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https://github.com/jart/cosmopolitan.git
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8da931a7f6
This program popped up on Hacker News recently. It's the only modern compiler I've ever seen that doesn't have dependencies and is easily modified. So I added all of the missing GNU extensions I like to use which means it might be possible soon to build on non-Linux and have third party not vendor gcc binaries.
33 lines
1.1 KiB
C
33 lines
1.1 KiB
C
#ifndef COSMOPOLITAN_LIBC_NEXGEN32E_BSF_H_
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#define COSMOPOLITAN_LIBC_NEXGEN32E_BSF_H_
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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COSMOPOLITAN_C_START_
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/*
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* BIT SCANNING 101
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* ctz(𝑥) 31^clz(𝑥) clz(𝑥)
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* uint32 𝑥 bsf(𝑥) tzcnt(𝑥) ffs(𝑥) bsr(𝑥) lzcnt(𝑥)
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* 0x00000000 wut 32 0 wut 32
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* 0x00000001 0 0 1 0 31
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* 0x80000001 0 0 1 31 0
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* 0x80000000 31 31 32 31 0
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* 0x00000010 4 4 5 4 27
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* 0x08000010 4 4 5 27 4
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* 0x08000000 27 27 28 27 4
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* 0xffffffff 0 0 1 31 0
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*/
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int bsf(int);
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int bsfl(long);
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int bsfll(long long);
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int bsfmax(uintmax_t);
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#ifdef __GNUC__
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#define bsf(u) __builtin_ctz(u)
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#define bsfl(u) __builtin_ctzl(u)
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#define bsfll(u) __builtin_ctzll(u)
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#endif
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COSMOPOLITAN_C_END_
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_NEXGEN32E_BSF_H_ */
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