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

[Jamsheed]

slight oversight, thought webrev provided 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
>