MIPS4(5) MIPS4(5)
NAME
mips4 - MIPS4 architecture extensions and the -mips4 compiler option
SYNOPSIS
cc -mips4 [ options ] ... file ...
f77 -mips4 [ options ] ... file ...
as -mips4 [ options ] ... file ...
DESCRIPTION
The MIPS4 instruction set extensions consist of a backward compatible
superset of the MIPS3 instruction set. The MIPS4 extensions are intended
primarily to provide better performance in floating point numeric
processing. These features are currently supported under IRIX 6.2 and
later releases running on machines with the R8000, R10000, or R5000
microprocessors.
The MIPS4 instruction set extensions provide the following features:
⊕ A new set of multiply-add instructions takes advantage of the fact
that the majority of floating point computations use the chained
multiply-add paradigm. These instructions have lower inherent
latency (temporary result need not be written back to a register)
and higher performance (fewer instructions to fetch and decode).
The multiple-add instructions on an R8000 (but not on R5000 or
R10000) does not perform intermediate rounding, for even lower
latency.
⊕ A register + register addressing mode for floating point loads and
stores eliminates the extra integer add required in many array
accesses. (Register + register addressing for integer memory
operations is not supported.)
⊕ A set of four conditional move operators allows some simple ``IF''
statements to be represented without branches. ``THEN'' and
``ELSE'' clauses are computed unconditionally and the results placed
in a temporary register. Conditional move operators then select the
correct temporary result.
⊕ Memory prefetch instructions to better manage data cache behavior in
memory intensive algorithms. [NOTE: prefetch instructions are not
supported on the R8000. See mipscheck(1) ]
Programs compiled with the -mips4 option conform to the Mips 64-bit
application binary interface (ABI64) or n32 ABI (ABIn32), rather than the
original MIPS ABI (ABIo32). Each of the 3 ABIs is distinct and object
files compiled to one ABI cannot be linked to object files (including
archives and DSOs) compiled to another ABI.
SEE ALSO
Assembly Language Programmer's Guide.
MIPSpro Application Porting and Transition Guide
MIPS RISC Architecture, Gerry Kane and Joe Heinrich, Prentice Hall.
Page 1
MIPS4(5) MIPS4(5)
MIPS R4000 User's Manual, Joseph Heinrich, Prentice Hall.
cc(1), f77(1), pc(1), CC(1), as(1), mips2(5)
Page 2