Optimize Frame::fill_rgb/fill_rgba clip function, reduce code in BoolReader::read_bool match statement
#72
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`BoolReader::read_bool` match statement Rearranging the order of clamping allows for better autovectorization. Extract shared clip and mulhi functions outside of `Frame` Remove no-op returning branch value in `BoolReader::read_bool` match statement
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clipandmulhifunctions outside ofFramemember functionsBoolReader::read_boolmatch statementThe
clipfunction can be done with an arithmetic shift and then two packed saturating truncation operations, letting SIMD instructions clamp while casting fromi32tou8.Currently, that's inhibited by clipping to
.max(0)first, which results in a lot of select code formaxandminin baseline X86 instructions.Example in
portable_simdof what to look forhttps://rust.godbolt.org/z/f6cxThK75
You can see some of the effect if you right-click on
L11in both editors and reveal linked code. It results in about 40% less instructions in the main loop at label.LBB0_9,L20in the editors with reveal linked code.https://rust.godbolt.org/z/h1nM6cG4K
Noticed while poking around the profile from #71.