> 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". For CRIS, shift counts (variable; literate ones are 5 bits) are truncated to 6 (six) bits, regardless of the mode of the shift result (NB, all standard-named shifts are define_expanded to SImode, though anon strict_low_part-matching patterns for other modes exist). See also <http://www.axis.com/files/manuals/etrax_fs_des_ref-070821.pdf>, <http://www.axis.com/files/tech_notes/etrax_100lx_prog_man-050519.pdf> and src/cpu/cris.cpu. So, if the result of the truncation has bit 5 set for SImode, the results is 0. For smaller modes, a size larger than the number of bits of the mode yields the extended result in those bits (i.e. all 1 or 0, depending on the operation). brgds, H-P
