1 files changed, 162 insertions, 66 deletions

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 5b12c92..196a847 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -156,7 +156,7 @@ namespace {
 ///
 class SCCPSolver : public InstVisitor<SCCPSolver> {
   const TargetData *TD;
-  SmallPtrSet<BasicBlock*, 8> BBExecutable;// The BBs that are executable.
+  SmallPtrSet<BasicBlock*, 8> BBExecutable; // The BBs that are executable.
   DenseMap<Value*, LatticeVal> ValueState;  // The state each value is in.
 
   /// StructValueState - This maintains ValueState for values that have
@@ -471,9 +471,9 @@ private:
   /// UsersOfOverdefinedPHIs map for PN, remove them now.
   void RemoveFromOverdefinedPHIs(Instruction *I, PHINode *PN) {
     if (UsersOfOverdefinedPHIs.empty()) return;
-    std::multimap<PHINode*, Instruction*>::iterator It, E;
-    tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN);
-    while (It != E) {
+    typedef std::multimap<PHINode*, Instruction*>::iterator ItTy;
+    std::pair<ItTy, ItTy> Range = UsersOfOverdefinedPHIs.equal_range(PN);
+    for (ItTy It = Range.first, E = Range.second; It != E;) {
       if (It->second == I)
         UsersOfOverdefinedPHIs.erase(It++);
       else
@@ -486,9 +486,9 @@ private:
   /// (Duplicate entries do not break anything directly, but can lead to
   /// exponential growth of the table in rare cases.)
   void InsertInOverdefinedPHIs(Instruction *I, PHINode *PN) {
-    std::multimap<PHINode*, Instruction*>::iterator J, E;
-    tie(J, E) = UsersOfOverdefinedPHIs.equal_range(PN);
-    for (; J != E; ++J)
+    typedef std::multimap<PHINode*, Instruction*>::iterator ItTy;
+    std::pair<ItTy, ItTy> Range = UsersOfOverdefinedPHIs.equal_range(PN);
+    for (ItTy J = Range.first, E = Range.second; J != E; ++J)
       if (J->second == I)
         return;
     UsersOfOverdefinedPHIs.insert(std::make_pair(PN, I));
@@ -515,6 +515,7 @@ private:
   void visitShuffleVectorInst(ShuffleVectorInst &I);
   void visitExtractValueInst(ExtractValueInst &EVI);
   void visitInsertValueInst(InsertValueInst &IVI);
+  void visitLandingPadInst(LandingPadInst &I) { markAnythingOverdefined(&I); }
 
   // Instructions that cannot be folded away.
   void visitStoreInst     (StoreInst &I);
@@ -528,8 +529,12 @@ private:
     visitTerminatorInst(II);
   }
   void visitCallSite      (CallSite CS);
+  void visitResumeInst    (TerminatorInst &I) { /*returns void*/ }
   void visitUnwindInst    (TerminatorInst &I) { /*returns void*/ }
   void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
+  void visitFenceInst     (FenceInst &I) { /*returns void*/ }
+  void visitAtomicCmpXchgInst (AtomicCmpXchgInst &I) { markOverdefined(&I); }
+  void visitAtomicRMWInst (AtomicRMWInst &I) { markOverdefined(&I); }
   void visitAllocaInst    (Instruction &I) { markOverdefined(&I); }
   void visitVAArgInst     (Instruction &I) { markAnythingOverdefined(&I); }
 
@@ -577,6 +582,10 @@ void SCCPSolver::getFeasibleSuccessors(TerminatorInst &TI,
   }
   
   if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
+    if (TI.getNumSuccessors() < 2) {
+      Succs[0] = true;
+      return;
+    }
     LatticeVal SCValue = getValueState(SI->getCondition());
     ConstantInt *CI = SCValue.getConstantInt();
     
@@ -637,6 +646,9 @@ bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
     return true;
   
   if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+    if (SI->getNumSuccessors() < 2)
+      return true;
+
     LatticeVal SCValue = getValueState(SI->getCondition());
     ConstantInt *CI = SCValue.getConstantInt();
     
@@ -692,13 +704,14 @@ void SCCPSolver::visitPHINode(PHINode &PN) {
     // There may be instructions using this PHI node that are not overdefined
     // themselves.  If so, make sure that they know that the PHI node operand
     // changed.
-    std::multimap<PHINode*, Instruction*>::iterator I, E;
-    tie(I, E) = UsersOfOverdefinedPHIs.equal_range(&PN);
-    if (I == E)
+    typedef std::multimap<PHINode*, Instruction*>::iterator ItTy;
+    std::pair<ItTy, ItTy> Range = UsersOfOverdefinedPHIs.equal_range(&PN);
+    
+    if (Range.first == Range.second)
       return;
     
     SmallVector<Instruction*, 16> Users;
-    for (; I != E; ++I)
+    for (ItTy I = Range.first, E = Range.second; I != E; ++I)
       Users.push_back(I->second);
     while (!Users.empty())
       visit(Users.pop_back_val());
@@ -1179,8 +1192,8 @@ void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
   }
 
   Constant *Ptr = Operands[0];
-  markConstant(&I, ConstantExpr::getGetElementPtr(Ptr, &Operands[0]+1,
-                                                  Operands.size()-1));
+  ArrayRef<Constant *> Indices(Operands.begin() + 1, Operands.end());
+  markConstant(&I, ConstantExpr::getGetElementPtr(Ptr, Indices));
 }
 
 void SCCPSolver::visitStoreInst(StoreInst &SI) {
@@ -1420,66 +1433,115 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
       if (I->getType()->isVoidTy()) continue;
       
       if (StructType *STy = dyn_cast<StructType>(I->getType())) {
-        // Only a few things that can be structs matter for undef.  Just send
-        // all their results to overdefined.  We could be more precise than this
-        // but it isn't worth bothering.
-        if (isa<CallInst>(I) || isa<SelectInst>(I)) {
-          for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
-            LatticeVal &LV = getStructValueState(I, i);
-            if (LV.isUndefined())
-              markOverdefined(LV, I);
-          }
+        // Only a few things that can be structs matter for undef.
+
+        // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
+        if (CallSite CS = CallSite(I))
+          if (Function *F = CS.getCalledFunction())
+            if (MRVFunctionsTracked.count(F))
+              continue;
+
+        // extractvalue and insertvalue don't need to be marked; they are
+        // tracked as precisely as their operands. 
+        if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
+          continue;
+
+        // Send the results of everything else to overdefined.  We could be
+        // more precise than this but it isn't worth bothering.
+        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+          LatticeVal &LV = getStructValueState(I, i);
+          if (LV.isUndefined())
+            markOverdefined(LV, I);
         }
         continue;
       }
-      
+
       LatticeVal &LV = getValueState(I);
       if (!LV.isUndefined()) continue;
 
-      // No instructions using structs need disambiguation.
-      if (I->getOperand(0)->getType()->isStructTy())
+      // extractvalue is safe; check here because the argument is a struct.
+      if (isa<ExtractValueInst>(I))
         continue;
 
-      // Get the lattice values of the first two operands for use below.
+      // Compute the operand LatticeVals, for convenience below.
+      // Anything taking a struct is conservatively assumed to require
+      // overdefined markings.
+      if (I->getOperand(0)->getType()->isStructTy()) {
+        markOverdefined(I);
+        return true;
+      }
       LatticeVal Op0LV = getValueState(I->getOperand(0));
       LatticeVal Op1LV;
       if (I->getNumOperands() == 2) {
-        // No instructions using structs need disambiguation.
-        if (I->getOperand(1)->getType()->isStructTy())
-          continue;
-        
-        // If this is a two-operand instruction, and if both operands are
-        // undefs, the result stays undef.
+        if (I->getOperand(1)->getType()->isStructTy()) {
+          markOverdefined(I);
+          return true;
+        }
+
         Op1LV = getValueState(I->getOperand(1));
-        if (Op0LV.isUndefined() && Op1LV.isUndefined())
-          continue;
       }
-      
       // If this is an instructions whose result is defined even if the input is
       // not fully defined, propagate the information.
       Type *ITy = I->getType();
       switch (I->getOpcode()) {
-      default: break;          // Leave the instruction as an undef.
+      case Instruction::Add:
+      case Instruction::Sub:
+      case Instruction::Trunc:
+      case Instruction::FPTrunc:
+      case Instruction::BitCast:
+        break; // Any undef -> undef
+      case Instruction::FSub:
+      case Instruction::FAdd:
+      case Instruction::FMul:
+      case Instruction::FDiv:
+      case Instruction::FRem:
+        // Floating-point binary operation: be conservative.
+        if (Op0LV.isUndefined() && Op1LV.isUndefined())
+          markForcedConstant(I, Constant::getNullValue(ITy));
+        else
+          markOverdefined(I);
+        return true;
       case Instruction::ZExt:
-        // After a zero extend, we know the top part is zero.  SExt doesn't have
-        // to be handled here, because we don't know whether the top part is 1's
-        // or 0's.
-      case Instruction::SIToFP:  // some FP values are not possible, just use 0.
-      case Instruction::UIToFP:  // some FP values are not possible, just use 0.
+      case Instruction::SExt:
+      case Instruction::FPToUI:
+      case Instruction::FPToSI:
+      case Instruction::FPExt:
+      case Instruction::PtrToInt:
+      case Instruction::IntToPtr:
+      case Instruction::SIToFP:
+      case Instruction::UIToFP:
+        // undef -> 0; some outputs are impossible
         markForcedConstant(I, Constant::getNullValue(ITy));
         return true;
       case Instruction::Mul:
       case Instruction::And:
+        // Both operands undef -> undef
+        if (Op0LV.isUndefined() && Op1LV.isUndefined())
+          break;
         // undef * X -> 0.   X could be zero.
         // undef & X -> 0.   X could be zero.
         markForcedConstant(I, Constant::getNullValue(ITy));
         return true;
 
       case Instruction::Or:
+        // Both operands undef -> undef
+        if (Op0LV.isUndefined() && Op1LV.isUndefined())
+          break;
         // undef | X -> -1.   X could be -1.
         markForcedConstant(I, Constant::getAllOnesValue(ITy));
         return true;
 
+      case Instruction::Xor:
+        // undef ^ undef -> 0; strictly speaking, this is not strictly
+        // necessary, but we try to be nice to people who expect this
+        // behavior in simple cases
+        if (Op0LV.isUndefined() && Op1LV.isUndefined()) {
+          markForcedConstant(I, Constant::getNullValue(ITy));
+          return true;
+        }
+        // undef ^ X -> undef
+        break;
+
       case Instruction::SDiv:
       case Instruction::UDiv:
       case Instruction::SRem:
@@ -1494,26 +1556,24 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
         return true;
         
       case Instruction::AShr:
-        // undef >>s X -> undef.  No change.
-        if (Op0LV.isUndefined()) break;
-        
-        // X >>s undef -> X.  X could be 0, X could have the high-bit known set.
-        if (Op0LV.isConstant())
-          markForcedConstant(I, Op0LV.getConstant());
-        else
-          markOverdefined(I);
+        // X >>a undef -> undef.
+        if (Op1LV.isUndefined()) break;
+
+        // undef >>a X -> all ones
+        markForcedConstant(I, Constant::getAllOnesValue(ITy));
         return true;
       case Instruction::LShr:
       case Instruction::Shl:
-        // undef >> X -> undef.  No change.
-        // undef << X -> undef.  No change.
-        if (Op0LV.isUndefined()) break;
-        
-        // X >> undef -> 0.  X could be 0.
-        // X << undef -> 0.  X could be 0.
+        // X << undef -> undef.
+        // X >> undef -> undef.
+        if (Op1LV.isUndefined()) break;
+
+        // undef << X -> 0
+        // undef >> X -> 0
         markForcedConstant(I, Constant::getNullValue(ITy));
         return true;
       case Instruction::Select:
+        Op1LV = getValueState(I->getOperand(1));
         // undef ? X : Y  -> X or Y.  There could be commonality between X/Y.
         if (Op0LV.isUndefined()) {
           if (!Op1LV.isConstant())  // Pick the constant one if there is any.
@@ -1533,9 +1593,35 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
         else
           markOverdefined(I);
         return true;
+      case Instruction::Load:
+        // A load here means one of two things: a load of undef from a global,
+        // a load from an unknown pointer.  Either way, having it return undef
+        // is okay.
+        break;
+      case Instruction::ICmp:
+        // X == undef -> undef.  Other comparisons get more complicated.
+        if (cast<ICmpInst>(I)->isEquality())
+          break;
+        markOverdefined(I);
+        return true;
       case Instruction::Call:
-        // If a call has an undef result, it is because it is constant foldable
-        // but one of the inputs was undef.  Just force the result to
+      case Instruction::Invoke: {
+        // There are two reasons a call can have an undef result
+        // 1. It could be tracked.
+        // 2. It could be constant-foldable.
+        // Because of the way we solve return values, tracked calls must
+        // never be marked overdefined in ResolvedUndefsIn.
+        if (Function *F = CallSite(I).getCalledFunction())
+          if (TrackedRetVals.count(F))
+            break;
+
+        // If the call is constant-foldable, we mark it overdefined because
+        // we do not know what return values are valid.
+        markOverdefined(I);
+        return true;
+      }
+      default:
+        // If we don't know what should happen here, conservatively mark it
         // overdefined.
         markOverdefined(I);
         return true;
@@ -1621,15 +1707,25 @@ FunctionPass *llvm::createSCCPPass() {
 static void DeleteInstructionInBlock(BasicBlock *BB) {
   DEBUG(dbgs() << "  BasicBlock Dead:" << *BB);
   ++NumDeadBlocks;
-  
-  // Delete the instructions backwards, as it has a reduced likelihood of
-  // having to update as many def-use and use-def chains.
-  while (!isa<TerminatorInst>(BB->begin())) {
-    Instruction *I = --BasicBlock::iterator(BB->getTerminator());
-    
-    if (!I->use_empty())
-      I->replaceAllUsesWith(UndefValue::get(I->getType()));
-    BB->getInstList().erase(I);
+
+  // Check to see if there are non-terminating instructions to delete.
+  if (isa<TerminatorInst>(BB->begin()))
+    return;
+
+  // Delete the instructions backwards, as it has a reduced likelihood of having
+  // to update as many def-use and use-def chains.
+  Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+  while (EndInst != BB->begin()) {
+    // Delete the next to last instruction.
+    BasicBlock::iterator I = EndInst;
+    Instruction *Inst = --I;
+    if (!Inst->use_empty())
+      Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
+    if (isa<LandingPadInst>(Inst)) {
+      EndInst = Inst;
+      continue;
+    }
+    BB->getInstList().erase(Inst);
     ++NumInstRemoved;
   }
 }