[foreign-jextract] [Rev 02] RFR: 8239493: Add classfile generation to jextract

[Maurizio Cimadamore]

On Tue, 7 Apr 2020 13:01:10 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Hi,
>> 
>> This patch adds class file generation to jextract using ASM, which in some places replaces the generation done by the
>> current source code generator. In particularly, it replaces the generation of all constant fields with static getters,
>> that use dynamic constants as backing storage rather than fields. This allows for more sharing between constants, and
>> also reduces the pressure on clinit code size a lot, enabling extraction of much bigger native header files. The new
>> scheme generates an extra constant helper class which holds all these constants, and the source generator generates the
>> high-level wrapper functions. The scheme can also be extended to generate multiple constant helper classes, should we
>> run out of constant pool indices (in rare cases).  This patch reworks the interface of JavaSourceBuilder, since extra
>> parameters are needed in order to do the new constant generation. For generating methods that need constants, it calls
>> into a new ConstantHelper class, which returns a DirectMethodHandleDesc describing the generated constant getter. A
>> call to this getter is then emitted.  This patch also merges the HandleSourceFactory and StaticWrapperSourceFactory
>> into OutputFactory, since only the latter was ever being used, but the split in code made it a lot harder to reason
>> about the correctness of for instance changing C identifiers into java-safe ones. Because of this, the diff for
>> OuputFactory looks a bit messy, so maybe it's easier to look at the resulting file as a whole.  The tests are changed
>> to look for the now generated static getters, instead of fields (`static final` fields don't work well with dynamic
>> constants, since they are eagerly initialized).  As a small bonus, this patch adds the missing ABI-agnostic
>> C_LONGDOUBLE constant (this was causing some test failures).  Thanks, Jorn
>
> Jorn Vernee has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Addressed review comments:
>    - Made Utils final, and added private constructor
>    - renamed some addXXX methods in JavaSourceBuilder to addXXXGetter for clarity
>    - renamed some getXXX method in JavaSourceBuilder to XXXGetCallString for clarity
>    - renamed some visitedXXX methods in OutputFactory to XXXSeen for clarity
>    - Factored out several calls to emitGetter in constantHelper into helper methods with more readable names
>  - Remove makeCString bootstrap and depend on Cstring::toCString instead
>  - Add class gen test

Looks good!

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Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.java.net/panama-foreign/pull/102