[SelectionDAG] Generalise SelectionDAG::computeOverflowKind to support other opcodes

[RKSimon]

Bugzilla Link	37761
Version	trunk
OS	Windows NT
CC	@deadalnix,@LebedevRI,@rotateright

Extended Description

SelectionDAG::computeOverflowKind is currently only to be used for additions; it'd be useful for it to also handle signed/unsigned ISD::SUB and ISD::MUL (to cover all the SADDO/UADD, SSUBO/USUBO and SMULO/UMULO nodes).

[RKSimon]

This has now been split into:

computeOverflowForSignedAdd
computeOverflowForUnsignedAdd
computeOverflowForSignedSub
computeOverflowForUnsignedSub

These more closely match the InstCombine methods, so we're just missing:

computeOverflowForSignedMul
computeOverflowForUnsignedMul

It might be useful to add similar helpers to detect exact shifts.

[llvmbot]

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[elhewaty]

I will work on this

[elhewaty]

@RKSimon Candidate Patch: https://reviews.llvm.org/D159406

[RKSimon]

We also need to extend the computeOverflowForSignedSub/computeOverflowForUnsignedSub implementations with ConstantRange - I think this will mainly involve adding test coverage.

[elhewaty]

OK, I am working on it now

[RKSimon]

computeOverflowForSignedMul
computeOverflowForUnsignedMul
Additional Tests: e086e0a
Fixed: 741c127

[elhewaty]

@RKSimon Here is the new pull : #67890