src/png/pnggccrd.c

   1 /* pnggccrd.c was removed from libpng-1.2.20. */
   2
   3 /* This code snippet is for use by configure's compilation test. */
   4
   5 #if (!defined _MSC_VER) && \
   6     defined(PNG_ASSEMBLER_CODE_SUPPORTED) && \
   7     defined(PNG_MMX_CODE_SUPPORTED)
   8
   9 int PNGAPI png_dummy_mmx_support(void);
  10
  11 static int _mmx_supported = 2; // 0: no MMX; 1: MMX supported; 2: not tested
  12
  13 int PNGAPI
  14 png_dummy_mmx_support(void) __attribute__((noinline));
  15
  16 int PNGAPI
  17 png_dummy_mmx_support(void)
  18 {
  19    int result;
  20 #if defined(PNG_MMX_CODE_SUPPORTED)  // superfluous, but what the heck
  21     __asm__ __volatile__ (
  22 #if defined(__x86_64__)
  23         "pushq %%rbx          \n\t"  // rbx gets clobbered by CPUID instruction
  24         "pushq %%rcx          \n\t"  // so does rcx...
  25         "pushq %%rdx          \n\t"  // ...and rdx (but rcx & rdx safe on Linux)
  26         "pushfq               \n\t"  // save Eflag to stack
  27         "popq %%rax           \n\t"  // get Eflag from stack into rax
  28         "movq %%rax, %%rcx    \n\t"  // make another copy of Eflag in rcx
  29         "xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
  30         "pushq %%rax          \n\t"  // save modified Eflag back to stack
  31         "popfq                \n\t"  // restore modified value to Eflag reg
  32         "pushfq               \n\t"  // save Eflag to stack
  33         "popq %%rax           \n\t"  // get Eflag from stack
  34         "pushq %%rcx          \n\t"  // save original Eflag to stack
  35         "popfq                \n\t"  // restore original Eflag
  36 #else
  37         "pushl %%ebx          \n\t"  // ebx gets clobbered by CPUID instruction
  38         "pushl %%ecx          \n\t"  // so does ecx...
  39         "pushl %%edx          \n\t"  // ...and edx (but ecx & edx safe on Linux)
  40         "pushfl               \n\t"  // save Eflag to stack
  41         "popl %%eax           \n\t"  // get Eflag from stack into eax
  42         "movl %%eax, %%ecx    \n\t"  // make another copy of Eflag in ecx
  43         "xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
  44         "pushl %%eax          \n\t"  // save modified Eflag back to stack
  45         "popfl                \n\t"  // restore modified value to Eflag reg
  46         "pushfl               \n\t"  // save Eflag to stack
  47         "popl %%eax           \n\t"  // get Eflag from stack
  48         "pushl %%ecx          \n\t"  // save original Eflag to stack
  49         "popfl                \n\t"  // restore original Eflag
  50 #endif
  51         "xorl %%ecx, %%eax    \n\t"  // compare new Eflag with original Eflag
  52         "jz 0f                \n\t"  // if same, CPUID instr. is not supported
  53
  54         "xorl %%eax, %%eax    \n\t"  // set eax to zero
  55 //      ".byte  0x0f, 0xa2    \n\t"  // CPUID instruction (two-byte opcode)
  56         "cpuid                \n\t"  // get the CPU identification info
  57         "cmpl $1, %%eax       \n\t"  // make sure eax return non-zero value
  58         "jl 0f                \n\t"  // if eax is zero, MMX is not supported
  59
  60         "xorl %%eax, %%eax    \n\t"  // set eax to zero and...
  61         "incl %%eax           \n\t"  // ...increment eax to 1.  This pair is
  62                                      // faster than the instruction "mov eax, 1"
  63         "cpuid                \n\t"  // get the CPU identification info again
  64         "andl $0x800000, %%edx \n\t" // mask out all bits but MMX bit (23)
  65         "cmpl $0, %%edx       \n\t"  // 0 = MMX not supported
  66         "jz 0f                \n\t"  // non-zero = yes, MMX IS supported
  67
  68         "movl $1, %%eax       \n\t"  // set return value to 1
  69         "jmp  1f              \n\t"  // DONE:  have MMX support
  70
  71     "0:                       \n\t"  // .NOT_SUPPORTED: target label for jump instructions
  72         "movl $0, %%eax       \n\t"  // set return value to 0
  73     "1:                       \n\t"  // .RETURN: target label for jump instructions
  74 #if defined(__x86_64__)
  75         "popq %%rdx           \n\t"  // restore rdx
  76         "popq %%rcx           \n\t"  // restore rcx
  77         "popq %%rbx           \n\t"  // restore rbx
  78 #else
  79         "popl %%edx           \n\t"  // restore edx
  80         "popl %%ecx           \n\t"  // restore ecx
  81         "popl %%ebx           \n\t"  // restore ebx
  82 #endif
  83
  84 //      "ret                  \n\t"  // DONE:  no MMX support
  85                                      // (fall through to standard C "ret")
  86
  87         : "=a" (result)              // output list
  88
  89         :                            // any variables used on input (none)
  90
  91                                      // no clobber list
  92 //      , "%ebx", "%ecx", "%edx"     // GRR:  we handle these manually
  93 //      , "memory"   // if write to a variable gcc thought was in a reg
  94 //      , "cc"       // "condition codes" (flag bits)
  95     );
  96     _mmx_supported = result;
  97 #else
  98     _mmx_supported = 0;
  99 #endif /* PNG_MMX_CODE_SUPPORTED */
 100
 101     return _mmx_supported;
 102 }
 103 #endif