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comparison ext/libpng-1.2.29/pnggccrd.c @ 0:4a0efb7baf70

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* Datasets becomes the new trunk and retires after that :-)
author mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
date Sun, 29 Jun 2008 18:44:17 +0000
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-1:000000000000 0:4a0efb7baf70
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