On Tue, Sep 11, 2012 at 11:06 AM, Jakub Jelinek <ja...@redhat.com> wrote: > On Tue, Sep 11, 2012 at 03:57:44AM -0500, Gabriel Dos Reis wrote: >> On Tue, Sep 11, 2012 at 3:42 AM, Richard Guenther >> <richard.guent...@gmail.com> wrote: >> >> > Btw, this then happily fits into my suggestion that the "elementalness" >> > can be autodetected by the compiler simply by means of a proper IPA >> > pass and thus be fully LTO / whole-program aware. No need for an >> > attribute (where you'd need to handle the case that the attribute was >> > placed >> > there by error). >> >> We are in violent agreement. > > For locally defined functions sure, the question is if we want the attribute > to be something for external functions. Something that would have ABI > implications (the external symbol would need to be provided in two forms (or > more?), one scalar with normal mangling, one vector with some other kind > of mangling/suffix/whatever), when compiling the definition of function with > such an attribute the compiler could verify its properties (i.e. autodetect > and if it is not autodetected elemental, complain?), and when using extern > function just rely on it being provided twice. Even with LTO, the function > can be defined in some other shared library etc. > > Nothing says the implementation of the vector version of the elemental > function necessary has to be vectorized, just that the arguments would need > to be passed in the expected vector registers, similarly for return value. > Say if the elemental function is compiled with -O0, then there could just be > a loop executing the scalar body several times and creating vectors.
Sure. And the "versioning" can happen from the C frontend then. Of course this one has the requirement of documenting the ABI. Richard. > Jakub
