[foreign-memaccess+abi] RFR: 8274912: Eagerly generate native invokers [v3]

[Nick Gasson]

On Mon, 11 Oct 2021 12:31:04 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Hi,
>> 
>> This patch is a refactoring of VM code pertaining to downcalls. As outlined in the JBS issue, this patch makes 'native invoker' generation currently done by C2 eager.
>> 
>> Most of the changes in this patch are moving around existing code:
>> - The native invoker generation code is moved from sharedRuntime*.cpp to universalNativeInvoker*.cpp, to match what is done for upcalls.
>> - C2 & nmethod scaffolding for registering native invokers has been removed (lifetime is now managed in Java code).
>> - Now, C2 will only intrinsify trivial downcalls, which means some of the code was simplified there.
>> - To reduce code duplication, several utilities have been added:
>>   - ArgumentShuffle (and impls of CallConvClosure): a utility class for computing argument shuffles and generating shuffling code. The shuffling code is heavily based on what is done today for optimized upcalls on x64.
>>   - To support the above, I've made a copy of the ComputeMoveOrder utility from SharedRuntime code (which was only implemented on x64), and adapted it to our use case.
>>   - RegSpillFill: similarly, a utility for computing and generating register spill and fill code (given a list of registers).
>>   - oop_cast: this was a pre-existing utility that was renamed (from 'cast') and moved into a separate file.
>> - The linkToNative method handle stub now just loads the invoker address from the appendix argument and jumps to it, instead of jumping to the fallback method handle.
>> 
>> The implementation passes all the jdk_foreign tests on Windows/x64, Linux/x64 (WSL), and Linux/AArch64. Though, there were some pre-exsiting test failures on AArch64 wrt variadic functions.
>> 
>> Thanks,
>> Jorn
>
> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address offline review comments

> 
> The implementation passes all the jdk_foreign tests on Windows/x64, Linux/x64 (WSL), and Linux/AArch64. Though, there were some pre-exsiting test failures on AArch64 wrt variadic functions.
> 

Looks like the varargs failures are caused by this change in #576:

https://github.com/openjdk/panama-foreign/pull/576/files#diff-9fbf245dc20c824d5e9f3b1864a18284f110ae808cf11782457f8462e8ad8ce0L211

The `STACK_VARARGS_ATTRIBUTE_NAME` attribute used to be set only on macOS and was used to force all variadic arguments onto the stack, but that now happens unconditionally on Linux as well.

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PR: https://git.openjdk.java.net/panama-foreign/pull/593