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Re: register allocation versus scheduling
- From: Falk Hueffner <falk dot hueffner at student dot uni-tuebingen dot de>
- To: Brad Lucier <lucier at math dot purdue dot edu>
- Cc: gcc at gcc dot gnu dot org, feeley at iro dot umontreal dot ca, matz at suse dot de
- Date: 06 Jan 2003 03:52:15 +0100
- Subject: Re: register allocation versus scheduling
- References: <200301060136.h061aNL21961@banach.math.purdue.edu>
Brad Lucier <lucier@math.purdue.edu> writes:
> -O1 -fno-trapping-math -fschedule-insns -fschedule-insns2 -fnew-ra -mcpu=7400
>
> which also schedules *before* register allocation is 50% slower,
> since the schedule pass before hard register allocation loads *all*
> the x-y-z information for all the atoms into pseudo-registers at the
> top of the routine, and requires many moves between the stack and
> registers when these values are actually needed for computations.
>
> Perhaps, since -fno-trapping-math is a relatively new option, this
> is a recent concern.
No, this has been a problem for some time, see
e. g. http://gcc.gnu.org/ml/gcc/2002-07/msg00646.html. The test case
there is similar, many FP loads (more than registers), work on them,
writing back.
--
Falk