--- old/src/hotspot/cpu/s390/vtableStubs_s390.cpp	2018-02-27 10:50:31.293655000 +0100
+++ new/src/hotspot/cpu/s390/vtableStubs_s390.cpp	2018-02-27 10:50:30.910624000 +0100
@@ -58,11 +58,13 @@
   ResourceMark    rm;
   CodeBuffer      cb(s->entry_point(), code_length);
   MacroAssembler *masm = new MacroAssembler(&cb);
+  int     padding_bytes = 0;
 
 #if (!defined(PRODUCT) && defined(COMPILER2))
   if (CountCompiledCalls) {
     // Count unused bytes
-    __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::nof_megamorphic_calls_addr(), true);
+    //                  worst case             actual size
+    padding_bytes += __ load_const_size() - __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::nof_megamorphic_calls_addr(), true);
 
     // Use generic emitter for direct memory increment.
     // Abuse Z_method as scratch register for generic emitter.
@@ -90,13 +92,17 @@
     // Check offset vs vtable length.
     const Register vtable_idx = Z_R0_scratch;
 
-    __ load_const_optimized_rtn_len(vtable_idx, vtable_index*vtableEntry::size_in_bytes(), true);
+    // Count unused bytes.
+    //                  worst case             actual size
+    padding_bytes += __ load_const_size() - __ load_const_optimized_rtn_len(vtable_idx, vtable_index*vtableEntry::size_in_bytes(), true);
 
     assert(Immediate::is_uimm12(in_bytes(Klass::vtable_length_offset())), "disp to large");
     __ z_cl(vtable_idx, in_bytes(Klass::vtable_length_offset()), rcvr_klass);
     __ z_brl(L);
     __ z_lghi(Z_ARG3, vtable_index);  // Debug code, don't optimize.
     __ call_VM(noreg, CAST_FROM_FN_PTR(address, bad_compiled_vtable_index), Z_ARG1, Z_ARG3, false);
+    // Count unused bytes (assume worst case here).
+    padding_bytes += 12;
     __ bind(L);
   }
 #endif
@@ -106,6 +112,8 @@
   // Duplicate safety code from enc_class Java_Dynamic_Call_dynTOC.
   if (Displacement::is_validDisp(v_off)) {
     __ z_lg(Z_method/*method oop*/, v_off, rcvr_klass/*class oop*/);
+    // Account for the load_const in the else path.
+    padding_bytes += __ load_const_size();
   } else {
     // Worse case, offset does not fit in displacement field.
     __ load_const(Z_method, v_off); // Z_method temporarily holds the offset value.
@@ -146,10 +154,13 @@
   ResourceMark    rm;
   CodeBuffer      cb(s->entry_point(), code_length);
   MacroAssembler *masm = new MacroAssembler(&cb);
+  int     padding_bytes = 0;
 
 #if (!defined(PRODUCT) && defined(COMPILER2))
   if (CountCompiledCalls) {
-    __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::nof_megamorphic_calls_addr(), true);
+    // Count unused bytes
+    //                  worst case             actual size
+    padding_bytes += __ load_const_size() - __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::nof_megamorphic_calls_addr(), true);
 
     // Use generic emitter for direct memory increment.
     // Use Z_tmp_1 as scratch register for generic emitter.
@@ -200,13 +211,14 @@
   __ z_lg(Z_R1_scratch, in_bytes(Method::from_compiled_offset()), Z_method);
   __ z_br(Z_R1_scratch);
 
-  __ bind(no_such_interface);
   // Handle IncompatibleClassChangeError in itable stubs.
-  // More detailed error message.
-  // We force resolving of the call site by jumping to the "handle
-  // wrong method" stub, and so let the interpreter runtime do all the
-  // dirty work.
-  __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::get_handle_wrong_method_stub(), true);
+  __ bind(no_such_interface);
+  // Count unused bytes
+  //                  worst case          actual size
+  // We force resolving of the call site by jumping to
+  // the "handle wrong method" stub, and so let the
+  // interpreter runtime do all the dirty work.
+  padding_bytes += __ load_const_size() - __ load_const_optimized_rtn_len(Z_R1_scratch, (long)SharedRuntime::get_handle_wrong_method_stub(), true);
   __ z_br(Z_R1_scratch);
 
   masm->flush();