------- Additional Comments From segher at kernel dot crashing dot org
2005-04-07 23:34 -------
Subject: Re: New: 64 bit shift by non-constant implemented as libcall on PPC32
> (O5 will give slightly better code for both, but let's start somewhere
> :P)
Well the code for the left shift can be replaced with
subfic r6,r5,32
addi r7,r5,-32
slw r3,r3,r5
srw r6,r4,r6
slw r7,r4,r7
slw r4,r4,r5
or r5,r6,r7
or r3,r3,r5
and similar for the right shift (and also for signed shift counts),
as shift counts < 0 and >= 64 are undefined here in C. If you want
to verify this, do take care with count == 32, as it's "special";
but you can also just look in Book I appendix C.1 and trust that.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20781
