Make the aliassettracker much more precise by actually tracking size

information for various accesses.  What a concept.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5647 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 53 insertions, 33 deletions

diff --git a/include/llvm/Analysis/AliasSetTracker.h b/include/llvm/Analysis/AliasSetTracker.h
index ad71d99ca2..713add5506 100644
--- a/include/llvm/Analysis/AliasSetTracker.h
+++ b/include/llvm/Analysis/AliasSetTracker.h
@@ -29,12 +29,19 @@ class AliasSet {
   class PointerRec {
     HashNodePair *NextInList;
     AliasSet *AS;
+    unsigned Size;
   public:
-    PointerRec() : NextInList(0), AS(0) {}
+    PointerRec() : NextInList(0), AS(0), Size(0) {}
 
     HashNodePair *getNext() const { return NextInList; }
     bool hasAliasSet() const { return AS != 0; }
 
+    void updateSize(unsigned NewSize) {
+      if (NewSize > Size) Size = NewSize;
+    }
+
+    unsigned getSize() const { return Size; }
+
     AliasSet *getAliasSet(AliasSetTracker &AST) { 
       assert(AS && "No AliasSet yet!");
       if (AS->Forward) {
@@ -87,7 +94,7 @@ class AliasSet {
   unsigned AliasTy : 1;
 
   /// Define an iterator for alias sets... this is just a forward iterator.
-  class iterator : public forward_iterator<Value*, ptrdiff_t> {
+  class iterator : public forward_iterator<HashNodePair, ptrdiff_t> {
     HashNodePair *CurNode;
   public:
     iterator(HashNodePair *CN = 0) : CurNode(CN) {}
@@ -102,11 +109,11 @@ class AliasSet {
       return *this;
     }
   
-    value_type operator*() const {
+    value_type &operator*() const {
       assert(CurNode && "Dereferencing AliasSet.end()!");
-      return CurNode->first;
+      return *CurNode;
     }
-    value_type operator->() const { return operator*(); }
+    value_type *operator->() const { return &operator*(); }
   
     iterator& operator++() {                // Preincrement
       assert(CurNode && "Advancing past AliasSet.end()!");
@@ -148,8 +155,8 @@ private:
   AliasSet() : PtrListHead(0), PtrListTail(0), Forward(0), RefCount(0),
                AccessTy(NoModRef), AliasTy(MustAlias) {
   }
-  Value *getSomePointer() const {
-    return PtrListHead ? PtrListHead->first : 0;
+  HashNodePair *getSomePointer() const {
+    return PtrListHead ? PtrListHead : 0;
   }
 
   /// getForwardedTarget - Return the real alias set this represents.  If this
@@ -170,13 +177,13 @@ private:
 
   void removeFromTracker(AliasSetTracker &AST);
 
-  void addPointer(AliasSetTracker &AST, HashNodePair &Entry);
+  void addPointer(AliasSetTracker &AST, HashNodePair &Entry, unsigned Size);
   void addCallSite(CallSite CS);
 
   /// aliasesPointer - Return true if the specified pointer "may" (or must)
   /// alias one of the members in the set.
   ///
-  bool aliasesPointer(const Value *Ptr, AliasAnalysis &AA) const;
+  bool aliasesPointer(const Value *Ptr, unsigned Size, AliasAnalysis &AA) const;
   bool aliasesCallSite(CallSite CS, AliasAnalysis &AA) const;
 };
 
@@ -219,7 +226,7 @@ public:
 
   /// getAliasSetForPointer - Return the alias set that the specified pointer
   /// lives in...
-  AliasSet &getAliasSetForPointer(Value *P);
+  AliasSet &getAliasSetForPointer(Value *P, unsigned Size);
 
   /// getAliasAnalysis - Return the underlying alias analysis object used by
   /// this tracker.
@@ -248,11 +255,11 @@ private:
                                             AliasSet::PointerRec())).first;
   }
 
-  void addPointer(Value *P, AliasSet::AccessType E) {
-    AliasSet &AS = getAliasSetForPointer(P);
+  void addPointer(Value *P, unsigned Size, AliasSet::AccessType E) {
+    AliasSet &AS = getAliasSetForPointer(P, Size);
     AS.AccessTy |= E;
   }
-  AliasSet *findAliasSetForPointer(const Value *Ptr);
+  AliasSet *findAliasSetForPointer(const Value *Ptr, unsigned Size);
 
   AliasSet *findAliasSetForCallSite(CallSite CS);
 };
diff --git a/lib/Analysis/AliasSetTracker.cpp b/lib/Analysis/AliasSetTracker.cpp
index acb200481a..f58aaa3e81 100644
--- a/lib/Analysis/AliasSetTracker.cpp
+++ b/lib/Analysis/AliasSetTracker.cpp
@@ -10,11 +10,10 @@
 #include "llvm/iOther.h"
 #include "llvm/iTerminators.h"
 #include "llvm/Pass.h"
+#include "llvm/Target/TargetData.h"
 #include "llvm/Assembly/Writer.h"
 #include "llvm/Support/InstIterator.h"
 
-// FIXME: This should keep sizes associated with pointers!
-
 /// mergeSetIn - Merge the specified alias set into this alias set...
 ///
 void AliasSet::mergeSetIn(AliasSet &AS) {
@@ -54,17 +53,25 @@ void AliasSet::removeFromTracker(AliasSetTracker &AST) {
   AST.removeAliasSet(this);
 }
 
-void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry){
+void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry,
+                          unsigned Size) {
   assert(!Entry.second.hasAliasSet() && "Entry already in set!");
 
   AliasAnalysis &AA = AST.getAliasAnalysis();
 
   if (isMustAlias())    // Check to see if we have to downgrade to _may_ alias
-    if (Value *V = getSomePointer())
-      if (AA.alias(V, ~0, Entry.first, ~0) == AliasAnalysis::MayAlias)
+    if (HashNodePair *P = getSomePointer()) {
+      AliasAnalysis::AliasResult Result =
+        AA.alias(P->first, P->second.getSize(), Entry.first, Size);
+      if (Result == AliasAnalysis::MayAlias)
         AliasTy = MayAlias;
+      else                  // First entry of must alias must have maximum size!
+        P->second.updateSize(Size);
+      assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
+    }
 
   Entry.second.setAliasSet(this);
+  Entry.second.updateSize(Size);
 
   // Add it to the end of the list...
   if (PtrListTail)
@@ -77,27 +84,28 @@ void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry){
 
 void AliasSet::addCallSite(CallSite CS) {
   CallSites.push_back(CS);
-  AliasTy = MayAlias;         // FIXME: Too conservative
+  AliasTy = MayAlias;         // FIXME: Too conservative?
 }
 
 /// aliasesPointer - Return true if the specified pointer "may" (or must)
 /// alias one of the members in the set.
 ///
-bool AliasSet::aliasesPointer(const Value *Ptr, AliasAnalysis &AA) const {
+bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size,
+                              AliasAnalysis &AA) const {
   if (AliasTy == MustAlias) {
     assert(CallSites.empty() && "Illegal must alias set!");
 
     // If this is a set of MustAliases, only check to see if the pointer aliases
     // SOME value in the set...
-    Value *SomePtr = getSomePointer();
+    HashNodePair *SomePtr = getSomePointer();
     assert(SomePtr && "Empty must-alias set??");
-    return AA.alias(SomePtr, ~0, Ptr, ~0);
+    return AA.alias(SomePtr->first, SomePtr->second.getSize(), Ptr, Size);
   }
 
   // If this is a may-alias set, we have to check all of the pointers in the set
   // to be sure it doesn't alias the set...
   for (iterator I = begin(), E = end(); I != E; ++I)
-    if (AA.alias(Ptr, ~0, *I, ~0))
+    if (AA.alias(Ptr, Size, I->first, I->second.getSize()))
       return true;
 
   // Check the call sites list and invoke list...
@@ -118,10 +126,11 @@ bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const {
 /// instruction referring to the pointer into.  If there are multiple alias sets
 /// that may alias the pointer, merge them together and return the unified set.
 ///
-AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr) {
+AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
+                                                  unsigned Size) {
   AliasSet *FoundSet = 0;
   for (iterator I = begin(), E = end(); I != E; ++I)
-    if (!I->Forward && I->aliasesPointer(Ptr, AA)) {
+    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
       if (FoundSet == 0) {  // If this is the first alias set ptr can go into...
         FoundSet = I;       // Remember it.
       } else {              // Otherwise, we must merge the sets...
@@ -151,31 +160,34 @@ AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
 
 /// getAliasSetForPointer - Return the alias set that the specified pointer
 /// lives in...
-AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer) {
+AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size){
   AliasSet::HashNodePair &Entry = getEntryFor(Pointer);
 
   // Check to see if the pointer is already known...
-  if (Entry.second.hasAliasSet()) {
+  if (Entry.second.hasAliasSet() && Size <= Entry.second.getSize()) {
     // Return the set!
     return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this);
-  } else if (AliasSet *AS = findAliasSetForPointer(Pointer)) {
+  } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) {
     // Add it to the alias set it aliases...
-    AS->addPointer(*this, Entry);
+    AS->addPointer(*this, Entry, Size);
     return *AS;
   } else {
     // Otherwise create a new alias set to hold the loaded pointer...
     AliasSets.push_back(AliasSet());
-    AliasSets.back().addPointer(*this, Entry);
+    AliasSets.back().addPointer(*this, Entry, Size);
     return AliasSets.back();
   }
 }
 
 void AliasSetTracker::add(LoadInst *LI) {
-  addPointer(LI->getOperand(0), AliasSet::Refs);
+  addPointer(LI->getOperand(0),
+             AA.getTargetData().getTypeSize(LI->getType()), AliasSet::Refs);
 }
 
 void AliasSetTracker::add(StoreInst *SI) {
-  addPointer(SI->getOperand(1), AliasSet::Mods);
+  addPointer(SI->getOperand(1),
+             AA.getTargetData().getTypeSize(SI->getOperand(0)->getType()),
+             AliasSet::Mods);
 }
 
 void AliasSetTracker::add(CallSite CS) {
@@ -221,7 +233,8 @@ void AliasSet::print(std::ostream &OS) const {
     OS << "Pointers: ";
     for (iterator I = begin(), E = end(); I != E; ++I) {
       if (I != begin()) OS << ", ";
-      WriteAsOperand(OS, *I);
+      WriteAsOperand(OS << "(", I->first);
+      OS << ", " << I->second.getSize() << ")";
     }
   }
   if (!CallSites.empty()) {