[LLVMdev] Dependence Analysis [was: Flow-Sensitive AA]

Daniel Berlin dberlin at dberlin.org
Fri Aug 22 14:14:26 PDT 2008

On Fri, Aug 22, 2008 at 5:03 PM, Vikram S. Adve <vadve at cs.uiuc.edu> wrote:
> Thanks!  This is all very interesting, and tells me that LLVM has a
> way to go to fully support all of these capabilities (if that is the
> right thing to do, which isn't clear).  OTOH, it looks like a lot of
> real-world software that is using LLVM already doesn't seem to be
> affected by the lack of them.
> Does anyone know of any C/C++ programs that require integer overflow
> on signed arithmetic (even though it is not strictly allowed by the
> standard)?

Yes, see the unending discussion on the gcc mailing list about
programs we are breaking that led to the introduction of this option.

My serious suggestion would be to tell any users who require this flag
to shove it.

(Otherwise you end up in a very dark place because there are a lot of
optimizations that make assumptions about overflow when rearranging
expressions, etc).

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