[PM/AA] Rework the names and comments in AliasSetTracker to more

accurately describe what is being tracked.

While these two enums do track mod/ref information and aliasing
information, they don't represent the exact same things as either the
mod/ref enums or the alias result enum in AA. They're definitions are
dominated by the structure of their lattice and the bit's various
semantics. This patch just calls them what they are and tries to spell
out usefully distinct names for these things.

This will clear the path for using a raw unscoped enum to represent some
of these concepts across LLVM's analysis library.

No functionality changed here.

Differential Revision: http://reviews.llvm.org/D10494

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240254 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/AliasSetTracker.h b/include/llvm/Analysis/AliasSetTracker.h
index ba2eae903da62d851548d8a9ae48631fcd5ebc12..dc9bf34f1701ee75166baa1fa254f15e60d50989 100644 (file)
--- a/include/llvm/Analysis/AliasSetTracker.h
+++ b/include/llvm/Analysis/AliasSetTracker.h
@@ -117,24 +117,30 @@ class AliasSet : public ilist_node<AliasSet> {
   // AliasSets forwarding to it.
   unsigned RefCount : 28;
 
-  /// AccessType - Keep track of whether this alias set merely refers to the
-  /// locations of memory, whether it modifies the memory, or whether it does
-  /// both.  The lattice goes from "NoModRef" to either Refs or Mods, then to
-  /// ModRef as necessary.
+  /// The kinds of access this alias set models.
   ///
-  enum AccessType {
-    NoModRef = 0, Refs = 1,         // Ref = bit 1
-    Mods     = 2, ModRef = 3        // Mod = bit 2
+  /// We keep track of whether this alias set merely refers to the locations of
+  /// memory (and not any particular access), whether it modifies or references
+  /// the memory, or whether it does both. The lattice goes from "NoAccess" to
+  /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
+  enum AccessLattice {
+    NoAccess = 0,
+    RefAccess = 1,
+    ModAccess = 2,
+    ModRefAccess = RefAccess | ModAccess
   };
-  unsigned AccessTy : 2;
+  unsigned Access : 2;
 
-  /// AliasType - Keep track the relationships between the pointers in the set.
-  /// Lattice goes from MustAlias to MayAlias.
+  /// The kind of alias relationship between pointers of the set.
   ///
-  enum AliasType {
-    MustAlias = 0, MayAlias = 1
+  /// These represent conservatively correct alias results between any members
+  /// of the set. We represent these independently of the values of alias
+  /// results in order to pack it into a single bit. Lattice goes from
+  /// MustAlias to MayAlias.
+  enum AliasLattice {
+    SetMustAlias = 0, SetMayAlias = 1
   };
-  unsigned AliasTy : 1;
+  unsigned Alias : 1;
 
   // Volatile - True if this alias set contains volatile loads or stores.
   bool Volatile : 1;
@@ -153,10 +159,10 @@ class AliasSet : public ilist_node<AliasSet> {
   
 public:
   /// Accessors...
-  bool isRef() const { return AccessTy & Refs; }
-  bool isMod() const { return AccessTy & Mods; }
-  bool isMustAlias() const { return AliasTy == MustAlias; }
-  bool isMayAlias()  const { return AliasTy == MayAlias; }
+  bool isRef() const { return Access & RefAccess; }
+  bool isMod() const { return Access & ModAccess; }
+  bool isMustAlias() const { return Alias == SetMustAlias; }
+  bool isMayAlias()  const { return Alias == SetMayAlias; }
 
   // isVolatile - Return true if this alias set contains volatile loads or
   // stores.
@@ -218,7 +224,7 @@ private:
   friend struct ilist_sentinel_traits<AliasSet>;
   AliasSet()
     : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0),
-      AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) {
+      Access(NoAccess), Alias(SetMustAlias), Volatile(false) {
   }
 
   AliasSet(const AliasSet &AS) = delete;
@@ -419,11 +425,11 @@ private:
   }
 
   AliasSet &addPointer(Value *P, uint64_t Size, const AAMDNodes &AAInfo,
-                       AliasSet::AccessType E,
+                       AliasSet::AccessLattice E,
                        bool &NewSet) {
     NewSet = false;
     AliasSet &AS = getAliasSetForPointer(P, Size, AAInfo, &NewSet);
-    AS.AccessTy |= E;
+    AS.Access |= E;
     return AS;
   }
   AliasSet *findAliasSetForPointer(const Value *Ptr, uint64_t Size,

diff --git a/lib/Analysis/AliasSetTracker.cpp b/lib/Analysis/AliasSetTracker.cpp
index f7a803c5f4ce16a9873c6ffaba64f48e4261d247..46030fb4c619aad054f4a1630e3dc60e4fe15c5a 100644 (file)
--- a/lib/Analysis/AliasSetTracker.cpp
+++ b/lib/Analysis/AliasSetTracker.cpp
@@ -32,11 +32,11 @@ void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
   assert(!Forward && "This set is a forwarding set!!");
 
   // Update the alias and access types of this set...
-  AccessTy |= AS.AccessTy;
-  AliasTy  |= AS.AliasTy;
+  Access |= AS.Access;
+  Alias  |= AS.Alias;
   Volatile |= AS.Volatile;
 
-  if (AliasTy == MustAlias) {
+  if (Alias == SetMustAlias) {
     // Check that these two merged sets really are must aliases.  Since both
     // used to be must-alias sets, we can just check any pointer from each set
     // for aliasing.
@@ -48,7 +48,7 @@ void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
     if (AA.alias(MemoryLocation(L->getValue(), L->getSize(), L->getAAInfo()),
                  MemoryLocation(R->getValue(), R->getSize(), R->getAAInfo())) !=
         AliasAnalysis::MustAlias)
-      AliasTy = MayAlias;
+      Alias = SetMayAlias;
   }
 
   bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
@@ -105,7 +105,7 @@ void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
           AA.alias(MemoryLocation(P->getValue(), P->getSize(), P->getAAInfo()),
                    MemoryLocation(Entry.getValue(), Size, AAInfo));
       if (Result != AliasAnalysis::MustAlias)
-        AliasTy = MayAlias;
+        Alias = SetMayAlias;
       else                  // First entry of must alias must have maximum size!
         P->updateSizeAndAAInfo(Size, AAInfo);
       assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
@@ -128,14 +128,14 @@ void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
   UnknownInsts.emplace_back(I);
 
   if (!I->mayWriteToMemory()) {
-    AliasTy = MayAlias;
-    AccessTy |= Refs;
+    Alias = SetMayAlias;
+    Access |= RefAccess;
     return;
   }
 
   // FIXME: This should use mod/ref information to make this not suck so bad
-  AliasTy = MayAlias;
-  AccessTy = ModRef;
+  Alias = SetMayAlias;
+  Access = ModRefAccess;
 }
 
 /// aliasesPointer - Return true if the specified pointer "may" (or must)
@@ -144,7 +144,7 @@ void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
 bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
                               const AAMDNodes &AAInfo,
                               AliasAnalysis &AA) const {
-  if (AliasTy == MustAlias) {
+  if (Alias == SetMustAlias) {
     assert(UnknownInsts.empty() && "Illegal must alias set!");
 
     // If this is a set of MustAliases, only check to see if the pointer aliases
@@ -296,7 +296,7 @@ AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
 
 bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo) {
   bool NewPtr;
-  addPointer(Ptr, Size, AAInfo, AliasSet::NoModRef, NewPtr);
+  addPointer(Ptr, Size, AAInfo, AliasSet::NoAccess, NewPtr);
   return NewPtr;
 }
 
@@ -307,11 +307,11 @@ bool AliasSetTracker::add(LoadInst *LI) {
   AAMDNodes AAInfo;
   LI->getAAMetadata(AAInfo);
 
-  AliasSet::AccessType ATy = AliasSet::Refs;
+  AliasSet::AccessLattice Access = AliasSet::RefAccess;
   bool NewPtr;
   AliasSet &AS = addPointer(LI->getOperand(0),
                             AA.getTypeStoreSize(LI->getType()),
-                            AAInfo, ATy, NewPtr);
+                            AAInfo, Access, NewPtr);
   if (LI->isVolatile()) AS.setVolatile();
   return NewPtr;
 }
@@ -322,12 +322,12 @@ bool AliasSetTracker::add(StoreInst *SI) {
   AAMDNodes AAInfo;
   SI->getAAMetadata(AAInfo);
 
-  AliasSet::AccessType ATy = AliasSet::Mods;
+  AliasSet::AccessLattice Access = AliasSet::ModAccess;
   bool NewPtr;
   Value *Val = SI->getOperand(0);
   AliasSet &AS = addPointer(SI->getOperand(1),
                             AA.getTypeStoreSize(Val->getType()),
-                            AAInfo, ATy, NewPtr);
+                            AAInfo, Access, NewPtr);
   if (SI->isVolatile()) AS.setVolatile();
   return NewPtr;
 }
@@ -338,7 +338,7 @@ bool AliasSetTracker::add(VAArgInst *VAAI) {
 
   bool NewPtr;
   addPointer(VAAI->getOperand(0), MemoryLocation::UnknownSize, AAInfo,
-             AliasSet::ModRef, NewPtr);
+             AliasSet::ModRefAccess, NewPtr);
   return NewPtr;
 }
 
@@ -397,7 +397,7 @@ void AliasSetTracker::add(const AliasSetTracker &AST) {
     for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
       AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
                                    ASI.getAAInfo(),
-                                   (AliasSet::AccessType)AS.AccessTy, X);
+                                   (AliasSet::AccessLattice)AS.Access, X);
       if (AS.isVolatile()) NewAS.setVolatile();
     }
   }
@@ -572,13 +572,13 @@ void AliasSetTracker::copyValue(Value *From, Value *To) {
 
 void AliasSet::print(raw_ostream &OS) const {
   OS << "  AliasSet[" << (const void*)this << ", " << RefCount << "] ";
-  OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
-  switch (AccessTy) {
-  case NoModRef: OS << "No access "; break;
-  case Refs    : OS << "Ref       "; break;
-  case Mods    : OS << "Mod       "; break;
-  case ModRef  : OS << "Mod/Ref   "; break;
-  default: llvm_unreachable("Bad value for AccessTy!");
+  OS << (Alias == SetMustAlias ? "must" : "may") << " alias, ";
+  switch (Access) {
+  case NoAccess:     OS << "No access "; break;
+  case RefAccess:    OS << "Ref       "; break;
+  case ModAccess:    OS << "Mod       "; break;
+  case ModRefAccess: OS << "Mod/Ref   "; break;
+  default: llvm_unreachable("Bad value for Access!");
   }
   if (isVolatile()) OS << "[volatile] ";
   if (Forward)