RFR (S): 8148994: Replacing MH::invokeBasic with a direct call breaks LF customization
john.r.rose at oracle.com
Thu Feb 4 18:52:06 UTC 2016
Looks good. Except I don't recall how is_inline interacts, if at all, with customization. It's not clear what is being gated, and which optimizations get let through.
Maybe a comment about that would be useful
> On Feb 4, 2016, at 7:51 AM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:
> JDK-8072008  introduced an optimization to bypass linker calls in generated code when target method can't be inlined.
> Unfortunately, it doesn't work well with MH::invokeBasic(), because it clashes with LambdaForm customization: if a call is not inlined, it is important for performance to update (customize) corresponding LambdaForm on-the-fly. MH::invokeBasic() linker does MH -> LF -> Method* -> _from_compiled_entry traversal on every invocation, while direct call points right to the _from_compiled_entry. So, any LambdaForm updates aren't visible until recompilation.
> The fix is to keep MH::invokeBasic linker, so up-to-date LambdaForm instance is used on every invocation.
> Also, cleaned up relevant tests a bit.
> Testing: octane, JPRT.
> Best regards,
> Vladimir Ivanov
>  https://bugs.openjdk.java.net/browse/JDK-8072008
> "Emit direct call instead of linkTo* for recursive indy/MH.invoke* calls"
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