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[llvm-reduce] Add reduction passes to reduce operands to undef/1/0

Authored by aeubanks on Oct 13 2021, 4:00 PM.

Description

[llvm-reduce] Add reduction passes to reduce operands to undef/1/0

Having non-undef constants in a final llvm-reduce output is nicer than
having undefs.

This splits the existing reduce-operands pass into three, one which does
the same as the current pass of reducing to undef, and two more to
reduce to the constant 1 and the constant 0. Do not reduce to undef if
the operand is a ConstantData, and do not reduce 0s to 1s.

Reducing GEP operands very frequently causes invalid IR (since types may
not match up if we index differently into a struct), so don't touch GEPs.

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D111765