X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FScalarEvolutionAliasAnalysis.cpp;h=6933f74150fd3c1a3efd38fab3ef031f020aaa3e;hb=2d18167483cf274413e52b4fa9513a7dffa6a7f8;hp=f95d4019f3e723831f8149e81a84290ec69c1ecc;hpb=4f46e14b8ab3861a8dbea14ed70cb9527ae24a06;p=oota-llvm.git

diff --git a/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp b/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
index f95d4019f3e..6933f74150f 100644
--- a/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
+++ b/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
@@ -19,9 +19,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Analysis/Passes.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
-#include "llvm/Analysis/Passes.h"
 #include "llvm/Pass.h"
 using namespace llvm;
 
@@ -34,23 +34,25 @@ namespace {
 
   public:
     static char ID; // Class identification, replacement for typeinfo
-    ScalarEvolutionAliasAnalysis() : FunctionPass(&ID), SE(0) {}
+    ScalarEvolutionAliasAnalysis() : FunctionPass(ID), SE(nullptr) {
+      initializeScalarEvolutionAliasAnalysisPass(
+        *PassRegistry::getPassRegistry());
+    }
 
     /// getAdjustedAnalysisPointer - This method is used when a pass implements
     /// an analysis interface through multiple inheritance.  If needed, it
     /// should override this to adjust the this pointer as needed for the
     /// specified pass info.
-    virtual void *getAdjustedAnalysisPointer(const PassInfo *PI) {
-      if (PI->isPassID(&AliasAnalysis::ID))
+    void *getAdjustedAnalysisPointer(AnalysisID PI) override {
+      if (PI == &AliasAnalysis::ID)
         return (AliasAnalysis*)this;
       return this;
     }
 
   private:
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
-    virtual bool runOnFunction(Function &F);
-    virtual AliasResult alias(const Value *V1, unsigned V1Size,
-                              const Value *V2, unsigned V2Size);
+    void getAnalysisUsage(AnalysisUsage &AU) const override;
+    bool runOnFunction(Function &F) override;
+    AliasResult alias(const Location &LocA, const Location &LocB) override;
 
     Value *GetBaseValue(const SCEV *S);
   };
@@ -58,11 +60,11 @@ namespace {
 
 // Register this pass...
 char ScalarEvolutionAliasAnalysis::ID = 0;
-static RegisterPass<ScalarEvolutionAliasAnalysis>
-X("scev-aa", "ScalarEvolution-based Alias Analysis", false, true);
-
-// Declare that we implement the AliasAnalysis interface
-static RegisterAnalysisGroup<AliasAnalysis> Y(X);
+INITIALIZE_AG_PASS_BEGIN(ScalarEvolutionAliasAnalysis, AliasAnalysis, "scev-aa",
+                   "ScalarEvolution-based Alias Analysis", false, true, false)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_AG_PASS_END(ScalarEvolutionAliasAnalysis, AliasAnalysis, "scev-aa",
+                    "ScalarEvolution-based Alias Analysis", false, true, false)
 
 FunctionPass *llvm::createScalarEvolutionAliasAnalysisPass() {
   return new ScalarEvolutionAliasAnalysis();
@@ -100,15 +102,21 @@ ScalarEvolutionAliasAnalysis::GetBaseValue(const SCEV *S) {
     return U->getValue();
   }
   // No Identified object found.
-  return 0;
+  return nullptr;
 }
 
 AliasAnalysis::AliasResult
-ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
-                                    const Value *B, unsigned BSize) {
+ScalarEvolutionAliasAnalysis::alias(const Location &LocA,
+                                    const Location &LocB) {
+  // If either of the memory references is empty, it doesn't matter what the
+  // pointer values are. This allows the code below to ignore this special
+  // case.
+  if (LocA.Size == 0 || LocB.Size == 0)
+    return NoAlias;
+
   // This is ScalarEvolutionAliasAnalysis. Get the SCEVs!
-  const SCEV *AS = SE->getSCEV(const_cast<Value *>(A));
-  const SCEV *BS = SE->getSCEV(const_cast<Value *>(B));
+  const SCEV *AS = SE->getSCEV(const_cast<Value *>(LocA.Ptr));
+  const SCEV *BS = SE->getSCEV(const_cast<Value *>(LocB.Ptr));
 
   // If they evaluate to the same expression, it's a MustAlias.
   if (AS == BS) return MustAlias;
@@ -118,14 +126,32 @@ ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
   if (SE->getEffectiveSCEVType(AS->getType()) ==
       SE->getEffectiveSCEVType(BS->getType())) {
     unsigned BitWidth = SE->getTypeSizeInBits(AS->getType());
-    APInt AI(BitWidth, ASize);
+    APInt ASizeInt(BitWidth, LocA.Size);
+    APInt BSizeInt(BitWidth, LocB.Size);
+
+    // Compute the difference between the two pointers.
     const SCEV *BA = SE->getMinusSCEV(BS, AS);
-    if (AI.ule(SE->getUnsignedRange(BA).getUnsignedMin())) {
-      APInt BI(BitWidth, BSize);
-      const SCEV *AB = SE->getMinusSCEV(AS, BS);
-      if (BI.ule(SE->getUnsignedRange(AB).getUnsignedMin()))
-        return NoAlias;
-    }
+
+    // Test whether the difference is known to be great enough that memory of
+    // the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
+    // are non-zero, which is special-cased above.
+    if (ASizeInt.ule(SE->getUnsignedRange(BA).getUnsignedMin()) &&
+        (-BSizeInt).uge(SE->getUnsignedRange(BA).getUnsignedMax()))
+      return NoAlias;
+
+    // Folding the subtraction while preserving range information can be tricky
+    // (because of INT_MIN, etc.); if the prior test failed, swap AS and BS
+    // and try again to see if things fold better that way.
+
+    // Compute the difference between the two pointers.
+    const SCEV *AB = SE->getMinusSCEV(AS, BS);
+
+    // Test whether the difference is known to be great enough that memory of
+    // the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
+    // are non-zero, which is special-cased above.
+    if (BSizeInt.ule(SE->getUnsignedRange(AB).getUnsignedMin()) &&
+        (-ASizeInt).uge(SE->getUnsignedRange(AB).getUnsignedMax()))
+      return NoAlias;
   }
 
   // If ScalarEvolution can find an underlying object, form a new query.
@@ -133,11 +159,15 @@ ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
   // inttoptr and ptrtoint operators.
   Value *AO = GetBaseValue(AS);
   Value *BO = GetBaseValue(BS);
-  if ((AO && AO != A) || (BO && BO != B))
-    if (alias(AO ? AO : A, AO ? ~0u : ASize,
-              BO ? BO : B, BO ? ~0u : BSize) == NoAlias)
+  if ((AO && AO != LocA.Ptr) || (BO && BO != LocB.Ptr))
+    if (alias(Location(AO ? AO : LocA.Ptr,
+                       AO ? +UnknownSize : LocA.Size,
+                       AO ? nullptr : LocA.TBAATag),
+              Location(BO ? BO : LocB.Ptr,
+                       BO ? +UnknownSize : LocB.Size,
+                       BO ? nullptr : LocB.TBAATag)) == NoAlias)
       return NoAlias;
 
   // Forward the query to the next analysis.
-  return AliasAnalysis::alias(A, ASize, B, BSize);
+  return AliasAnalysis::alias(LocA, LocB);
 }