Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -1851,6 +1851,11 @@
                         clang::AMDGPU::LastTSBuiltin - Builtin::FirstTSBuiltin);
   }
 
+  bool isCLZForZeroUndef() const override {
+    // It is -1 instead of expected for intrinsic.
+    return true;
+  }
+
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override {
     if (getTriple().getArch() == llvm::Triple::amdgcn)
Index: test/CodeGenOpenCL/builtins-generic-amdgcn.cl
===================================================================
--- /dev/null
+++ test/CodeGenOpenCL/builtins-generic-amdgcn.cl
@@ -0,0 +1,16 @@
+// REQUIRES: amdgpu-registered-target
+// RUN: %clang_cc1 -triple amdgcn-unknown-unknown -S -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: @test_builtin_clz(
+// CHECK: tail call i32 @llvm.ctlz.i32(i32 %a, i1 true)
+void test_builtin_clz(global int* out, int a)
+{
+  *out = __builtin_clz(a);
+}
+
+// CHECK-LABEL: @test_builtin_clzl(
+// CHECK: tail call i64 @llvm.ctlz.i64(i64 %a, i1 true)
+void test_builtin_clzl(global long* out, long a)
+{
+  *out = __builtin_clzl(a);
+}