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| author | Lasse Collin <lasse.collin@tukaani.org> | 2008-03-22 14:39:34 +0200 |
|---|---|---|
| committer | Lasse Collin <lasse.collin@tukaani.org> | 2008-03-22 14:39:34 +0200 |
| commit | ad999efd279d95f1e7ac555b14170e8e9020488c (patch) | |
| tree | cdce2697597ab1e52511ff336fe3819840a821c8 | |
| parent | Added autoconf check to detect if we can use arithmetic (diff) | |
| download | xz-ad999efd279d95f1e7ac555b14170e8e9020488c.tar.xz | |
Take advantage of arithmetic right shift in range decoder.
| -rw-r--r-- | src/liblzma/rangecoder/range_decoder.h | 52 |
1 files changed, 37 insertions, 15 deletions
diff --git a/src/liblzma/rangecoder/range_decoder.h b/src/liblzma/rangecoder/range_decoder.h index f3dcc84e..a6a92b0b 100644 --- a/src/liblzma/rangecoder/range_decoder.h +++ b/src/liblzma/rangecoder/range_decoder.h @@ -121,14 +121,26 @@ do { \ } while (0) -#define rc_decode_direct(dest, count) \ -do { \ - rc_normalize(); \ - rc.range >>= 1; \ - rc_bound = (rc.code - rc.range) >> 31; \ - rc.code -= rc.range & (rc_bound - 1); \ - dest = ((dest) << 1) | (1 - rc_bound);\ -} while (--count > 0) +#ifdef HAVE_ARITHMETIC_RSHIFT +# define rc_decode_direct(dest, count) \ + do { \ + rc_normalize(); \ + rc.range >>= 1; \ + rc.code -= rc.range; \ + rc_bound = (uint32_t)((int32_t)(rc.code) >> 31); \ + dest = (dest << 1) + (rc_bound + 1); \ + rc.code += rc.range & rc_bound; \ + } while (--count > 0) +#else +# define rc_decode_direct(dest, count) \ + do { \ + rc_normalize(); \ + rc.range >>= 1; \ + rc_bound = (rc.code - rc.range) >> 31; \ + rc.code -= rc.range & (rc_bound - 1); \ + dest = ((dest) << 1) | (1 - rc_bound);\ + } while (--count > 0) +#endif // Dummy versions don't update prob or dest. @@ -143,13 +155,23 @@ do { \ } while (0) -#define rc_decode_direct_dummy(count) \ -do { \ - rc_normalize(); \ - rc.range >>= 1; \ - rc_bound = (rc.code - rc.range) >> 31; \ - rc.code -= rc.range & (rc_bound - 1); \ -} while (--count > 0) +#ifdef HAVE_ARITHMETIC_RSHIFT +# define rc_decode_direct_dummy(count) \ + do { \ + rc_normalize(); \ + rc.range >>= 1; \ + rc.code -= rc.range; \ + rc.code += rc.range & ((uint32_t)((int32_t)(rc.code) >> 31)); \ + } while (--count > 0) +#else +# define rc_decode_direct_dummy(count) \ + do { \ + rc_normalize(); \ + rc.range >>= 1; \ + rc_bound = (rc.code - rc.range) >> 31; \ + rc.code -= rc.range & (rc_bound - 1); \ + } while (--count > 0) +#endif /////////////////////// |