[llvm-dev] Interest in fast BitVector?

David Greene via llvm-dev llvm-dev at lists.llvm.org
Thu Sep 20 10:19:59 PDT 2018

Some time ago I developed a fast BitVector class to use in some research
here.  It uses expression templates to fuse operation loops and runs
much faster than the existing BitVector for some important use-cases.
It also has the ability to efficiently report if a BitVector's contents
changed after some operation.  For example:

ETBitVector A = ...
ETBitVector B = ...
ETBitVector C = ...

bool Changed = A.assign(A & B | ~C);  // Bit operation loops fused

Using this resulted in 100x or more speedup over BitVector.  Obviously,
the speedup is greater the more operations are chained together.  For a
simple A.assign(A & B) it wouldn't be terribly faster.  But the ability
to report a change efficiently can be useful even for simple operations.

I based this off an old version of BitVector.  At the time it was a
drop-in replacement but it would need some updating to conform to the
current BitVector interface.

Before I do that work, is there any interest in this?


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