mirror of
https://git.code.sf.net/p/libpng/code.git
synced 2025-07-10 18:04:09 +02:00
104 lines
4.7 KiB
C
104 lines
4.7 KiB
C
/* pnggccrd.c was removed from libpng-1.2.20. */
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/* This code snippet is for use by configure's compilation test. */
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#if (!defined _MSC_VER) && \
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defined(PNG_ASSEMBLER_CODE_SUPPORTED) && \
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defined(PNG_MMX_CODE_SUPPORTED)
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int PNGAPI png_dummy_mmx_support(void);
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static int _mmx_supported = 2; // 0: no MMX; 1: MMX supported; 2: not tested
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int PNGAPI
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png_dummy_mmx_support(void) __attribute__((noinline));
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int PNGAPI
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png_dummy_mmx_support(void)
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{
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int result;
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#ifdef PNG_MMX_CODE_SUPPORTED // superfluous, but what the heck
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__asm__ __volatile__ (
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#ifdef __x86_64__
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"pushq %%rbx \n\t" // rbx gets clobbered by CPUID instruction
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"pushq %%rcx \n\t" // so does rcx...
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"pushq %%rdx \n\t" // ...and rdx (but rcx & rdx safe on Linux)
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"pushfq \n\t" // save Eflag to stack
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"popq %%rax \n\t" // get Eflag from stack into rax
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"movq %%rax, %%rcx \n\t" // make another copy of Eflag in rcx
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"xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
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"pushq %%rax \n\t" // save modified Eflag back to stack
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"popfq \n\t" // restore modified value to Eflag reg
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"pushfq \n\t" // save Eflag to stack
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"popq %%rax \n\t" // get Eflag from stack
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"pushq %%rcx \n\t" // save original Eflag to stack
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"popfq \n\t" // restore original Eflag
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#else
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"pushl %%ebx \n\t" // ebx gets clobbered by CPUID instruction
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"pushl %%ecx \n\t" // so does ecx...
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"pushl %%edx \n\t" // ...and edx (but ecx & edx safe on Linux)
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"pushfl \n\t" // save Eflag to stack
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"popl %%eax \n\t" // get Eflag from stack into eax
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"movl %%eax, %%ecx \n\t" // make another copy of Eflag in ecx
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"xorl $0x200000, %%eax \n\t" // toggle ID bit in Eflag (i.e., bit 21)
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"pushl %%eax \n\t" // save modified Eflag back to stack
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"popfl \n\t" // restore modified value to Eflag reg
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"pushfl \n\t" // save Eflag to stack
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"popl %%eax \n\t" // get Eflag from stack
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"pushl %%ecx \n\t" // save original Eflag to stack
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"popfl \n\t" // restore original Eflag
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#endif
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"xorl %%ecx, %%eax \n\t" // compare new Eflag with original Eflag
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"jz 0f \n\t" // if same, CPUID instr. is not supported
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"xorl %%eax, %%eax \n\t" // set eax to zero
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// ".byte 0x0f, 0xa2 \n\t" // CPUID instruction (two-byte opcode)
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"cpuid \n\t" // get the CPU identification info
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"cmpl $1, %%eax \n\t" // make sure eax return non-zero value
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"jl 0f \n\t" // if eax is zero, MMX is not supported
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"xorl %%eax, %%eax \n\t" // set eax to zero and...
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"incl %%eax \n\t" // ...increment eax to 1. This pair is
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// faster than the instruction "mov eax, 1"
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"cpuid \n\t" // get the CPU identification info again
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"andl $0x800000, %%edx \n\t" // mask out all bits but MMX bit (23)
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"cmpl $0, %%edx \n\t" // 0 = MMX not supported
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"jz 0f \n\t" // non-zero = yes, MMX IS supported
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"movl $1, %%eax \n\t" // set return value to 1
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"jmp 1f \n\t" // DONE: have MMX support
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"0: \n\t" // .NOT_SUPPORTED: target label for jump instructions
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"movl $0, %%eax \n\t" // set return value to 0
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"1: \n\t" // .RETURN: target label for jump instructions
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#ifdef __x86_64__
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"popq %%rdx \n\t" // restore rdx
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"popq %%rcx \n\t" // restore rcx
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"popq %%rbx \n\t" // restore rbx
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#else
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"popl %%edx \n\t" // restore edx
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"popl %%ecx \n\t" // restore ecx
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"popl %%ebx \n\t" // restore ebx
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#endif
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// "ret \n\t" // DONE: no MMX support
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// (fall through to standard C "ret")
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: "=a" (result) // output list
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: // any variables used on input (none)
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// no clobber list
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// , "%ebx", "%ecx", "%edx" // GRR: we handle these manually
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// , "memory" // if write to a variable gcc thought was in a reg
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// , "cc" // "condition codes" (flag bits)
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);
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_mmx_supported = result;
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#else
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_mmx_supported = 0;
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#endif /* PNG_MMX_CODE_SUPPORTED */
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return _mmx_supported;
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}
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#endif
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