diff --git a/include/llvm/Attributes.h b/include/llvm/Attributes.h
index 1e995f9a858..097ee3c7aaa 100644
--- a/include/llvm/Attributes.h
+++ b/include/llvm/Attributes.h
@@ -84,7 +84,8 @@ public:
     StackProtectReq = 24,  ///< Stack protection required.
     StructRet       = 25,  ///< Hidden pointer to structure to return
     UWTable         = 26,  ///< Function must be in a unwind table
-    ZExt            = 27   ///< Zero extended before/after call
+    ZExt            = 27,  ///< Zero extended before/after call
+    ForceSizeOpt    = 28  ///< Function must be optimized for size first
   };
 private:
   AttributesImpl *Attrs;
@@ -152,7 +153,8 @@ public:
       hasAttribute(Attributes::UWTable) ||
       hasAttribute(Attributes::NonLazyBind) ||
       hasAttribute(Attributes::ReturnsTwice) ||
-      hasAttribute(Attributes::AddressSafety);
+      hasAttribute(Attributes::AddressSafety) ||
+      hasAttribute(Attributes::ForceSizeOpt);
   }
 
   bool operator==(const Attributes &A) const {
@@ -263,7 +265,8 @@ public:
       .removeAttribute(Attributes::UWTable)
       .removeAttribute(Attributes::NonLazyBind)
       .removeAttribute(Attributes::ReturnsTwice)
-      .removeAttribute(Attributes::AddressSafety);
+      .removeAttribute(Attributes::AddressSafety)
+      .removeAttribute(Attributes::ForceSizeOpt);
   }
 
   uint64_t Raw() const { return Bits; }
diff --git a/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index 2ad0010fd12..464dfd51d67 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -557,6 +557,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(naked);
   KEYWORD(nonlazybind);
   KEYWORD(address_safety);
+  KEYWORD(forcesizeopt);
 
   KEYWORD(type);
   KEYWORD(opaque);
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 60e1741d694..cc7cc312460 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -953,6 +953,7 @@ bool LLParser::ParseOptionalAttrs(AttrBuilder &B, unsigned AttrKind) {
     case lltok::kw_naked:           B.addAttribute(Attributes::Naked); break;
     case lltok::kw_nonlazybind:     B.addAttribute(Attributes::NonLazyBind); break;
     case lltok::kw_address_safety:  B.addAttribute(Attributes::AddressSafety); break;
+    case lltok::kw_forcesizeopt:    B.addAttribute(Attributes::ForceSizeOpt); break;
 
     case lltok::kw_alignstack: {
       unsigned Alignment;
@@ -1011,6 +1012,7 @@ bool LLParser::ParseOptionalAttrs(AttrBuilder &B, unsigned AttrKind) {
     case lltok::kw_nonlazybind:
     case lltok::kw_returns_twice:
     case lltok::kw_address_safety:
+    case lltok::kw_forcesizeopt:
       if (AttrKind != 2)
         HaveError |= Error(AttrLoc, "invalid use of function-only attribute");
       break;
diff --git a/lib/AsmParser/LLToken.h b/lib/AsmParser/LLToken.h
index 0859f6a288f..ff6d68f0da4 100644
--- a/lib/AsmParser/LLToken.h
+++ b/lib/AsmParser/LLToken.h
@@ -109,6 +109,7 @@ namespace lltok {
     kw_naked,
     kw_nonlazybind,
     kw_address_safety,
+    kw_forcesizeopt,
 
     kw_type,
     kw_opaque,
diff --git a/lib/VMCore/Attributes.cpp b/lib/VMCore/Attributes.cpp
index 4f55fb203bd..642d4fcffb8 100644
--- a/lib/VMCore/Attributes.cpp
+++ b/lib/VMCore/Attributes.cpp
@@ -127,7 +127,7 @@ uint64_t Attributes::encodeLLVMAttributesForBitcode(Attributes Attrs) {
   uint64_t EncodedAttrs = Attrs.Raw() & 0xffff;
   if (Attrs.hasAttribute(Attributes::Alignment))
     EncodedAttrs |= Attrs.getAlignment() << 16;
-  EncodedAttrs |= (Attrs.Raw() & (0xfffULL << 21)) << 11;
+  EncodedAttrs |= (Attrs.Raw() & (0xffffULL << 21)) << 11;
   return EncodedAttrs;
 }
 
@@ -145,7 +145,7 @@ Attributes Attributes::decodeLLVMAttributesForBitcode(LLVMContext &C,
   AttrBuilder B(EncodedAttrs & 0xffff);
   if (Alignment)
     B.addAlignmentAttr(Alignment);
-  B.addRawValue((EncodedAttrs & (0xfffULL << 32)) >> 11);
+  B.addRawValue((EncodedAttrs & (0xffffULL << 32)) >> 11);
   return Attributes::get(C, B);
 }
 
@@ -201,6 +201,8 @@ std::string Attributes::getAsString() const {
     Result += "nonlazybind ";
   if (hasAttribute(Attributes::AddressSafety))
     Result += "address_safety ";
+  if (hasAttribute(Attributes::ForceSizeOpt))
+    Result += "forcesizeopt ";
   if (hasAttribute(Attributes::StackAlignment)) {
     Result += "alignstack(";
     Result += utostr(getStackAlignment());
@@ -324,6 +326,7 @@ uint64_t AttributesImpl::getAttrMask(uint64_t Val) {
   case Attributes::UWTable:         return 1 << 30;
   case Attributes::NonLazyBind:     return 1U << 31;
   case Attributes::AddressSafety:   return 1ULL << 32;
+  case Attributes::ForceSizeOpt:    return 1ULL << 33;
   }
   llvm_unreachable("Unsupported attribute type");
 }