RFR(XS): 8234645: ARM32: C1: PatchingStub for field access: not enough bytes

[christoph.goettschkes at microdoc.com]

Hi Martin,

thanks for looking into the issue.
I executed the tier1 hotspot tests with your patch applied and it looks 
good. Tests which were failing before pass now. I have some, but unrelated 
failures, which I will start looking into now.

One small remark:
When I encountered the problem, I was very much confused by the constant 
instruction size of 8 [1]. Maybe it would be more clear to define the 
instruction size to be 4, and instead, in "num_bytes_to_end_of_patch()", 
return "instruction_size * 2"?

Best regards,
Christoph

[1]
https://hg.openjdk.java.net/jdk/jdk/file/a2441ac23eeb/src/hotspot/cpu/arm/nativeInst_arm_32.hpp

"Doerr, Martin" <martin.doerr at sap.com> wrote on 2019-11-26 17:21:58:

> From: "Doerr, Martin" <martin.doerr at sap.com>
> To: "christoph.goettschkes at microdoc.com" 
> <christoph.goettschkes at microdoc.com>, "'hotspot-compiler-
> dev at openjdk.java.net'" <hotspot-compiler-dev at openjdk.java.net>
> Date: 2019-11-26 17:22
> Subject: RFR(XS): 8234645: ARM32: C1: PatchingStub for field access: 
> not enough bytes
> 
> Hi Christoph,
> 
> thanks for reporting the bug
> https://bugs.openjdk.java.net/browse/JDK-8234645
> 
> Seems like the large offset fix in mem2reg and reg2mem missed the first
> patching stub in the long/double cases.
> We should have nop padding there, too (for same reason as for the 2nd 
> patching stub).
> NativeMovRegMem should always consist of 2 instructions on arm32 in 
> order to support larger offsets.
> 
> Webrev:
> http://cr.openjdk.java.net/~mdoerr/8234645_arm_padding/webrev.00/
> 
> May I ask you to test this fix? We don’t have arm32 in our testing 
landscape.
> 
> Best regards,
> Martin
>