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eeb20775d2
This will help C++ code that uses exceptions to be tinier. For example, this change shaves away 1000 lines of assembly code from LLVM's libcxx, which is 0.7% of all assembly instructions in the entire library.
25 lines
1.1 KiB
C
25 lines
1.1 KiB
C
#ifndef COSMOPOLITAN_LIBC_BITS_POPCNT_H_
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#define COSMOPOLITAN_LIBC_BITS_POPCNT_H_
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#include "libc/nexgen32e/x86feature.h"
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COSMOPOLITAN_C_START_
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libcesque size_t _countbits(const void *, size_t);
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libcesque unsigned long popcnt(unsigned long) pureconst;
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#if defined(__GNUC__) && !defined(__STRICT_ANSI__) && defined(__x86_64__)
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#define popcnt(X) \
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(__builtin_constant_p(X) ? __builtin_popcountll(X) : ({ \
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unsigned long PoP = (X); \
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if (X86_HAVE(POPCNT)) { \
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asm("popcnt\t%0,%0" : "+r"(PoP) : /* no inputs */ : "cc"); \
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} else { \
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PoP = (popcnt)(PoP); \
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} \
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PoP; \
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}))
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#else
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#define popcnt(x) __builtin_popcountll(x)
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#endif /* GNUC && !ANSI */
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COSMOPOLITAN_C_END_
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#endif /* COSMOPOLITAN_LIBC_BITS_POPCNT_H_ */
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