RFR: 8330851: C2: More efficient TypeFunc creation

[Amit Kumar]

On Tue, 5 Nov 2024 06:53:46 GMT, Dean Long <dlong at openjdk.org> wrote:

>> with that change I am getting this error: 
>> 
>> === Output from failing command(s) repeated here ===
>> * For target hotspot_variant-server_libjvm_objs_BUILD_LIBJVM_run_ld:
>> Undefined symbols for architecture arm64:
>>   "LockNode::_lock_type_tf", referenced from:
>>       GraphKit::shared_lock(Node*) in graphKit.o
>>       LockNode::lock_type_init() in type.o
>> ld: symbol(s) not found for architecture arm64
>> clang++: error: linker command failed with exit code 1 (use -v to see invocation)
>> 
>> 
>> Here is shorter version: 
>> 
>> class Temp {
>> public:
>>   static const int* ptr;
>> 
>> public:
>>   static void set_ptr() {
>>     const int *abs = new int(20);
>>     ptr = abs;
>>   }
>> };
>> 
>> // Initialize static member;
>> const int* Temp::ptr = nullptr;
>> 
>> int main() {
>>   Temp::set_ptr();
>>   cout << *Temp::ptr << endl;
>>   return 0;
>> }
>> 
>> 
>> If I comment out `const int* Temp::ptr = nullptr;` then I am getting the similar error as I pasted above which I got from the build failure. Here we might need to give the definition out of scope of the class. 
>> 
>> 
>> Another solution is making the data-field inline: 
>> 
>> class Temp {
>> public:
>>   static inline const int* ptr = nullptr;
>> 
>> public:
>>   static void set_ptr() {
>>     const int *abs = new int(20);
>>     ptr = abs;
>>   }
>> };
>> 
>> // Initialize static member;
>> //const int* Temp::ptr = nullptr;
>> 
>> int main() {
>>   Temp::set_ptr();
>>   cout << *Temp::ptr << endl;
>>   return 0;
>> }
>> 
>> 
>> Here If we mark `ptr` as inline variable that is also acceptable, though C++17 started accepting it, but hotspot code is throwing warning over there as well.
>
>> Here we might need to give the definition out of scope of the class.
> 
> Yes.  For example, in callnode.cpp:
> 
> const TypeFunc *LockNode::_lock_type_tf = nullptr;

@dean-long I have updated the patch, please have a look at the current changes :-)

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PR Comment: https://git.openjdk.org/jdk/pull/21782#issuecomment-2457088617