Cleanups and Shenandoah-specific changes.

Author: christianhaeubl

README.md

@@ -81,7 +81,10 @@ In some code parts, `Unimplemented()` serves as a placeholder for GC-specific fu
   - `src/hotspot/share/gc/shared/hSpaceCounters.cpp`
   - `src/hotspot/share/gc/shared/ageTable.cpp`
 
-Besides that, the length of 0 for `GCThreadLocalData` in `src/hotspot/share/gc/shared/gcThreadLocalData.hpp` is a placeholder as well.
+Besides that, there are a few places where values are hardcoded at the moment.
+Those need to be replaced with the correct GC-specific values:
+- the length of `GCThreadLocalData` in `src/hotspot/share/gc/shared/gcThreadLocalData.hpp` is hardcoded to 0
+- `log_of_heap_region_grain_bytes` in `src/hotspot/svm/svmToGC.cpp` is hardcoded to 20
 
 ## Build
 

src/hotspot/SubMakefile

@@ -101,7 +101,7 @@ DEBUG_LEVEL_FILE_SUFFIX.debug := -debug
 DEBUG_LEVEL_FILE_SUFFIX := $(DEBUG_LEVEL_FILE_SUFFIX.$(DEBUG_LEVEL))
 
 BUILD_DIR := $(BUILD_ROOT)/$(DEBUG_LEVEL)-$(COMPRESSED_REFERENCES_SUFFIX)$(TARGET_EXT)
-TARGET_FILE := $(BUILD_ROOT)/libsvmgc$(DEBUG_LEVEL_FILE_SUFFIX)-$(COMPRESSED_REFERENCES_SUFFIX)$(TARGET_EXT)
+TARGET_FILE := $(BUILD_ROOT)/libshenandoahgc$(DEBUG_LEVEL_FILE_SUFFIX)-$(COMPRESSED_REFERENCES_SUFFIX)$(TARGET_EXT)
 
 CPP_FILES_TO_EXCLUDE.amd64 := aarch64
 CPP_FILES_TO_EXCLUDE.aarch64 := x86

src/hotspot/share/runtime/mutex.cpp

@@ -119,13 +119,13 @@ void Mutex::lock_contended(Thread* self) {
     if (thread->has_status_vm()) {
       while (true) {
         // do a transition to native thread status so that we can safely block below without preventing a safepoint
-        SVMGlobalData::_transition_vm_to_native(heap_base, thread);
+        SVMGlobalData::_transition_vm_to_native(thread);
 
         _lock.lock();
 
         // do a transition back to VM state so that this thread can be sure that no safepoints are happening concurrently
         assert(thread->has_status_native_or_safepoint(), "must be");
-        if (SVMGlobalData::_try_fast_transition_native_to_vm(heap_base, thread)) {
+        if (SVMGlobalData::_try_fast_transition_native_to_vm(thread)) {
           // The fast path succeeded, so we have the lock and we are back in VM state.
           assert(thread->has_status_vm(), "must be");
           break;
@@ -134,7 +134,7 @@ void Mutex::lock_contended(Thread* self) {
           // try to lock it again after the safepoint ends. Otherwise, we could end up with a deadlock between this thread
           // and the VM thread.
           _lock.unlock();
-          SVMGlobalData::_slow_transition_native_to_vm(heap_base, thread);
+          SVMGlobalData::_slow_transition_native_to_vm(thread);
           assert(thread->has_status_vm(), "must be");
         }
       }

src/hotspot/share/runtime/thread.hpp

@@ -45,7 +45,7 @@
 #endif
 #ifdef SVM
 #include "svmIsolateThread.hpp"
-#include "exports/sharedGCStructs.hpp"
+#include "exports/sharedGCStructs.h"
 #endif // SVM
 
 

src/hotspot/svm/exports/sharedGCStructs.hpp renamed to src/hotspot/svm/exports/sharedGCStructs.h

@@ -23,47 +23,18 @@
  * questions.
  */
 
-#ifndef SVM_SHARED_STRUCTS_HPP
-#define SVM_SHARED_STRUCTS_HPP
+#ifndef SVM_SHARED_GC_STRUCTS_HPP
+#define SVM_SHARED_GC_STRUCTS_HPP
 
 #include <sys/types.h>
-// forward declarations
 
 #ifdef __cplusplus
-  namespace svm_gc {
+namespace svm_gc {
 #endif
 
+// forward declarations
 typedef struct CodeInfo CodeInfo;
 
-struct HeapOptions {
-  size_t max_heap_size;
-  size_t heap_address_space_size;
-  size_t physical_memory_size;
-};
-
-struct GCConstants {
-  void* card_table_address;
-  void* gc_total_collections_address;
-  int tlab_top_offset;
-  int tlab_end_offset;
-  int card_table_shift;
-  int java_thread_size;
-  int vm_operation_data_size;
-  int vm_operation_wrapper_data_size;
-  char dirty_card_value;
-};
-
-struct GCInternalState {
-  unsigned int total_collections;
-  unsigned int full_collections;
-
-  void* card_table_start;
-  size_t card_table_size;
-
-  void* block_offset_table_start;
-  size_t block_offset_table_size;
-};
-
 // data structures for frames that are currently on the stack
 struct StackFrame {
   u_char *stack_pointer;
@@ -92,9 +63,8 @@ struct CodeInfosPerThread {
   struct CodeInfos *threads[0]; // variable-sized array
 };
 
-
 #ifdef __cplusplus
-  } // namespace svm_gc
+} // namespace svm_gc
 #endif
 
-#endif // SVM_SHARED_STRUCTS_HPP
+#endif // SVM_SHARED_GC_STRUCTS_HPP

src/hotspot/svm/exports/shenandoahGCStructs.h

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2025, 2025, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#ifndef SVM_SHENANDOAH_GC_STRUCTS_H
+#define SVM_SHENANDOAH_GC_STRUCTS_H
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+namespace svm_gc {
+#endif
+
+struct ShenandoahHeapOptions {
+  size_t max_heap_size;
+  size_t heap_address_space_size;
+  size_t physical_memory_size;
+};
+
+struct ShenandoahInitState {
+  void* card_table_address;
+  int tlab_top_offset;
+  int tlab_end_offset;
+  int card_table_shift;
+  int log_of_heap_region_grain_bytes;
+  int java_thread_size;
+  int vm_operation_data_size;
+  int vm_operation_wrapper_data_size;
+  char dirty_card_value;
+};
+
+struct ShenandoahRegionBoundaries {
+  u_char *bottom;
+  u_char *top;
+};
+
+struct ShenandoahRegionInfo {
+  u_char *bottom;
+  u_char *top;
+  u_char *end;
+  char region_type;
+};
+
+struct ShenandoahInternalState {
+  unsigned int total_collections;
+  unsigned int full_collections;
+
+  void* card_table_start;
+  size_t card_table_size;
+};
+
+#ifdef __cplusplus
+} // namespace svm_gc
+#endif
+
+#endif // SVM_SHENANDOAH_GC_STRUCTS_H
+

src/hotspot/svm/share/oops/stackChunkOop.cpp

@@ -37,7 +37,7 @@
 #include "runtime/smallRegisterMap.inline.hpp"
 #include "runtime/stackChunkFrameStream.inline.hpp"
 #ifdef SVM
-#include "exports/sharedGCStructs.hpp"
+#include "exports/sharedGCStructs.h"
 #include "svmCodeReferenceMapDecoder.hpp"
 #endif // SVM
 

src/hotspot/svm/share/runtime/vmOperation.hpp

@@ -62,7 +62,7 @@ namespace svm_gc {
 
 class VM_Operation;
 
-// The layout of this class must match the NativeVMOperationData on the Java-side.
+// The layout of this class must match the NativeGCVMOperationData on the Java-side.
 // It must always be allocated as a part of a VM_Operation (i.e., it must never exist on its own)
 // and it must not contain a vtable. The blackbox fields are only accessed on native-image side.
 class VM_OperationData {

src/hotspot/svm/share/runtime/vmThread.cpp

@@ -104,7 +104,7 @@ void VMThread::execute(VM_Operation* op) {
 
   assert(isolate_thread == nullptr || isolate_thread->has_status_vm(), "isolate thread must be in VM state");
   if (isolate_thread != nullptr && !current_thread->is_VM_thread()) {
-    SVMGlobalData::_transition_vm_to_native(heap_base, isolate_thread);
+    SVMGlobalData::_transition_vm_to_native(isolate_thread);
   }
 
   VM_OperationData *op_data = op->data();
@@ -131,7 +131,7 @@ void VMThread::execute(VM_Operation* op) {
 
       if (isolate_thread != nullptr) {
         // The fast transition is always possible because no one can request a safepoint while the VM operation thread is blocked.
-        bool in_vm = SVMGlobalData::_try_fast_transition_native_to_vm(heap_base, isolate_thread);
+        bool in_vm = SVMGlobalData::_try_fast_transition_native_to_vm(isolate_thread);
         assert(in_vm && isolate_thread->has_status_vm(), "must be back in VM state");
       }
 
@@ -141,7 +141,7 @@ void VMThread::execute(VM_Operation* op) {
     } else {
       if (isolate_thread != nullptr) {
         // The fast transition is always possible because no one can request a safepoint while the VM operation thread is blocked.
-        bool in_vm = SVMGlobalData::_try_fast_transition_native_to_vm(heap_base, isolate_thread);
+        bool in_vm = SVMGlobalData::_try_fast_transition_native_to_vm(isolate_thread);
         assert(in_vm && isolate_thread->has_status_vm(), "must be back in VM state");
       }
 

src/hotspot/svm/svmCodeReferenceMapDecoder.cpp

@@ -25,7 +25,7 @@
 
 #include "code/compressedStream.hpp"
 #include "compiler/oopMap.hpp"
-#include "exports/sharedGCStructs.hpp"
+#include "exports/sharedGCStructs.h"
 #include "svmCodeReferenceMapDecoder.hpp"
 
 /**