Move all the logic for function attributes and call attributes out of the

AliasAnalysis base class and into BasicAliasAnalyais. This avoids confusion
about where such logic is happening when there are other AliasAnalysis
implementations present.

Move the logic for translating two-callsite getModRefInfo queries into
other AliasAnalysis queries out of BasicAliasAnalysis and into the
AliasAnalysis base class, as it is useful for other AliasAnalysis
implementations.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110421 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 238 insertions, 179 deletions

diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 2eb0bf34ed..16131cbc11 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -65,9 +65,127 @@ void AliasAnalysis::copyValue(Value *From, Value *To) {
 }
 
 AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
+                             const Value *P, unsigned Size) {
+  // Don't assert AA because BasicAA calls us in order to make use of the
+  // logic here.
+
+  ModRefBehavior MRB = getModRefBehavior(CS);
+  if (MRB == DoesNotAccessMemory)
+    return NoModRef;
+
+  ModRefResult Mask = ModRef;
+  if (MRB == OnlyReadsMemory)
+    Mask = Ref;
+  else if (MRB == AliasAnalysis::AccessesArguments) {
+    bool doesAlias = false;
+    for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+         AI != AE; ++AI)
+      if (!isNoAlias(*AI, ~0U, P, Size)) {
+        doesAlias = true;
+        break;
+      }
+
+    if (!doesAlias)
+      return NoModRef;
+  }
+
+  // If P points to a constant memory location, the call definitely could not
+  // modify the memory location.
+  if ((Mask & Mod) && pointsToConstantMemory(P))
+    Mask = ModRefResult(Mask & ~Mod);
+
+  // If this is BasicAA, don't forward.
+  if (!AA) return Mask;
+
+  // Otherwise, fall back to the next AA in the chain. But we can merge
+  // in any mask we've managed to compute.
+  return ModRefResult(AA->getModRefInfo(CS, P, Size) & Mask);
+}
+
+AliasAnalysis::ModRefResult
 AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
+  // Don't assert AA because BasicAA calls us in order to make use of the
+  // logic here.
+
+  // If CS1 or CS2 are readnone, they don't interact.
+  ModRefBehavior CS1B = getModRefBehavior(CS1);
+  if (CS1B == DoesNotAccessMemory) return NoModRef;
+
+  ModRefBehavior CS2B = getModRefBehavior(CS2);
+  if (CS2B == DoesNotAccessMemory) return NoModRef;
+
+  // If they both only read from memory, there is no dependence.
+  if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
+    return NoModRef;
+
+  AliasAnalysis::ModRefResult Mask = ModRef;
+
+  // If CS1 only reads memory, the only dependence on CS2 can be
+  // from CS1 reading memory written by CS2.
+  if (CS1B == OnlyReadsMemory)
+    Mask = ModRefResult(Mask & Ref);
+
+  // If CS2 only access memory through arguments, accumulate the mod/ref
+  // information from CS1's references to the memory referenced by
+  // CS2's arguments.
+  if (CS2B == AccessesArguments) {
+    AliasAnalysis::ModRefResult R = NoModRef;
+    for (ImmutableCallSite::arg_iterator
+         I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+      R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
+      if (R == Mask)
+        break;
+    }
+    return R;
+  }
+
+  // If CS1 only accesses memory through arguments, check if CS2 references
+  // any of the memory referenced by CS1's arguments. If not, return NoModRef.
+  if (CS1B == AccessesArguments) {
+    AliasAnalysis::ModRefResult R = NoModRef;
+    for (ImmutableCallSite::arg_iterator
+         I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
+      if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
+        R = Mask;
+        break;
+      }
+    if (R == NoModRef)
+      return R;
+  }
+
+  // If this is BasicAA, don't forward.
+  if (!AA) return Mask;
+
+  // Otherwise, fall back to the next AA in the chain. But we can merge
+  // in any mask we've managed to compute.
+  return ModRefResult(AA->getModRefInfo(CS1, CS2) & Mask);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+  // Don't assert AA because BasicAA calls us in order to make use of the
+  // logic here.
+
+  ModRefBehavior Min = UnknownModRefBehavior;
+
+  // Call back into the alias analysis with the other form of getModRefBehavior
+  // to see if it can give a better response.
+  if (const Function *F = CS.getCalledFunction())
+    Min = getModRefBehavior(F);
+
+  // If this is BasicAA, don't forward.
+  if (!AA) return Min;
+
+  // Otherwise, fall back to the next AA in the chain. But we can merge
+  // in any result we've managed to compute.
+  return std::min(AA->getModRefBehavior(CS), Min);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(const Function *F) {
   assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
-  return AA->getModRefInfo(CS1, CS2);
+  return AA->getModRefBehavior(F);
 }
 
 
@@ -112,70 +230,12 @@ AliasAnalysis::getModRefInfo(const StoreInst *S, const Value *P, unsigned Size)
 }
 
 AliasAnalysis::ModRefBehavior
-AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
-  if (CS.doesNotAccessMemory())
-    // Can't do better than this.
-    return DoesNotAccessMemory;
-  ModRefBehavior MRB = getModRefBehavior(CS.getCalledFunction());
-  if (MRB != DoesNotAccessMemory && CS.onlyReadsMemory())
-    return OnlyReadsMemory;
-  return MRB;
-}
-
-AliasAnalysis::ModRefBehavior
-AliasAnalysis::getModRefBehavior(const Function *F) {
-  if (F) {
-    if (F->doesNotAccessMemory())
-      // Can't do better than this.
-      return DoesNotAccessMemory;
-    if (F->onlyReadsMemory())
-      return OnlyReadsMemory;
-    if (unsigned id = F->getIntrinsicID())
-      return getIntrinsicModRefBehavior(id);
-  }
-  return UnknownModRefBehavior;
-}
-
-AliasAnalysis::ModRefBehavior
 AliasAnalysis::getIntrinsicModRefBehavior(unsigned iid) {
 #define GET_INTRINSIC_MODREF_BEHAVIOR
 #include "llvm/Intrinsics.gen"
 #undef GET_INTRINSIC_MODREF_BEHAVIOR
 }
 
-AliasAnalysis::ModRefResult
-AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
-                             const Value *P, unsigned Size) {
-  ModRefBehavior MRB = getModRefBehavior(CS);
-  if (MRB == DoesNotAccessMemory)
-    return NoModRef;
-  
-  ModRefResult Mask = ModRef;
-  if (MRB == OnlyReadsMemory)
-    Mask = Ref;
-  else if (MRB == AliasAnalysis::AccessesArguments) {
-    bool doesAlias = false;
-    for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
-         AI != AE; ++AI)
-      if (!isNoAlias(*AI, ~0U, P, Size)) {
-        doesAlias = true;
-        break;
-      }
-
-    if (!doesAlias)
-      return NoModRef;
-  }
-
-  if (!AA) return Mask;
-
-  // If P points to a constant memory location, the call definitely could not
-  // modify the memory location.
-  if ((Mask & Mod) && AA->pointsToConstantMemory(P))
-    Mask = ModRefResult(Mask & ~Mod);
-
-  return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
-}
-
 // AliasAnalysis destructor: DO NOT move this to the header file for
 // AliasAnalysis or else clients of the AliasAnalysis class may not depend on
 // the AliasAnalysis.o file in the current .a file, causing alias analysis
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 5ecc99355f..ec58a42352 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -152,6 +152,13 @@ namespace {
       return MayAlias;
     }
 
+    virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
+      return UnknownModRefBehavior;
+    }
+    virtual ModRefBehavior getModRefBehavior(const Function *F) {
+      return UnknownModRefBehavior;
+    }
+
     virtual bool pointsToConstantMemory(const Value *P) { return false; }
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
                                        const Value *P, unsigned Size) {
@@ -217,8 +224,8 @@ namespace {
     static char ID; // Class identification, replacement for typeinfo
     BasicAliasAnalysis() : NoAA(&ID) {}
 
-    AliasResult alias(const Value *V1, unsigned V1Size,
-                      const Value *V2, unsigned V2Size) {
+    virtual AliasResult alias(const Value *V1, unsigned V1Size,
+                              const Value *V2, unsigned V2Size) {
       assert(Visited.empty() && "Visited must be cleared after use!");
       assert(notDifferentParent(V1, V2) &&
              "BasicAliasAnalysis doesn't support interprocedural queries.");
@@ -227,14 +234,26 @@ namespace {
       return Alias;
     }
 
-    ModRefResult getModRefInfo(ImmutableCallSite CS,
-                               const Value *P, unsigned Size);
-    ModRefResult getModRefInfo(ImmutableCallSite CS1,
-                               ImmutableCallSite CS2);
+    virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+                                       const Value *P, unsigned Size);
+
+    virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+                                       ImmutableCallSite CS2) {
+      // The AliasAnalysis base class has some smarts, lets use them.
+      return AliasAnalysis::getModRefInfo(CS1, CS2);
+    }
 
     /// pointsToConstantMemory - Chase pointers until we find a (constant
     /// global) or not.
-    bool pointsToConstantMemory(const Value *P);
+    virtual bool pointsToConstantMemory(const Value *P);
+
+    /// getModRefBehavior - Return the behavior when calling the given
+    /// call site.
+    virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+
+    /// getModRefBehavior - Return the behavior when calling the given function.
+    /// For use when the call site is not known.
+    virtual ModRefBehavior getModRefBehavior(const Function *F);
 
     /// getAdjustedAnalysisPointer - This method is used when a pass implements
     /// an analysis interface through multiple inheritance.  If needed, it
@@ -290,9 +309,42 @@ bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
     // global to be marked constant in some modules and non-constant in others.
     // GV may even be a declaration, not a definition.
     return GV->isConstant();
-  return false;
+
+  return NoAA::pointsToConstantMemory(P);
 }
 
+/// getModRefBehavior - Return the behavior when calling the given call site.
+AliasAnalysis::ModRefBehavior
+BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+  if (CS.doesNotAccessMemory())
+    // Can't do better than this.
+    return DoesNotAccessMemory;
+
+  ModRefBehavior Min = UnknownModRefBehavior;
+
+  // If the callsite knows it only reads memory, don't return worse
+  // than that.
+  if (CS.onlyReadsMemory())
+    Min = OnlyReadsMemory;
+
+  // The AliasAnalysis base class has some smarts, lets use them.
+  return std::min(AliasAnalysis::getModRefBehavior(CS), Min);
+}
+
+/// getModRefBehavior - Return the behavior when calling the given function.
+/// For use when the call site is not known.
+AliasAnalysis::ModRefBehavior
+BasicAliasAnalysis::getModRefBehavior(const Function *F) {
+  if (F->doesNotAccessMemory())
+    // Can't do better than this.
+    return DoesNotAccessMemory;
+  if (F->onlyReadsMemory())
+    return OnlyReadsMemory;
+  if (unsigned id = F->getIntrinsicID())
+    return getIntrinsicModRefBehavior(id);
+
+  return NoAA::getModRefBehavior(F);
+}
 
 /// getModRefInfo - Check to see if the specified callsite can clobber the
 /// specified memory object.  Since we only look at local properties of this
@@ -346,128 +398,75 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
 
   // Finally, handle specific knowledge of intrinsics.
   const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
-  if (II == 0)
-    return AliasAnalysis::getModRefInfo(CS, P, Size);
-
-  switch (II->getIntrinsicID()) {
-  default: break;
-  case Intrinsic::memcpy:
-  case Intrinsic::memmove: {
-    unsigned Len = UnknownSize;
-    if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
-      Len = LenCI->getZExtValue();
-    Value *Dest = II->getArgOperand(0);
-    Value *Src = II->getArgOperand(1);
-    if (isNoAlias(Dest, Len, P, Size)) {
-      if (isNoAlias(Src, Len, P, Size))
-        return NoModRef;
-      return Ref;
-    }
-    break;
-  }
-  case Intrinsic::memset:
-    // Since memset is 'accesses arguments' only, the AliasAnalysis base class
-    // will handle it for the variable length case.
-    if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
-      unsigned Len = LenCI->getZExtValue();
+  if (II != 0)
+    switch (II->getIntrinsicID()) {
+    default: break;
+    case Intrinsic::memcpy:
+    case Intrinsic::memmove: {
+      unsigned Len = UnknownSize;
+      if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
+        Len = LenCI->getZExtValue();
       Value *Dest = II->getArgOperand(0);
-      if (isNoAlias(Dest, Len, P, Size))
+      Value *Src = II->getArgOperand(1);
+      if (isNoAlias(Dest, Len, P, Size)) {
+        if (isNoAlias(Src, Len, P, Size))
+          return NoModRef;
+        return Ref;
+      }
+      break;
+    }
+    case Intrinsic::memset:
+      // Since memset is 'accesses arguments' only, the AliasAnalysis base class
+      // will handle it for the variable length case.
+      if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
+        unsigned Len = LenCI->getZExtValue();
+        Value *Dest = II->getArgOperand(0);
+        if (isNoAlias(Dest, Len, P, Size))
+          return NoModRef;
+      }
+      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 (TD) {
+        Value *Op1 = II->getArgOperand(0);
+        unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
+        if (isNoAlias(Op1, Op1Size, P, Size))
+          return NoModRef;
+      }
+      break;
+    case Intrinsic::lifetime_start:
+    case Intrinsic::lifetime_end:
+    case Intrinsic::invariant_start: {
+      unsigned PtrSize =
+        cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
+      if (isNoAlias(II->getArgOperand(1), PtrSize, P, Size))
         return NoModRef;
+      break;
     }
-    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 (TD) {
-      Value *Op1 = II->getArgOperand(0);
-      unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
-      if (isNoAlias(Op1, Op1Size, P, Size))
+    case Intrinsic::invariant_end: {
+      unsigned PtrSize =
+        cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
+      if (isNoAlias(II->getArgOperand(2), PtrSize, P, Size))
         return NoModRef;
+      break;
+    }
     }
-    break;
-  case Intrinsic::lifetime_start:
-  case Intrinsic::lifetime_end:
-  case Intrinsic::invariant_start: {
-    unsigned PtrSize = cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
-    if (isNoAlias(II->getArgOperand(1), PtrSize, P, Size))
-      return NoModRef;
-    break;
-  }
-  case Intrinsic::invariant_end: {
-    unsigned PtrSize = cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
-    if (isNoAlias(II->getArgOperand(2), PtrSize, P, Size))
-      return NoModRef;
-    break;
-  }
-  }
 
   // The AliasAnalysis base class has some smarts, lets use them.
   return AliasAnalysis::getModRefInfo(CS, P, Size);
 }
 
 
-AliasAnalysis::ModRefResult 
-BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
-                                  ImmutableCallSite CS2) {
-  // If CS1 or CS2 are readnone, they don't interact.
-  ModRefBehavior CS1B = AliasAnalysis::getModRefBehavior(CS1);
-  if (CS1B == DoesNotAccessMemory) return NoModRef;
-  
-  ModRefBehavior CS2B = AliasAnalysis::getModRefBehavior(CS2);
-  if (CS2B == DoesNotAccessMemory) return NoModRef;
-  
-  // If they both only read from memory, there is no dependence.
-  if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
-    return NoModRef;
-
-  AliasAnalysis::ModRefResult Mask = ModRef;
-
-  // If CS1 only reads memory, the only dependence on CS2 can be
-  // from CS1 reading memory written by CS2.
-  if (CS1B == OnlyReadsMemory)
-    Mask = ModRefResult(Mask & Ref);
-  
-  // If CS2 only access memory through arguments, accumulate the mod/ref
-  // information from CS1's references to the memory referenced by
-  // CS2's arguments.
-  if (CS2B == AccessesArguments) {
-    AliasAnalysis::ModRefResult R = NoModRef;
-    for (ImmutableCallSite::arg_iterator
-         I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
-      R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
-      if (R == Mask)
-        break;
-    }
-    return R;
-  }
-
-  // If CS1 only accesses memory through arguments, check if CS2 references
-  // any of the memory referenced by CS1's arguments. If not, return NoModRef.
-  if (CS1B == AccessesArguments) {
-    AliasAnalysis::ModRefResult R = NoModRef;
-    for (ImmutableCallSite::arg_iterator
-         I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
-      if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
-        R = Mask;
-        break;
-      }
-    if (R == NoModRef)
-      return R;
-  }
-
-  // Otherwise, fall back to NoAA (mod+ref).
-  return ModRefResult(NoAA::getModRefInfo(CS1, CS2) & Mask);
-}
-
 /// GetIndexDifference - Dest and Src are the variable indices from two
 /// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
 /// pointers.  Subtract the GEP2 indices from GEP1 to find the symbolic
@@ -843,7 +842,7 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
   if (const SelectInst *S1 = dyn_cast<SelectInst>(V1))
     return aliasSelect(S1, V1Size, V2, V2Size);
 
-  return MayAlias;
+  return NoAA::alias(V1, V1Size, V2, V2Size);
 }
 
 // Make sure that anything that uses AliasAnalysis pulls in this file.