Invokedynamic and recursive method call

Remi Forax forax at
Tue Dec 30 19:48:44 UTC 2014

Hi guys,
I've found a bug in the interaction between the lambda form and inlining 
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)


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 
   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 :(


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