Actual source code: sseenabled.c
petsc-3.10.5 2019-03-28
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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:   char           Intel[13]="GenuineIntel";
     14:   char           AMD[13]  ="AuthenticAMD";

     17:   PetscMalloc1(13,&vendor);
     18:   strcpy(vendor,"************");
     19:   CPUID_GET_VENDOR(vendor);
     20:   if (!strcmp(vendor,Intel) || !strcmp(vendor,AMD)) {
     21:     /* Both Intel and AMD use bit 25 of CPUID_FEATURES */
     22:     /* to denote availability of SSE Support */
     23:     unsigned long myeax,myebx,myecx,myedx;
     24:     CPUID(CPUID_FEATURES,&myeax,&myebx,&myecx,&myedx);
     25:     if (myedx & SSE_FEATURE_FLAG) *flag = PETSC_TRUE;
     26:     else *flag = PETSC_FALSE;
     27:   }
     28:   PetscFree(vendor);
     29:   return(0);
     30: }

     32: #if defined(PETSC_HAVE_FORK)
     33: #include <signal.h>
     34: /*
     35:    Early versions of the Linux kernel disables SSE hardware because
     36:    it does not know how to preserve the SSE state at a context switch.
     37:    To detect this feature, try an sse instruction in another process.
     38:    If it works, great!  If not, an illegal instruction signal will be thrown,
     39:    so catch it and return an error code.
     40: */
     41: #define PetscSSEOSEnabledTest(arg) PetscSSEOSEnabledTest_Linux(arg)

     43: static void PetscSSEDisabledHandler(int sig)
     44: {
     45:   signal(SIGILL,SIG_IGN);
     46:   exit(-1);
     47: }

     49: PetscErrorCode  PetscSSEOSEnabledTest_Linux(PetscBool  *flag)
     50: {
     51:   int status, pid = 0;

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

     67: #else
     68: /*
     69:    Windows 95/98/NT4 should have a Windows Update/Service Patch which enables this hardware.
     70:    Windows ME/2000 doesn't disable SSE Hardware
     71: */
     72: #define PetscSSEOSEnabledTest(arg) PetscSSEOSEnabledTest_TRUE(arg)
     73: #endif

     75: PetscErrorCode  PetscSSEOSEnabledTest_TRUE(PetscBool  *flag)
     76: {
     78:   if (flag) *flag = PETSC_TRUE;
     79:   return(0);
     80: }

     82: #else  /* Not defined PETSC_HAVE_SSE */

     84: #define PetscSSEHardwareTest(arg) PetscSSEEnabledTest_FALSE(arg)
     85: #define PetscSSEOSEnabledTest(arg) PetscSSEEnabledTest_FALSE(arg)

     87: PetscErrorCode  PetscSSEEnabledTest_FALSE(PetscBool  *flag)
     88: {
     90:   if (flag) *flag = PETSC_FALSE;
     91:   return(0);
     92: }

     94: #endif /* defined PETSC_HAVE_SSE */

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

    101:      Collective on MPI_Comm

    103:      Input Parameter:
    104: .    comm - the MPI Communicator

    106:      Output Parameters:
    107: .    lflag - Local Flag:  PETSC_TRUE if enabled in this process
    108: .    gflag - Global Flag: PETSC_TRUE if enabled for all processes in comm

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

    113:      Options Database Keys:
    114: .    -disable_sse - Disable use of hand tuned Intel SSE implementations

    116:      Level: developer
    117: @*/
    118: static PetscBool petsc_sse_local_is_untested  = PETSC_TRUE;
    119: static PetscBool petsc_sse_enabled_local      = PETSC_FALSE;
    120: static PetscBool petsc_sse_global_is_untested = PETSC_TRUE;
    121: static PetscBool petsc_sse_enabled_global     = PETSC_FALSE;
    122: PetscErrorCode  PetscSSEIsEnabled(MPI_Comm comm,PetscBool  *lflag,PetscBool  *gflag)
    123: {
    125:   PetscBool      disabled_option;

    128:   if (petsc_sse_local_is_untested && petsc_sse_global_is_untested) {
    129:     disabled_option = PETSC_FALSE;

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

    139:     if (petsc_sse_local_is_untested) {
    140:       PetscSSEHardwareTest(&petsc_sse_enabled_local);
    141:       if (petsc_sse_enabled_local) {
    142:         PetscSSEOSEnabledTest(&petsc_sse_enabled_local);
    143:       }
    144:       petsc_sse_local_is_untested = PETSC_FALSE;
    145:     }

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

    150:       petsc_sse_global_is_untested = PETSC_FALSE;
    151:     }
    152:   }

    154:   if (lflag) *lflag = petsc_sse_enabled_local;
    155:   if (gflag) *gflag = petsc_sse_enabled_global;
    156:   return(0);
    157: }