nuclear@14: /* pnggccrd.c was removed from libpng-1.2.20. */
nuclear@14: 
nuclear@14: /* This code snippet is for use by configure's compilation test. */
nuclear@14: 
nuclear@14: #if (!defined _MSC_VER) && \
nuclear@14:     defined(PNG_ASSEMBLER_CODE_SUPPORTED) && \
nuclear@14:     defined(PNG_MMX_CODE_SUPPORTED)
nuclear@14: 
nuclear@14: int PNGAPI png_dummy_mmx_support(void);
nuclear@14: 
nuclear@14: static int _mmx_supported = 2; // 0: no MMX; 1: MMX supported; 2: not tested
nuclear@14: 
nuclear@14: int PNGAPI
nuclear@14: png_dummy_mmx_support(void) __attribute__((noinline));
nuclear@14: 
nuclear@14: int PNGAPI
nuclear@14: png_dummy_mmx_support(void)
nuclear@14: {
nuclear@14:    int result;
nuclear@14: #if defined(PNG_MMX_CODE_SUPPORTED)  // superfluous, but what the heck
nuclear@14:     __asm__ __volatile__ (
nuclear@14: #if defined(__x86_64__)
nuclear@14:         "pushq %%rbx          \n\t"  // rbx gets clobbered by CPUID instruction
nuclear@14:         "pushq %%rcx          \n\t"  // so does rcx...
nuclear@14:         "pushq %%rdx          \n\t"  // ...and rdx (but rcx & rdx safe on Linux)
nuclear@14:         "pushfq               \n\t"  // save Eflag to stack
nuclear@14:         "popq %%rax           \n\t"  // get Eflag from stack into rax
nuclear@14:         "movq %%rax, %%rcx    \n\t"  // make another copy of Eflag in rcx
nuclear@14:         "xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
nuclear@14:         "pushq %%rax          \n\t"  // save modified Eflag back to stack
nuclear@14:         "popfq                \n\t"  // restore modified value to Eflag reg
nuclear@14:         "pushfq               \n\t"  // save Eflag to stack
nuclear@14:         "popq %%rax           \n\t"  // get Eflag from stack
nuclear@14:         "pushq %%rcx          \n\t"  // save original Eflag to stack
nuclear@14:         "popfq                \n\t"  // restore original Eflag
nuclear@14: #else
nuclear@14:         "pushl %%ebx          \n\t"  // ebx gets clobbered by CPUID instruction
nuclear@14:         "pushl %%ecx          \n\t"  // so does ecx...
nuclear@14:         "pushl %%edx          \n\t"  // ...and edx (but ecx & edx safe on Linux)
nuclear@14:         "pushfl               \n\t"  // save Eflag to stack
nuclear@14:         "popl %%eax           \n\t"  // get Eflag from stack into eax
nuclear@14:         "movl %%eax, %%ecx    \n\t"  // make another copy of Eflag in ecx
nuclear@14:         "xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
nuclear@14:         "pushl %%eax          \n\t"  // save modified Eflag back to stack
nuclear@14:         "popfl                \n\t"  // restore modified value to Eflag reg
nuclear@14:         "pushfl               \n\t"  // save Eflag to stack
nuclear@14:         "popl %%eax           \n\t"  // get Eflag from stack
nuclear@14:         "pushl %%ecx          \n\t"  // save original Eflag to stack
nuclear@14:         "popfl                \n\t"  // restore original Eflag
nuclear@14: #endif
nuclear@14:         "xorl %%ecx, %%eax    \n\t"  // compare new Eflag with original Eflag
nuclear@14:         "jz 0f                \n\t"  // if same, CPUID instr. is not supported
nuclear@14: 
nuclear@14:         "xorl %%eax, %%eax    \n\t"  // set eax to zero
nuclear@14: //      ".byte  0x0f, 0xa2    \n\t"  // CPUID instruction (two-byte opcode)
nuclear@14:         "cpuid                \n\t"  // get the CPU identification info
nuclear@14:         "cmpl $1, %%eax       \n\t"  // make sure eax return non-zero value
nuclear@14:         "jl 0f                \n\t"  // if eax is zero, MMX is not supported
nuclear@14: 
nuclear@14:         "xorl %%eax, %%eax    \n\t"  // set eax to zero and...
nuclear@14:         "incl %%eax           \n\t"  // ...increment eax to 1.  This pair is
nuclear@14:                                      // faster than the instruction "mov eax, 1"
nuclear@14:         "cpuid                \n\t"  // get the CPU identification info again
nuclear@14:         "andl $0x800000, %%edx \n\t" // mask out all bits but MMX bit (23)
nuclear@14:         "cmpl $0, %%edx       \n\t"  // 0 = MMX not supported
nuclear@14:         "jz 0f                \n\t"  // non-zero = yes, MMX IS supported
nuclear@14: 
nuclear@14:         "movl $1, %%eax       \n\t"  // set return value to 1
nuclear@14:         "jmp  1f              \n\t"  // DONE:  have MMX support
nuclear@14: 
nuclear@14:     "0:                       \n\t"  // .NOT_SUPPORTED: target label for jump instructions
nuclear@14:         "movl $0, %%eax       \n\t"  // set return value to 0
nuclear@14:     "1:                       \n\t"  // .RETURN: target label for jump instructions
nuclear@14: #if defined(__x86_64__)
nuclear@14:         "popq %%rdx           \n\t"  // restore rdx
nuclear@14:         "popq %%rcx           \n\t"  // restore rcx
nuclear@14:         "popq %%rbx           \n\t"  // restore rbx
nuclear@14: #else
nuclear@14:         "popl %%edx           \n\t"  // restore edx
nuclear@14:         "popl %%ecx           \n\t"  // restore ecx
nuclear@14:         "popl %%ebx           \n\t"  // restore ebx
nuclear@14: #endif
nuclear@14: 
nuclear@14: //      "ret                  \n\t"  // DONE:  no MMX support
nuclear@14:                                      // (fall through to standard C "ret")
nuclear@14: 
nuclear@14:         : "=a" (result)              // output list
nuclear@14: 
nuclear@14:         :                            // any variables used on input (none)
nuclear@14: 
nuclear@14:                                      // no clobber list
nuclear@14: //      , "%ebx", "%ecx", "%edx"     // GRR:  we handle these manually
nuclear@14: //      , "memory"   // if write to a variable gcc thought was in a reg
nuclear@14: //      , "cc"       // "condition codes" (flag bits)
nuclear@14:     );
nuclear@14:     _mmx_supported = result;
nuclear@14: #else
nuclear@14:     _mmx_supported = 0;
nuclear@14: #endif /* PNG_MMX_CODE_SUPPORTED */
nuclear@14: 
nuclear@14:     return _mmx_supported;
nuclear@14: }
nuclear@14: #endif