NAME
ggGetSwarType - Get CPU features
SYNOPSIS
#include <ggi/gg.h>
#if defined GG_HAVE_INT64
#endif
#if defined GG_LITTLE_ENDIAN
#endif
#if defined GG_BIG_ENDIAN
#endif
gg_swartype ggGetSwarType(void);
DESCRIPTION
The GG_HAVE_INT64 macro is defined on 64-bit architectures where 64-bit
integer values function as normal integer values with respect to C
operations. Otherwise it is not defined.
The GG_LITTLE_ENDIAN or GG_BIG_ENDIAN are defined, respectively, when
the architecture stores values in little or big endian order. One of
the two will be defined, the other undefined, accordingly.
SWAR stands for SIMD Within A Register. The most well known example of
SWAR is Intel MMX technology.
ggGetSwarType tells which specific SWAR instruction sets the CPU
implements. This is useful to choose at runtime a machine-specific
implementation of a very calculation-intensive routine. SWAR detection
is done once during ggInit(3) and the value is cached for future use,
thus it should be fast enough to choose implementations on the fly.
However, due to this, SMP machines must have identical feature sets in
all processors in order to ensure accurate results (see the GG_OPTS
option description below.)
RETURN VALUE
ggGetSwarType returns an integer in which each bit set means that a
specific SWAR instruction set is available. The integer value may be
32 bits long or 64 bits long, depending on whether LibGG was compiled
for a 32-bit or 64-bit machine, as per the GG_HAVE_INT64 macro.
RECOGNIZED SWARS
The following flags are defined for all architectures. All of these
flags can be OR’ed and are exclusive even between architectures. Note
at this stage of development some of these SIMD sets are not yet
detected correctly.
GG_SWAR_NONE
The CPU can run a vanilla C program. (hopefully! :-)
GG_SWAR_32BITC
The CPU can perform 32-bit math fast enough to give an advantage
over 16-bit math for software SWAR implementations. Almost all
computers will have this capability today.
GG_SWAR_ALTIVEC
The CPU has an AltiVec matrix coprocessor (Motorola G4.)
GG_SWAR_SSE
The CPU supports Intel Streaming SIMD Extensions.
GG_SWAR_SSE2
The CPU supports Intel Streaming SIMD Extensions Version 2.
GG_SWAR_SSE3
The CPU supports Intel Streaming SIMD Extensions Version 3.
GG_SWAR_MMX
The CPU supports Intel Multimedia Extensions.
GG_SWAR_MMXPLUS
The CPU supports Cyrix enhancements to Intel Multimedia
Extensions.
GG_SWAR_3DNOW
The CPU supports AMD 3DNOW! instructions.
GG_SWAR_ADV3DNOW
The CPU supports AMD Advanced 3DNOW! instructions.
GG_SWAR_MAX
The CPU supports PA-RISC MAX Instructions.
GG_SWAR_SIGD
The CPU supports Microunity Mediaprocessor SIGD instructions.
Additionally, 64 bits architectures define the following flags:
GG_SWAR_64BITC
The CPU can perform 64-bit math fast enough to give an advantage
over 32-bit and 16-bit math for software SWAR implementations.
GG_SWAR_MVI
The CPU supports DEC (Compaq) Alpha Motion Video Instructions.
GG_SWAR_MAX2
The CPU supports PA-RISC MAX2 Instructions.
GG_SWAR_MDMX
The CPU supports MIPS Digital Media Extension (MaDMaX)
Instructions.
GG_SWAR_MAJC
The CPU supports SUN Microprocessor Architecture for Java
Computing.
GG_SWAR_VIS
The CPU supports the SUN Visual Instruction Set
ENVIRONMENT VARIABLE
If the "-banswar=0xhexnumber" option is present in the GG_OPTS
environment variable when ggInit is first called, bits set in the
0xhexnumber field will not be presented to the application in the
return value of ggGetSwarType. This feature can be used for
performance benchmarking, to disable the use of certain SWAR
implementations. It may also be used if a multiproccesor machine mis-
detects the usable SWAR instruction set because the processors are not
identical.
BUGS
No support is currently implemented for PDP endian machines.
SWAR detection code is incomplete for many architectures, and as such
LibGG may may fail to detect SWAR in the CPU.