query other
       /// predecessor blocks.
-      NonLocal
+      NonLocal = 0x4,
+      /// NonFuncLocal - This marker indicates that the query has no
+      /// dependency in the specified function.
+      NonFuncLocal = 0x8,
+      /// Unknown - This marker indicates that the query dependency
+      /// is unknown.
+      Unknown = 0xc
     };
+
     typedef PointerIntPair<Instruction*, 2, DepType> PairTy;
     PairTy Value;
     explicit MemDepResult(PairTy V) : Value(V) {}
@@ -98,19 +111,21 @@ namespace llvm {
       return MemDepResult(PairTy(Inst, Clobber));
     }
     static MemDepResult getNonLocal() {
-      return MemDepResult(PairTy(0, NonLocal));
+      return MemDepResult(
+        PairTy(reinterpret_cast<Instruction*>(NonLocal), Other));
+    }
+    static MemDepResult getNonFuncLocal() {
+      return MemDepResult(
+        PairTy(reinterpret_cast<Instruction*>(NonFuncLocal), Other));
     }
     static MemDepResult getUnknown() {
-      return MemDepResult(PairTy(0, Clobber));
+      return MemDepResult(
+        PairTy(reinterpret_cast<Instruction*>(Unknown), Other));
     }
 
     /// isClobber - Return true if this MemDepResult represents a query that is
     /// a instruction clobber dependency.
-    bool isClobber() const { return Value.getInt() == Clobber && getInst(); }
+    bool isClobber() const { return Value.getInt() == Clobber; }
-
-    /// isUnknown - Return true if this MemDepResult represents a query which
-    /// cannot and/or will not be computed.
-    bool isUnknown() const { return Value.getInt() == Clobber && !getInst(); }
 
     /// isDef - Return true if this MemDepResult represents a query that is
     /// a instruction definition dependency.
@@ -119,11 +134,31 @@ namespace llvm {
     /// isNonLocal - Return true if this MemDepResult represents a query that
     /// is transparent to the start of the block, but where a non-local hasn't
     /// been done.
-    bool isNonLocal() const { return Value.getInt() == NonLocal; }
+    bool isNonLocal() const {
+      return Value.getInt() == Other
+        && Value.getPointer() == reinterpret_cast<Instruction*>(NonLocal);
+    }
+
+    /// isNonFuncLocal - Return true if this MemDepResult represents a query
+    /// that is transparent to the start of the function.
+    bool isNonFuncLocal() const {
+      return Value.getInt() == Other
+        && Value.getPointer() == reinterpret_cast<Instruction*>(NonFuncLocal);
+    }
+    
+    /// isUnknown - Return true if this MemDepResult represents a query which
+    /// cannot and/or will not be computed.
+    bool isUnknown() const {
+      return Value.getInt() == Other
+        && Value.getPointer() == reinterpret_cast<Instruction*>(Unknown);
+    }
 
     /// getInst() - If this is a normal dependency, return the instruction that
     /// is depended on.  Otherwise, return null.
-    Instruction *getInst() const { return Value.getPointer(); }
+    Instruction *getInst() const {
+      if (Value.getInt() == Other) return NULL;
+      return Value.getPointer();
+    }
     
     bool operator==(const MemDepResult &M) const { return Value == M.Value; }
     bool operator!=(const MemDepResult &M) const { return Value != M.Value; }

lib/Analysis/MemDepPrinter.cpp

@@ -25,8 +25,17 @@ namespace {
   struct MemDepPrinter : public FunctionPass {
     const Function *F;
 
-    typedef PointerIntPair<const Instruction *, 1> InstAndClobberFlag;
+    enum DepType {
-    typedef std::pair<InstAndClobberFlag, const BasicBlock *> Dep;
+      Clobber = 0,
+      Def,
+      NonFuncLocal,
+      Unknown
+    };
+
+    static const char* DepTypeStr[];
+
+    typedef PointerIntPair<const Instruction *, 2, DepType> InstTypePair;
+    typedef std::pair<InstTypePair, const BasicBlock *> Dep;
     typedef SmallSetVector<Dep, 4> DepSet;
     typedef DenseMap<const Instruction *, DepSet> DepSetMap;
     DepSetMap Deps;
@@ -50,6 +59,21 @@ namespace {
       Deps.clear();
       F = 0;
     }
+
+  private:
+    static InstTypePair getInstTypePair(MemDepResult dep) {
+      if (dep.isClobber())
+        return InstTypePair(dep.getInst(), Clobber);
+      if (dep.isDef())
+        return InstTypePair(dep.getInst(), Def);
+      if (dep.isNonFuncLocal())
+        return InstTypePair(dep.getInst(), NonFuncLocal);
+      assert(dep.isUnknown() && "unexptected dependence type");
+      return InstTypePair(dep.getInst(), Unknown);
+    }
+    static InstTypePair getInstTypePair(const Instruction* inst, DepType type) {
+      return InstTypePair(inst, type);
+    }
   };
 }
 
@@ -64,6 +88,9 @@ FunctionPass *llvm::createMemDepPrinter() {
   return new MemDepPrinter();
 }
 
+const char* MemDepPrinter::DepTypeStr[]
+  = {"Clobber", "Def", "NonFuncLocal", "Unknown"};
+
 bool MemDepPrinter::runOnFunction(Function &F) {
   this->F = &F;
   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
@@ -79,10 +106,7 @@ bool MemDepPrinter::runOnFunction(Function &F) {
 
     MemDepResult Res = MDA.getDependency(Inst);
     if (!Res.isNonLocal()) {
-      assert((Res.isUnknown() || Res.isClobber() || Res.isDef()) &&
+      Deps[Inst].insert(std::make_pair(getInstTypePair(Res),
-              "Local dep should be unknown, def or clobber!");
-      Deps[Inst].insert(std::make_pair(InstAndClobberFlag(Res.getInst(),
-                                                          Res.isClobber()),
                                        static_cast<BasicBlock *>(0)));
     } else if (CallSite CS = cast<Value>(Inst)) {
       const MemoryDependenceAnalysis::NonLocalDepInfo &NLDI =
@@ -92,19 +116,14 @@ bool MemDepPrinter::runOnFunction(Function &F) {
       for (MemoryDependenceAnalysis::NonLocalDepInfo::const_iterator
            I = NLDI.begin(), E = NLDI.end(); I != E; ++I) {
         const MemDepResult &Res = I->getResult();
-        assert((Res.isUnknown() || Res.isClobber() || Res.isDef()) &&
+        InstDeps.insert(std::make_pair(getInstTypePair(Res), I->getBB()));
-                "Resolved non-local call dep should be unknown, def or "
-                "clobber!");
-        InstDeps.insert(std::make_pair(InstAndClobberFlag(Res.getInst(),
-                                                          Res.isClobber()),
-                                       I->getBB()));
       }
     } else {
       SmallVector<NonLocalDepResult, 4> NLDI;
       if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
         if (!LI->isUnordered()) {
           // FIXME: Handle atomic/volatile loads.
-          Deps[Inst].insert(std::make_pair(InstAndClobberFlag(0, false),
+          Deps[Inst].insert(std::make_pair(getInstTypePair(0, Unknown),
                                            static_cast<BasicBlock *>(0)));
           continue;
         }
@@ -113,7 +132,7 @@ bool MemDepPrinter::runOnFunction(Function &F) {
       } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
         if (!LI->isUnordered()) {
           // FIXME: Handle atomic/volatile stores.
-          Deps[Inst].insert(std::make_pair(InstAndClobberFlag(0, false),
+          Deps[Inst].insert(std::make_pair(getInstTypePair(0, Unknown),
                                            static_cast<BasicBlock *>(0)));
           continue;
         }
@@ -130,11 +149,7 @@ bool MemDepPrinter::runOnFunction(Function &F) {
       for (SmallVectorImpl<NonLocalDepResult>::const_iterator
            I = NLDI.begin(), E = NLDI.end(); I != E; ++I) {
         const MemDepResult &Res = I->getResult();
-        assert(Res.isClobber() != Res.isDef() &&
+        InstDeps.insert(std::make_pair(getInstTypePair(Res), I->getBB()));
-               "Resolved non-local pointer dep should be def or clobber!");
-        InstDeps.insert(std::make_pair(InstAndClobberFlag(Res.getInst(),
-                                                          Res.isClobber()),
-                                       I->getBB()));
       }
     }
   }
@@ -155,26 +170,18 @@ void MemDepPrinter::print(raw_ostream &OS, const Module *M) const {
     for (DepSet::const_iterator I = InstDeps.begin(), E = InstDeps.end();
          I != E; ++I) {
       const Instruction *DepInst = I->first.getPointer();
-      bool isClobber = I->first.getInt();
+      DepType type = I->first.getInt();
       const BasicBlock *DepBB = I->second;
 
       OS << "    ";
-      if (!DepInst)
+      OS << DepTypeStr[type];
-        OS << "Unknown";
-      else if (isClobber)
-        OS << "Clobber";
-      else
-        OS << "    Def";
       if (DepBB) {
         OS << " in block ";
         WriteAsOperand(OS, DepBB, /*PrintType=*/false, M);
       }
       if (DepInst) {
         OS << " from: ";
-        if (DepInst == Inst)
+        DepInst->print(OS);
-          OS << "<unspecified>";
-        else
-          DepInst->print(OS);
       }
       OS << "\n";
     }

lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -238,7 +238,7 @@ getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
   // unknown, otherwise it is non-local.
   if (BB != &BB->getParent()->getEntryBlock())
     return MemDepResult::getNonLocal();
-  return MemDepResult::getUnknown();
+  return MemDepResult::getNonFuncLocal();
 }
 
 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
@@ -499,7 +499,7 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
   // unknown, otherwise it is non-local.
   if (BB != &BB->getParent()->getEntryBlock())
     return MemDepResult::getNonLocal();
-  return MemDepResult::getUnknown();
+  return MemDepResult::getNonFuncLocal();
 }
 
 /// getDependency - Return the instruction on which a memory operation
@@ -532,7 +532,7 @@ MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
     if (QueryParent != &QueryParent->getParent()->getEntryBlock())
       LocalCache = MemDepResult::getNonLocal();
     else
-      LocalCache = MemDepResult::getUnknown();
+      LocalCache = MemDepResult::getNonFuncLocal();
   } else {
     AliasAnalysis::Location MemLoc;
     AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
@@ -688,7 +688,7 @@ MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
       // a clobber, otherwise it is unknown.
       Dep = MemDepResult::getNonLocal();
     } else {
-      Dep = MemDepResult::getUnknown();
+      Dep = MemDepResult::getNonFuncLocal();
     }
     
     // If we had a dirty entry for the block, update it.  Otherwise, just add
@@ -806,7 +806,7 @@ GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
   // If the block has a dependency (i.e. it isn't completely transparent to
   // the value), remember the reverse association because we just added it
   // to Cache!
-  if (Dep.isNonLocal() || Dep.isUnknown())
+  if (!Dep.isDef() && !Dep.isClobber())
     return Dep;
   
   // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently

lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -441,7 +441,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
 
     // Ignore any store where we can't find a local dependence.
     // FIXME: cross-block DSE would be fun. :)
-    if (InstDep.isNonLocal() || InstDep.isUnknown())
+    if (!InstDep.isDef() && !InstDep.isClobber())
       continue;
 
     // If we're storing the same value back to a pointer that we just
@@ -477,7 +477,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
     if (Loc.Ptr == 0)
       continue;
 
-    while (!InstDep.isNonLocal() && !InstDep.isUnknown()) {
+    while (InstDep.isDef() || InstDep.isClobber()) {
       // Get the memory clobbered by the instruction we depend on.  MemDep will
       // skip any instructions that 'Loc' clearly doesn't interact with.  If we
       // end up depending on a may- or must-aliased load, then we can't optimize
@@ -545,7 +545,7 @@ bool DSE::HandleFree(CallInst *F) {
 
   MemDepResult Dep = MD->getDependency(F);
 
-  while (!Dep.isNonLocal() && !Dep.isUnknown()) {
+  while (Dep.isDef() || Dep.isClobber()) {
     Instruction *Dependency = Dep.getInst();
     if (!hasMemoryWrite(Dependency) || !isRemovable(Dependency))
       return MadeChange;

lib/Transforms/Scalar/GVN.cpp

@@ -1279,7 +1279,9 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
 
   // If we had a phi translation failure, we'll have a single entry which is a
   // clobber in the current block.  Reject this early.
-  if (Deps.size() == 1 && Deps[0].getResult().isUnknown()) {
+  if (Deps.size() == 1
+      && !Deps[0].getResult().isDef() && !Deps[0].getResult().isClobber())
+  {
     DEBUG(
       dbgs() << "GVN: non-local load ";
       WriteAsOperand(dbgs(), LI);
@@ -1299,7 +1301,7 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
     BasicBlock *DepBB = Deps[i].getBB();
     MemDepResult DepInfo = Deps[i].getResult();
 
-    if (DepInfo.isUnknown()) {
+    if (!DepInfo.isDef() && !DepInfo.isClobber()) {
       UnavailableBlocks.push_back(DepBB);
       continue;
     }
@@ -1364,7 +1366,7 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
       continue;
     }
 
-    assert(DepInfo.isDef() && "Expecting def here");
+    // DepInfo.isDef() here
 
     Instruction *DepInst = DepInfo.getInst();
 
@@ -1761,7 +1763,11 @@ bool GVN::processLoad(LoadInst *L) {
     return false;
   }
 
-  if (Dep.isUnknown()) {
+  // If it is defined in another block, try harder.
+  if (Dep.isNonLocal())
+    return processNonLocalLoad(L);
+
+  if (!Dep.isDef()) {
     DEBUG(
       // fast print dep, using operator<< on instruction is too slow.
       dbgs() << "GVN: load ";
@@ -1771,12 +1777,6 @@ bool GVN::processLoad(LoadInst *L) {
     return false;
   }
 
-  // If it is defined in another block, try harder.
-  if (Dep.isNonLocal())
-    return processNonLocalLoad(L);
-
-  assert(Dep.isDef() && "Expecting def here");
-
   Instruction *DepInst = Dep.getInst();
   if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) {
     Value *StoredVal = DepSI->getValueOperand();