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| author | Tavian Barnes <tavianator@tavianator.com> | 2016-06-11 10:20:38 -0400 |
|---|---|---|
| committer | Tavian Barnes <tavianator@tavianator.com> | 2016-06-11 10:20:38 -0400 |
| commit | b0d923ffd5feb4a1d432082718857ead67c9b49d (patch) | |
| tree | 3ade306881cd55421b4882b668f4b16a97468be8 /RELEASES.md | |
| parent | 88cc26afec80dae40d8e08de0e6db6c308e64f79 (diff) | |
| download | bfs-b0d923ffd5feb4a1d432082718857ead67c9b49d.tar.xz | |
RELEASES.md: Be less verbose about optimization levels.
Diffstat (limited to 'RELEASES.md')
| -rw-r--r-- | RELEASES.md | 41 |
1 files changed, 7 insertions, 34 deletions
diff --git a/RELEASES.md b/RELEASES.md index 3d75210..cdfd778 100644 --- a/RELEASES.md +++ b/RELEASES.md @@ -10,41 +10,14 @@ 62/76 GNU find features supported. - Rework optimization levels - - `-O1` (logical simplification): - - Constant propagation (`! -false <==> -true`, `! -true <==> -false`) - - Double negation (`! ! X <==> X`) - - Conjunction elimination: - - `-true -a X <==> X` - - `X -a -true <==> X` - - Disjunctive syllogism: - - `-false -o X <==> X` - - `X -o -false <==> X` - - Short-circuiting: - - `-false -a X <==> -false` - - `-true -o X <==> -true` - - De Morgan's laws (**new**): - - `( ! X -a ! Y ) <==> ! ( X -o Y )` - - `( ! X -o ! Y ) <==> ! ( X -a Y )` - - `! ( X -a ! Y ) <==> ( ! X -o Y )` - - `! ( X -o ! Y ) <==> ( ! X -a Y )` - - `! ( ! X -a Y ) <==> ( X -o ! Y )` - - `! ( ! X -o Y ) <==> ( X -a ! Y )` - - Unused result (**new**): `! X , Y <==> X , Y` - - `-O2` (purity): - - (These optimizations take the purity of predicates into account, allowing side-effect-free tests like `-name` or `-type` to be moved or removed) - - `PURE -a -false <==> -false` - - `PURE -o -true <==> -true` - - `PURE , X <==> X` - - Top-level unused result (**new**): `X (-a|-o|,) PURE <==> X` - - `-O3` (cost-based, **default**): + - `-O1` + - Simple boolean simplification + - `-O2` + - Purity-based optimizations, allowing side-effect-free tests like `-name` or `-type` to be moved or removed + - `-O3` (**default**): - Re-order tests to reduce the expected cost (TODO) - - `-O4` (aggressive): - - (These are very aggressive optimizations that may have surprising effects on warning/error messages and runtime, but still should not affect the resulting output) - - Change top-level expressions with no actions to `-false` (**new**): - - For example, `bfs -O4 -true -o -print` becomes `-false`, because `-print` is unreachable - - Skip the entire traversal if the top-level expression is `-false` - - `bfs -O4 -false` (or anything that optimizes to `-false`) will exit immediately - - This may cause messages about non-existent files, symbolic link cycles, etc. to be skipped + - `-O4` + - Aggressive optimizations that may have surprising effects on warning/error messages and runtime, but should not otherwise affect the results - `-Ofast`: - Always the highest level, currently the same as `-O4` - Color files with multiple hard links correctly |