Invokedynamic and recursive method call

[Remi Forax]

ping ?

Rémi

On 12/30/2014 08:48 PM, Remi Forax wrote:
> Hi guys,
> I've found a bug in the interaction between the lambda form and 
> inlining algorithm,
> basically if the inlining heuristic bailout because the method is 
> recursive and already inlined once,
> instead to emit a code to do a direct call, it revert to do call to 
> linkStatic with the method
> as MemberName.
>
> I think it's a regression because before the introduction of lambda 
> forms,
> I'm pretty sure that the JIT was emitting a direct call.
>
> Step to reproduce with nashorn, run this JavaScript code
> function fibo(n) {
>   return (n < 2)? 1: fibo(n - 1) + fibo(n - 2)
> }
>
> print(fibo(45))
>
> like this:
>   /usr/jdk/jdk1.9.0/bin/jjs -J-XX:+UnlockDiagnosticVMOptions 
> -J-XX:+PrintAssembly fibo.js > log.txt
>
> look for a method 'fibo' from the tail of the log, you will find 
> something like this:
>
>   0x00007f97e4b4743f: mov    $0x76d08f770,%r8   ;   {oop(a 
> 'java/lang/invoke/MemberName' = {method} {0x00007f97dcff8e40} 'fibo' 
> '(Ljdk/nashorn/internal/runtime/ScriptFunction;Ljava/lang/Object;I)I' 
> in 'jdk/nashorn/internal/scripts/Script$Recompilation$2$fibo')}
>   0x00007f97e4b47449: xchg   %ax,%ax
>   0x00007f97e4b4744b: callq  0x00007f97dd0446e0
>
> I hope this can be fixed. My demonstration that I can have fibo 
> written with a dynamic language
> that run as fast as written in Java doesn't work anymore :(
>
> cheers,
> Rémi
>
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