[cfe-dev] [ubsan] Add -fsanitize-warn-once, only emit runtime error once per check

[Will Dietz]

Whoops, missed the ubsan commit yesterday so those don't apply cleanly.

Updated patches attached!

On Thu, Dec 13, 2012 at 11:33 AM, Will Dietz <willdtz at gmail.com> wrote:
> This flag causes clang to emit a byte for each check that is used by the
> runtime to track whether we've already printed an error for that check.
>
>  Often failed checks are triggered many times dynamically, but a user
>  is only interested in which checks failed (with example dynamic values
>  to aid in debugging).  This flag lets the user make such runs much
>  more efficient and generate more manageable output.
> ----------------
>
> Requires corresponding patch to compiler-rt, both are attached.
> Staging as cc1 option, since for now recovery is a cc1 flag as well.
> If this goes in, would like to promote it along the recovery to driver
> flags.
>
> Anyway, I was concerned this would cause problems performance-wise
> (another argument, another register), but impact on SPEC CINT2006 is a
> tad noisy but overall seems like it has neglible impact.  Usual chart
> attached.
>
> Thoughts/review appreciated, thanks!
>
> ~Will
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