> Date: Sat, 14 Mar 2009 13:07:04 +0100
> From: Paolo Bonzini <bonz...@gnu.org>
> Hans-Peter Nilsson wrote:
> >> Date: Fri, 13 Mar 2009 12:34:49 +0100
> >> From: Paolo Bonzini <bonz...@gnu.org>
> >
> >> I would like to know whether for avr,bfin,cris,frv,h8300,pdp11,rs6000
> >> (which define SHIFT_COUNT_TRUNCATED as 0) and for mcore,sh,vax (which
> >> do not define it at all) it is right that shift counts are never
> >> truncated.
> >
> > The answer to the question is "no", but I'd guess the more
> > useful answer is "yes", for different definitions of "truncate".
FWIW, the bit-test-instruction "btst" truncates the count in the
register operand to 5 (five) bits. Not that it'd count as a
*shift*, but perhaps as a bitfield insn; it's modelled as a
bitfield test.
> Ok, after my patches you will be able to teach GCC about this definition
> of truncate.
(I presume you mean truncating to 6 instead of 5 bits.)
Hm, I see @deftypefn {Target Hook} int TARGET_SHIFT_TRUNCATION_MASK in tm.texi
which says I *should* be able to do that already, but its usage
in gcc seems quite limited.
brgds, H-P
