RFR: 8365047: Remove exception handler stub code in C2 [v7]

[Andrew Haley]

On Thu, 23 Oct 2025 09:41:29 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

> > I meant to refer to this check implementation, which reads 8 bytes from where LR points to and checks whether they contain the NOP+MOVK sequence.
> 
> Ah, my apologies for misunderstanding you and also and what was going on in this code. It is indeed reading two instructions at once and checking them both in one go.
> 
> I agree with you that this is best split up into two separate reads+checks to deal with the case where we don't have a NOP and might drop off the end of the current buffer. I think this will still be less work than using SafeFetch but @theRealAph may want to override me here.

I think I do want to. We shouldn't leave such fragile code in once we've noticed it. IMO it's a false economy to avoid SafeFetch on efficiency grounds. If needs be, there are ways to make it faster.

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PR Comment: https://git.openjdk.org/jdk/pull/26678#issuecomment-3466810293