RFR(XS): Provide information when hitting a HaltNode for architectures other than x86

[Doerr, Martin]

Hi Xin,

I think Andrew's trap based version will be much better. But I'll leave the AArch64 part up to other people.

> Another thing is I don't understand what's the benefit to
> use the signal handler for that.
Shorter code in the code cache (signal handler takes care of saving registers), better hs_err file (includes registers and instructions at the point at which the signal occurred, better stack trace: no nasty C-frames).

Best regards,
Martin


> -----Original Message-----
> From: Liu, Xin <xxinliu at amazon.com>
> Sent: Mittwoch, 27. Mai 2020 00:58
> To: aph at redhat.com; Ningsheng Jian <ningsheng.jian at arm.com>; aarch64-
> port-dev at openjdk.java.net
> Cc: Doerr, Martin <martin.doerr at sap.com>; hotspot-compiler-
> dev at openjdk.java.net
> Subject: Re: RFR(XS): Provide information when hitting a HaltNode for
> architectures other than x86
> 
> Hi,
> 
> I make a new revision of JDK-8230552. May I ask the arm reviewers to take a
> look?
> http://cr.openjdk.java.net/~xliu/8230552/01/webrev/
> 
> I haven't made aarch64 stop() uses the trap mechanism because it deserves
> a standalone JBS.  Another thing is I don't understand what's the benefit to
> use the signal handler for that.
> 
> I do manage to reduce stop() code size per Ningsheng's request.  It avoids
> from generating pusha if ShowMessageBoxOnError is off (default). It still acts
> as expect no matter ShowMessageBoxOnError is set or not.  Since we now
> have got rid of the HaltNode right after Uncommon_trap callnode in release
> build, I don't think code bloat is an issue anymore.
> 
> Thanks,
> --lx
> 
> 
> 
> On 5/6/20, 1:19 AM, "aph at redhat.com" <aph at redhat.com> wrote:
> 
>     CAUTION: This email originated from outside of the organization. Do not
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> 
> 
>     On 5/6/20 8:25 AM, Liu, Xin wrote:
>     >     Currently in AArch64 MacroAssembler::stop(), it will generate many
>     >     register saving instructions by pusha() before calling to debug64(). But
>     >     I think debug64() only uses the regs[] and pc arguments when
>     >     ShowMessageBoxOnError is on. Maybe we should at least only do the
> saving
>     >     and pc arg passing when ShowMessageBoxOnError is on in
>     >     MacroAssembler::stop(), as what x86 does in
> macroAssembler_x86.cpp?
> 
>     Maybe we should think about a better way to do it. All we have
>     to do, after all, is put the reason into, say, r8, and execute
>     a trap. We don't need to push and pop anything because the trap
>     handler will do that.
> 
>     --
>     Andrew Haley  (he/him)
>     Java Platform Lead Engineer
>     Red Hat UK Ltd. <https://www.redhat.com>
>     https://keybase.io/andrewhaley
>     EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
>