Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -655,6 +655,12 @@
   let Documentation = [Undocumented];
 }
 
+def OpenCLUnrollHint : InheritableAttr {
+  let Spellings = [GNU<"opencl_unroll_hint">];
+  let Args = [UnsignedArgument<"UnrollHint">];
+  let Documentation = [OpenCLUnrollHintDocs];
+}
+
 // This attribute is both a type attribute, and a declaration attribute (for
 // parameter variables).
 def OpenCLImageAccess : Attr {
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td
+++ include/clang/Basic/AttrDocs.td
@@ -1562,6 +1562,19 @@
   }];
 }
 
+def OpenCLUnrollHintDocs : Documentation {
+  let Category = DocCatStmt;
+  let Heading = "__attribute__((opencl_unroll_hint))";
+  let Content = [{
+The opencl_unroll_hint attribute qualifier can be used to specify that a loop
+(for, while and do loops) can be unrolled. This attribute qualifier can be
+used to specify full unrolling or partial unrolling by a specified amount.
+This is a compiler hint and the compiler may ignore this directive. See
+`OpenCL v2.0 <https://www.khronos.org/registry/cl/specs/opencl-2.0.pdf>`_
+s6.11.5 for details.
+  }];
+}
+
 def DocOpenCLAddressSpaces : DocumentationCategory<"OpenCL Address Spaces"> {
   let Content = [{
 The address space qualifier may be used to specify the region of memory that is
Index: include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- include/clang/Basic/DiagnosticParseKinds.td
+++ include/clang/Basic/DiagnosticParseKinds.td
@@ -902,6 +902,9 @@
 def err_pragma_optimize_extra_argument : Error<
   "unexpected extra argument '%0' to '#pragma clang optimize'">;
 
+def err_opencl_unroll_hint_on_non_loop : Error<
+  "OpenCL only supports 'opencl_unroll_hint' attribute on for, while, and do statements">;
+
 // OpenCL EXTENSION pragma (OpenCL 1.1 [9.1])
 def warn_pragma_expected_colon : Warning<
   "missing ':' after %0 - ignoring">, InGroup<IgnoredPragmas>;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2117,6 +2117,10 @@
 def err_attribute_invalid_vector_type : Error<"invalid vector element type %0">;
 def err_attribute_bad_neon_vector_size : Error<
   "Neon vector size must be 64 or 128 bits">;
+def err_attribute_requires_positive_integer : Error<
+  "%0 attribute requires a positive integral compile time constant expression">;
+def err_attribute_requires_opencl_version : Error<
+  "%0 attribute requires OpenCL version %1 or above">;
 def warn_unsupported_target_attribute
     : Warning<"Ignoring unsupported '%0' in the target attribute string">,
     InGroup<IgnoredAttributes>;
Index: include/clang/Parse/Parser.h
===================================================================
--- include/clang/Parse/Parser.h
+++ include/clang/Parse/Parser.h
@@ -2195,8 +2195,19 @@
   SourceLocation SkipExtendedMicrosoftTypeAttributes();
   void ParseMicrosoftInheritanceClassAttributes(ParsedAttributes &attrs);
   void ParseBorlandTypeAttributes(ParsedAttributes &attrs);
-  void ParseOpenCLAttributes(ParsedAttributes &attrs);
+  void ParseOpenCLKernelAttributes(ParsedAttributes &attrs);
   void ParseOpenCLQualifiers(ParsedAttributes &Attrs);
+  /// \brief Parses opencl_unroll_hint attribute if language is OpenCL v2.0
+  /// or higher.
+  /// \return false if error happens.
+  bool MaybeParseOpenCLUnrollHintAttribute(ParsedAttributes &Attrs) {
+    if (getLangOpts().OpenCL)
+      return ParseOpenCLUnrollHintAttribute(Attrs);
+    return true;
+  }
+  /// \brief Parses opencl_unroll_hint attribute.
+  /// \return false if error happens.
+  bool ParseOpenCLUnrollHintAttribute(ParsedAttributes &Attrs);
   void ParseNullabilityTypeSpecifiers(ParsedAttributes &attrs);
 
   VersionTuple ParseVersionTuple(SourceRange &Range);
Index: lib/CodeGen/CGLoopInfo.cpp
===================================================================
--- lib/CodeGen/CGLoopInfo.cpp
+++ lib/CodeGen/CGLoopInfo.cpp
@@ -115,20 +115,41 @@
   // Identify loop hint attributes from Attrs.
   for (const auto *Attr : Attrs) {
     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(Attr);
+    const OpenCLUnrollHintAttr *OpenCLHint =
+        dyn_cast<OpenCLUnrollHintAttr>(Attr);
 
     // Skip non loop hint attributes
-    if (!LH)
+    if (!LH && !OpenCLHint) {
       continue;
+    }
 
-    auto *ValueExpr = LH->getValue();
+    LoopHintAttr::OptionType Option = LoopHintAttr::Unroll;
+    LoopHintAttr::LoopHintState State = LoopHintAttr::Disable;
     unsigned ValueInt = 1;
-    if (ValueExpr) {
-      llvm::APSInt ValueAPS = ValueExpr->EvaluateKnownConstInt(Ctx);
-      ValueInt = ValueAPS.getSExtValue();
-    }
+    // Translate opencl_unroll_hint attribute argument to
+    // equivalent LoopHintAttr enums.
+    // OpenCL v2.0 s6.11.5:  
+    // 0 - full unroll (no argument).
+    // 1 - disable unroll.
+    // other positive integer n - unroll by n.
+    if (OpenCLHint) {
+      ValueInt = OpenCLHint->getUnrollHint();
+      if (ValueInt == 0) {
+        State = LoopHintAttr::Full;
+      } else if (ValueInt != 1) {
+        Option = LoopHintAttr::UnrollCount;
+        State = LoopHintAttr::Numeric;
+      }
+    } else if (LH) {
+      auto *ValueExpr = LH->getValue();
+      if (ValueExpr) {
+        llvm::APSInt ValueAPS = ValueExpr->EvaluateKnownConstInt(Ctx);
+        ValueInt = ValueAPS.getSExtValue();
+      }
 
-    LoopHintAttr::OptionType Option = LH->getOption();
-    LoopHintAttr::LoopHintState State = LH->getState();
+      Option = LH->getOption();
+      State = LH->getState();
+    }
     switch (State) {
     case LoopHintAttr::Disable:
       switch (Option) {
Index: lib/Parse/ParseDecl.cpp
===================================================================
--- lib/Parse/ParseDecl.cpp
+++ lib/Parse/ParseDecl.cpp
@@ -670,7 +670,7 @@
   }
 }
 
-void Parser::ParseOpenCLAttributes(ParsedAttributes &attrs) {
+void Parser::ParseOpenCLKernelAttributes(ParsedAttributes &attrs) {
   // Treat these like attributes
   while (Tok.is(tok::kw___kernel)) {
     IdentifierInfo *AttrName = Tok.getIdentifierInfo();
@@ -3084,7 +3084,7 @@
 
     // OpenCL single token adornments.
     case tok::kw___kernel:
-      ParseOpenCLAttributes(DS.getAttributes());
+      ParseOpenCLKernelAttributes(DS.getAttributes());
       continue;
 
     // Nullability type specifiers.
Index: lib/Parse/ParseStmt.cpp
===================================================================
--- lib/Parse/ParseStmt.cpp
+++ lib/Parse/ParseStmt.cpp
@@ -107,6 +107,8 @@
 
   ParsedAttributesWithRange Attrs(AttrFactory);
   MaybeParseCXX11Attributes(Attrs, nullptr, /*MightBeObjCMessageSend*/ true);
+  if (!MaybeParseOpenCLUnrollHintAttribute(Attrs))
+    return StmtError();
 
   StmtResult Res = ParseStatementOrDeclarationAfterAttributes(
       Stmts, Allowed, TrailingElseLoc, Attrs);
@@ -2208,3 +2210,19 @@
   }
   Braces.consumeClose();
 }
+
+bool Parser::ParseOpenCLUnrollHintAttribute(ParsedAttributes &Attrs) {
+  MaybeParseGNUAttributes(Attrs);
+
+  if (Attrs.empty())
+    return true;
+
+  if (Attrs.getList()->getKind() != AttributeList::AT_OpenCLUnrollHint)
+    return true;
+
+  if (!(Tok.is(tok::kw_for) || Tok.is(tok::kw_while) || Tok.is(tok::kw_do))) {
+    Diag(Tok, diag::err_opencl_unroll_hint_on_non_loop);
+    return false;
+  }
+  return true;
+}
Index: lib/Sema/SemaStmtAttr.cpp
===================================================================
--- lib/Sema/SemaStmtAttr.cpp
+++ lib/Sema/SemaStmtAttr.cpp
@@ -203,6 +203,52 @@
   }
 }
 
+static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const AttributeList &A,
+                                    SourceRange Range) {
+  // OpenCL v2.0 s6.11.5 - opencl_unroll_hint can have 0 arguments (compiler
+  // determines unrolling factor) or 1 argument (the unroll factor provided
+  // by the user).
+
+  if (S.getLangOpts().OpenCLVersion < 200) {
+    S.Diag(A.getLoc(), diag::err_attribute_requires_opencl_version)
+        << A.getName() << "2.0";
+    return nullptr;
+  }
+
+  unsigned NumArgs = A.getNumArgs();
+
+  if (NumArgs > 1) {
+    S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A.getName()
+                                                               << 1;
+    return nullptr;
+  }
+
+  unsigned UnrollFactor = 0;
+
+  if (NumArgs == 1) {
+    Expr *E = A.getArgAsExpr(0);
+    llvm::APSInt ArgVal(32);
+
+    if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
+      S.Diag(A.getLoc(), diag::err_attribute_argument_type)
+          << A.getName() << AANT_ArgumentIntegerConstant << E->getSourceRange();
+      return nullptr;
+    }
+
+    int Val = ArgVal.getSExtValue();
+
+    if (Val <= 0) {
+      S.Diag(A.getRange().getBegin(),
+             diag::err_attribute_requires_positive_integer)
+          << A.getName();
+      return nullptr;
+    }
+    UnrollFactor = Val;
+  }
+
+  return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor);
+}
+
 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
                                   SourceRange Range) {
   switch (A.getKind()) {
@@ -215,6 +261,8 @@
     return handleFallThroughAttr(S, St, A, Range);
   case AttributeList::AT_LoopHint:
     return handleLoopHintAttr(S, St, A, Range);
+  case AttributeList::AT_OpenCLUnrollHint:
+    return handleOpenCLUnrollHint(S, St, A, Range);
   default:
     // if we're here, then we parsed a known attribute, but didn't recognize
     // it as a statement attribute => it is declaration attribute
Index: test/CodeGenOpenCL/unroll-hint.cl
===================================================================
--- /dev/null
+++ test/CodeGenOpenCL/unroll-hint.cl
@@ -0,0 +1,96 @@
+// RUN: %clang_cc1 -emit-llvm -O0 -cl-std=CL2.0 -o - %s | FileCheck %s
+
+/*** for ***/
+void for_count()
+{
+// CHECK-LABEL: for_count
+    __attribute__((opencl_unroll_hint(8)))
+    for( int i = 0; i < 1000; ++i);
+// CHECK: br label %{{.*}}, !llvm.loop ![[FOR_COUNT:.*]]
+}
+
+void for_disable()
+{
+// CHECK-LABEL: for_disable
+    __attribute__((opencl_unroll_hint(1)))
+    for( int i = 0; i < 1000; ++i);
+// CHECK: br label %{{.*}}, !llvm.loop ![[FOR_DISABLE:.*]]
+}
+
+void for_full()
+{
+// CHECK-LABEL: for_full
+    __attribute__((opencl_unroll_hint))
+    for( int i = 0; i < 1000; ++i);
+// CHECK: br label %{{.*}}, !llvm.loop ![[FOR_FULL:.*]]
+}
+
+/*** while ***/
+void while_count()
+{
+// CHECK-LABEL: while_count
+    int i = 1000;
+    __attribute__((opencl_unroll_hint(8)))
+    while(i-->0);
+// CHECK: br label %{{.*}}, !llvm.loop ![[WHILE_COUNT:.*]]
+}
+
+void while_disable()
+{
+// CHECK-LABEL: while_disable
+    int i = 1000;
+    __attribute__((opencl_unroll_hint(1)))
+    while(i-->0);
+// CHECK: br label %{{.*}}, !llvm.loop ![[WHILE_DISABLE:.*]]
+}
+
+void while_full()
+{
+// CHECK-LABEL: while_full
+    int i = 1000;
+    __attribute__((opencl_unroll_hint))
+    while(i-->0);
+// CHECK: br label %{{.*}}, !llvm.loop ![[WHILE_FULL:.*]]
+}
+
+/*** do ***/
+void do_count()
+{
+// CHECK-LABEL: do_count
+    int i = 1000;
+    __attribute__((opencl_unroll_hint(8)))
+    do {} while(i--> 0);
+// CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !llvm.loop ![[DO_COUNT:.*]]
+}
+
+void do_disable()
+{
+// CHECK-LABEL: do_disable
+    int i = 1000;
+    __attribute__((opencl_unroll_hint(1)))
+    do {} while(i--> 0);
+// CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !llvm.loop ![[DO_DISABLE:.*]]
+}
+
+void do_full()
+{
+// CHECK-LABEL: do_full
+    int i = 1000;
+    __attribute__((opencl_unroll_hint))
+    do {} while(i--> 0);
+// CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !llvm.loop ![[DO_FULL:.*]]
+}
+
+
+// CHECK: ![[FOR_COUNT]]     =  distinct !{![[FOR_COUNT]],  ![[COUNT:.*]]}
+// CHECK: ![[COUNT]]         =  !{!"llvm.loop.unroll.count", i32 8}
+// CHECK: ![[FOR_DISABLE]]   =  distinct !{![[FOR_DISABLE]],  ![[DISABLE:.*]]}
+// CHECK: ![[DISABLE]]       =  !{!"llvm.loop.unroll.disable"}
+// CHECK: ![[FOR_FULL]]      =  distinct !{![[FOR_FULL]],  ![[FULL:.*]]}
+// CHECK: ![[FULL]]          =  !{!"llvm.loop.unroll.full"}
+// CHECK: ![[WHILE_COUNT]]   =  distinct !{![[WHILE_COUNT]],    ![[COUNT]]}
+// CHECK: ![[WHILE_DISABLE]] =  distinct !{![[WHILE_DISABLE]],  ![[DISABLE]]}
+// CHECK: ![[WHILE_FULL]]    =  distinct !{![[WHILE_FULL]],     ![[FULL]]}
+// CHECK: ![[DO_COUNT]]      =  distinct !{![[DO_COUNT]],       ![[COUNT]]}
+// CHECK: ![[DO_DISABLE]]    =  distinct !{![[DO_DISABLE]],     ![[DISABLE]]}
+// CHECK: ![[DO_FULL]]       =  distinct !{![[DO_FULL]],        ![[FULL]]}
Index: test/Parser/opencl-unroll-hint.cl
===================================================================
--- /dev/null
+++ test/Parser/opencl-unroll-hint.cl
@@ -0,0 +1,8 @@
+//RUN: %clang_cc1 -O0 -cl-std=CL2.0 -fsyntax-only -verify %s
+
+kernel void B (global int *x) {
+  __attribute__((opencl_unroll_hint(42)))
+  if (x[0])                             // expected-error {{OpenCL only supports 'opencl_unroll_hint' attribute on for, while, and do statements}}
+    x[0] = 15;
+}
+
Index: test/SemaOpenCL/unroll-hint.cl
===================================================================
--- /dev/null
+++ test/SemaOpenCL/unroll-hint.cl
@@ -0,0 +1,30 @@
+//RUN: %clang_cc1 -O0 -fsyntax-only -verify %s
+//RUN: %clang_cc1 -O0 -cl-std=CL2.0 -fsyntax-only -verify -DCL20 %s
+
+kernel void D (global int *x) {
+  int i = 10;
+#ifndef CL20
+  // expected-error@+2 {{'opencl_unroll_hint' attribute requires OpenCL version 2.0 or above}}
+#endif
+  __attribute__((opencl_unroll_hint))
+  do {
+  } while(i--);
+}
+
+#ifdef CL20
+kernel void C (global int *x) {
+  int I = 3;
+  __attribute__((opencl_unroll_hint(I))) // expected-error {{'opencl_unroll_hint' attribute requires an integer constant}}
+  while (I--);
+}
+
+kernel void E() {
+  __attribute__((opencl_unroll_hint(2,4))) // expected-error {{'opencl_unroll_hint' attribute takes no more than 1 argument}}
+  for(int i=0; i<100; i++);
+}
+
+kernel void F() {
+  __attribute__((opencl_unroll_hint(-1))) // expected-error {{'opencl_unroll_hint' attribute requires a positive integral compile time constant expression}}
+  for(int i=0; i<100; i++);
+}
+#endif