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| author | drh <drh@noemail.net> | 2017-08-17 20:53:07 +0000 |
|---|---|---|
| committer | drh <drh@noemail.net> | 2017-08-17 20:53:07 +0000 |
| commit | ceb4b1dbdde735e851b3bf0d8656cfbe3c29b11a (patch) | |
| tree | 5fb309e0db55ceae92269aac6a92a892c5c4a6b3 /src/util.c | |
| parent | dceed86d07146bedbe8b54a613601d2db0d937f8 (diff) | |
| download | sqlite-ceb4b1dbdde735e851b3bf0d8656cfbe3c29b11a.tar.gz sqlite-ceb4b1dbdde735e851b3bf0d8656cfbe3c29b11a.zip | |
Use the __builtin_clzll() function of gcc to improve the performance and
reduce the size of the sqlite3LogEst() routine.
FossilOrigin-Name: a42a438cbbd721765ca55e71c464552dbaa494050cf472593599b8c7f0249516
Diffstat (limited to 'src/util.c')
| -rw-r--r-- | src/util.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/util.c b/src/util.c index 7c9c5f54b..a6d349296 100644 --- a/src/util.c +++ b/src/util.c @@ -1413,8 +1413,14 @@ LogEst sqlite3LogEst(u64 x){ if( x<2 ) return 0; while( x<8 ){ y -= 10; x <<= 1; } }else{ +#if GCC_VERSION>=5004000 + int i = 60 - __builtin_clzll(x); + y += i*10; + x >>= i; +#else while( x>255 ){ y += 40; x >>= 4; } /*OPTIMIZATION-IF-TRUE*/ while( x>15 ){ y += 10; x >>= 1; } +#endif } return a[x&7] + y - 10; } |