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qemu/host-utils.h: Reduce the operation count in the fallback ctpop 

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
master
Richard Henderson 2016-11-21 12:30:34 +01:00
parent 4885c3c495
commit 7bdcecb7b2
1 changed files with 11 additions and 14 deletions
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25
include/qemu/host-utils.h
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@ -327,7 +327,7 @@ static inline int ctpop8(uint8_t val)
#else
val = (val & 0x55) + ((val >> 1) & 0x55);
val = (val & 0x33) + ((val >> 2) & 0x33);
val = (val & 0x0f) + ((val >> 4) & 0x0f);
val = (val + (val >> 4)) & 0x0f;
return val;
#endif
@ -344,8 +344,8 @@ static inline int ctpop16(uint16_t val)
#else
val = (val & 0x5555) + ((val >> 1) & 0x5555);
val = (val & 0x3333) + ((val >> 2) & 0x3333);
val = (val & 0x0f0f) + ((val >> 4) & 0x0f0f);
val = (val & 0x00ff) + ((val >> 8) & 0x00ff);
val = (val + (val >> 4)) & 0x0f0f;
val = (val + (val >> 8)) & 0x00ff;
return val;
#endif
@ -360,11 +360,10 @@ static inline int ctpop32(uint32_t val)
#if QEMU_GNUC_PREREQ(3, 4)
return __builtin_popcount(val);
#else
val = (val & 0x55555555) + ((val >> 1) & 0x55555555);
val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
val = (val & 0x0f0f0f0f) + ((val >> 4) & 0x0f0f0f0f);
val = (val & 0x00ff00ff) + ((val >> 8) & 0x00ff00ff);
val = (val & 0x0000ffff) + ((val >> 16) & 0x0000ffff);
val = (val & 0x55555555) + ((val >> 1) & 0x55555555);
val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
val = (val + (val >> 4)) & 0x0f0f0f0f;
val = (val * 0x01010101) >> 24;
return val;
#endif
@ -379,12 +378,10 @@ static inline int ctpop64(uint64_t val)
#if QEMU_GNUC_PREREQ(3, 4)
return __builtin_popcountll(val);
#else
val = (val & 0x5555555555555555ULL) + ((val >> 1) & 0x5555555555555555ULL);
val = (val & 0x3333333333333333ULL) + ((val >> 2) & 0x3333333333333333ULL);
val = (val & 0x0f0f0f0f0f0f0f0fULL) + ((val >> 4) & 0x0f0f0f0f0f0f0f0fULL);
val = (val & 0x00ff00ff00ff00ffULL) + ((val >> 8) & 0x00ff00ff00ff00ffULL);
val = (val & 0x0000ffff0000ffffULL) + ((val >> 16) & 0x0000ffff0000ffffULL);
val = (val & 0x00000000ffffffffULL) + ((val >> 32) & 0x00000000ffffffffULL);
val = (val & 0x5555555555555555ULL) + ((val >> 1) & 0x5555555555555555ULL);
val = (val & 0x3333333333333333ULL) + ((val >> 2) & 0x3333333333333333ULL);
val = (val + (val >> 4)) & 0x0f0f0f0f0f0f0f0fULL;
val = (val * 0x0101010101010101ULL) >> 56;
return val;
#endif