Re: question on optimizing calls to library functions

[Toon Moene <toon at moene dot org>]

Paolo Bonzini wrote:

> > The main difference that springs to mind: SIN is built-in, MATMUL is a library 
> > function. In gcc/builtin.defs, one finds 
>
> Not just that: SIN is a pure (or const, depending on -frounding-math)
> function, which can be subject to CSE and DCE.  I don't see anything
> suggesting that for MATMUL in intrinsic.c.  In fact, since MATMUL
> receives the return array by reference and writes to it, it would be
> very wrong to make MATMUL const or pure.

While this is true on the level the middle end looks at things, on the 
level of the Fortran front end, MATMUL simply is a constant function 
that takes two arrays and returns one (result) array.

I talked about that at the GCC Summit 2007; see 
http://moene.org/~toon/GCCSummit-2007.pdf.

Cheers,

--
Toon Moene - e-mail: toon@moene.org (*NEW*) - phone: +31 346 214290
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