This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [RFC] Combine related fail of gcc.target/powerpc/ti_math1.c


On Thu, 2015-05-21 at 11:59 -0700, Richard Henderson wrote:
> On 05/21/2015 11:44 AM, Segher Boessenkool wrote:
> > On Thu, May 21, 2015 at 11:34:14AM -0700, Richard Henderson wrote:
> >> Actually, I believe that the way CA is modeled at the moment is dangerous.
> >> It's not a 64-bit value, but a 1-bit value.
> > 
> > It's a fixed register and it is only ever set to 0 or 1.  There are
> > more targets that do such things, and it is safe.
> 
> Old Cygnus proverb: Lie to the compiler and it will always bite you in the end.

Just for the record, the same is being done on SH with the T bit.  It's
a fixed 1 bit hardreg, but declared and treated as SImode, because all
the other integer arithmetic is done primarily in SImode, too.  No
significant problems with that.

Cheers,
Oleg


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]