Add scoped-noalias metadata

This commit adds scoped noalias metadata. The primary motivations for this
feature are:
  1. To preserve noalias function attribute information when inlining
  2. To provide the ability to model block-scope C99 restrict pointers

Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.

What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:

!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }

Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:

... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }

When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.

Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.

[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]

Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.

llvm-svn: 213864

18 files changed, 508 insertions, 9 deletions

diff --git a/llvm/lib/Analysis/Analysis.cpp b/llvm/lib/Analysis/Analysis.cpp
index c58012f3a8c..010ad7440e6 100644
--- a/llvm/lib/Analysis/Analysis.cpp
+++ b/llvm/lib/Analysis/Analysis.cpp
@@ -66,6 +66,7 @@ void llvm::initializeAnalysis(PassRegistry &Registry) {
   initializeScalarEvolutionAliasAnalysisPass(Registry);
   initializeTargetTransformInfoAnalysisGroup(Registry);
   initializeTypeBasedAliasAnalysisPass(Registry);
+  initializeScopedNoAliasAAPass(Registry);
 }
 
 void LLVMInitializeAnalysis(LLVMPassRegistryRef R) {
diff --git a/llvm/lib/Analysis/CMakeLists.txt b/llvm/lib/Analysis/CMakeLists.txt
index d1632fd26ac..a6734772c07 100644
--- a/llvm/lib/Analysis/CMakeLists.txt
+++ b/llvm/lib/Analysis/CMakeLists.txt
@@ -53,6 +53,7 @@ add_llvm_library(LLVMAnalysis
   TargetTransformInfo.cpp
   Trace.cpp
   TypeBasedAliasAnalysis.cpp
+  ScopedNoAliasAA.cpp
   ValueTracking.cpp
   )
 
diff --git a/llvm/lib/Analysis/ScopedNoAliasAA.cpp b/llvm/lib/Analysis/ScopedNoAliasAA.cpp
new file mode 100644
index 00000000000..f197f1c48a6
--- /dev/null
+++ b/llvm/lib/Analysis/ScopedNoAliasAA.cpp
@@ -0,0 +1,243 @@
+//===- ScopedNoAliasAA.cpp - Scoped No-Alias Alias Analysis ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the ScopedNoAlias alias-analysis pass, which implements
+// metadata-based scoped no-alias support.
+//
+// Alias-analysis scopes are defined similar to TBAA nodes:
+//
+// !scope0 = metadata !{ metadata !"scope of foo()" }
+// !scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
+// !scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
+// !scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
+// !scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
+//
+// Loads and stores can be tagged with an alias-analysis scope, and also, with
+// a noalias tag for a specific scope:
+//
+// ... = load %ptr1, !alias.scope !{ !scope1 }
+// ... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
+//
+// When evaluating an aliasing query, if one of the instructions is associated
+// with an alias.scope id that is identical to the noalias scope associated
+// with the other instruction, or is a descendant (in the scope hierarchy) of
+// the noalias scope associated with the other instruction, then the two memory
+// accesses are assumed not to alias.
+//
+// Note that if the first element of the scope metadata is a string, then it
+// can be combined accross functions and translation units. The string can be
+// replaced by a self-reference to create globally unqiue scope identifiers.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+using namespace llvm;
+
+// A handy option for disabling scoped no-alias functionality. The same effect
+// can also be achieved by stripping the associated metadata tags from IR, but
+// this option is sometimes more convenient.
+static cl::opt<bool>
+EnableScopedNoAlias("enable-scoped-noalias", cl::init(true));
+
+namespace {
+/// AliasScopeNode - This is a simple wrapper around an MDNode which provides
+/// a higher-level interface by hiding the details of how alias analysis
+/// information is encoded in its operands.
+class AliasScopeNode {
+  const MDNode *Node;
+
+public:
+  AliasScopeNode() : Node(0) {}
+  explicit AliasScopeNode(const MDNode *N) : Node(N) {}
+
+  /// getNode - Get the MDNode for this AliasScopeNode.
+  const MDNode *getNode() const { return Node; }
+
+  /// getParent - Get this AliasScopeNode's Alias tree parent.
+  AliasScopeNode getParent() const {
+    if (Node->getNumOperands() < 2)
+      return AliasScopeNode();
+    MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(1));
+    if (!P)
+      return AliasScopeNode();
+    // Ok, this node has a valid parent. Return it.
+    return AliasScopeNode(P);
+  }
+};
+
+/// ScopedNoAliasAA - This is a simple alias analysis
+/// implementation that uses scoped-noalias metadata to answer queries.
+class ScopedNoAliasAA : public ImmutablePass, public AliasAnalysis {
+public:
+  static char ID; // Class identification, replacement for typeinfo
+  ScopedNoAliasAA() : ImmutablePass(ID) {
+    initializeScopedNoAliasAAPass(*PassRegistry::getPassRegistry());
+  }
+
+  virtual void initializePass() {
+    InitializeAliasAnalysis(this);
+  }
+
+  /// 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 void *PI) {
+    if (PI == &AliasAnalysis::ID)
+      return (AliasAnalysis*)this;
+    return this;
+  }
+
+protected:
+  bool mayAlias(const MDNode *A, const MDNode *B) const;
+  bool mayAliasInScopes(const MDNode *Scopes, const MDNode *NoAlias) const;
+
+private:
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+  virtual AliasResult alias(const Location &LocA, const Location &LocB);
+  virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
+  virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+  virtual ModRefBehavior getModRefBehavior(const Function *F);
+  virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+                                     const Location &Loc);
+  virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+                                     ImmutableCallSite CS2);
+};
+}  // End of anonymous namespace
+
+// Register this pass...
+char ScopedNoAliasAA::ID = 0;
+INITIALIZE_AG_PASS(ScopedNoAliasAA, AliasAnalysis, "scoped-noalias",
+                   "Scoped NoAlias Alias Analysis", false, true, false)
+
+ImmutablePass *llvm::createScopedNoAliasAAPass() {
+  return new ScopedNoAliasAA();
+}
+
+void
+ScopedNoAliasAA::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+  AliasAnalysis::getAnalysisUsage(AU);
+}
+
+/// mayAlias - Test whether the scope represented by A may alias the
+/// scope represented by B. Specifically, A is the target scope, and B is the
+/// noalias scope.
+bool
+ScopedNoAliasAA::mayAlias(const MDNode *A,
+                          const MDNode *B) const {
+  // Climb the tree from A to see if we reach B.
+  for (AliasScopeNode T(A); ; ) {
+    if (T.getNode() == B)
+      // B is an ancestor of A.
+      return false;
+
+    T = T.getParent();
+    if (!T.getNode())
+      break;
+  }
+
+  return true;
+}
+
+bool
+ScopedNoAliasAA::mayAliasInScopes(const MDNode *Scopes,
+                                  const MDNode *NoAlias) const {
+  if (!Scopes || !NoAlias)
+    return true;
+
+  for (unsigned i = 0, ie = Scopes->getNumOperands(); i != ie; ++i)
+    if (const MDNode *SMD = dyn_cast<MDNode>(Scopes->getOperand(i)))
+      for (unsigned j = 0, je = NoAlias->getNumOperands(); j != je; ++j)
+        if (const MDNode *NAMD = dyn_cast<MDNode>(NoAlias->getOperand(j)))
+          if (!mayAlias(SMD, NAMD))
+            return false;
+
+  return true; 
+}
+
+AliasAnalysis::AliasResult
+ScopedNoAliasAA::alias(const Location &LocA, const Location &LocB) {
+  if (!EnableScopedNoAlias)
+    return AliasAnalysis::alias(LocA, LocB);
+
+  // Get the attached MDNodes.
+  const MDNode *AScopes = LocA.AATags.Scope,
+               *BScopes = LocB.AATags.Scope;
+
+  const MDNode *ANoAlias = LocA.AATags.NoAlias,
+               *BNoAlias = LocB.AATags.NoAlias;
+
+  if (!mayAliasInScopes(AScopes, BNoAlias))
+    return NoAlias;
+
+  if (!mayAliasInScopes(BScopes, ANoAlias))
+    return NoAlias;
+
+  // If they may alias, chain to the next AliasAnalysis.
+  return AliasAnalysis::alias(LocA, LocB);
+}
+
+bool ScopedNoAliasAA::pointsToConstantMemory(const Location &Loc,
+                                             bool OrLocal) {
+  return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+}
+
+AliasAnalysis::ModRefBehavior
+ScopedNoAliasAA::getModRefBehavior(ImmutableCallSite CS) {
+  return AliasAnalysis::getModRefBehavior(CS);
+}
+
+AliasAnalysis::ModRefBehavior
+ScopedNoAliasAA::getModRefBehavior(const Function *F) {
+  return AliasAnalysis::getModRefBehavior(F);
+}
+
+AliasAnalysis::ModRefResult
+ScopedNoAliasAA::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
+  if (!EnableScopedNoAlias)
+    return AliasAnalysis::getModRefInfo(CS, Loc);
+
+  if (!mayAliasInScopes(Loc.AATags.Scope,
+        CS.getInstruction()->getMetadata(LLVMContext::MD_noalias)))
+    return NoModRef;
+
+  if (!mayAliasInScopes(
+        CS.getInstruction()->getMetadata(LLVMContext::MD_alias_scope),
+        Loc.AATags.NoAlias))
+    return NoModRef;
+
+  return AliasAnalysis::getModRefInfo(CS, Loc);
+}
+
+AliasAnalysis::ModRefResult
+ScopedNoAliasAA::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
+  if (!EnableScopedNoAlias)
+    return AliasAnalysis::getModRefInfo(CS1, CS2);
+
+  if (!mayAliasInScopes(
+        CS1.getInstruction()->getMetadata(LLVMContext::MD_alias_scope),
+        CS2.getInstruction()->getMetadata(LLVMContext::MD_noalias)))
+    return NoModRef;
+
+  if (!mayAliasInScopes(
+        CS2.getInstruction()->getMetadata(LLVMContext::MD_alias_scope),
+        CS1.getInstruction()->getMetadata(LLVMContext::MD_noalias)))
+    return NoModRef;
+
+  return AliasAnalysis::getModRefInfo(CS1, CS2);
+}
+
diff --git a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
index c68ba5af9aa..27b469a43b0 100644
--- a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -618,5 +618,17 @@ void Instruction::getAAMetadata(AAMDNodes &N, bool Merge) const {
                                         getMetadata(LLVMContext::MD_tbaa));
   else
     N.TBAA = getMetadata(LLVMContext::MD_tbaa);
+
+  if (Merge)
+    N.Scope = MDNode::intersect(N.Scope,
+                                getMetadata(LLVMContext::MD_alias_scope));
+  else
+    N.Scope = getMetadata(LLVMContext::MD_alias_scope);
+
+  if (Merge)
+    N.NoAlias = MDNode::intersect(N.NoAlias,
+                                  getMetadata(LLVMContext::MD_noalias));
+  else
+    N.NoAlias = getMetadata(LLVMContext::MD_noalias);
 }
 
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 06cce92caee..c9fe23448e7 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -523,6 +523,34 @@ raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineMemOperand &MMO) {
     OS << ")";
   }
 
+  // Print AA scope info.
+  if (const MDNode *ScopeInfo = MMO.getAAInfo().Scope) {
+    OS << "(alias.scope=";
+    if (ScopeInfo->getNumOperands() > 0)
+      for (unsigned i = 0, ie = ScopeInfo->getNumOperands(); i != ie; ++i) {
+        ScopeInfo->getOperand(i)->printAsOperand(OS, /*PrintType=*/false);
+        if (i != ie-1)
+          OS << ",";
+      }
+    else
+      OS << "<unknown>";
+    OS << ")";
+  }
+
+  // Print AA noalias scope info.
+  if (const MDNode *NoAliasInfo = MMO.getAAInfo().NoAlias) {
+    OS << "(noalias=";
+    if (NoAliasInfo->getNumOperands() > 0)
+      for (unsigned i = 0, ie = NoAliasInfo->getNumOperands(); i != ie; ++i) {
+        NoAliasInfo->getOperand(i)->printAsOperand(OS, /*PrintType=*/false);
+        if (i != ie-1)
+          OS << ",";
+      }
+    else
+      OS << "<unknown>";
+    OS << ")";
+  }
+
   // Print nontemporal info.
   if (MMO.isNonTemporal())
     OS << "(nontemporal)";
diff --git a/llvm/lib/CodeGen/Passes.cpp b/llvm/lib/CodeGen/Passes.cpp
index 6e86c8f2109..bac0433dc87 100644
--- a/llvm/lib/CodeGen/Passes.cpp
+++ b/llvm/lib/CodeGen/Passes.cpp
@@ -377,6 +377,7 @@ void TargetPassConfig::addIRPasses() {
   // BasicAliasAnalysis wins if they disagree. This is intended to help
   // support "obvious" type-punning idioms.
   addPass(createTypeBasedAliasAnalysisPass());
+  addPass(createScopedNoAliasAAPass());
   addPass(createBasicAliasAnalysisPass());
 
   // Before running any passes, run the verifier to determine if the input
diff --git a/llvm/lib/IR/IRBuilder.cpp b/llvm/lib/IR/IRBuilder.cpp
index 435e54f0ea2..7448e50bd82 100644
--- a/llvm/lib/IR/IRBuilder.cpp
+++ b/llvm/lib/IR/IRBuilder.cpp
@@ -62,7 +62,8 @@ static CallInst *createCallHelper(Value *Callee, ArrayRef<Value *> Ops,
 
 CallInst *IRBuilderBase::
 CreateMemSet(Value *Ptr, Value *Val, Value *Size, unsigned Align,
-             bool isVolatile, MDNode *TBAATag) {
+             bool isVolatile, MDNode *TBAATag, MDNode *ScopeTag,
+             MDNode *NoAliasTag) {
   Ptr = getCastedInt8PtrValue(Ptr);
   Value *Ops[] = { Ptr, Val, Size, getInt32(Align), getInt1(isVolatile) };
   Type *Tys[] = { Ptr->getType(), Size->getType() };
@@ -74,13 +75,20 @@ CreateMemSet(Value *Ptr, Value *Val, Value *Size, unsigned Align,
   // Set the TBAA info if present.
   if (TBAATag)
     CI->setMetadata(LLVMContext::MD_tbaa, TBAATag);
-  
+
+  if (ScopeTag)
+    CI->setMetadata(LLVMContext::MD_alias_scope, ScopeTag);
+ 
+  if (NoAliasTag)
+    CI->setMetadata(LLVMContext::MD_noalias, NoAliasTag);
+ 
   return CI;
 }
 
 CallInst *IRBuilderBase::
 CreateMemCpy(Value *Dst, Value *Src, Value *Size, unsigned Align,
-             bool isVolatile, MDNode *TBAATag, MDNode *TBAAStructTag) {
+             bool isVolatile, MDNode *TBAATag, MDNode *TBAAStructTag,
+             MDNode *ScopeTag, MDNode *NoAliasTag) {
   Dst = getCastedInt8PtrValue(Dst);
   Src = getCastedInt8PtrValue(Src);
 
@@ -98,13 +106,20 @@ CreateMemCpy(Value *Dst, Value *Src, Value *Size, unsigned Align,
   // Set the TBAA Struct info if present.
   if (TBAAStructTag)
     CI->setMetadata(LLVMContext::MD_tbaa_struct, TBAAStructTag);
-  
+ 
+  if (ScopeTag)
+    CI->setMetadata(LLVMContext::MD_alias_scope, ScopeTag);
+ 
+  if (NoAliasTag)
+    CI->setMetadata(LLVMContext::MD_noalias, NoAliasTag);
+ 
   return CI;  
 }
 
 CallInst *IRBuilderBase::
 CreateMemMove(Value *Dst, Value *Src, Value *Size, unsigned Align,
-              bool isVolatile, MDNode *TBAATag) {
+              bool isVolatile, MDNode *TBAATag, MDNode *ScopeTag,
+              MDNode *NoAliasTag) {
   Dst = getCastedInt8PtrValue(Dst);
   Src = getCastedInt8PtrValue(Src);
   
@@ -118,7 +133,13 @@ CreateMemMove(Value *Dst, Value *Src, Value *Size, unsigned Align,
   // Set the TBAA info if present.
   if (TBAATag)
     CI->setMetadata(LLVMContext::MD_tbaa, TBAATag);
-  
+ 
+  if (ScopeTag)
+    CI->setMetadata(LLVMContext::MD_alias_scope, ScopeTag);
+ 
+  if (NoAliasTag)
+    CI->setMetadata(LLVMContext::MD_noalias, NoAliasTag);
+ 
   return CI;  
 }
 
diff --git a/llvm/lib/IR/LLVMContext.cpp b/llvm/lib/IR/LLVMContext.cpp
index de825f00b20..d4ba83dfa62 100644
--- a/llvm/lib/IR/LLVMContext.cpp
+++ b/llvm/lib/IR/LLVMContext.cpp
@@ -66,6 +66,16 @@ LLVMContext::LLVMContext() : pImpl(new LLVMContextImpl(*this)) {
   unsigned InvariantLdId = getMDKindID("invariant.load");
   assert(InvariantLdId == MD_invariant_load && "invariant.load kind id drifted");
   (void)InvariantLdId;
+
+  // Create the 'alias.scope' metadata kind.
+  unsigned AliasScopeID = getMDKindID("alias.scope");
+  assert(AliasScopeID == MD_alias_scope && "alias.scope kind id drifted");
+  (void)AliasScopeID;
+
+  // Create the 'noalias' metadata kind.
+  unsigned NoAliasID = getMDKindID("noalias");
+  assert(NoAliasID == MD_noalias && "noalias kind id drifted");
+  (void)NoAliasID;
 }
 LLVMContext::~LLVMContext() { delete pImpl; }
 
diff --git a/llvm/lib/IR/MDBuilder.cpp b/llvm/lib/IR/MDBuilder.cpp
index 65cdf388521..103915f5ae5 100644
--- a/llvm/lib/IR/MDBuilder.cpp
+++ b/llvm/lib/IR/MDBuilder.cpp
@@ -60,10 +60,15 @@ MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {
   return MDNode::get(Context, Range);
 }
 
-MDNode *MDBuilder::createAnonymousTBAARoot() {
+MDNode *MDBuilder::createAnonymousAARoot(StringRef Name) {
   // To ensure uniqueness the root node is self-referential.
-  MDNode *Dummy = MDNode::getTemporary(Context, ArrayRef<Value *>());
-  MDNode *Root = MDNode::get(Context, Dummy);
+  MDNode *Dummy = MDNode::getTemporary(Context, ArrayRef<Value*>());
+
+  SmallVector<Value *, 2> Args(1, Dummy);
+  if (!Name.empty())
+    Args.push_back(createString(Name));
+  MDNode *Root = MDNode::get(Context, Args);
+
   // At this point we have
   //   !0 = metadata !{}            <- dummy
   //   !1 = metadata !{metadata !0} <- root
@@ -93,6 +98,15 @@ MDNode *MDBuilder::createTBAANode(StringRef Name, MDNode *Parent,
   }
 }
 
+MDNode *MDBuilder::createAliasScopeRoot(StringRef Name) {
+  return MDNode::get(Context, createString(Name));
+}
+
+MDNode *MDBuilder::createAliasScopeNode(StringRef Name, MDNode *Parent) {
+  Value *Ops[2] = { createString(Name), Parent };
+  return MDNode::get(Context, Ops);
+}
+
 /// \brief Return metadata for a tbaa.struct node with the given
 /// struct field descriptions.
 MDNode *MDBuilder::createTBAAStructNode(ArrayRef<TBAAStructField> Fields) {
diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index d7d64641bdb..a017bd3c0c0 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -406,6 +406,41 @@ void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {
   }
 }
 
+MDNode *MDNode::concatenate(MDNode *A, MDNode *B) {
+  if (!A)
+    return B;
+  if (!B)
+    return A;
+
+  SmallVector<Value *, 4> Vals(A->getNumOperands() +
+                               B->getNumOperands());
+
+  unsigned j = 0;
+  for (unsigned i = 0, ie = A->getNumOperands(); i != ie; ++i)
+    Vals[j++] = A->getOperand(i);
+  for (unsigned i = 0, ie = B->getNumOperands(); i != ie; ++i)
+    Vals[j++] = B->getOperand(i);
+
+  return MDNode::get(A->getContext(), Vals);
+}
+
+MDNode *MDNode::intersect(MDNode *A, MDNode *B) {
+  if (!A || !B)
+    return nullptr;
+
+  SmallVector<Value *, 4> Vals;
+  for (unsigned i = 0, ie = A->getNumOperands(); i != ie; ++i) {
+    Value *V = A->getOperand(i);
+    for (unsigned j = 0, je = B->getNumOperands(); j != je; ++j)
+      if (V == B->getOperand(j)) {
+        Vals.push_back(V);
+        break;
+      }
+  }
+
+  return MDNode::get(A->getContext(), Vals);
+}
+
 MDNode *MDNode::getMostGenericFPMath(MDNode *A, MDNode *B) {
   if (!A || !B)
     return nullptr;
@@ -689,6 +724,8 @@ void Instruction::setMetadata(unsigned KindID, MDNode *Node) {
 
 void Instruction::setAAMetadata(const AAMDNodes &N) {
   setMetadata(LLVMContext::MD_tbaa, N.TBAA);
+  setMetadata(LLVMContext::MD_alias_scope, N.Scope);
+  setMetadata(LLVMContext::MD_noalias, N.NoAlias);
 }
 
 MDNode *Instruction::getMetadataImpl(unsigned KindID) const {
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 701fb462b4f..98477b5d71f 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -107,6 +107,7 @@ PassManagerBuilder::addInitialAliasAnalysisPasses(PassManagerBase &PM) const {
   // BasicAliasAnalysis wins if they disagree. This is intended to help
   // support "obvious" type-punning idioms.
   PM.add(createTypeBasedAliasAnalysisPass());
+  PM.add(createScopedNoAliasAAPass());
   PM.add(createBasicAliasAnalysisPass());
 }
 
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 43ccb995958..7135874003d 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1791,6 +1791,19 @@ static void patchReplacementInstruction(Instruction *I, Value *Repl) {
       case LLVMContext::MD_tbaa:
         ReplInst->setMetadata(Kind, MDNode::getMostGenericTBAA(IMD, ReplMD));
         break;
+      case LLVMContext::MD_alias_scope:
+      case LLVMContext::MD_noalias:
+        // FIXME: If both the original and replacement value are part of the
+        // same control-flow region (meaning that the execution of one
+        // guarentees the executation of the other), then we can combine the
+        // noalias scopes here and do better than the general conservative
+        // answer.
+
+        // In general, GVN unifies expressions over different control-flow
+        // regions, and so we need a conservative combination of the noalias
+        // scopes.
+        ReplInst->setMetadata(Kind, MDNode::intersect(IMD, ReplMD));
+        break;
       case LLVMContext::MD_range:
         ReplInst->setMetadata(Kind, MDNode::getMostGenericRange(IMD, ReplMD));
         break;
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index de724d419a4..12df676df87 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -203,6 +203,10 @@ void LLVMAddTypeBasedAliasAnalysisPass(LLVMPassManagerRef PM) {
   unwrap(PM)->add(createTypeBasedAliasAnalysisPass());
 }
 
+void LLVMAddScopedNoAliasAAPass(LLVMPassManagerRef PM) {
+  unwrap(PM)->add(createScopedNoAliasAAPass());
+}
+
 void LLVMAddBasicAliasAnalysisPass(LLVMPassManagerRef PM) {
   unwrap(PM)->add(createBasicAliasAnalysisPass());
 }
diff --git a/llvm/lib/Transforms/Scalar/Scalarizer.cpp b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
index 7a73f113b1d..813041ab255 100644
--- a/llvm/lib/Transforms/Scalar/Scalarizer.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
@@ -312,6 +312,8 @@ bool Scalarizer::canTransferMetadata(unsigned Tag) {
           || Tag == LLVMContext::MD_fpmath
           || Tag == LLVMContext::MD_tbaa_struct
           || Tag == LLVMContext::MD_invariant_load
+          || Tag == LLVMContext::MD_alias_scope
+          || Tag == LLVMContext::MD_noalias
           || Tag == ParallelLoopAccessMDKind);
 }
 
diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index f0a9f2b1fcb..f4152dd490a 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -13,10 +13,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/CFG.h"
@@ -28,6 +31,7 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Transforms/Utils/Local.h"
 using namespace llvm;
@@ -260,6 +264,100 @@ static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
   InvokeDest->removePredecessor(II->getParent());
 }
 
+/// CloneAliasScopeMetadata - When inlining a function that contains noalias
+/// scope metadata, this metadata needs to be cloned so that the inlined blocks
+/// have different "unqiue scopes" at every call site. Were this not done, then
+/// aliasing scopes from a function inlined into a caller multiple times could
+/// not be differentiated (and this would lead to miscompiles because the
+/// non-aliasing property communicated by the metadata could have
+/// call-site-specific control dependencies).
+static void CloneAliasScopeMetadata(CallSite CS, ValueToValueMapTy &VMap) {
+  const Function *CalledFunc = CS.getCalledFunction();
+  SetVector<const MDNode *> MD;
+
+  // Note: We could only clone the metadata if it is already used in the
+  // caller. I'm omitting that check here because it might confuse
+  // inter-procedural alias analysis passes. We can revisit this if it becomes
+  // an efficiency or overhead problem.
+
+  for (Function::const_iterator I = CalledFunc->begin(), IE = CalledFunc->end();
+       I != IE; ++I)
+    for (BasicBlock::const_iterator J = I->begin(), JE = I->end(); J != JE; ++J) {
+      if (const MDNode *M = J->getMetadata(LLVMContext::MD_alias_scope))
+        MD.insert(M);
+      if (const MDNode *M = J->getMetadata(LLVMContext::MD_noalias))
+        MD.insert(M);
+    }
+
+  if (MD.empty())
+    return;
+
+  // Walk the existing metadata, adding the complete (perhaps cyclic) chain to
+  // the set.
+  SmallVector<const Value *, 16> Queue(MD.begin(), MD.end());
+  while (!Queue.empty()) {
+    const MDNode *M = cast<MDNode>(Queue.pop_back_val());
+    for (unsigned i = 0, ie = M->getNumOperands(); i != ie; ++i)
+      if (const MDNode *M1 = dyn_cast<MDNode>(M->getOperand(i)))
+        if (MD.insert(M1))
+          Queue.push_back(M1);
+  }
+
+  // Now we have a complete set of all metadata in the chains used to specify
+  // the noalias scopes and the lists of those scopes.
+  SmallVector<MDNode *, 16> DummyNodes;
+  DenseMap<const MDNode *, TrackingVH<MDNode> > MDMap;
+  for (SetVector<const MDNode *>::iterator I = MD.begin(), IE = MD.end();
+       I != IE; ++I) {
+    MDNode *Dummy = MDNode::getTemporary(CalledFunc->getContext(),
+                                         ArrayRef<Value*>());
+    DummyNodes.push_back(Dummy);
+    MDMap[*I] = Dummy;
+  }
+
+  // Create new metadata nodes to replace the dummy nodes, replacing old
+  // metadata references with either a dummy node or an already-created new
+  // node.
+  for (SetVector<const MDNode *>::iterator I = MD.begin(), IE = MD.end();
+       I != IE; ++I) {
+    SmallVector<Value *, 4> NewOps;
+    for (unsigned i = 0, ie = (*I)->getNumOperands(); i != ie; ++i) {
+      const Value *V = (*I)->getOperand(i);
+      if (const MDNode *M = dyn_cast<MDNode>(V))
+        NewOps.push_back(MDMap[M]);
+      else
+        NewOps.push_back(const_cast<Value *>(V));
+    }
+
+    MDNode *NewM = MDNode::get(CalledFunc->getContext(), NewOps),
+           *TempM = MDMap[*I];
+
+    TempM->replaceAllUsesWith(NewM);
+  }
+
+  // Now replace the metadata in the new inlined instructions with the
+  // repacements from the map.
+  for (ValueToValueMapTy::iterator VMI = VMap.begin(), VMIE = VMap.end();
+       VMI != VMIE; ++VMI) {
+    if (!VMI->second)
+      continue;
+
+    Instruction *NI = dyn_cast<Instruction>(VMI->second);
+    if (!NI)
+      continue;
+
+    if (MDNode *M = NI->getMetadata(LLVMContext::MD_alias_scope))
+      NI->setMetadata(LLVMContext::MD_alias_scope, MDMap[M]);
+
+    if (MDNode *M = NI->getMetadata(LLVMContext::MD_noalias))
+      NI->setMetadata(LLVMContext::MD_noalias, MDMap[M]);
+  }
+
+  // Now that everything has been replaced, delete the dummy nodes.
+  for (unsigned i = 0, ie = DummyNodes.size(); i != ie; ++i)
+    MDNode::deleteTemporary(DummyNodes[i]);
+}
+
 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
 /// into the caller, update the specified callgraph to reflect the changes we
 /// made.  Note that it's possible that not all code was copied over, so only
@@ -648,6 +746,9 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
 
     // Update inlined instructions' line number information.
     fixupLineNumbers(Caller, FirstNewBlock, TheCall);
+
+    // Clone existing noalias metadata if necessary.
+    CloneAliasScopeMetadata(CS, VMap);
   }
 
   // If there are any alloca instructions in the block that used to be the entry
diff --git a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
index 28ec83bf868..9ee0ffb03bb 100644
--- a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -2982,6 +2982,10 @@ namespace {
       case LLVMContext::MD_tbaa:
         K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
         break;
+      case LLVMContext::MD_alias_scope:
+      case LLVMContext::MD_noalias:
+        K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
+        break;
       case LLVMContext::MD_fpmath:
         K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
         break;
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index b60ce61886c..a88eb490e40 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -535,6 +535,8 @@ static void propagateMetadata(Instruction *To, const Instruction *From) {
     // non-speculated memory access when the condition was false, this would be
     // caught by the runtime overlap checks).
     if (Kind != LLVMContext::MD_tbaa &&
+        Kind != LLVMContext::MD_alias_scope &&
+        Kind != LLVMContext::MD_noalias &&
         Kind != LLVMContext::MD_fpmath)
       continue;
 
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 53a43d9851e..bbfdb4e4fa9 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -230,6 +230,10 @@ static Instruction *propagateMetadata(Instruction *I, ArrayRef<Value *> VL) {
       case LLVMContext::MD_tbaa:
         MD = MDNode::getMostGenericTBAA(MD, IMD);
         break;
+      case LLVMContext::MD_alias_scope:
+      case LLVMContext::MD_noalias:
+        MD = MDNode::intersect(MD, IMD);
+        break;
       case LLVMContext::MD_fpmath:
         MD = MDNode::getMostGenericFPMath(MD, IMD);
         break;