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NNTP-Posting-Date: Tue, 12 Jul 2011 14:38:39 -0500
Date: Tue, 12 Jul 2011 12:38:40 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Arithmetic overflow checking
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On 7/12/2011 11:39 AM, Gene Wirchenko wrote:
> On Tue, 12 Jul 2011 02:22:41 -0700 (PDT), tm<thomas.mertes@gmx.at>
> wrote:
>
> [snip]
>
>> Yes, but it must be checked after every operation.
>> A hardware that triggers an interrupt, would save this
>> extra checks.
>
>       No, it would not.  The check would simply be implemented in
> hardware. It will still take time.

It would not necessarily directly take time. It could be done in
parallel with the stage that writes results back to register files, or
bypasses them to other instructions.

As has already been pointed out, there may be a tiny performance cost
because the space taken by the check logic might have been used for
something else.

Patricia