[llvm-dev] InstSimplify and computeKnownBits

[Craig Topper via llvm-dev]

Today, InstSimplify calls computeKnownBits to try to fold to a constant
ONLY if it can't find any other simplifications for an instruction.

I think this means if we are able to find an earlier simplification we are
LESS aggressive about creating a constant because we won't even look at
known bits. This seems surprising to me.

Should we be looking at known bits always, or should we remove this save
the compile time? How often does this allow us to simplify to a constant?

~Craig
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