RFR: 8144083 [JVMCI] CompilationResult should be finalized by JVMCI compiler and made effectively final

[Doug Simon]

> On 30 Nov 2015, at 18:32, Christian Thalinger <christian.thalinger at oracle.com> wrote:
> 
> Forgot one comment:
> 
>     /**
>      * Gets the assumptions made during compilation.
> +     *
> +     * The caller must not modify the contents of the returned array.
>      */

Good catch.

>     public Assumption[] getAssumptions() {
>         return assumptions;
>     }
> 
> Should we file an enhancement to somehow enforce this contract?  Or should we just clone the array?

We want to avoid copying/cloning to minimize code installation time.

This is a value that will assigned to HotSpotCompiledCode.assumptions which in turn will be read directly by the VM so we want a simple data type like an array. As far as I know, there’s no way to enforce array contents as being treated constant/final.

> 
>> On Nov 30, 2015, at 7:30 AM, Christian Thalinger <christian.thalinger at oracle.com> wrote:
>> 
>> Looks good.
>> 
>>> On Nov 26, 2015, at 3:33 AM, Doug Simon <doug.simon at oracle.com> wrote:
>>> 
>>> The CompilationResult object is a mutable object built by a JVMCI compiler backend during code generation. Currently, clients of the compiler are required to finalize construction of a CompilationResult once the compilation has completed. Furthermore, the HotSpotCompiledCode constructor takes a partially-constructed CompilationResult and then completes its construction. This non-locality of mutation is not just bad software design but in this case means a single CompilationResult cannot be used to create multiple HotSpotCompiledCode objects. 
>>> 
>>> We propose to address this by requiring the JVMCI compiler to do all construction of a CompilationResult and then close it to further updating.
>>> 
>>> https://bugs.openjdk.java.net/browse/JDK-8144083
>>> http://cr.openjdk.java.net/~dnsimon/8144083/
>>> 
>>> -Doug
>> 
>