-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Tue, Jan 03, 2006 at 05:25:55PM +0000, Joern RENNECKE wrote: > In http://gcc.gnu.org/ml/gcc/2005-12/msg00642.html, Bernd Jendrissek > wrote: > > Which leads me to the subject. Would it be a win to have a macro > > HARD_REGNO_MODE_OK_FOR_CLASS (REGNO, MODE, CLASS) which would be the > > authoritative test for this loop in find_reg()? On my port, and I > > imagine on many others too, I think a default > > > > #ifndef HARD_REGNO_MODE_OK_FOR_CLASS > > #define HARD_REGNO_MODE_OK_FOR_CLASS(REGNO, MODE, CLASS) \ > > HARD_REGNO_MODE_OK ((REGNO), (MODE)) > > #endif > > > > would be okay. > > It's not that simple. For example, consider multi-word integer arithmetic. > If you want to allocate a 32 bit integer register on your 16 bit x86, > all the integer registers are suitable as parts of the allocation. > However, if you start with the last integer register, the second part > will end up in a hard register which is not an integer register. > So to make this work, you's have to say that the last integer register is > not suitable for SImode, SFmode or CHImode, the last three ones are not > suitable for DImode, DFmode, CSImode or SCmode etc.
That's true, but it's also true of HARD_REGNO_MODE_OK already, isn't it? Maybe it's just a misunderstanding on my part but my definition for HARD_REGNO_MODE_OK already excludes the last (2^N)-1 registers from allocation to a integer of size N units. But... for other ports, it would be a problem. It *also* couldn't be #ifndef HARD_REGNO_MODE_OK_FOR_CLASS #define HARD_REGNO_MODE_OK_FOR_CLASS(REGNO, MODE, CLASS) \ (HARD_REGNO_MODE_OK ((REGNO), (MODE)) && HARD_REGNO_MODE_OK ((REGNO) + GET_MODE_SIZE ((MODE)) - 1, (MODE))) #endif since it would ignore boundaries between disjoint register classes which it may be illegal to cross. Hmm, how about this? #ifndef HARD_REGNO_MODE_OK_FOR_CLASS #define HARD_REGNO_MODE_OK_FOR_CLASS(REGNO, MODE, CLASS) \ (HARD_REGNO_MODE_OK ((REGNO), (MODE)) && REG_IN_CLASS_P ((REGNO), (CLASS)) && HARD_REGNO_MODE_OK ((REGNO) + GET_MODE_SIZE ((MODE)) - 1, (MODE)) && REG_IN_CLASS_P ((REGNO) + GET_MODE_SIZE ((MODE)) - 1, (CLASS))) #endif (Leaving REG_IN_CLASS_P as an exercise to the reader.) This does assume though that register classes consist of exactly one contiguous series of registers. Bleh, I think I'll just bite the bullet and use up all my remaining constraint characters for now. Thanks for the replies. - -- "If you lie to the compiler, it will get its revenge." - Henry Spencer -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) Comment: Please fetch my new key 804177F8 from hkp://wwwkeys.eu.pgp.net/ iD8DBQFDv7THwyMv24BBd/gRAsLBAJ0X6LQuBoWJfNoD2+lLDAXYzvM7LwCbByid FFjZg0GAtEq8vmwbG6/nY7I= =kEtK -----END PGP SIGNATURE-----
