To avoid bloat, I’m not going to add the CPU detection stuff to SDL.
However, detecting what CPU features are available is certainly useful,
so I’m including code that we’ll use at Loki here. For code that works
with nearly every x86 platform, check out the MGL public source code:
http://www.scitechsoft.com/dp_mgl.html
I may add a single “get CPU features” function at some point, but not
right now. 
Hmm… I just noticed that the Cyrix EMMX detection is broken.
See ya!
-Sam Lantinga (slouken at devolution.com)
Lead Programmer, Loki Entertainment Software–
“Any sufficiently advanced bug is indistinguishable from a feature”
– Rich Kulawiec
-------------- next part --------------
/* Code to detect certain processor features */
#include “loki_cpuinfo.h”
/* Heheh, inline ASM - Sam */
int loki_getcpuflags(void)
{
int flags;
flags = 0;
#if defined(GNUC) && defined(i386)
/* Taken with thanks from mmx.h:
MultiMedia eXtensions GCC interface library for IA32.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR ANY PARTICULAR PURPOSE.
1997-98 by H. Dietz and R. Fisher
Bug fixes and SSE detection by Sam Lantinga
/
{
/ Returns 1 if MMX instructions are supported,
3 if Cyrix MMX and Extended MMX instructions are supported
5 if AMD MMX and 3DNow! instructions are supported
0 if hardware does not support any of these
*/
asm volatile (
“pushl %%ebx\n\t”
“pushl %%ecx\n\t”
“pushl %%edx\n\t”
/* See if CPUID instruction is supported ... */
/* ... Get copies of EFLAGS into eax and ecx */
"pushf\n\t"
"popl %%eax\n\t"
"movl %%eax, %%ecx\n\t"
/* ... Toggle the ID bit in one copy and store */
/* to the EFLAGS reg */
"xorl $0x200000, %%eax\n\t"
"push %%eax\n\t"
"popf\n\t"
/* ... Get the (hopefully modified) EFLAGS */
"pushf\n\t"
"popl %%eax\n\t"
/* ... Compare and test result */
"xorl %%eax, %%ecx\n\t"
"testl $0x200000, %%ecx\n\t"
"jz NotSupported\n\t" /* Nothing supported */
/* Get standard CPUID information, and
go to a specific vendor section */
"movl $0, %%eax\n\t"
"cpuid\n\t"
/* Check for Intel */
"cmpl $0x756e6547, %%ebx\n\t"
"jne TryAMD\n\t"
"cmpl $0x49656e69, %%edx\n\t"
"jne TryAMD\n\t"
"cmpl $0x6c65746e, %%ecx\n"
"jne TryAMD\n\t"
"jmp Intel\n\t"
/* Check for AMD */
"\nTryAMD:\n\t"
"cmpl $0x68747541, %%ebx\n\t"
"jne TryCyrix\n\t"
"cmpl $0x69746e65, %%edx\n\t"
"jne TryCyrix\n\t"
"cmpl $0x444d4163, %%ecx\n"
"jne TryCyrix\n\t"
"jmp AMD\n\t"
/* Check for Cyrix */
"\nTryCyrix:\n\t"
"cmpl $0x69727943, %%ebx\n\t"
"jne NotSupported\n\t"
"cmpl $0x736e4978, %%edx\n\t"
"jne NotSupported\n\t"
"cmpl $0x64616574, %%ecx\n\t"
"jne NotSupported\n\t"
/* Drop through to Cyrix... */
/* Cyrix Section */
/* See if extended CPUID is supported */
"movl $0x80000000, %%eax\n\t"
"cpuid\n\t"
"cmpl $0x80000000, %%eax\n\t"
"jl MMXtest\n\t" /* Try standard CPUID instead */
/* Extended CPUID supported, so get extended features */
"movl $0x80000001, %%eax\n\t"
"cpuid\n\t"
"testl $0x00800000, %%eax\n\t" /* Test for MMX */
"jz NotSupported\n\t" /* MMX not supported */
"movl $1, %0\n\n\t" /* MMX Supported */
"testl $0x01000000, %%eax\n\t" /* Test for Ext'd MMX */
"jz Return\n\t"
"addl $2, %0\n\n\t" /* EMMX also supported */
"jmp Return\n\t"
/* AMD Section */
"AMD:\n\t"
/* See if extended CPUID is supported */
"movl $0x80000000, %%eax\n\t"
"cpuid\n\t"
"cmpl $0x80000000, %%eax\n\t"
"jl MMXtest\n\t" /* Try standard CPUID instead */
/* Extended CPUID supported, so get extended features */
"movl $0x80000001, %%eax\n\t"
"cpuid\n\t"
"testl $0x00800000, %%edx\n\t" /* Test for MMX */
"jz NotSupported\n\t" /* MMX not supported */
"movl $1, %0\n\n\t" /* MMX Supported */
"testl $0x80000000, %%edx\n\t" /* Test for 3DNow! */
"jz Return\n\t"
"addl $4, %0\n\n\t" /* 3DNow! also supported */
"jmp Return\n\t"
/* Intel Section */
"Intel:\n\t"
/* Check for MMX */
"MMXtest:\n\t"
"movl $1, %%eax\n\t"
"cpuid\n\t"
"testl $0x00800000, %%edx\n\t" /* Test for MMX */
"jz NotSupported\n\t" /* MMX Not supported */
"movl $1, %0\n\n\t" /* MMX Supported */
"testl $0x02000000, %%edx\n\t" /* Test for SSE */
"jz Return\n\t" /* SSE Not supported */
"addl $8, %0\n\n\t" /* SSE Supported */
"jmp Return\n\t"
/* Nothing supported */
"NotSupported:\n\t"
"movl $0, %0\n\n\t"
"Return:\n\t"
"popl %%edx\n\t"
"popl %%ecx\n\t"
"popl %%ebx\n\t"
: "=a" (flags)
: /* no input */
/*
: “ebx”, “ecx”, “edx”
/
: “memory”
);
}
#endif / GCC and x86 */
return flags;
}
#ifdef TEST_MAIN
#include <stdio.h>
int main(int argc, char *argv[])
{
int cpu_flags;
cpu_flags = loki_getcpuflags();
printf("CPU flags: 0x%4.4x", cpu_flags);
if ( cpu_flags & CPU_HAS_MMX ) {
printf(" MMX");
}
if ( cpu_flags & CPU_HAS_EMMX ) {
printf(" (exended)");
}
if ( cpu_flags & CPU_HAS_3DNOW ) {
printf(" 3DNow!");
}
if ( cpu_flags & CPU_HAS_SSE ) {
printf(" SSE");
}
printf("\n");
exit(0);
}
#endif /* TEST_MAIN */
-------------- next part --------------
/* Code to detect certain processor features */
#ifndef _loki_cpuinfo_h
#define _loki_cpuinfo_h
/* There is some interesting code in MGL, but I’m not sure of the license
issues.
*/
#define CPU_HAS_MMX 0x0001 /* Pentium II MMX /
#define CPU_HAS_EMMX 0x0002 / Cyrix extended MMX /
#define CPU_HAS_3DNOW 0x0004 / AMD 3DNow! /
#define CPU_HAS_SSE 0x0008 / Pentium III SSE */
extern int loki_getcpuflags(void);
#endif /* _loki_cpuinfo_h */