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

[Doug Simon]

> 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
>