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[Bitstream] Define VBRZ encoding, and use VBRZ6 for unabbreviated values
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Authored by sammccall on May 19 2022, 5:55 PM.
This is a draft revision that has not yet been submitted for review.

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Summary

When we don't know what we're encoding, chances are it's zero often
enough that providing a 1-bit encoding of zero is a win.

This seems to be roughly size-neutral on LLVM bitcode, and reduces Clang
PCH files by ~9%.

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sammccall created this revision.May 19 2022, 5:55 PM
Herald added a project: Restricted Project. · View Herald TranscriptMay 19 2022, 5:55 PM
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MaskRay added inline comments.
llvm/lib/Bitstream/Reader/BitstreamReader.cpp
110

Why is this unconditionally true?