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Re: [PATCH, rs6000] Fold vector absolutes in GIMPLE
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: will_schmidt at vnet dot ibm dot com, GCC Patches <gcc-patches at gcc dot gnu dot org>, David Edelsohn <dje dot gcc at gmail dot com>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Date: Mon, 29 May 2017 07:21:20 -0500
- Subject: Re: [PATCH, rs6000] Fold vector absolutes in GIMPLE
- Authentication-results: sourceware.org; auth=none
- References: <1495819159.15163.170.camel@brimstone.rchland.ibm.com> <CAFiYyc3QrvoAKgfmu0nL233C1ggWH=NTmCiBO8LEB7MC6z=fEQ@mail.gmail.com> <20170529102444.GI19687@gate.crashing.org> <A41966D2-362E-4278-9989-0A2474541696@gmail.com>
On Mon, May 29, 2017 at 01:35:22PM +0200, Richard Biener wrote:
> >> What's the documented behavior for vec_abs with respect to an
> >argument
> >> of value INT_MIN?
> >
> >The documentation says:
> >
> > "For integer vectors, the arithmetic is modular."
>
> This means that folding as ABS_EXPR is not safe for !TYPE_OVERFLOW_WRAPS
> Integral vector types.
Is it still fine if TYPE_OVERFLOW_UNDEFINED? So essentially always
except with -ftrapv?
Segher