RFR: 8282224: Correct TIG::bang_stack_shadow_pages comments

[Aleksey Shipilev]

On Tue, 22 Feb 2022 06:54:59 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> When reviewing the RISC-V port of the change, I noticed the comment in the x86 code is worded incorrectly:
> 
> 
>   // Record a new watermark, unless the update is above the safe limit.
>   __ cmpptr(rsp, Address(thread, JavaThread::shadow_zone_safe_limit()));
>   __ jccb(Assembler::belowEqual, L_done);
> 
> 
> Stacks grow downwards, so we are recording a new watermark *when* update is above the safe limit.

Friendly reminder, anyone has any... ahem... comments?

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PR: https://git.openjdk.java.net/jdk/pull/7569