1 files changed, 32 insertions, 10 deletions

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 3721c99883b8..f3c30c258c19 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -233,6 +233,26 @@ static bool isObjectSmallerThan(const Value *V, uint64_t Size,
   return ObjectSize != MemoryLocation::UnknownSize && ObjectSize < Size;
 }
 
+/// Return the minimal extent from \p V to the end of the underlying object,
+/// assuming the result is used in an aliasing query. E.g., we do use the query
+/// location size and the fact that null pointers cannot alias here.
+static uint64_t getMinimalExtentFrom(const Value &V,
+                                     const LocationSize &LocSize,
+                                     const DataLayout &DL,
+                                     bool NullIsValidLoc) {
+  // If we have dereferenceability information we know a lower bound for the
+  // extent as accesses for a lower offset would be valid. We need to exclude
+  // the "or null" part if null is a valid pointer.
+  bool CanBeNull;
+  uint64_t DerefBytes = V.getPointerDereferenceableBytes(DL, CanBeNull);
+  DerefBytes = (CanBeNull && NullIsValidLoc) ? 0 : DerefBytes;
+  // If queried with a precise location size, we assume that location size to be
+  // accessed, thus valid.
+  if (LocSize.isPrecise())
+    DerefBytes = std::max(DerefBytes, LocSize.getValue());
+  return DerefBytes;
+}
+
 /// Returns true if we can prove that the object specified by V has size Size.
 static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
                          const TargetLibraryInfo &TLI, bool NullIsValidLoc) {
@@ -481,7 +501,7 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
         // because it should be in sync with CaptureTracking. Not using it may
         // cause weird miscompilations where 2 aliasing pointers are assumed to
         // noalias.
-        if (auto *RP = getArgumentAliasingToReturnedPointer(Call)) {
+        if (auto *RP = getArgumentAliasingToReturnedPointer(Call, false)) {
           V = RP;
           continue;
         }
@@ -1792,10 +1812,12 @@ AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,
   // If the size of one access is larger than the entire object on the other
   // side, then we know such behavior is undefined and can assume no alias.
   bool NullIsValidLocation = NullPointerIsDefined(&F);
-  if ((V1Size.isPrecise() && isObjectSmallerThan(O2, V1Size.getValue(), DL, TLI,
-                                                 NullIsValidLocation)) ||
-      (V2Size.isPrecise() && isObjectSmallerThan(O1, V2Size.getValue(), DL, TLI,
-                                                 NullIsValidLocation)))
+  if ((isObjectSmallerThan(
+          O2, getMinimalExtentFrom(*V1, V1Size, DL, NullIsValidLocation), DL,
+          TLI, NullIsValidLocation)) ||
+      (isObjectSmallerThan(
+          O1, getMinimalExtentFrom(*V2, V2Size, DL, NullIsValidLocation), DL,
+          TLI, NullIsValidLocation)))
     return NoAlias;
 
   // Check the cache before climbing up use-def chains. This also terminates
@@ -2053,8 +2075,9 @@ bool BasicAAWrapperPass::runOnFunction(Function &F) {
   auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
   auto *PVWP = getAnalysisIfAvailable<PhiValuesWrapperPass>();
 
-  Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), F, TLIWP.getTLI(),
-                                 ACT.getAssumptionCache(F), &DTWP.getDomTree(),
+  Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), F,
+                                 TLIWP.getTLI(F), ACT.getAssumptionCache(F),
+                                 &DTWP.getDomTree(),
                                  LIWP ? &LIWP->getLoopInfo() : nullptr,
                                  PVWP ? &PVWP->getResult() : nullptr));
 
@@ -2071,8 +2094,7 @@ void BasicAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 
 BasicAAResult llvm::createLegacyPMBasicAAResult(Pass &P, Function &F) {
   return BasicAAResult(
-      F.getParent()->getDataLayout(),
-      F,
-      P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
+      F.getParent()->getDataLayout(), F,
+      P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F),
       P.getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));
 }