8342011: Conditionally compile ReservedHeapSpace compressed heap support

Reviewed-by: stefank, dholmes

Author: Kim Barrett

src/hotspot/share/memory/virtualspace.cpp

@@ -369,6 +369,9 @@ ReservedSpace ReservedSpace::space_for_range(char* base, size_t size, size_t ali
   return space;
 }
 
+// Compressed oop support is not relevant in 32bit builds.
+#ifdef _LP64
+
 static size_t noaccess_prefix_size(size_t alignment) {
   return lcm(os::vm_page_size(), alignment);
 }
@@ -594,8 +597,8 @@ void ReservedHeapSpace::initialize_compressed_heap(const size_t size, size_t ali
     // Try to attach at addresses that are aligned to OopEncodingHeapMax. Disjointbase mode.
     char** addresses = get_attach_addresses_for_disjoint_mode();
     int i = 0;
-    while (addresses[i] &&                                 // End of array not yet reached.
-           ((_base == nullptr) ||                             // No previous try succeeded.
+    while ((addresses[i] != nullptr) &&                    // End of array not yet reached.
+           ((_base == nullptr) ||                          // No previous try succeeded.
             (_base + size >  (char *)OopEncodingHeapMax && // Not zerobased or unscaled address.
              !CompressedOops::is_disjoint_heap_base_address((address)_base)))) {  // Not disjoint address.
       char* const attach_point = addresses[i];
@@ -612,6 +615,8 @@ void ReservedHeapSpace::initialize_compressed_heap(const size_t size, size_t ali
   }
 }
 
+#endif // _LP64
+
 ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t alignment, size_t page_size, const char* heap_allocation_directory) : ReservedSpace() {
 
   if (size == 0) {
@@ -636,13 +641,17 @@ ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t alignment, size_t page_
   guarantee(is_aligned(size, alignment), "set by caller");
 
   if (UseCompressedOops) {
+#ifdef _LP64
     initialize_compressed_heap(size, alignment, page_size);
     if (_size > size) {
       // We allocated heap with noaccess prefix.
       // It can happen we get a zerobased/unscaled heap with noaccess prefix,
       // if we had to try at arbitrary address.
       establish_noaccess_prefix();
     }
+#else
+    ShouldNotReachHere();
+#endif // _LP64
   } else {
     initialize(size, alignment, page_size, nullptr, false);
   }

src/hotspot/share/memory/virtualspace.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 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
@@ -133,6 +133,10 @@ ReservedSpace ReservedSpace::partition(size_t offset, size_t partition_size)
 // Class encapsulating behavior specific of memory space reserved for Java heap.
 class ReservedHeapSpace : public ReservedSpace {
  private:
+
+  // Compressed oop support is not relevant in 32bit builds.
+#ifdef _LP64
+
   void try_reserve_heap(size_t size, size_t alignment, size_t page_size,
                         char *requested_address);
   void try_reserve_range(char *highest_start, char *lowest_start,
@@ -141,6 +145,9 @@ class ReservedHeapSpace : public ReservedSpace {
   void initialize_compressed_heap(const size_t size, size_t alignment, size_t page_size);
   // Create protection page at the beginning of the space.
   void establish_noaccess_prefix();
+
+#endif // _LP64
+
  public:
   // Constructor. Tries to find a heap that is good for compressed oops.
   // heap_allocation_directory is the path to the backing memory for Java heap. When set, Java heap will be allocated