RFR: [11u] 8217368: AArch64: C2 recursive stack locking optimisation not triggered

[Nick Gasson]

Hi Andrew,

> 
> This is tricky to review because the actual bug fix is swamped by the change
> from expanded inline code to do the three CASes. As far as I can tell the
> bug fix itself is just a few instructions:
> 

[snip]

> 
> Am I right?
> 

Not quite: you also need to swap the usage of tmp and disp_hdr in the 
"// Compare object markOop with mark ..." block (line 4785 in 11u).

The original webrev.0 contains a more minimal patch, with just the logic 
change. The final patch also included some refactoring to use 
MacroAssembler::cmpxchg which doesn't affect the behaviour but does 
improve the readability significantly.

http://cr.openjdk.java.net/~ngasson/8217368/webrev.0/src/hotspot/cpu/aarch64/aarch64.ad.udiff.html


Thanks,
Nick