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发表于 2004-6-2 08:25:15
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可能是gcc在对循环结构进行循环展开。
[quote:c13bb0fcea="cnhnln"]用了优化参数编译以后快慢感觉不到,倒是明显发现编译出的程序大了不少
另外,看了一下 http://www.freehackers.org/gentoo/gccflags/faq.html
它是通过gcc-3.2/gcc/toplevel.c和gcc-3.2/gcc/config/i386/i386.c来确定优化参数的。
gcc3.4的i386.c里有如下的定义
[code:1] const processor_alias_table[] =
{
{"i386", PROCESSOR_I386, 0},
{"i486", PROCESSOR_I486, 0},
{"i586", PROCESSOR_PENTIUM, 0},
{"pentium", PROCESSOR_PENTIUM, 0},
{"pentium-mmx", PROCESSOR_PENTIUM, PTA_MMX},
{"winchip-c6", PROCESSOR_I486, PTA_MMX},
{"winchip2", PROCESSOR_I486, PTA_MMX | PTA_3DNOW},
{"c3", PROCESSOR_I486, PTA_MMX | PTA_3DNOW},
{"c3-2", PROCESSOR_PENTIUMPRO, PTA_MMX | PTA_PREFETCH_SSE | PTA_SSE},
{"i686", PROCESSOR_PENTIUMPRO, 0},
{"pentiumpro", PROCESSOR_PENTIUMPRO, 0},
{"pentium2", PROCESSOR_PENTIUMPRO, PTA_MMX},
{"pentium3", PROCESSOR_PENTIUMPRO, PTA_MMX | PTA_SSE | PTA_PREFETCH_SSE},
{"pentium4", PROCESSOR_PENTIUM4, PTA_SSE | PTA_SSE2 |
PTA_MMX | PTA_PREFETCH_SSE},
{"k6", PROCESSOR_K6, PTA_MMX},
{"k6-2", PROCESSOR_K6, PTA_MMX | PTA_3DNOW},
{"k6-3", PROCESSOR_K6, PTA_MMX | PTA_3DNOW},
{"athlon", PROCESSOR_ATHLON, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW
| PTA_3DNOW_A},
{"athlon-tbird", PROCESSOR_ATHLON, PTA_MMX | PTA_PREFETCH_SSE
| PTA_3DNOW | PTA_3DNOW_A},
{"athlon-4", PROCESSOR_ATHLON, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW
| PTA_3DNOW_A | PTA_SSE},
{"athlon-xp", PROCESSOR_ATHLON, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW
| PTA_3DNOW_A | PTA_SSE},
{"athlon-mp", PROCESSOR_ATHLON, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW
| PTA_3DNOW_A | PTA_SSE},
{"x86-64", PROCESSOR_K8, PTA_MMX | PTA_PREFETCH_SSE | PTA_64BIT
| PTA_SSE | PTA_SSE2 },
{"k8", PROCESSOR_K8, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW | PTA_64BIT
| PTA_3DNOW_A | PTA_SSE | PTA_SSE2},
{"opteron", PROCESSOR_K8, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW | PTA_64BIT
| PTA_3DNOW_A | PTA_SSE | PTA_SSE2},
{"athlon64", PROCESSOR_K8, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW | PTA_64BIT
| PTA_3DNOW_A | PTA_SSE | PTA_SSE2},
{"athlon-fx", PROCESSOR_K8, PTA_MMX | PTA_PREFETCH_SSE | PTA_3DNOW | PTA_64BIT
| PTA_3DNOW_A | PTA_SSE | PTA_SSE2},
};[/code:1]
但是toplevel.c的定义方式变了,看不明白。请教![/quote] |
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