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ABI(5) Last changed: 1-28-99
NNAAMMEE
AABBII - Application Binary Interface
IIMMPPLLEEMMEENNTTAATTIIOONN
IRIX systems
DDEESSCCRRIIPPTTIIOONN
This man page is a quick reference for the three Application Binary
Interfaces (ABI) that are supported by IRIX.
GGEENNEERRAALL IINNFFOORRMMAATTIIOONN
An ABI defines a system interface for executing compiled programs. It
defines which Instruction Set Architectures (ISA) it supports as well
as defining object file formats and calling conventions.
IRIX supports three ABIs:
oo3322 The old 32-bit ABI which was standard on IRIX 5 systems.
nn6644 The 64-bit ABI which was introduced on IRIX 6.0 systems.
nn3322 The new high performance 32-bit ABI which was introduced on IRIX
6.2.
Each of these ABIs defines unique interfaces which make it impossible
to link object files of one ABI with object files of another ABI.
The MIPS ABI is a subset of the above mentioned oo3322 ABI and is
designed to provide application portability across a variety of vendor
platforms. See the NOTES section which follows for reference
information.
Default ABI and ISA settings described in this man page can be
overridden by changing the default settings for a given system,
contained in the //eettcc//ccoommppiilleerr..ddeeffaauullttss file; or by changing the
SSGGII__AABBII environment variable, which can be used to specify default ABI
values.
oo3322 IInnffoorrmmaattiioonn
The oo3322 ABI supports the mmiippss22 ISA (by default) and mmiippss11 ISA. The
resulting program binary is in ELF32 format (COFF is no longer
supported) whose symbol table is in ..mmddeebbuugg format. The oo3322 calling
convention allows a maximum of four registers ($$aa00....$$aa33) to be used to
pass integer arguments.
When an oo3322 program executes, IRIX sets the FFRR bit in the status
register of the MIPS microprocessor to 0. Under this setting, only 16
double precision floating point registers are enabled.
C language integer types (iinntt), long integer types (lloonngg), and pointer
types (cchhaarr **) are all 32-bits wide in programs compiled for this ABI.
A program is compiled for the oo3322 ABI under the following
circumstances:
* By default on systems that are not based on the R8000 (if the
environment variable SSGGII__AABBII is not set), as in this example:
cc foo.c
* By using the --3322 compilation flag; this overrides any SSGGII__AABBII
setting, as in this example:
cc -32 foo.c
* By using the --mmiippss22 or --mmiippss11 compilation flags, as in this example:
cc -mips2 foo.c
* By setting the SSGGII__AABBII environment variable to --3322 and doing a
default compilation, as in this example:
setenv SGI_ABI -32
cc foo.c
* By setting the default ABI to --3322 in the //eettcc//ccoommppiilleerr..ddeeffaauullttss
file, as in this example:
cat /etc/compiler.defaults
-DEFAULT:abi=o32
An oo3322 compilation generates certain predefined variables whose values
can be used by conditional compilation directives. The names of these
variables and their values are as follows:
_MIPS_FPSET = 16
_MIPS_ISA = 2
_ABIO32 = 1
_MIPS_SIM = _ABIO32
_MIPS_SZINT = 32
_MIPS_SZLONG = 32
_MIPS_SZPTR = 32
For more information about these predefined variables, see the
<<ssggiiddeeffss..hh>> include file.
nn6644 IInnffoorrmmaattiioonn
The nn6644 ABI supports the mmiippss44 ISA (by default) and mmiippss33 ISA. The
resulting program binary is in ELF64 format whose symbol table is in
DWARF format. The nn6644 calling convention is different from the oo3322
calling convention in that it allows a maximum of eight registers
($$aa00....$$aa77) to be used to pass integer arguments. It also allows a
maximum of eight floating point registers to be used to pass floating
point arguments. A full description of this calling convention can be
found in the _M_I_P_S_p_r_o _6_4-_B_i_t _P_o_r_t_i_n_g _a_n_d _T_r_a_n_s_i_t_i_o_n _G_u_i_d_e.
When an nn6644 program executes, IRIX sets the FFRR bit in the status
register of the MIPS microprocessor to 1. Under this setting, all 32
double precision floating point registers are enabled. This improves
performance, but old assembly code that accesses a double precision
floating point register as a pair (one even and one odd) of single
precision floating point registers will not work.
C language integer types (iinntt) are 32 bits wide, while long integer
types (lloonngg), and pointer types (cchhaarr **) are both 64-bits wide in
programs compiled for this ABI.
A program is compiled for the nn6644 ABI under the following
circumstances:
* By default on systems that are based on the R8000 (if the
environment variable SSGGII__AABBII is not set), as in this example:
cc foo.c
* By using the --6644 compilation flag; this overrides any SSGGII__AABBII
setting, as in this example:
cc -64 foo.c
* By using the --mmiippss44 or --mmiippss33 compilation flags, as in this example:
cc -mips4 foo.c
* By setting the SSGGII__AABBII environment variable to --6644 and doing a
default compilation, as in this example:
setenv SGI_ABI -64
cc foo.c
* By setting the default ABI to --6644 in the //eettcc//ccoommppiilleerr..ddeeffaauullttss
file, as in this example:
cat /etc/compiler.defaults
-DEFAULT:abi=64
An nn6644 compilation generates certain predefined variables whose values
can be used by conditional compilation directives. The names of these
variables and their values are as follows:
_MIPS_FPSET = 32
_MIPS_ISA = 4
_ABI64 = 3
_MIPS_SIM = _ABI64
_MIPS_SZINT = 32
_MIPS_SZLONG = 64
_MIPS_SZPTR = 64
nn3322 IInnffoorrmmaattiioonn
The nn3322 ABI supports the mmiippss33 (by default) and mmiippss44 ISA. The
resulting program binary is in ELF32 format whose symbol table is in
DWARF format. The nn3322 calling convention is the same as the nn6644
calling convention. A full description of this calling convention can
be found in the _M_I_P_S_p_r_o _N_3_2 _A_B_I _H_a_n_d_b_o_o_k.
When an nn3322 program executes, IRIX sets the FFRR bit in the status
register of the MIPS microprocessor to 1, just as it does for an nn6644
program. Under this setting, all 32 double precision floating point
registers are enabled. This has the same performance and
compatibility implications as with nn6644.
C language integer types (iinntt), long integer types (lloonngg), and pointer
types (cchhaarr **) are all 32-bits wide in programs compiled for this ABI.
A program is compiled for the nn3322 ABI under the following
circumstances:
* By using the --nn3322 compilation flag; this overrides any SSGGII__AABBII
setting, as in this example:
cc -n32 foo.c
* By setting the SSGGII__AABBII environment variable to --nn3322 and doing a
default compilation, as in this example:
setenv SGI_ABI -n32
cc foo.c
* By setting the default ABI to --nn3322 in the //eettcc//ccoommppiilleerr..ddeeffaauullttss
file.
cat /etc/compiler.defaults
-DEFAULT:abi=n32
An N32 compilation will generate certain predefined variables whose
values can be used by conditional compilation directives. The names
of these variables and their values are as follows:
_MIPS_FPSET = 32
_MIPS_ISA = 4
_ABI64 = 3
_MIPS_SIM = _NABI32
_MIPS_SZINT = 32
_MIPS_SZLONG = 32
_MIPS_SZPTR = 32
SSUUMMMMAARRYY TTAABBLLEE
The table below summarizes the characteristics of the three ABI's.
-----------------------------------------------------------------
Category O32 nn6644 nn3322
-----------------------------------------------------------------
Command Line Switch --3322 --6644 --nn3322
Supported ISA mmiippss11,,22 mmiippss 33,,44 mmiippss 33,,44
Default ISA mmiippss22 mmiippss44 mmiippss33
Object file format ELF32 ELF64 ELF32
Symbol table format DWARF DWARF
Number of double 16 32 32
precision floating
point registers
sizeof(iinntt) 32 32 32
sizeof(lloonngg) 32 64 32
sizeof(cchhaarr **)) 32 64 32
-----------------------------------------------------------------
SSEEEE AALLSSOO
The _M_I_P_S_p_r_o _N_3_2 _A_B_I _H_a_n_d_b_o_o_k and the _M_I_P_S_p_r_o _6_4-_B_i_t _P_o_r_t_i_n_g _a_n_d
_T_r_a_n_s_i_t_i_o_n _G_u_i_d_e provide information about the calling convention as
well as background on these ABIs.
mmiippss__eexxtt(5)
This man page is available only online.