third_party/zlib/x86.c

   1 /*
   2  * x86 feature check
   3  *
   4  * Copyright (C) 2013 Intel Corporation. All rights reserved.
   5  * Author:
   6  *  Jim Kukunas
   7  *
   8  * For conditions of distribution and use, see copyright notice in zlib.h
   9  */
  10
  11 #include "x86.h"
  12
  13 int x86_cpu_enable_simd = 0;
  14
  15 #ifndef _MSC_VER
  16 #include <pthread.h>
  17
  18 pthread_once_t cpu_check_inited_once = PTHREAD_ONCE_INIT;
  19 static void _x86_check_features(void);
  20
  21 void x86_check_features(void)
  22 {
  23   pthread_once(&cpu_check_inited_once, _x86_check_features);
  24 }
  25
  26 static void _x86_check_features(void)
  27 {
  28     int x86_cpu_has_sse2;
  29     int x86_cpu_has_sse42;
  30     int x86_cpu_has_pclmulqdq;
  31     unsigned eax, ebx, ecx, edx;
  32
  33     eax = 1;
  34 #ifdef __i386__
  35     __asm__ __volatile__ (
  36         "xchg %%ebx, %1\n\t"
  37         "cpuid\n\t"
  38         "xchg %1, %%ebx\n\t"
  39     : "+a" (eax), "=S" (ebx), "=c" (ecx), "=d" (edx)
  40     );
  41 #else
  42     __asm__ __volatile__ (
  43         "cpuid\n\t"
  44     : "+a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
  45     );
  46 #endif  /* (__i386__) */
  47
  48     x86_cpu_has_sse2 = edx & 0x4000000;
  49     x86_cpu_has_sse42 = ecx & 0x100000;
  50     x86_cpu_has_pclmulqdq = ecx & 0x2;
  51
  52     x86_cpu_enable_simd = x86_cpu_has_sse2 &&
  53                           x86_cpu_has_sse42 &&
  54                           x86_cpu_has_pclmulqdq;
  55 }
  56 #else
  57 #include <intrin.h>
  58 #include <windows.h>
  59 #include <stdint.h>
  60
  61 static volatile int32_t once_control = 0;
  62 static void _x86_check_features(void);
  63 static int fake_pthread_once(volatile int32_t *once_control,
  64                              void (*init_routine)(void));
  65
  66 void x86_check_features(void)
  67 {
  68     fake_pthread_once(&once_control, _x86_check_features);
  69 }
  70
  71 /* Copied from "perftools_pthread_once" in tcmalloc */
  72 static int fake_pthread_once(volatile int32_t *once_control,
  73                              void (*init_routine)(void)) {
  74     // Try for a fast path first. Note: this should be an acquire semantics read
  75     // It is on x86 and x64, where Windows runs.
  76     if (*once_control != 1) {
  77         while (1) {
  78             switch (InterlockedCompareExchange(once_control, 2, 0)) {
  79                 case 0:
  80                     init_routine();
  81                     InterlockedExchange(once_control, 1);
  82                     return 0;
  83                 case 1:
  84                     // The initializer has already been executed
  85                     return 0;
  86                 default:
  87                     // The initializer is being processed by another thread
  88                     SwitchToThread();
  89             }
  90         }
  91     }
  92     return 0;
  93 }
  94
  95 static void _x86_check_features(void)
  96 {
  97     int x86_cpu_has_sse2;
  98     int x86_cpu_has_sse42;
  99     int x86_cpu_has_pclmulqdq;
 100     int regs[4];
 101
 102     __cpuid(regs, 1);
 103
 104     x86_cpu_has_sse2 = regs[3] & 0x4000000;
 105     x86_cpu_has_sse42= regs[2] & 0x100000;
 106     x86_cpu_has_pclmulqdq = regs[2] & 0x2;
 107
 108     x86_cpu_enable_simd = x86_cpu_has_sse2 &&
 109                           x86_cpu_has_sse42 &&
 110                           x86_cpu_has_pclmulqdq;
 111 }
 112 #endif  /* _MSC_VER */