I don't know the ultimate reasons why SGI choose ILP32 for n32, but one could certainly be portability. As defined, n32 provides all the benefits of 64-bit data (yes, you have to use long long to get to it), and 100% backward compatability with o32 sources that assume (sizeof(void *)) = sizeof(long), plus binary data file compatability with o32 as all structures are exactly identical between o32 and n32. /Hartvig Maciej W. Rozycki writes: > > On Thu, 5 Sep 2002, Kevin D. Kissell wrote: > > > n32 has the same data types as o32, an "ILP32" C integer > > model. n64 is a pretty normal "LP64" C integer model. > > > > What do you consider to be broken, and how would you > > have preferred it to have been done? > > For n32 it would be natural to have: > > - sizeof(int) = 32 > > - sizeof(long) = 64 > > - sizeof(void *) = 32 > > as the underlying hardware directly supports 64-bit operations (n32 > requires at least MIPS III). Thus there is no penalty for 64-bit > arithmetics and if one uses longs one normally wants the largest native > integer type -- using long long typically (i.e. on most platforms) implies > double-precision arithmetics with all the drawbacks, especially for the > division and multiplication operations. > > With 32-bit long on 64-bit hardware software has no easy way to figure > using 64-bit operations is still optimal performance-wise. I can't see > any technical benefit from such a setup -- is there any? I doubt it. > > -- > + Maciej W. Rozycki, Technical University of Gdansk, Poland + > +--------------------------------------------------------------+ > + e-mail: macro@ds2.pg.gda.pl, PGP key available + > > > -- _ _ _____ ____ Hartvig Ekner Mailto:hartvige@mips.com |\ /| | |____)(____ Direct: +45 4486 5503 | \/ | | | _____) MIPS Denmark Switch: +45 4486 5555 T E C H N O L O G I E S http://www.mips.com Fax...: +45 4486 5556
