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