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cpu.c

/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2008                *
 * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
 *                                                                  *
 ********************************************************************

 CPU capability detection for x86 processors.
  Originally written by Rudolf Marek.

 function:
  last mod: $Id: cpu.c 15427 2008-10-21 02:36:19Z xiphmont $

 ********************************************************************/

#include "cpu.h"

#if !defined(USE_ASM)
static ogg_uint32_t oc_cpu_flags_get(void){
  return 0;
}
#else
# if !defined(_MSC_VER)
#  if defined(__amd64__)||defined(__x86_64__)
/*On x86-64, gcc seems to be able to figure out how to save %rbx for us when
   compiling with -fPIC.*/
#   define cpuid(_op,_eax,_ebx,_ecx,_edx) \
  __asm__ __volatile__( \
   "cpuid\n\t" \
   :[eax]"=a"(_eax),[ebx]"=b"(_ebx),[ecx]"=c"(_ecx),[edx]"=d"(_edx) \
   :"a"(_op) \
   :"cc" \
  )
#  else
/*On x86-32, not so much.*/
#   define cpuid(_op,_eax,_ebx,_ecx,_edx) \
  __asm__ __volatile__( \
   "xchgl %%ebx,%[ebx]\n\t" \
   "cpuid\n\t" \
   "xchgl %%ebx,%[ebx]\n\t" \
   :[eax]"=a"(_eax),[ebx]"=r"(_ebx),[ecx]"=c"(_ecx),[edx]"=d"(_edx) \
   :"a"(_op) \
   :"cc" \
  )
#  endif
# else
/*Why does MSVC need this complicated rigamarole?
  At this point I honestly do not care.*/

/*Visual C cpuid helper function.
  For VS2005 we could as well use the _cpuid builtin, but that wouldn't work
   for VS2003 users, so we do it in inline assembler.*/
static void oc_cpuid_helper(ogg_uint32_t _cpu_info[4],ogg_uint32_t _op){
  _asm{
    mov eax,[_op]
    mov esi,_cpu_info
    cpuid
    mov [esi+0],eax
    mov [esi+4],ebx
    mov [esi+8],ecx
    mov [esi+12],edx
  }
}

#  define cpuid(_op,_eax,_ebx,_ecx,_edx) \
  do{ \
    ogg_uint32_t cpu_info[4]; \
    oc_cpuid_helper(cpu_info,_op); \
    (_eax)=cpu_info[0]; \
    (_ebx)=cpu_info[1]; \
    (_ecx)=cpu_info[2]; \
    (_edx)=cpu_info[3]; \
  }while(0)

static void oc_detect_cpuid_helper(ogg_uint32_t *_eax,ogg_uint32_t *_ebx){
  _asm{
    pushfd
    pushfd
    pop eax
    mov ebx,eax
    xor eax,200000h
    push eax
    popfd
    pushfd
    pop eax
    popfd
    mov ecx,_eax
    mov [ecx],eax
    mov ecx,_ebx
    mov [ecx],ebx
  }
}
# endif

static ogg_uint32_t oc_parse_intel_flags(ogg_uint32_t _edx,ogg_uint32_t _ecx){
  ogg_uint32_t flags;
  /*If there isn't even MMX, give up.*/
  if(!(_edx&0x00800000))return 0;
  flags=OC_CPU_X86_MMX;
  if(_edx&0x02000000)flags|=OC_CPU_X86_MMXEXT|OC_CPU_X86_SSE;
  if(_edx&0x04000000)flags|=OC_CPU_X86_SSE2;
  if(_ecx&0x00000001)flags|=OC_CPU_X86_PNI;
  if(_ecx&0x00000100)flags|=OC_CPU_X86_SSSE3;
  if(_ecx&0x00080000)flags|=OC_CPU_X86_SSE4_1;
  if(_ecx&0x00100000)flags|=OC_CPU_X86_SSE4_2;
  return flags;
}

static ogg_uint32_t oc_parse_amd_flags(ogg_uint32_t _edx,ogg_uint32_t _ecx){
  ogg_uint32_t flags;
  /*If there isn't even MMX, give up.*/
  if(!(_edx&0x00800000))return 0;
  flags=OC_CPU_X86_MMX;
  if(_edx&0x00400000)flags|=OC_CPU_X86_MMXEXT;
  if(_edx&0x80000000)flags|=OC_CPU_X86_3DNOW;
  if(_edx&0x40000000)flags|=OC_CPU_X86_3DNOWEXT;
  if(_ecx&0x00000040)flags|=OC_CPU_X86_SSE4A;
  if(_ecx&0x00000800)flags|=OC_CPU_X86_SSE5;
  return flags;
}

static ogg_uint32_t oc_cpu_flags_get(void){
  ogg_uint32_t flags;
  ogg_uint32_t eax;
  ogg_uint32_t ebx;
  ogg_uint32_t ecx;
  ogg_uint32_t edx;
# if !defined(__amd64__)&&!defined(__x86_64__)
  /*Not all x86-32 chips support cpuid, so we have to check.*/
#  if !defined(_MSC_VER)
  __asm__ __volatile__(
   "pushfl\n\t"
   "pushfl\n\t"
   "popl %[a]\n\t"
   "movl %[a],%[b]\n\t"
   "xorl $0x200000,%[a]\n\t"
   "pushl %[a]\n\t"
   "popfl\n\t"
   "pushfl\n\t"
   "popl %[a]\n\t"
   "popfl\n\t"
   :[a]"=r"(eax),[b]"=r"(ebx)
   :
   :"cc"
  );
#  else
  oc_detect_cpuid_helper(&eax,&ebx);
#  endif
  /*No cpuid.*/
  if(eax==ebx)return 0;
# endif
  cpuid(0,eax,ebx,ecx,edx);
  /*         l e t n          I e n i          u n e G*/
  if(ecx==0x6C65746E&&edx==0x49656E69&&ebx==0x756E6547||
   /*      6 8 x M          T e n i          u n e G*/
   ecx==0x3638784D&&edx==0x54656E69&&ebx==0x756E6547){
    /*Intel, Transmeta (tested with Crusoe TM5800):*/
    cpuid(1,eax,ebx,ecx,edx);
    flags=oc_parse_intel_flags(edx,ecx);
  }
  /*              D M A c          i t n e          h t u A*/
  else if(ecx==0x444D4163&&edx==0x69746E65&&ebx==0x68747541||
   /*      C S N            y b   e          d o e G*/
   ecx==0x43534E20&&edx==0x79622065&&ebx==0x646F6547){
    /*AMD, Geode:*/
    cpuid(0x80000000,eax,ebx,ecx,edx);
    if(eax<0x80000001)flags=0;
    else{
      cpuid(0x80000001,eax,ebx,ecx,edx);
      flags=oc_parse_amd_flags(edx,ecx);
    }
    /*Also check for SSE.*/
    cpuid(1,eax,ebx,ecx,edx);
    flags|=oc_parse_intel_flags(edx,ecx);
  }
  /*Technically some VIA chips can be configured in the BIOS to return any
     string here the user wants.
    There is a special detection method that can be used to identify such
     processors, but in my opinion, if the user really wants to change it, they
     deserve what they get.*/
  /*              s l u a          H r u a          t n e C*/
  else if(ecx==0x736C7561&&edx==0x48727561&&ebx==0x746E6543){
    /*VIA:*/
    /*I only have documentation for the C7 (Esther) and Isaiah (forthcoming)
       chips (thanks to the engineers from Centaur Technology who provided it).
      These chips support Intel-like cpuid info.
      The C3-2 (Nehemiah) cores appear to, as well.*/
    cpuid(1,eax,ebx,ecx,edx);
    flags=oc_parse_intel_flags(edx,ecx);
    cpuid(0x80000000,eax,ebx,ecx,edx);
    if(eax>=0x80000001){
      /*The (non-Nehemiah) C3 processors support AMD-like cpuid info.
        We need to check this even if the Intel test succeeds to pick up 3DNow!
         support on these processors.
        Unlike actual AMD processors, we cannot _rely_ on this info, since
         some cores (e.g., the 693 stepping of the Nehemiah) claim to support
         this function, yet return edx=0, despite the Intel test indicating
         MMX support.
        Therefore the features detected here are strictly added to those
         detected by the Intel test.*/
      /*TODO: How about earlier chips?*/
      cpuid(0x80000001,eax,ebx,ecx,edx);
      /*Note: As of the C7, this function returns Intel-style extended feature
         flags, not AMD-style.
        Currently, this only defines bits 11, 20, and 29 (0x20100800), which
         do not conflict with any of the AMD flags we inspect.
        For the remaining bits, Intel tells us, "Do not count on their value",
         but VIA assures us that they will all be zero (at least on the C7 and
         Isaiah chips).
        In the (unlikely) event a future processor uses bits 18, 19, 30, or 31
         (0xC0C00000) for something else, we will have to add code to detect
         the model to decide when it is appropriate to inspect them.*/
      flags|=oc_parse_amd_flags(edx,ecx);
    }
  }
  else{
    /*Implement me.*/
    flags=0;
  }
  return flags;
}
#endif

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