Preparing for IRIX 6.2 & 64-bit

A Nutshell view and series of pointers
by Donna Yobs, yobs@engr.sgi.com

Developers have 3 paths to choose from on IRIX 6.2 (giving the flexibility to the customer):

O32: 32-bit IRIX 5 binaries "just run" on IRIX 6
N32: New or existing 32-bit applications can be recompiled to take full advantage of the additional floating-point and argument registers available on the MIPS R4400, R5000, R8000, and R10000 processors
Full 64: Applications can be ported or recompiled to take advantage of the exceptional performance and data capacities of 64-bit systems

What Developers Can Do To Get Ready

The new compilers have very strict ANSI warnings, thus you will need to Compile -fullwarn with existing compilers
Make source as lint free as possible
Use function prototypes (ANSI)
Use supercomputer transition support (libraries - COMPLIB, compiler flags)
For header files: Use only one version of C structs. Don't #ifdef for 32 vs 64, rather use typedef types for fields which are to be a constant bit size or which are to be a natural size. See the header file /usr/include/inttypes.h
Porting needed if your program uses system-specific features:
- Users of precise exceptions (maybe)
- Users of hard coded 4K page sizes (16K on 64-bit kernels). It is possible for a program to determine the kernel size via sysconf(_SC_KERN_POINTERS) which returns either 32 or 64.
- Users of nlist to access kernel data (a new nlist64 should be used)
- Users of kernel interfaces (like /proc or /dev/kmem)
- Device drivers need to be ported
Remember you cannot mix o32/n32/64 bit binaries.
Port IRIX GL programs to OpenGL

O32 option

As long as the executable is ELF (non-coff/IRIX4 binary) it should work, obvious caveats are programs that know about kernel structures as in device drivers).
If you have a COFF binary, just recompile on IRIX 5.3 (without the IRIX4 environment variable) or IRIX 6.2.

N32 option

Recompile on IRIX 5.3 with -fullwarn on, thus finding any strong ansi errors.
Recompile on IRIX 6.2 and resolve any warnings
Follow the recommendations in the MIPSpro N32 ABI Handbook.
Since no differences occur in the sizes of fundamental types between o32 and n32, porting to n32 requires no source code changes for applications written in high-level languages such as C, C++, and Fortran. The only exception to this is that C functions that accept variable numbers of floating point arguments must be prototyped.

64 option

Recompile on IRIX 5.3 with -fullwarn on, thus finding any strong ansi errors.
Recompile on IRIX 6.2 and resolve any warnings
Follow the recommendations in the MIPSpro(TM) 64-Bit Porting and Transition Guide.

64-BIT DOCUMENTS:

GENERAL 6.2 DOCUMENTS:

Other Resources:

datasheet

tech report

DATA MODELS

Differences in Data Type Sizes
C type 32-bit 64-bit
ILP32 LP64
char 8 8
short int 16 16
int 32 32
long int 32 64
long long int 64 64
pointer 32 64
float 32 32
double 64 64
void* 32 64

Differences in Data Type Sizes
C type	32-bit	64-bit
	ILP32	LP64
char	8	8
short int	16	16
int	32	32
long int	32	64
long long int	64	64
pointer	32	64
float	32	32
double	64	64
void*	32	64

ABI Information:

-32 -n32 -64

Register width 32-bit 64-bit 64-bit

Data width ilp32 ilp32 lp64

Address space 32-bit 32-bit 64-bit

Parameter registers 4 8 8

	-32	-n32	-64
Register width	32-bit	64-bit	64-bit
Data width	ilp32	ilp32	lp64
Address space	32-bit	32-bit	64-bit
Parameter registers	4	8	8