[13] RFR: 8227223: [Graal] Implement basic type consistency checks for Low level MH intrinsics

[Jamsheed]

Hi Vladimir,

Thanks for the review.

Best regards,

Jamsheed

On 05/07/19 12:52 AM, Vladimir Kozlov wrote:
> Good ;)
>
> Thank you.
>
> Vladimir
>
> On 7/4/19 11:12 AM, Jamsheed wrote:
>> slight oversight, i thought webrev provided by Vladimir Kozlov was 
>> based on jdk14 and it cleanly applied on jdk13. it was indeed jdk13 
>> based. removed duplicates.
>>
>> On 04/07/19 9:09 PM, Jamsheed wrote:
>>> Request for review for the backport of JDK-8221577 [1] .
>>>
>>> The fix [2] was integrated into JDK 14 as part of 
>>> JDK-8225497:"Update Graal" [1].
>>>
>>> jdk13 backport webrev: 
>>> https://cr.openjdk.java.net/~kvn/8221577/webrev.00/ (Thank you, 
>>> Vladimir Kozlov)
>>>
>>> bug: https://bugs.openjdk.java.net/browse/JDK-8227223
>>>
>>> Description of problem by Vladimir Ivanov:
>>>
>>> "Method handle linkers (MethodHandle.linkTo*) are inherently unsafe: 
>>> it's possible to use arbitrary signature to invoke a method and 
>>> behavior is implementation/platform-specific when argument type 
>>> mismatch occurs (e.g., int vs float). Type checking for method 
>>> handle invocation happens earlier: either in 
>>> MethodHandle.invoke/invokeExact() or as part of invokedynamic 
>>> linkage. MH linkers implement low-level semantics of different 
>>> invocation modes.
>>>
>>> Though such type mismatches (int vs float) shouldn't occur at 
>>> runtime (it's guaranteed by how method handles are constructed), 
>>> JIT-compiler can observe it on unreachable branches which can't be 
>>> proved as such at compile-time. (See JDK-8166110 for an example.)
>>>
>>> In order to avoid paradoxes in IR, C2 doesn't inline through 
>>> MH.linkTo* methods if there's type mismatch for any argument or 
>>> return type (decision is made in ciMethod::is_consistent_info())."
>>>
>>> Best Regards,
>>>
>>> Jamsheed
>>>
>>> [1] https://bugs.openjdk.java.net/browse/JDK-8221577
>>>
>>> [2] 
>>> https://github.com/oracle/graal/commit/d880341edf09d6a14021e2c7f09f70eda56c1c9d
>>>