[3.4-BIB] Add i386 trunc/nearbyint patterns II
Richard Henderson
rth@redhat.com
Mon Nov 25 15:53:00 GMT 2002
On Tue, Nov 26, 2002 at 12:35:27AM +0100, Jan Hubicka wrote:
> Another problem is that I need different values of control word around.
> Currently I have default and round_toward_zero (the round_down in patch
> is confused). I think only way I can handle more values is to declare
> each saved copy an separate entity for pre-reload mode switching pass
> and use fixed pseudo to hold value of the default control word so the
> initialization code for other entities don't have to initialize it.
If you have N+1 modes for switching, and
0: read fpcw into mem slot A
1: construct round to zero at mem slot B
2: construct round to -inf at mem slot C
...
then the bits that emit code for (1) can assume that (0) has been
done, and so does not have to re-read the fpcw. I don't see much
advantage to a fixed pseudo since we've got to have the default
fpcw value in memory anyhow.
r~
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