Actual source code: sseenabled.c
petsc-3.13.6 2020-09-29
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      2:  #include <petscsys.h>

      4: #if defined(PETSC_HAVE_SSE)

      6: #include PETSC_HAVE_SSE
      7: #define SSE_FEATURE_FLAG 0x2000000 /* Mask for bit 25 (from bit 0) */

      9: PetscErrorCode  PetscSSEHardwareTest(PetscBool  *flag)
     10: {
     12:   char           vendor[13];
     13:   char           Intel[13]="GenuineIntel";
     14:   char           AMD[13]  ="AuthenticAMD";
     15:   char           Hygon[13]="HygonGenuine";
     16:   PetscBool      flg;

     19:   PetscStrncpy(vendor,"************",sizeof(vendor));
     20:   CPUID_GET_VENDOR(vendor);
     21:   PetscStrcmp(vendor,Intel,&flg);
     22:   if (!flg) {PetscStrcmp(vendor,AMD,&flg);}
     23:   if (!flg) {PetscStrcmp(vendor,Hygon,&flg);
     24:     if (flg) {
     25:     /* Intel, AMD, and Hygon use bit 25 of CPUID_FEATURES */
     26:     /* to denote availability of SSE Support */
     27:     unsigned long myeax,myebx,myecx,myedx;
     28:     CPUID(CPUID_FEATURES,&myeax,&myebx,&myecx,&myedx);
     29:     if (myedx & SSE_FEATURE_FLAG) *flag = PETSC_TRUE;
     30:     else *flag = PETSC_FALSE;
     31:   }
     32:   return(0);
     33: }

     35: #if defined(PETSC_HAVE_FORK)
     36: #include <signal.h>
     37: /*
     38:    Early versions of the Linux kernel disables SSE hardware because
     39:    it does not know how to preserve the SSE state at a context switch.
     40:    To detect this feature, try an sse instruction in another process.
     41:    If it works, great!  If not, an illegal instruction signal will be thrown,
     42:    so catch it and return an error code.
     43: */
     44: #define PetscSSEOSEnabledTest(arg) PetscSSEOSEnabledTest_Linux(arg)

     46: static void PetscSSEDisabledHandler(int sig)
     47: {
     48:   signal(SIGILL,SIG_IGN);
     49:   exit(-1);
     50: }

     52: PetscErrorCode  PetscSSEOSEnabledTest_Linux(PetscBool  *flag)
     53: {
     54:   int status, pid = 0;

     57:   signal(SIGILL,PetscSSEDisabledHandler);
     58:   pid = fork();
     59:   if (pid==0) {
     60:     SSE_SCOPE_BEGIN;
     61:     XOR_PS(XMM0,XMM0);
     62:     SSE_SCOPE_END;
     63:     exit(0);
     64:   } else wait(&status);
     65:   if (!status) *flag = PETSC_TRUE;
     66:   else *flag = PETSC_FALSE;
     67:   return(0);
     68: }

     70: #else
     71: /*
     72:    Windows 95/98/NT4 should have a Windows Update/Service Patch which enables this hardware.
     73:    Windows ME/2000 doesn't disable SSE Hardware
     74: */
     75: #define PetscSSEOSEnabledTest(arg) PetscSSEOSEnabledTest_TRUE(arg)
     76: #endif

     78: PetscErrorCode  PetscSSEOSEnabledTest_TRUE(PetscBool  *flag)
     79: {
     81:   if (flag) *flag = PETSC_TRUE;
     82:   return(0);
     83: }

     85: #else  /* Not defined PETSC_HAVE_SSE */

     87: #define PetscSSEHardwareTest(arg) PetscSSEEnabledTest_FALSE(arg)
     88: #define PetscSSEOSEnabledTest(arg) PetscSSEEnabledTest_FALSE(arg)

     90: PetscErrorCode  PetscSSEEnabledTest_FALSE(PetscBool  *flag)
     91: {
     93:   if (flag) *flag = PETSC_FALSE;
     94:   return(0);
     95: }

     97: #endif /* defined PETSC_HAVE_SSE */

     99: /*@C
    100:      PetscSSEIsEnabled - Determines if Intel Streaming SIMD Extensions (SSE) to the x86 instruction
    101:      set can be used.  Some operating systems do not allow the use of these instructions despite
    102:      hardware availability.

    104:      Collective

    106:      Input Parameter:
    107: .    comm - the MPI Communicator

    109:      Output Parameters:
    110: +    lflag - Local Flag:  PETSC_TRUE if enabled in this process
    111: -    gflag - Global Flag: PETSC_TRUE if enabled for all processes in comm

    113:      Notes:
    114:      NULL can be specified for lflag or gflag if either of these values are not desired.

    116:      Options Database Keys:
    117: .    -disable_sse - Disable use of hand tuned Intel SSE implementations

    119:      Level: developer
    120: @*/
    121: static PetscBool petsc_sse_local_is_untested  = PETSC_TRUE;
    122: static PetscBool petsc_sse_enabled_local      = PETSC_FALSE;
    123: static PetscBool petsc_sse_global_is_untested = PETSC_TRUE;
    124: static PetscBool petsc_sse_enabled_global     = PETSC_FALSE;
    125: PetscErrorCode  PetscSSEIsEnabled(MPI_Comm comm,PetscBool  *lflag,PetscBool  *gflag)
    126: {
    128:   PetscBool      disabled_option;

    131:   if (petsc_sse_local_is_untested && petsc_sse_global_is_untested) {
    132:     disabled_option = PETSC_FALSE;

    134:     PetscOptionsGetBool(NULL,NULL,"-disable_sse",&disabled_option,NULL);
    135:     if (disabled_option) {
    136:       petsc_sse_local_is_untested  = PETSC_FALSE;
    137:       petsc_sse_enabled_local      = PETSC_FALSE;
    138:       petsc_sse_global_is_untested = PETSC_FALSE;
    139:       petsc_sse_enabled_global     = PETSC_FALSE;
    140:     }

    142:     if (petsc_sse_local_is_untested) {
    143:       PetscSSEHardwareTest(&petsc_sse_enabled_local);
    144:       if (petsc_sse_enabled_local) {
    145:         PetscSSEOSEnabledTest(&petsc_sse_enabled_local);
    146:       }
    147:       petsc_sse_local_is_untested = PETSC_FALSE;
    148:     }

    150:     if (gflag && petsc_sse_global_is_untested) {
    151:       MPIU_Allreduce(&petsc_sse_enabled_local,&petsc_sse_enabled_global,1,MPIU_BOOL,MPI_LAND,comm);

    153:       petsc_sse_global_is_untested = PETSC_FALSE;
    154:     }
    155:   }

    157:   if (lflag) *lflag = petsc_sse_enabled_local;
    158:   if (gflag) *gflag = petsc_sse_enabled_global;
    159:   return(0);
    160: }