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| author | Cosmin Cojocar <cosmin.cojocar@gmail.com> | 2010-04-18 18:25:06 +0200 |
|---|---|---|
| committer | Cosmin Cojocar <cosmin.cojocar@gmail.com> | 2010-04-20 22:13:26 +0200 |
| commit | e339343c9c698a887681771372ba6cc58a79c707 (patch) | |
| tree | 237302fed1f7a04f82776488cb922b66b55d2d56 /dexdump | |
| parent | b16b78db118036d7df2cf5705baa18f34bd42eec (diff) | |
| download | android_dalvik-e339343c9c698a887681771372ba6cc58a79c707.tar.gz android_dalvik-e339343c9c698a887681771372ba6cc58a79c707.tar.bz2 android_dalvik-e339343c9c698a887681771372ba6cc58a79c707.zip | |
Improve the implementation of countOnes function to use only 12 operations.
Change-Id: I01b62606a0c87b2937572f8cb7beafc956867353
Diffstat (limited to 'dexdump')
| -rw-r--r-- | dexdump/DexDump.c | 12 |
1 files changed, 3 insertions, 9 deletions
diff --git a/dexdump/DexDump.c b/dexdump/DexDump.c index 6fed7aaf4..ccb6e0afc 100644 --- a/dexdump/DexDump.c +++ b/dexdump/DexDump.c @@ -225,20 +225,14 @@ static const char* quotedVisibility(u4 accessFlags) /* * Count the number of '1' bits in a word. - * - * Having completed this, I'm ready for an interview at Google. - * - * TODO? there's a parallel version w/o loops. Performance not currently - * important. */ static int countOnes(u4 val) { int count = 0; - while (val != 0) { - val &= val-1; - count++; - } + val = val - ((val >> 1) & 0x55555555); + val = (val & 0x33333333) + ((val >> 2) & 0x33333333); + count = (((val + (val >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24; return count; } |