On Thu, 2014-10-09 at 19:50 +0000, Joseph S. Myers wrote:
> On Thu, 9 Oct 2014, Steve Ellcey wrote:
>
> > Do you know which pass does the simple
> > '(float)function((double)float_val)' demotion? Maybe that would be a
> > good place to extend things.
>
> convert.c does such transformations. Maybe the transformations in there
> could move to the match-and-simplify infrastructure - convert.c is not a
> particularly good place for optimization, and having similar
> transformations scattered around (fold-const, convert.c, front ends, SSA
> optimizers) isn't helpful; hopefully match-and-simplify will allow some
> unification of this sort of optimization.
I did a quick and dirty experiment with the match-and-simplify branch
just to get an idea of what it might be like. The branch built for MIPS
right out of the box so that was great and I added a couple of rules
(see below) just to see if it would trigger the optimization I wanted
and it did. I was impressed with the match-and-simplify infrastructure,
it seemed to work quite well. Will this branch be included in GCC 5.0?
Steve Ellcey
sell...@mips.com
Code added to match-builtin.pd:
(if (flag_unsafe_math_optimizations)
/* Optimize "(float) expN(x)" [where x is type double] to
"expNf((float) x)", i.e. call the 'f' single precision func */
(simplify
(convert (BUILT_IN_LOG @0))
(if ((TYPE_MODE (type) == SFmode) && (TYPE_MODE (TREE_TYPE (@0)) == DFmode))
(BUILT_IN_LOGF (convert @0))))
)
(if (flag_unsafe_math_optimizations)
/* Optimize "(float) expN(x)" [where x is type double] to
"expNf((float) x)", i.e. call the 'f' single precision func */
(simplify
(convert (BUILT_IN_SIN @0))
(if ((TYPE_MODE (type) == SFmode) && (TYPE_MODE (TREE_TYPE (@0)) == DFmode))
(BUILT_IN_SINF (convert @0))))
)
