add support for caching pointer dependence queries. Nothing uses this yet

[oota-llvm.git] / lib / Analysis / BasicAliasAnalysis.cpp

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index aa47fb3be5085006d68bb28d11bd14a4210d97c7..5b65fb1199c38bea1fbb3cbb5c51fdc3cd6c2ca4 100644 (file)
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -76,30 +76,6 @@ static bool AddressMightEscape(const Value *V) {
   return false;
 }
 
-/// getUnderlyingObject - This traverses the use chain to figure out what object
-/// the specified value points to.  If the value points to, or is derived from,
-/// a unique object or an argument, return it.  This returns:
-///    Arguments, GlobalVariables, Functions, Allocas, Mallocs.
-static const Value *getUnderlyingObject(const Value *V) {
-  if (!isa<PointerType>(V->getType())) return V;
-
-  // If we are at some type of object, return it. GlobalValues and Allocations
-  // have unique addresses. 
-  if (isa<GlobalValue>(V) || isa<AllocationInst>(V) || isa<Argument>(V))
-    return V;
-
-  // Traverse through different addressing mechanisms...
-  if (const Instruction *I = dyn_cast<Instruction>(V)) {
-    if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I))
-      return getUnderlyingObject(I->getOperand(0));
-  } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
-    if (CE->getOpcode() == Instruction::BitCast || 
-        CE->getOpcode() == Instruction::GetElementPtr)
-      return getUnderlyingObject(CE->getOperand(0));
-  }
-  return V;
-}
-
 static const User *isGEP(const Value *V) {
   if (isa<GetElementPtrInst>(V) ||
       (isa<ConstantExpr>(V) &&
@@ -128,14 +104,24 @@ static const Value *GetGEPOperands(const Value *V,
   return V;
 }
 
+/// isNoAliasCall - Return true if this pointer is returned by a noalias
+/// function.
+static bool isNoAliasCall(const Value *V) {
+  if (isa<CallInst>(V) || isa<InvokeInst>(V))
+    return CallSite(const_cast<Instruction*>(cast<Instruction>(V)))
+      .paramHasAttr(0, Attribute::NoAlias);
+  return false;
+}
+
 /// 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
+///    NoAlias returns
 ///
 static bool isIdentifiedObject(const Value *V) {
-  if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
+  if (isa<GlobalValue>(V) || isa<AllocationInst>(V) || isNoAliasCall(V))
     return true;
   if (const Argument *A = dyn_cast<Argument>(V))
     return A->hasNoAliasAttr() || A->hasByValAttr();
@@ -162,7 +148,7 @@ 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))
+  if (isa<AllocationInst>(V) || isNoAliasCall(V))
     return !AddressMightEscape(V);
       
   // If this is an argument that corresponds to a byval or noalias argument,
@@ -314,7 +300,7 @@ ImmutablePass *llvm::createBasicAliasAnalysisPass() {
 /// global) or not.
 bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
   if (const GlobalVariable *GV = 
-        dyn_cast<GlobalVariable>(getUnderlyingObject(P)))
+        dyn_cast<GlobalVariable>(P->getUnderlyingObject()))
     return GV->isConstant();
   return false;
 }
@@ -327,7 +313,7 @@ bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
 AliasAnalysis::ModRefResult
 BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
   if (!isa<Constant>(P)) {
-    const Value *Object = getUnderlyingObject(P);
+    const Value *Object = P->getUnderlyingObject();
     
     // If this is a tail call and P points to a stack location, we know that
     // the tail call cannot access or modify the local stack.
@@ -379,8 +365,7 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
   // 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)
+  if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
     return NoAlias;  // Scalars cannot alias each other
 
   // Strip off cast instructions...
@@ -390,19 +375,19 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
     return alias(V1, V1Size, I->getOperand(0), V2Size);
 
   // Figure out what objects these things are pointing to if we can...
-  const Value *O1 = getUnderlyingObject(V1);
-  const Value *O2 = getUnderlyingObject(V2);
+  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)))
+    // 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)))