Codechange: Add fast path to catenary drawing in MaskWireBits #8841
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JGRennison
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michicc
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MaskWireBits always returns its input unchanged if the input has only 0 or 1 track bits set. Having only 0 or 1 track bits sets (i.e. non junction tiles) is by far the most common case. Examining the state of neighbouring tiles and the subsequent masking logic is relatively expensive and can be omitted in this case.
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michicc
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Motivation / Problem
MaskWireBits always returns its input unchanged if the input has only 0 or 1 track bits set.
Having only 0 or 1 track bits sets (i.e. non junction tiles) is by far the most common case.
Examining the state of neighbouring tiles and the subsequent masking logic is relatively expensive and can be omitted in this case.
Description
Return immediately in the common/trivial case of only 0 or 1 set track bits in the input.
This produces a measurable improvement in catenary drawing performance. (Measured previously in my branch using valgrind/callgrind/FPS window).
Limitations
N/A
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.