8335667: Fix simple -Wzero-as-null-pointer-constant warnings in compiler code

Reviewed-by: chagedorn

Author: Kim Barrett

src/hotspot/share/ci/ciStreams.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2024, Oracle and/or its affiliates. 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
@@ -66,7 +66,7 @@ class ciBytecodeStream : StackObj {
   Bytecodes::Code _raw_bc;         // Current bytecode, raw form
 
   void reset( address base, unsigned int size ) {
-    _bc_start =_was_wide = 0;
+    _bc_start = _was_wide = nullptr;
     _start = _pc = base; _end = base + size;
   }
 

src/hotspot/share/code/exceptionHandlerTable.hpp

@@ -148,7 +148,7 @@ class ImplicitExceptionTable {
   ReallocMark          _nesting;  // assertion check for reallocations
 
 public:
-  ImplicitExceptionTable( ) :  _size(0), _len(0), _data(0) { }
+  ImplicitExceptionTable( ) :  _size(0), _len(0), _data(nullptr) { }
   // (run-time) construction from nmethod
   ImplicitExceptionTable(const nmethod *nm);