--- a/src/hotspot/os/aix/porting_aix.cpp	Tue Feb 12 15:31:40 2019 +0100
+++ b/src/hotspot/os/aix/porting_aix.cpp	Tue Feb 05 17:40:15 2019 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2013 SAP SE. All rights reserved.
+ * Copyright (c) 2012, 2019 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,7 +34,15 @@
 #include "utilities/align.hpp"
 #include "utilities/debug.hpp"
 
+// distinguish old xlc and xlclang++, where
+// <ibmdemangle.h> is suggested but not found in GA release (might come with a fix)
+#if defined(__clang__)
+#define DISABLE_DEMANGLE
+// #include <ibmdemangle.h>
+#else
 #include <demangle.h>
+#endif
+
 #include <sys/debug.h>
 #include <pthread.h>
 #include <ucontext.h>
@@ -237,6 +245,7 @@
       p_name[i] = '\0';
 
       // If it is a C++ name, try and demangle it using the Demangle interface (see demangle.h).
+#ifndef DISABLE_DEMANGLE
       if (demangle) {
         char* rest;
         Name* const name = Demangle(p_name, rest);
@@ -249,6 +258,7 @@
           delete name;
         }
       }
+#endif
     } else {
       strncpy(p_name, "<nameless function>", namelen-1);
       p_name[namelen-1] = '\0';

--- a/src/hotspot/os_cpu/aix_ppc/prefetch_aix_ppc.inline.hpp	Tue Feb 12 15:31:40 2019 +0100
+++ b/src/hotspot/os_cpu/aix_ppc/prefetch_aix_ppc.inline.hpp	Tue Feb 05 17:40:15 2019 +0100
@@ -43,7 +43,7 @@
 }
 
 inline void Prefetch::write(void *loc, intx interval) {
-#if !defined(USE_XLC_PREFETCH_WRITE_BUILTIN)
+#if !defined(USE_XLC_BUILTINS)
   __asm__ __volatile__ (
     "   dcbtst 0, %0       \n"
     :

--- a/src/hotspot/share/runtime/arguments.cpp	Tue Feb 12 15:31:40 2019 +0100
+++ b/src/hotspot/share/runtime/arguments.cpp	Tue Feb 05 17:40:15 2019 +0100
@@ -3794,8 +3794,8 @@
 #endif
 
 #if defined(AIX)
-  UNSUPPORTED_OPTION(AllocateHeapAt);
-  UNSUPPORTED_OPTION(AllocateOldGenAt);
+  UNSUPPORTED_OPTION_NULL(AllocateHeapAt);
+  UNSUPPORTED_OPTION_NULL(AllocateOldGenAt);
 #endif
 
 #ifndef PRODUCT

--- a/src/hotspot/share/runtime/arguments.hpp	Tue Feb 12 15:31:40 2019 +0100
+++ b/src/hotspot/share/runtime/arguments.hpp	Tue Feb 05 17:40:15 2019 +0100
@@ -663,4 +663,16 @@
   }                                                      \
 } while(0)
 
+// similar to UNSUPPORTED_OPTION but sets flag to NULL
+#define UNSUPPORTED_OPTION_NULL(opt)                     \
+do {                                                     \
+  if (opt) {                                             \
+    if (FLAG_IS_CMDLINE(opt)) {                          \
+      warning("-XX flag " #opt " not supported in this VM"); \
+    }                                                    \
+    FLAG_SET_DEFAULT(opt, NULL);                         \
+  }                                                      \
+} while(0)
+
+
 #endif // SHARE_RUNTIME_ARGUMENTS_HPP

--- a/src/hotspot/share/utilities/globalDefinitions_xlc.hpp	Tue Feb 12 15:31:40 2019 +0100
+++ b/src/hotspot/share/utilities/globalDefinitions_xlc.hpp	Tue Feb 05 17:40:15 2019 +0100
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2017 SAP SE. All rights reserved.
+ * Copyright (c) 2012, 2019 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -51,51 +51,43 @@
 
 #include <stdint.h>
 
+// __IBMCPP__ is not defined any more with xlclang++
+#ifdef __IBMCPP__
+#if __IBMCPP__ < 1200
+#error "xlc < 12 not supported"
+#endif
+#endif
+
+#ifndef _AIX
+#error "missing AIX-specific definition _AIX"
+#endif
+
 // Use XLC compiler builtins instead of inline assembler
 #define USE_XLC_BUILTINS
+
 #ifdef USE_XLC_BUILTINS
 #include <builtins.h>
-  #if __IBMCPP__ < 1000
-  // the funtion prototype for __dcbtst(void *) is missing in XLC V8.0
-  // I could compile a little test, where I provided the prototype.
-  // The generated code was correct there. This is the prototype:
-  // extern "builtin" void __dcbtst (void *);
-  // For now we don't make use of it when compiling with XLC V8.0
-  #else
-  // __IBMCPP__ >= 1000
-  // XLC V10 provides the prototype for __dcbtst (void *);
-  #define USE_XLC_PREFETCH_WRITE_BUILTIN
-  #endif
+// XLC V10 and higher provide the prototype for __dcbtst (void *);
 #endif // USE_XLC_BUILTINS
 
 // NULL vs NULL_WORD:
-// On Linux NULL is defined as a special type '__null'. Assigning __null to
-// integer variable will cause gcc warning. Use NULL_WORD in places where a
-// pointer is stored as integer value.  On some platforms, sizeof(intptr_t) >
-// sizeof(void*), so here we want something which is integer type, but has the
-// same size as a pointer.
-#ifdef __GNUC__
-  #error XLC and __GNUC__?
-#else
-  #define NULL_WORD  NULL
-#endif
+// Some platform/tool-chain combinations can't assign NULL to an integer
+// type so we define NULL_WORD to use in those contexts. For xlc they are the same.
+#define NULL_WORD  NULL
 
 // AIX also needs a 64 bit NULL to work as a null address pointer.
 // Most system includes on AIX would define it as an int 0 if not already defined with one
 // exception: /usr/include/dirent.h will unconditionally redefine NULL to int 0 again.
 // In this case you need to copy the following defines to a position after #include <dirent.h>
-// (see jmv_aix.h).
-#ifdef AIX
-  #include <dirent.h>
-  #ifdef _LP64
-    #undef NULL
-    #define NULL 0L
-  #else
-    #ifndef NULL
-      #define NULL 0
-    #endif
+#include <dirent.h>
+#ifdef _LP64
+  #undef NULL
+  #define NULL 0L
+#else
+  #ifndef NULL
+    #define NULL 0
   #endif
-#endif // AIX
+#endif
 
 // Compiler-specific primitive types
 // All defs of int (uint16_6 etc) are defined in AIX' /usr/include/stdint.h
@@ -108,21 +100,14 @@
 typedef uint64_t julong;
 
 // checking for nanness
-#ifdef AIX
 inline int g_isnan(float  f) { return isnan(f); }
 inline int g_isnan(double f) { return isnan(f); }
-#else
-#error "missing platform-specific definition here"
-#endif
 
 // Checking for finiteness
-
 inline int g_isfinite(jfloat  f)                 { return finite(f); }
 inline int g_isfinite(jdouble f)                 { return finite(f); }
 
-
 // Wide characters
-
 inline int wcslen(const jchar* x) { return wcslen((const wchar_t*)x); }