diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
index ba46d205caa6..1aa733efbf88 100644
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -461,11 +461,12 @@ Attribute typeIncompatible(Type *Ty);
 /// is a breaking change to bitcode compatibility.
 uint64_t encodeLLVMAttributesForBitcode(AttributeSet Attrs, unsigned Index);
 
-/// \brief This returns an attribute bitset containing the LLVM attributes that
-/// have been decoded from the given integer.  This function must stay in sync
-/// with 'encodeLLVMAttributesForBitcode'.
-Attribute decodeLLVMAttributesForBitcode(LLVMContext &C,
-                                         uint64_t EncodedAttrs);
+/// \brief This fills an AttrBuilder object with the LLVM attributes that have
+/// been decoded from the given integer. This function must stay in sync with
+/// 'encodeLLVMAttributesForBitcode'.
+/// N.B. This should be used only by the bitcode reader!
+void decodeLLVMAttributesForBitcode(LLVMContext &C, AttrBuilder &B,
+                                    uint64_t EncodedAttrs);
 
 } // end AttributeFuncs namespace
 
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 2e1a5125fe96..ca299c007c66 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -464,15 +464,10 @@ bool BitcodeReader::ParseAttributeBlock() {
         return Error("Invalid ENTRY record");
 
       for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
-        Attribute ReconstitutedAttr =
-          AttributeFuncs::decodeLLVMAttributesForBitcode(Context, Record[i+1]);
-        Record[i+1] = ReconstitutedAttr.Raw();
-      }
-
-      for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
-        AttrBuilder B(Record[i+1]);
-        if (B.hasAttributes())
-          Attrs.push_back(AttributeSet::get(Context, Record[i], B));
+        AttrBuilder B;
+        AttributeFuncs::decodeLLVMAttributesForBitcode(Context, B,
+                                                       Record[i+1]);
+        Attrs.push_back(AttributeSet::get(Context, Record[i], B));
       }
 
       MAttributes.push_back(AttributeSet::get(Context, Attrs));
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index d947ffffd8f7..825033087102 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -377,9 +377,9 @@ uint64_t AttributeSetImpl::Raw(uint64_t Index) const {
 // AttributeSet Construction and Mutation Methods
 //===----------------------------------------------------------------------===//
 
-AttributeSet AttributeSet::getImpl(LLVMContext &C,
-                                   ArrayRef<std::pair<unsigned,
-                                                   AttributeSetNode*> > Attrs) {
+AttributeSet
+AttributeSet::getImpl(LLVMContext &C,
+                      ArrayRef<std::pair<unsigned, AttributeSetNode*> > Attrs) {
   LLVMContextImpl *pImpl = C.pImpl;
   FoldingSetNodeID ID;
   AttributeSetImpl::Profile(ID, Attrs);
@@ -855,6 +855,8 @@ bool AttrBuilder::operator==(const AttrBuilder &B) {
 }
 
 AttrBuilder &AttrBuilder::addRawValue(uint64_t Val) {
+  if (!Val) return *this;
+
   for (Attribute::AttrKind I = Attribute::None; I != Attribute::EndAttrKinds;
        I = Attribute::AttrKind(I + 1)) {
     if (uint64_t A = (Val & AttributeImpl::getAttrMask(I))) {
@@ -914,6 +916,7 @@ Attribute AttributeFuncs::typeIncompatible(Type *Ty) {
 /// \brief This returns an integer containing an encoding of all the LLVM
 /// attributes found in the given attribute bitset.  Any change to this encoding
 /// is a breaking change to bitcode compatibility.
+/// N.B. This should be used only by the bitcode reader!
 uint64_t AttributeFuncs::encodeLLVMAttributesForBitcode(AttributeSet Attrs,
                                                         unsigned Index) {
   // FIXME: It doesn't make sense to store the alignment information as an
@@ -932,21 +935,22 @@ uint64_t AttributeFuncs::encodeLLVMAttributesForBitcode(AttributeSet Attrs,
   return EncodedAttrs;
 }
 
-/// \brief This returns an attribute bitset containing the LLVM attributes that
-/// have been decoded from the given integer.  This function must stay in sync
-/// with 'encodeLLVMAttributesForBitcode'.
-Attribute AttributeFuncs::decodeLLVMAttributesForBitcode(LLVMContext &C,
-                                                         uint64_t EncodedAttrs){
+/// \brief This fills an AttrBuilder object with the LLVM attributes that have
+/// been decoded from the given integer. This function must stay in sync with
+/// 'encodeLLVMAttributesForBitcode'.
+/// N.B. This should be used only by the bitcode reader!
+void AttributeFuncs::decodeLLVMAttributesForBitcode(LLVMContext &C,
+                                                    AttrBuilder &B,
+                                                    uint64_t EncodedAttrs) {
   // The alignment is stored as a 16-bit raw value from bits 31--16.  We shift
   // the bits above 31 down by 11 bits.
   unsigned Alignment = (EncodedAttrs & (0xffffULL << 16)) >> 16;
   assert((!Alignment || isPowerOf2_32(Alignment)) &&
          "Alignment must be a power of two.");
 
-  AttrBuilder B(EncodedAttrs & 0xffff);
+  B.addRawValue(EncodedAttrs & 0xffff);
   if (Alignment)
     B.addAlignmentAttr(Alignment);
   B.addRawValue((EncodedAttrs & (0xffffULL << 32)) >> 11);
-  return Attribute::get(C, B);
 }