[aarch64-port-dev ] RFR: 8169529: AArch64: Revert old JDK-8167595 changes after JDK-8159035 fix is pushed

[Rahul Raghavan]

Hi, 

Sorry I missed that JDK-8159035 was Oracle closed bug.
Thank you Tobias for forwarding the open changeset link
and thanks for all review comments.
I will check the pointers from Andrew Dinn and will submit revised webrev for review.

- Rahul

> -----Original Message-----
> From: Andrew Dinn [mailto:adinn at redhat.com]
> Sent: Thursday, November 17, 2016 6:14 PM
> To: Tobias Hartmann; Andrew Haley; Rahul Raghavan; ningsheng.jian at linaro.org; Vladimir Kozlov; aarch64-port-
> dev at openjdk.java.net
> Cc: hotspot-compiler-dev at openjdk.java.net
> Subject: Re: RFR: 8169529: AArch64: Revert old JDK-8167595 changes after JDK-8159035 fix is pushed
> 
> On 17/11/16 11:57, Tobias Hartmann wrote:
> > this looks good to me. Here are the changes for JDK-8159035 (should have been reviewed in the open):
> > http://hg.openjdk.java.net/jdk9/hs/jdk/rev/0e98c765ce9b
> 
> Thanks, Tobias.
> 
> I understand that a zero check is no longer needed but I am not sure it
> is correct to revert the AArch64 change. For example, at line 2820+ the
> following change is being backed out
> 
> -      __ subw(len_reg, len_reg, 16);
> -      __ cbnzw(len_reg, L_aes_loop);
> +      __ sub(len_reg, len_reg, 16);
> +      __ cbnz(len_reg, L_aes_loop);
> 
> I think the use of subw and cbnzw was one of Andrew's mods to the
> originally proposed patch. It ensures that the contents of len_reg are
> correctly treated as a 32-bit int. Similarly, the proposed removal of
> the zero test at line 2759 once again risks treating the 32 bit length
> as a 64 bit quantity
> 
> -      __ subsw(rscratch2, len_reg, zr);
> -      __ br(Assembler::LE, _L_finish);
> +      __ mov(rscratch2, len_reg);
> 
> I think that should revert to a movw (of course this still makes the
> change to add label L_finish redundant).
> 
> So, rather than completely /revert/ the change I think it needs
> /correcting/ just to remove the zero check.
> 
> regards,
> 
> 
> Andrew Dinn
> -----------
> Senior Principal Software Engineer
> Red Hat UK Ltd
> Registered in England and Wales under Company Registration No. 03798903
> Directors: Michael Cunningham, Michael ("Mike") O'Neill, Eric Shander