[IRSim] Adding support for isomorphic predicates

[AndrewLitteken]

Summary

Some predicates, can be considered the same as long as the operands are flipped. For example, a > b gives the same result as b > a. This maps instructions in a greater than form, to their appropriate less than form, swapping the operands in the IRInstructionData only, allowing for more flexible matching.

Tests:

• llvm/test/Transforms/IROutliner/outlining-isomorphic-predicates.ll
• llvm/unittests/Analysis/IRSimilarityIdentifierTest.cpp

[jroelofs]

llvm/lib/Analysis/IRSimilarityIdentifier.cpp

87

Should equality and inequality also be canonicalized? Maybe your hash function can be tweaked to use an operation that's commutative specifically in that case.

[jroelofs]

llvm/lib/Analysis/IRSimilarityIdentifier.cpp

87

Oh, I see that's being handled here: https://reviews.llvm.org/D87311

[jroelofs]

LGTM

llvm/include/llvm/Analysis/IRSimilarityIdentifier.h

138–139

Since we generally don't build with exceptions turned on, it makes more sense to talk about what's allowed/not in the function's contract, rather than mentioning that assertion failures "throw".

[AndrewLitteken]

A few things changed just enough since OperTypes was removed, so updating the diff to reflect this.