RFR: 8164358: [JVMCI] expose Hotspot intrinsics and HotSpotIntrinsicCandidate info to JVMCI compilers

[Tom Rodriguez]

Is the intent to save space or time?  Interning the strings is another solution that gets all possible sharing.

tom

> On Aug 19, 2016, at 8:01 AM, Doug Simon <doug.simon at oracle.com> wrote:
> 
> I changed it to only try reuse the declaringClass string (which has the most overlap):
> 
> http://cr.openjdk.java.net/~dnsimon/8164358v2/
> 
> -Doug
> 
>> On 18 Aug 2016, at 23:59, Doug Simon <doug.simon at oracle.com> wrote:
>> 
>> 
>>> On 18 Aug 2016, at 20:01, Christian Thalinger <cthalinger at twitter.com> wrote:
>>> 
>>> src/jdk.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/CompilerToVM.java
>>> 
>>>     *         [String name, Long value, ...] vmAddresses,
>>> 
>>> +     *         [String name, Long value, ...] vmAddresses,
>>> 
>>>     *         VMFlag[] vmFlags
>>> 
>>> +     *         VMIntrinsicMethod[] vmIntrinsics
>>> Looks like a copy-paste problem.
>> 
>> Oops! Will fix.
>> 
>>> src/share/vm/jvmci/jvmciCompilerToVM.cpp
>>> 
>>> Why do we have to do the prev_##var##_sid == sid dance?  I guess it’s some optimization but does it really matter?
>> 
>> It cuts down the number Strings allocated by about 35% (900 vs 582). With full string interning, the savings is around 55% (415) but the overhead of using a HashSet from VM code is prohibitive. I won’t argue strongly that it makes a big difference but since the one-element cache (per VMIntrinsicMethod string field) is fast and cheap, I don’t see why not to use it. The alternative code would look something like this:
>> 
>> objArrayHandle vmIntrinsics = oopFactory::new_objArray(VMIntrinsicMethod::klass(), (vmIntrinsics::ID_LIMIT - 1), CHECK_NULL);
>> int index = 0;
>> #define VM_SYMBOL_TO_STRING(s) java_lang_String::create_from_symbol(vmSymbols::symbol_at(vmSymbols::VM_SYMBOL_ENUM_NAME(s)), THREAD)
>> #define VM_INTRINSIC_INFO(id, kls, name, sig, ignore_fcode) {                  \
>>   instanceHandle vmIntrinsicMethod = InstanceKlass::cast(VMIntrinsicMethod::klass())->allocate_instance_handle(CHECK_NULL); \
>>   Handle kls_string = VM_SYMBOL_TO_STRING(kls);                              \
>>   Handle name_string = VM_SYMBOL_TO_STRING(name);                            \
>>   Handle sig_string = VM_SYMBOL_TO_STRING(sig);                              \
>>   VMIntrinsicMethod::set_declaringClass(vmIntrinsicMethod, kls_string());    \
>>   VMIntrinsicMethod::set_name(vmIntrinsicMethod, name_string());             \
>>   VMIntrinsicMethod::set_descriptor(vmIntrinsicMethod, sig_string());        \
>>   VMIntrinsicMethod::set_id(vmIntrinsicMethod, vmIntrinsics::id);            \
>>   vmIntrinsics->obj_at_put(index++, vmIntrinsicMethod());                    \
>> }
>> 
>> VM_INTRINSICS_DO(VM_INTRINSIC_INFO, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE)
>> #undef VM_SYMBOL_TO_STRING
>> #undef VM_INTRINSIC_INFO
>> 
>> Better?
>> 
>> -Doug
>> 
>>> If we don’t have to do that I would prefer is that macro would be a method (or two).
>>> 
>>>> On Aug 18, 2016, at 6:50 AM, Doug Simon <doug.simon at oracle.com> wrote:
>>>> 
>>>> Please review this change which allows JVMCI compilers to see what intrinsics are defined by the VM and which methods have been annotated by HotSpotIntrisicCandidate.
>>>> 
>>>> https://bugs.openjdk.java.net/browse/JDK-8164358
>>>> http://cr.openjdk.java.net/~dnsimon/8164358/
>>>> 
>>>> Thanks,
>>>> 
>>>> -Doug
>>> 
>> 
>