RFR: JDK-8288824: [arm32] Display isetstate in register output

[Dmitry Samersoff]

On Tue, 21 Jun 2022 08:25:52 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> When analyzing [JDK-8288719](https://bugs.openjdk.org/browse/JDK-8288719), to know the current isetstate was useful. It would be nice if that were printed clearly in the register output to save some mental cycles parsing CPSR.
> 
> Looks like this:
> 
> Registers:
>   r0  = 0x00000000
>   r1  = 0xbe9e7fb8
>   r2  = 0x00000000
>   r3  = 0xb6f860ac
>   r4  = 0xbe9e7fb8
>   r5  = 0xb6f864e0
>   r6  = 0xbe9e8060
>   r7  = 0xbe9e7fb0
>   r8  = 0xb6da8798
>   r9  = 0x00000000
>   r10 = 0x00000000
>   fp  = 0x00000001
>   r12 = 0xb6da87ec
>   sp  = 0xbe9e7fb0
>   lr  = 0xb6bc7dfb
>   pc  = 0xb6bc7dfa
>   cpsr = 0x800e0030
> isetstate: Thumb
> 
> Registers:
>   r0  = 0xb6be3664
>   r1  = 0xbe947c70
>   r2  = 0x00000058
>   r3  = 0xb6f3e000
>   r4  = 0xbe947c70
>   r5  = 0xb6f3f510
>   r6  = 0xb6c95bdc
>   r7  = 0xbe947d18
>   r8  = 0xbe947d98
>   r9  = 0x00000000
>   r10 = 0x00000000
>   fp  = 0xbe947d14
>   r12 = 0xb6c95f84
>   sp  = 0xbe947c68
>   lr  = 0xb6e97218
>   pc  = 0xb6793f3c
>   cpsr = 0x60000010
> isetstate: ARM 
> 
> 
> I refrained from parsing more information from the CPSR because I did not want to blow up the patch. ISETSTATE proved to be useful. More information can be added if needed.

Changes requested by dsamersoff (Reviewer).

src/hotspot/os_cpu/linux_arm/os_linux_arm.cpp line 459:

> 457:   case 2: st->print_cr("Jazelle"); break;
> 458:   case 3: st->print_cr("ThumbEE"); break;
> 459:   default: ShouldNotReachHere();

Should we print here something like "undefined" rather than abort VM?

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PR: https://git.openjdk.org/jdk/pull/9223