X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FBasicAliasAnalysis.cpp;h=900a5b61ee96e9a64bffc8535d1d3f489894943d;hb=497f61940a2b682bff79a0e2ada0caa65508f80c;hp=22b73b28400c6f2f9e4f456d68575e3f512c7709;hpb=5d0392c6b370758750b397e254a6c6f028479969;p=oota-llvm.git

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 22b73b28400..900a5b61ee9 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -14,6 +14,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/MallocHelper.h"
 #include "llvm/Analysis/Passes.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
@@ -21,13 +23,15 @@
 #include "llvm/GlobalVariable.h"
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Operator.h"
 #include "llvm/Pass.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/GetElementPtrTypeIterator.h"
-#include "llvm/Support/ManagedStatic.h"
 #include <algorithm>
 using namespace llvm;
 
@@ -35,57 +39,12 @@ using namespace llvm;
 // Useful predicates
 //===----------------------------------------------------------------------===//
 
-// Determine if an AllocationInst instruction escapes from the function it is
-// contained in. If it does not escape, there is no way for another function to
-// mod/ref it.  We do this by looking at its uses and determining if the uses
-// can escape (recursively).
-static bool AddressMightEscape(const Value *V) {
-  for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
-       UI != E; ++UI) {
-    const Instruction *I = cast<Instruction>(*UI);
-    switch (I->getOpcode()) {
-    case Instruction::Load: 
-      break; //next use.
-    case Instruction::Store:
-      if (I->getOperand(0) == V)
-        return true; // Escapes if the pointer is stored.
-      break; // next use.
-    case Instruction::GetElementPtr:
-      if (AddressMightEscape(I))
-        return true;
-      break; // next use.
-    case Instruction::BitCast:
-      if (AddressMightEscape(I))
-        return true;
-      break; // next use
-    case Instruction::Ret:
-      // If returned, the address will escape to calling functions, but no
-      // callees could modify it.
-      break; // next use
-    case Instruction::Call:
-      // If the call is to a few known safe intrinsics, we know that it does
-      // not escape.
-      // TODO: Eventually just check the 'nocapture' attribute.
-      if (!isa<MemIntrinsic>(I))
-        return true;
-      break;  // next use
-    default:
-      return true;
-    }
-  }
-  return false;
-}
-
-static const User *isGEP(const Value *V) {
-  if (isa<GetElementPtrInst>(V) ||
-      (isa<ConstantExpr>(V) &&
-       cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
-    return cast<User>(V);
-  return 0;
+static const GEPOperator *isGEP(const Value *V) {
+  return dyn_cast<GEPOperator>(V);
 }
 
 static const Value *GetGEPOperands(const Value *V, 
-                                   SmallVector<Value*, 16> &GEPOps){
+                                   SmallVector<Value*, 16> &GEPOps) {
   assert(GEPOps.empty() && "Expect empty list to populate!");
   GEPOps.insert(GEPOps.end(), cast<User>(V)->op_begin()+1,
                 cast<User>(V)->op_end());
@@ -104,20 +63,6 @@ static const Value *GetGEPOperands(const Value *V,
   return V;
 }
 
-/// isIdentifiedObject - Return true if this pointer refers to a distinct and
-/// identifiable object.  This returns true for:
-///    Global Variables and Functions
-///    Allocas and Mallocs
-///    ByVal and NoAlias Arguments
-///
-static bool isIdentifiedObject(const Value *V) {
-  if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
-    return true;
-  if (const Argument *A = dyn_cast<Argument>(V))
-    return A->hasNoAliasAttr() || A->hasByValAttr();
-  return false;
-}
-
 /// isKnownNonNull - Return true if we know that the specified value is never
 /// null.
 static bool isKnownNonNull(const Value *V) {
@@ -138,14 +83,19 @@ static bool isKnownNonNull(const Value *V) {
 /// object that never escapes from the function.
 static bool isNonEscapingLocalObject(const Value *V) {
   // If this is a local allocation, check to see if it escapes.
-  if (isa<AllocationInst>(V))
-    return !AddressMightEscape(V);
-      
+  if (isa<AllocationInst>(V) || isNoAliasCall(V))
+    return !PointerMayBeCaptured(V, false);
+
   // If this is an argument that corresponds to a byval or noalias argument,
-  // it can't escape either.
+  // then it has not escaped before entering the function.  Check if it escapes
+  // inside the function.
   if (const Argument *A = dyn_cast<Argument>(V))
-    if (A->hasByValAttr() || A->hasNoAliasAttr())
-      return !AddressMightEscape(V);
+    if (A->hasByValAttr() || A->hasNoAliasAttr()) {
+      // Don't bother analyzing arguments already known not to escape.
+      if (A->hasNoCaptureAttr())
+        return true;
+      return !PointerMayBeCaptured(V, false);
+    }
   return false;
 }
 
@@ -153,21 +103,32 @@ static bool isNonEscapingLocalObject(const Value *V) {
 /// isObjectSmallerThan - Return true if we can prove that the object specified
 /// by V is smaller than Size.
 static bool isObjectSmallerThan(const Value *V, unsigned Size,
-                                const TargetData &TD) {
-  const Type *AccessTy = 0;
-  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+                                LLVMContext &Context, const TargetData &TD) {
+  const Type *AccessTy;
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
     AccessTy = GV->getType()->getElementType();
-  
-  if (const AllocationInst *AI = dyn_cast<AllocationInst>(V))
+  } else if (const AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
     if (!AI->isArrayAllocation())
       AccessTy = AI->getType()->getElementType();
-
-  if (const Argument *A = dyn_cast<Argument>(V))
+    else
+      return false;
+  } else if (const CallInst* CI = extractMallocCall(V)) {
+    if (!isArrayMalloc(V, Context, &TD))
+      // The size is the argument to the malloc call.
+      if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getOperand(1)))
+        return (C->getZExtValue() < Size);
+    return false;
+  } else if (const Argument *A = dyn_cast<Argument>(V)) {
     if (A->hasByValAttr())
       AccessTy = cast<PointerType>(A->getType())->getElementType();
+    else
+      return false;
+  } else {
+    return false;
+  }
   
-  if (AccessTy && AccessTy->isSized())
-    return TD.getABITypeSize(AccessTy) < Size;
+  if (AccessTy->isSized())
+    return TD.getTypeAllocSize(AccessTy) < Size;
   return false;
 }
 
@@ -187,11 +148,10 @@ namespace {
     explicit NoAA(void *PID) : ImmutablePass(PID) { }
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-      AU.addRequired<TargetData>();
     }
 
     virtual void initializePass() {
-      TD = &getAnalysis<TargetData>();
+      TD = getAnalysisIfAvailable<TargetData>();
     }
 
     virtual AliasResult alias(const Value *V1, unsigned V1Size,
@@ -199,14 +159,9 @@ namespace {
       return MayAlias;
     }
 
-    virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
-                                         std::vector<PointerAccessInfo> *Info) {
-      return UnknownModRefBehavior;
-    }
-
     virtual void getArgumentAccesses(Function *F, CallSite CS,
                                      std::vector<PointerAccessInfo> &Info) {
-      assert(0 && "This method may not be called on this function!");
+      llvm_unreachable("This method may not be called on this function!");
     }
 
     virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals) { }
@@ -249,9 +204,7 @@ namespace {
                       const Value *V2, unsigned V2Size);
 
     ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
-    ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
-      return NoAA::getModRefInfo(CS1,CS2);
-    }
+    ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
 
     /// hasNoModRefInfoForCalls - We can provide mod/ref information against
     /// non-escaping allocations.
@@ -262,6 +215,11 @@ namespace {
     bool pointsToConstantMemory(const Value *P);
 
   private:
+    // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+    // against another.
+    AliasResult aliasGEP(const Value *V1, unsigned V1Size,
+                         const Value *V2, unsigned V2Size);
+
     // CheckGEPInstructions - Check two GEP instructions with known
     // must-aliasing base pointers.  This checks to see if the index expressions
     // preclude the pointers from aliasing...
@@ -295,6 +253,7 @@ bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
   return false;
 }
 
+
 // getModRefInfo - Check to see if the specified callsite can clobber the
 // specified memory object.  Since we only look at local properties of this
 // function, we really can't say much about this query.  We do, however, use
@@ -318,7 +277,7 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
     // If the pointer is to a locally allocated object that does not escape,
     // then the call can not mod/ref the pointer unless the call takes the
     // argument without capturing it.
-    if (isNonEscapingLocalObject(Object)) {
+    if (isNonEscapingLocalObject(Object) && CS.getInstruction() != Object) {
       bool passedAsArg = false;
       // TODO: Eventually only check 'nocapture' arguments.
       for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
@@ -330,6 +289,27 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
       if (!passedAsArg)
         return NoModRef;
     }
+
+    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+      switch (II->getIntrinsicID()) {
+      default: break;
+      case Intrinsic::atomic_cmp_swap:
+      case Intrinsic::atomic_swap:
+      case Intrinsic::atomic_load_add:
+      case Intrinsic::atomic_load_sub:
+      case Intrinsic::atomic_load_and:
+      case Intrinsic::atomic_load_nand:
+      case Intrinsic::atomic_load_or:
+      case Intrinsic::atomic_load_xor:
+      case Intrinsic::atomic_load_max:
+      case Intrinsic::atomic_load_min:
+      case Intrinsic::atomic_load_umax:
+      case Intrinsic::atomic_load_umin:
+        if (alias(II->getOperand(1), Size, P, Size) == NoAlias)
+          return NoModRef;
+        break;
+      }
+    }
   }
 
   // The AliasAnalysis base class has some smarts, lets use them.
@@ -337,92 +317,64 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
 }
 
 
-// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
-// as array references.  Note that this function is heavily tail recursive.
-// Hopefully we have a smart C++ compiler.  :)
-//
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
-                          const Value *V2, unsigned V2Size) {
-  // Strip off any constant expression casts if they exist
-  if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V1))
-    if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
-      V1 = CE->getOperand(0);
-  if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V2))
-    if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
-      V2 = CE->getOperand(0);
-
-  // Are we checking for alias of the same value?
-  if (V1 == V2) return MustAlias;
-
-  if ((!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType())) &&
-      V1->getType() != Type::Int64Ty && V2->getType() != Type::Int64Ty)
-    return NoAlias;  // Scalars cannot alias each other
-
-  // Strip off cast instructions...
-  if (const BitCastInst *I = dyn_cast<BitCastInst>(V1))
-    return alias(I->getOperand(0), V1Size, V2, V2Size);
-  if (const BitCastInst *I = dyn_cast<BitCastInst>(V2))
-    return alias(V1, V1Size, I->getOperand(0), V2Size);
-
-  // Figure out what objects these things are pointing to if we can...
-  const Value *O1 = V1->getUnderlyingObject();
-  const Value *O2 = V2->getUnderlyingObject();
-
-  if (O1 != O2) {
-    // If V1/V2 point to two different objects we know that we have no alias.
-    if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
-      return NoAlias;
-  
-    // Incoming argument cannot alias locally allocated object!
-    if ((isa<Argument>(O1) && isa<AllocationInst>(O2)) ||
-        (isa<Argument>(O2) && isa<AllocationInst>(O1)))
-      return NoAlias;
-    
-    // Most objects can't alias null.
-    if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
-        (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
-      return NoAlias;
-  }
+AliasAnalysis::ModRefResult 
+BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
+  // If CS1 or CS2 are readnone, they don't interact.
+  ModRefBehavior CS1B = AliasAnalysis::getModRefBehavior(CS1);
+  if (CS1B == DoesNotAccessMemory) return NoModRef;
   
-  // If the size of one access is larger than the entire object on the other
-  // side, then we know such behavior is undefined and can assume no alias.
-  const TargetData &TD = getTargetData();
-  if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, TD)) ||
-      (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, TD)))
-    return NoAlias;
+  ModRefBehavior CS2B = AliasAnalysis::getModRefBehavior(CS2);
+  if (CS2B == DoesNotAccessMemory) return NoModRef;
   
-  // If one pointer is the result of a call/invoke and the other is a
-  // non-escaping local object, then we know the object couldn't escape to a
-  // point where the call could return it.
-  if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
-      isNonEscapingLocalObject(O2))
-    return NoAlias;
-  if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
-      isNonEscapingLocalObject(O1))
-    return NoAlias;
+  // If they both only read from memory, just return ref.
+  if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
+    return Ref;
   
+  // Otherwise, fall back to NoAA (mod+ref).
+  return NoAA::getModRefInfo(CS1, CS2);
+}
+
+// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+// against another.
+//
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::aliasGEP(const Value *V1, unsigned V1Size,
+                             const Value *V2, unsigned V2Size) {
   // If we have two gep instructions with must-alias'ing base pointers, figure
   // out if the indexes to the GEP tell us anything about the derived pointer.
   // Note that we also handle chains of getelementptr instructions as well as
   // constant expression getelementptrs here.
   //
   if (isGEP(V1) && isGEP(V2)) {
+    const User *GEP1 = cast<User>(V1);
+    const User *GEP2 = cast<User>(V2);
+    
+    // If V1 and V2 are identical GEPs, just recurse down on both of them.
+    // This allows us to analyze things like:
+    //   P = gep A, 0, i, 1
+    //   Q = gep B, 0, i, 1
+    // by just analyzing A and B.  This is even safe for variable indices.
+    if (GEP1->getType() == GEP2->getType() &&
+        GEP1->getNumOperands() == GEP2->getNumOperands() &&
+        GEP1->getOperand(0)->getType() == GEP2->getOperand(0)->getType() &&
+        // All operands are the same, ignoring the base.
+        std::equal(GEP1->op_begin()+1, GEP1->op_end(), GEP2->op_begin()+1))
+      return alias(GEP1->getOperand(0), V1Size, GEP2->getOperand(0), V2Size);
+    
+    
     // Drill down into the first non-gep value, to test for must-aliasing of
     // the base pointers.
-    const User *G = cast<User>(V1);
-    while (isGEP(G->getOperand(0)) &&
-           G->getOperand(1) ==
-           Constant::getNullValue(G->getOperand(1)->getType()))
-      G = cast<User>(G->getOperand(0));
-    const Value *BasePtr1 = G->getOperand(0);
-
-    G = cast<User>(V2);
-    while (isGEP(G->getOperand(0)) &&
-           G->getOperand(1) ==
-           Constant::getNullValue(G->getOperand(1)->getType()))
-      G = cast<User>(G->getOperand(0));
-    const Value *BasePtr2 = G->getOperand(0);
+    while (isGEP(GEP1->getOperand(0)) &&
+           GEP1->getOperand(1) ==
+           Constant::getNullValue(GEP1->getOperand(1)->getType()))
+      GEP1 = cast<User>(GEP1->getOperand(0));
+    const Value *BasePtr1 = GEP1->getOperand(0);
+
+    while (isGEP(GEP2->getOperand(0)) &&
+           GEP2->getOperand(1) ==
+           Constant::getNullValue(GEP2->getOperand(1)->getType()))
+      GEP2 = cast<User>(GEP2->getOperand(0));
+    const Value *BasePtr2 = GEP2->getOperand(0);
 
     // Do the base pointers alias?
     AliasResult BaseAlias = alias(BasePtr1, ~0U, BasePtr2, ~0U);
@@ -455,79 +407,137 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
   // instruction.  If one pointer is a GEP with a non-zero index of the other
   // pointer, we know they cannot alias.
   //
-  if (isGEP(V2)) {
-    std::swap(V1, V2);
-    std::swap(V1Size, V2Size);
-  }
-
-  if (V1Size != ~0U && V2Size != ~0U)
-    if (isGEP(V1)) {
-      SmallVector<Value*, 16> GEPOperands;
-      const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
-
-      AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
-      if (R == MustAlias) {
-        // If there is at least one non-zero constant index, we know they cannot
-        // alias.
-        bool ConstantFound = false;
-        bool AllZerosFound = true;
-        for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
-          if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
-            if (!C->isNullValue()) {
-              ConstantFound = true;
-              AllZerosFound = false;
-              break;
-            }
-          } else {
-            AllZerosFound = false;
-          }
+  if (V1Size == ~0U || V2Size == ~0U)
+    return MayAlias;
 
-        // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
-        // the ptr, the end result is a must alias also.
-        if (AllZerosFound)
-          return MustAlias;
+  SmallVector<Value*, 16> GEPOperands;
+  const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
+
+  AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
+  if (R == MustAlias) {
+    // If there is at least one non-zero constant index, we know they cannot
+    // alias.
+    bool ConstantFound = false;
+    bool AllZerosFound = true;
+    for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
+      if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
+        if (!C->isNullValue()) {
+          ConstantFound = true;
+          AllZerosFound = false;
+          break;
+        }
+      } else {
+        AllZerosFound = false;
+      }
 
-        if (ConstantFound) {
-          if (V2Size <= 1 && V1Size <= 1)  // Just pointer check?
-            return NoAlias;
+    // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
+    // the ptr, the end result is a must alias also.
+    if (AllZerosFound)
+      return MustAlias;
 
-          // Otherwise we have to check to see that the distance is more than
-          // the size of the argument... build an index vector that is equal to
-          // the arguments provided, except substitute 0's for any variable
-          // indexes we find...
-          if (cast<PointerType>(
-                BasePtr->getType())->getElementType()->isSized()) {
-            for (unsigned i = 0; i != GEPOperands.size(); ++i)
-              if (!isa<ConstantInt>(GEPOperands[i]))
-                GEPOperands[i] =
-                  Constant::getNullValue(GEPOperands[i]->getType());
-            int64_t Offset =
-              getTargetData().getIndexedOffset(BasePtr->getType(),
-                                               &GEPOperands[0],
-                                               GEPOperands.size());
-
-            if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
-              return NoAlias;
-          }
-        }
+    if (ConstantFound) {
+      if (V2Size <= 1 && V1Size <= 1)  // Just pointer check?
+        return NoAlias;
+
+      // Otherwise we have to check to see that the distance is more than
+      // the size of the argument... build an index vector that is equal to
+      // the arguments provided, except substitute 0's for any variable
+      // indexes we find...
+      if (TD &&
+          cast<PointerType>(BasePtr->getType())->getElementType()->isSized()) {
+        for (unsigned i = 0; i != GEPOperands.size(); ++i)
+          if (!isa<ConstantInt>(GEPOperands[i]))
+            GEPOperands[i] = Constant::getNullValue(GEPOperands[i]->getType());
+        int64_t Offset =
+          TD->getIndexedOffset(BasePtr->getType(),
+                               &GEPOperands[0],
+                               GEPOperands.size());
+
+        if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
+          return NoAlias;
       }
     }
+  }
 
   return MayAlias;
 }
 
-// This function is used to determin if the indices of two GEP instructions are
+// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
+// as array references.
+//
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
+                          const Value *V2, unsigned V2Size) {
+  // Strip off any casts if they exist.
+  V1 = V1->stripPointerCasts();
+  V2 = V2->stripPointerCasts();
+
+  // Are we checking for alias of the same value?
+  if (V1 == V2) return MustAlias;
+
+  if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
+    return NoAlias;  // Scalars cannot alias each other
+
+  // Figure out what objects these things are pointing to if we can.
+  const Value *O1 = V1->getUnderlyingObject();
+  const Value *O2 = V2->getUnderlyingObject();
+
+  if (O1 != O2) {
+    // If V1/V2 point to two different objects we know that we have no alias.
+    if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
+      return NoAlias;
+  
+    // Arguments can't alias with local allocations or noalias calls.
+    if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
+        (isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
+      return NoAlias;
+
+    // Most objects can't alias null.
+    if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
+        (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
+      return NoAlias;
+  }
+  
+  // If the size of one access is larger than the entire object on the other
+  // side, then we know such behavior is undefined and can assume no alias.
+  LLVMContext &Context = V1->getContext();
+  if (TD)
+    if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
+        (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
+      return NoAlias;
+  
+  // If one pointer is the result of a call/invoke and the other is a
+  // non-escaping local object, then we know the object couldn't escape to a
+  // point where the call could return it.
+  if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
+      isNonEscapingLocalObject(O2) && O1 != O2)
+    return NoAlias;
+  if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
+      isNonEscapingLocalObject(O1) && O1 != O2)
+    return NoAlias;
+
+  if (!isGEP(V1) && isGEP(V2)) {
+    std::swap(V1, V2);
+    std::swap(V1Size, V2Size);
+  }
+  if (isGEP(V1))
+    return aliasGEP(V1, V1Size, V2, V2Size);
+
+  return MayAlias;
+}
+
+// This function is used to determine if the indices of two GEP instructions are
 // equal. V1 and V2 are the indices.
-static bool IndexOperandsEqual(Value *V1, Value *V2) {
+static bool IndexOperandsEqual(Value *V1, Value *V2, LLVMContext &Context) {
   if (V1->getType() == V2->getType())
     return V1 == V2;
   if (Constant *C1 = dyn_cast<Constant>(V1))
     if (Constant *C2 = dyn_cast<Constant>(V2)) {
       // Sign extend the constants to long types, if necessary
-      if (C1->getType() != Type::Int64Ty)
-        C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
-      if (C2->getType() != Type::Int64Ty) 
-        C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
+      if (C1->getType() != Type::getInt64Ty(Context))
+        C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(Context));
+      if (C2->getType() != Type::getInt64Ty(Context)) 
+        C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(Context));
       return C1 == C2;
     }
   return false;
@@ -548,6 +558,8 @@ BasicAliasAnalysis::CheckGEPInstructions(
 
   const PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
 
+  LLVMContext &Context = GEPPointerTy->getContext();
+
   // Find the (possibly empty) initial sequence of equal values... which are not
   // necessarily constants.
   unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
@@ -555,7 +567,8 @@ BasicAliasAnalysis::CheckGEPInstructions(
   unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
   unsigned UnequalOper = 0;
   while (UnequalOper != MinOperands &&
-         IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
+         IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper],
+         Context)) {
     // Advance through the type as we go...
     ++UnequalOper;
     if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
@@ -619,10 +632,10 @@ BasicAliasAnalysis::CheckGEPInstructions(
         if (Constant *G2OC = dyn_cast<ConstantInt>(const_cast<Value*>(G2Oper))){
           if (G1OC->getType() != G2OC->getType()) {
             // Sign extend both operands to long.
-            if (G1OC->getType() != Type::Int64Ty)
-              G1OC = ConstantExpr::getSExt(G1OC, Type::Int64Ty);
-            if (G2OC->getType() != Type::Int64Ty) 
-              G2OC = ConstantExpr::getSExt(G2OC, Type::Int64Ty);
+            if (G1OC->getType() != Type::getInt64Ty(Context))
+              G1OC = ConstantExpr::getSExt(G1OC, Type::getInt64Ty(Context));
+            if (G2OC->getType() != Type::getInt64Ty(Context)) 
+              G2OC = ConstantExpr::getSExt(G2OC, Type::getInt64Ty(Context));
             GEP1Ops[FirstConstantOper] = G1OC;
             GEP2Ops[FirstConstantOper] = G2OC;
           }
@@ -630,18 +643,39 @@ BasicAliasAnalysis::CheckGEPInstructions(
           if (G1OC != G2OC) {
             // Handle the "be careful" case above: if this is an array/vector
             // subscript, scan for a subsequent variable array index.
-            if (isa<SequentialType>(BasePtr1Ty))  {
-              const Type *NextTy =
-                cast<SequentialType>(BasePtr1Ty)->getElementType();
+            if (const SequentialType *STy =
+                  dyn_cast<SequentialType>(BasePtr1Ty)) {
+              const Type *NextTy = STy;
               bool isBadCase = false;
               
-              for (unsigned Idx = FirstConstantOper+1;
+              for (unsigned Idx = FirstConstantOper;
                    Idx != MinOperands && isa<SequentialType>(NextTy); ++Idx) {
                 const Value *V1 = GEP1Ops[Idx], *V2 = GEP2Ops[Idx];
                 if (!isa<Constant>(V1) || !isa<Constant>(V2)) {
                   isBadCase = true;
                   break;
                 }
+                // If the array is indexed beyond the bounds of the static type
+                // at this level, it will also fall into the "be careful" case.
+                // It would theoretically be possible to analyze these cases,
+                // but for now just be conservatively correct.
+                if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
+                  if (cast<ConstantInt>(G1OC)->getZExtValue() >=
+                        ATy->getNumElements() ||
+                      cast<ConstantInt>(G2OC)->getZExtValue() >=
+                        ATy->getNumElements()) {
+                    isBadCase = true;
+                    break;
+                  }
+                if (const VectorType *VTy = dyn_cast<VectorType>(STy))
+                  if (cast<ConstantInt>(G1OC)->getZExtValue() >=
+                        VTy->getNumElements() ||
+                      cast<ConstantInt>(G2OC)->getZExtValue() >=
+                        VTy->getNumElements()) {
+                    isBadCase = true;
+                    break;
+                  }
+                STy = cast<SequentialType>(NextTy);
                 NextTy = cast<SequentialType>(NextTy)->getElementType();
               }
               
@@ -672,6 +706,10 @@ BasicAliasAnalysis::CheckGEPInstructions(
   // However, one GEP may have more operands than the other.  If this is the
   // case, there may still be hope.  Check this now.
   if (FirstConstantOper == MinOperands) {
+    // Without TargetData, we won't know what the offsets are.
+    if (!TD)
+      return MayAlias;
+
     // Make GEP1Ops be the longer one if there is a longer one.
     if (NumGEP1Ops < NumGEP2Ops) {
       std::swap(GEP1Ops, GEP2Ops);
@@ -691,13 +729,12 @@ BasicAliasAnalysis::CheckGEPInstructions(
               GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
           // Okay, now get the offset.  This is the relative offset for the full
           // instruction.
-          const TargetData &TD = getTargetData();
-          int64_t Offset1 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
-                                                NumGEP1Ops);
+          int64_t Offset1 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops,
+                                                 NumGEP1Ops);
 
           // Now check without any constants at the end.
-          int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
-                                                MinOperands);
+          int64_t Offset2 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops,
+                                                 MinOperands);
 
           // Make sure we compare the absolute difference.
           if (Offset1 > Offset2)
@@ -733,7 +770,8 @@ BasicAliasAnalysis::CheckGEPInstructions(
   const Type *ZeroIdxTy = GEPPointerTy;
   for (unsigned i = 0; i != FirstConstantOper; ++i) {
     if (!isa<StructType>(ZeroIdxTy))
-      GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Type::Int32Ty);
+      GEP1Ops[i] = GEP2Ops[i] = 
+                              Constant::getNullValue(Type::getInt32Ty(Context));
 
     if (const CompositeType *CT = dyn_cast<CompositeType>(ZeroIdxTy))
       ZeroIdxTy = CT->getTypeAtIndex(GEP1Ops[i]);
@@ -774,9 +812,13 @@ BasicAliasAnalysis::CheckGEPInstructions(
           // value possible.
           //
           if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
-            GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,AT->getNumElements()-1);
+            GEP1Ops[i] =
+                  ConstantInt::get(Type::getInt64Ty(Context), 
+                                   AT->getNumElements()-1);
           else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty))
-            GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,VT->getNumElements()-1);
+            GEP1Ops[i] = 
+                  ConstantInt::get(Type::getInt64Ty(Context),
+                                   VT->getNumElements()-1);
         }
       }
 
@@ -811,11 +853,11 @@ BasicAliasAnalysis::CheckGEPInstructions(
     }
   }
 
-  if (GEPPointerTy->getElementType()->isSized()) {
+  if (TD && GEPPointerTy->getElementType()->isSized()) {
     int64_t Offset1 =
-      getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops);
+      TD->getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops);
     int64_t Offset2 = 
-      getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops);
+      TD->getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops);
     assert(Offset1 != Offset2 &&
            "There is at least one different constant here!");