RFR: 8338745: Intrinsify Continuation.pin() and Continuation.unpin() [v2]

[Yudi Zheng]

On Thu, 22 Aug 2024 11:13:17 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Greetings,
>> 
>> Please help review this change set that implements C2 intrinsics for jdk.internal.vm.Continuation.pin() and jdk.internal.vm.Continuation.unpin().
>> 
>> This work is a consequence of [JDK-8338417](https://bugs.openjdk.org/browse/JDK-8338417), which required us to introduce explicit pin constructs for Virtual threads in a relatively performance-sensitive path.
>> 
>> Testing: jdk_jfr, loom testing
>> 
>> Comment: I changed the type of the ContinuationEntry::_pin_count field from uint to uin32_t to make the size explicit and to access it uniformly from the intrinsic code using T_INT.
>> 
>> Thanks
>> Markus
>
> Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Deoptimization::Action_none for no deopt

src/hotspot/share/opto/library_call.cpp line 3733:

> 3731:   // TLS
> 3732:   Node* tls_ptr = _gvn.transform(new ThreadLocalNode());
> 3733:   Node* last_continuation_offset = basic_plus_adr(top(), tls_ptr, in_bytes(JavaThread::cont_entry_offset()));

Could you please export `JavaThread::_cont_entry` and `ContinuationEntry::_pin_count` to JVMCI? Thanks!

diff --git a/src/hotspot/share/jvmci/vmStructs_jvmci.cpp b/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
index 688691fb976..a25ecd2bab5 100644
--- a/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
+++ b/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
@@ -35,6 +35,7 @@
 #include "oops/methodCounters.hpp"
 #include "oops/objArrayKlass.hpp"
 #include "prims/jvmtiThreadState.hpp"
+#include "runtime/continuationEntry.hpp"
 #include "runtime/deoptimization.hpp"
 #include "runtime/flags/jvmFlag.hpp"
 #include "runtime/osThread.hpp"
@@ -244,10 +245,13 @@
   nonstatic_field(JavaThread,                  _held_monitor_count,                           intx)                                  \
   nonstatic_field(JavaThread,                  _lock_stack,                                   LockStack)                             \
   nonstatic_field(JavaThread,                  _om_cache,                                     OMCache)                               \
+  nonstatic_field(JavaThread,                  _cont_entry,                                   ContinuationEntry*)                    \
   JVMTI_ONLY(nonstatic_field(JavaThread,       _is_in_VTMS_transition,                        bool))                                 \
   JVMTI_ONLY(nonstatic_field(JavaThread,       _is_in_tmp_VTMS_transition,                    bool))                                 \
   JVMTI_ONLY(nonstatic_field(JavaThread,       _is_disable_suspend,                           bool))                                 \
                                                                                                                                      \
+  nonstatic_field(ContinuationEntry,           _pin_count,                                    uint32_t)                              \
+                                                                                                                                     \
   nonstatic_field(LockStack,                   _top,                                          uint32_t)                              \
                                                                                                                                      \
   JVMTI_ONLY(static_field(JvmtiVTMSTransitionDisabler, _VTMS_notify_jvmti_events,             bool))                                 \
diff --git a/src/hotspot/share/runtime/continuationEntry.hpp b/src/hotspot/share/runtime/continuationEntry.hpp
index 459321f444c..ac76cd6f088 100644
--- a/src/hotspot/share/runtime/continuationEntry.hpp
+++ b/src/hotspot/share/runtime/continuationEntry.hpp
@@ -39,6 +39,7 @@ class RegisterMap;
 
 // Metadata stored in the continuation entry frame
 class ContinuationEntry {
+  friend class JVMCIVMStructs;
   ContinuationEntryPD _pd;
 #ifdef ASSERT
 private:

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20664#discussion_r1726876549