Extend the AliasAnalysis::pointsToConstantMemory interface to allow it

to optionally look for constant or local (alloca) memory.

Teach BasicAliasAnalysis::pointsToConstantMemory to look through Select
and Phi nodes, and to support looking for local memory.

Remove FunctionAttrs' PointsToLocalOrConstantMemory function, now that
AliasAnalysis knows all the tricks that it knew.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118412 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 71 insertions, 23 deletions

diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 472d57ab40..d513ebbc2a 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -49,9 +49,10 @@ AliasAnalysis::alias(const Location &LocA, const Location &LocB) {
   return AA->alias(LocA, LocB);
 }
 
-bool AliasAnalysis::pointsToConstantMemory(const Location &Loc) {
+bool AliasAnalysis::pointsToConstantMemory(const Location &Loc,
+                                           bool OrLocal) {
   assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
-  return AA->pointsToConstantMemory(Loc);
+  return AA->pointsToConstantMemory(Loc, OrLocal);
 }
 
 void AliasAnalysis::deleteValue(Value *V) {
diff --git a/lib/Analysis/AliasAnalysisCounter.cpp b/lib/Analysis/AliasAnalysisCounter.cpp
index a82d959829..23be94ffb0 100644
--- a/lib/Analysis/AliasAnalysisCounter.cpp
+++ b/lib/Analysis/AliasAnalysisCounter.cpp
@@ -95,8 +95,8 @@ namespace {
     }
     
     // FIXME: We could count these too...
-    bool pointsToConstantMemory(const Location &Loc) {
-      return getAnalysis<AliasAnalysis>().pointsToConstantMemory(Loc);
+    bool pointsToConstantMemory(const Location &Loc, bool OrLocal) {
+      return getAnalysis<AliasAnalysis>().pointsToConstantMemory(Loc, OrLocal);
     }
 
     // Forwarding functions: just delegate to a real AA implementation, counting
diff --git a/lib/Analysis/AliasDebugger.cpp b/lib/Analysis/AliasDebugger.cpp
index 4b9aefcb11..f15c05153e 100644
--- a/lib/Analysis/AliasDebugger.cpp
+++ b/lib/Analysis/AliasDebugger.cpp
@@ -113,9 +113,9 @@ namespace {
       return AliasAnalysis::getModRefInfo(CS1,CS2);
     }
     
-    bool pointsToConstantMemory(const Location &Loc) {
+    bool pointsToConstantMemory(const Location &Loc, bool OrLocal) {
       assert(Vals.find(Loc.Ptr) != Vals.end() && "Never seen value in AA before");
-      return AliasAnalysis::pointsToConstantMemory(Loc);
+      return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
     }
 
     virtual void deleteValue(Value *V) {
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 221c8639e0..db493eeedc 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -456,7 +456,7 @@ namespace {
 
     /// pointsToConstantMemory - Chase pointers until we find a (constant
     /// global) or not.
-    virtual bool pointsToConstantMemory(const Location &Loc);
+    virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
 
     /// getModRefBehavior - Return the behavior when calling the given
     /// call site.
@@ -517,18 +517,61 @@ ImmutablePass *llvm::createBasicAliasAnalysisPass() {
   return new BasicAliasAnalysis();
 }
 
+/// pointsToConstantMemory - Returns whether the given pointer value
+/// points to memory that is local to the function, with global constants being
+/// considered local to all functions.
+bool
+BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc, bool OrLocal) {
+  assert(Visited.empty() && "Visited must be cleared after use!");
 
-/// pointsToConstantMemory - Chase pointers until we find a (constant
-/// global) or not.
-bool BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc) {
-  if (const GlobalVariable *GV = 
-        dyn_cast<GlobalVariable>(Loc.Ptr->getUnderlyingObject()))
-    // Note: this doesn't require GV to be "ODR" because it isn't legal for a
-    // 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();
+  SmallVector<const Value *, 16> Worklist;
+  Worklist.push_back(Loc.Ptr);
+  do {
+    const Value *V = Worklist.pop_back_val()->getUnderlyingObject();
+    if (!Visited.insert(V)) {
+      Visited.clear();
+      return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+    }
+
+    // An alloca instruction defines local memory.
+    if (OrLocal && isa<AllocaInst>(V))
+      continue;
+
+    // A global constant counts as local memory for our purposes.
+    if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
+      // Note: this doesn't require GV to be "ODR" because it isn't legal for a
+      // global to be marked constant in some modules and non-constant in
+      // others.  GV may even be a declaration, not a definition.
+      if (!GV->isConstant()) {
+        Visited.clear();
+        return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+      }
+      continue;
+    }
+
+    // If both select values point to local memory, then so does the select.
+    if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
+      Worklist.push_back(SI->getTrueValue());
+      Worklist.push_back(SI->getFalseValue());
+      continue;
+    }
+
+    // If all values incoming to a phi node point to local memory, then so does
+    // the phi.
+    if (const PHINode *PN = dyn_cast<PHINode>(V)) {
+      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+        Worklist.push_back(PN->getIncomingValue(i));
+      continue;
+    }
+
+    // Otherwise be conservative.
+    Visited.clear();
+    return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+
+  } while (!Worklist.empty());
 
-  return AliasAnalysis::pointsToConstantMemory(Loc);
+  Visited.clear();
+  return true;
 }
 
 /// getModRefBehavior - Return the behavior when calling the given call site.
diff --git a/lib/Analysis/NoAliasAnalysis.cpp b/lib/Analysis/NoAliasAnalysis.cpp
index 7602149edc..ab7a69241e 100644
--- a/lib/Analysis/NoAliasAnalysis.cpp
+++ b/lib/Analysis/NoAliasAnalysis.cpp
@@ -50,7 +50,10 @@ namespace {
       return UnknownModRefBehavior;
     }
 
-    virtual bool pointsToConstantMemory(const Location &Loc) { return false; }
+    virtual bool pointsToConstantMemory(const Location &Loc,
+                                        bool OrLocal) {
+      return false;
+    }
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
                                        const Location &Loc) {
       return ModRef;
diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 0516d64a71..044a93f866 100644
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -138,7 +138,7 @@ namespace {
   private:
     virtual void getAnalysisUsage(AnalysisUsage &AU) const;
     virtual AliasResult alias(const Location &LocA, const Location &LocB);
-    virtual bool pointsToConstantMemory(const Location &Loc);
+    virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
                                        const Location &Loc);
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
@@ -225,19 +225,20 @@ TypeBasedAliasAnalysis::alias(const Location &LocA,
   return NoAlias;
 }
 
-bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) {
+bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc,
+                                                    bool OrLocal) {
   if (!EnableTBAA)
-    return AliasAnalysis::pointsToConstantMemory(Loc);
+    return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
 
   const MDNode *M = Loc.TBAATag;
-  if (!M) return AliasAnalysis::pointsToConstantMemory(Loc);
+  if (!M) return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
 
   // If this is an "immutable" type, we can assume the pointer is pointing
   // to constant memory.
   if (TBAANode(M).TypeIsImmutable())
     return true;
 
-  return AliasAnalysis::pointsToConstantMemory(Loc);
+  return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
 }
 
 AliasAnalysis::ModRefResult