RFR (S) 8249137: Remove CollectedHeap::obj_size

[Aleksey Shipilev]

RFE:
  https://bugs.openjdk.java.net/browse/JDK-8249137

It was added by JDK-8211270 to support old-style Shenandoah that needed a separate fwdptr slot.
After JDK-8224584 it does not need this anymore. Additionally, CH::obj_size may disagree with other
code that pokes at layout helper directly, for example GraphKit::new_instance.

This also avoids a virtual call on some paths, although those paths are not very performance-sensitive.

The patch is a simple series of few-liners:

diff -r 9cc348ebdc82 src/hotspot/share/gc/shared/collectedHeap.cpp
--- a/src/hotspot/share/gc/shared/collectedHeap.cpp     Thu Jul 09 04:32:30 2020 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.cpp     Thu Jul 09 08:05:46 2020 +0200
@@ -578,6 +578,2 @@

-size_t CollectedHeap::obj_size(oop obj) const {
-  return obj->size();
-}
-
 uint32_t CollectedHeap::hash_oop(oop obj) const {
diff -r 9cc348ebdc82 src/hotspot/share/gc/shared/collectedHeap.hpp
--- a/src/hotspot/share/gc/shared/collectedHeap.hpp     Thu Jul 09 04:32:30 2020 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.hpp     Thu Jul 09 08:05:46 2020 +0200
@@ -495,4 +495,2 @@

-  virtual size_t obj_size(oop obj) const;
-
   // Non product verification and debugging.
diff -r 9cc348ebdc82 src/hotspot/share/prims/jvmtiEnv.cpp
--- a/src/hotspot/share/prims/jvmtiEnv.cpp      Thu Jul 09 04:32:30 2020 +0200
+++ b/src/hotspot/share/prims/jvmtiEnv.cpp      Thu Jul 09 08:05:46 2020 +0200
@@ -488,3 +488,3 @@
   NULL_CHECK(mirror, JVMTI_ERROR_INVALID_OBJECT);
-  *size_ptr = (jlong)Universe::heap()->obj_size(mirror) * wordSize;
+  *size_ptr = (jlong)mirror->size() * wordSize;
   return JVMTI_ERROR_NONE;
diff -r 9cc348ebdc82 src/hotspot/share/prims/jvmtiExport.cpp
--- a/src/hotspot/share/prims/jvmtiExport.cpp   Thu Jul 09 04:32:30 2020 +0200
+++ b/src/hotspot/share/prims/jvmtiExport.cpp   Thu Jul 09 08:05:46 2020 +0200
@@ -1067,3 +1067,3 @@
      _jobj = (jobject)to_jobject(obj);
-     _size = Universe::heap()->obj_size(obj) * wordSize;
+     _size = obj->size() * wordSize;
    };
diff -r 9cc348ebdc82 src/hotspot/share/prims/whitebox.cpp
--- a/src/hotspot/share/prims/whitebox.cpp      Thu Jul 09 04:32:30 2020 +0200
+++ b/src/hotspot/share/prims/whitebox.cpp      Thu Jul 09 08:05:46 2020 +0200
@@ -389,3 +389,3 @@
   oop p = JNIHandles::resolve(obj);
-  return Universe::heap()->obj_size(p) * HeapWordSize;
+  return p->size() * HeapWordSize;
 WB_END

Testing: tier{1,2}; jdk-submit (running)

-- 
Thanks,
-Aleksey