JIT: Expand optRelopImpliesRelop for constants as op1

[jakobbotsch]

VN does not guarantee that constants in relops are first, so swap them if this isn't the case.

Need this to be able to utilize optRelopImpliesRelop to answer overflow related questions for strength reduction.

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[jakobbotsch]

cc @dotnet/jit-contrib PTAL @EgorBo @AndyAyersMS

Diffs

[tannergooding]

If not being handled in this PR, could you log an issue for enabling the same to be done for TYP_SIMD?

We have all the same relops and same transforms that are valid there as well, so it'd be nice to ensure consistency

[jakobbotsch]

I'm not really sure what that would entail. We already give up on relops between floating points because many of these inferences don't hold there.
I think you should open an issue about the inferences you think we should be able to make for these.

[tannergooding]

Commutative swapping should still apply. That is, x > y is the same as y < x even for floating-point.

What doesn't hold true is that x > y is not the same as !(x <= y) (but only due to NaN, so if we know the inputs aren't NaN it becomes safe)

[tannergooding]

I'll work on getting an issue open for it

[jakobbotsch]

This PR doesn't do the kind of general canonicalization of VNs we were discussing on Discord the other day. Since @SingleAccretion pointed out that this came with non-trivial TP considerations, I just decided to do the easy thing and canonicalize right at this point, which is part of RBO's reasoning about inequalities. This PR doesn't really change much except it allows some of that reasoning to apply for a few more cases.

[EgorBo]

Regarding swap relops, I think I've seen locally the same diffs If I put it here

runtime/src/coreclr/jit/valuenum.cpp

Lines 2629 to 2639 in 776ff7e

	// We canonicalize commutative operations.
	// (Perhaps should eventually handle associative/commutative [AC] ops -- but that gets complicated...)
	if (VNFuncIsCommutative(func))
	{
	// Order arg0 arg1 by numerical VN value.
	if (arg0VN > arg1VN)
	{
	std::swap(arg0VN, arg1VN);
	}
	}

Namely, oper is compare and op1 is IsVNConstant (but not handle!) -> swap

[jakobbotsch]

Regarding swap relops, I think I've seen locally the same diffs If I put it here

runtime/src/coreclr/jit/valuenum.cpp

Lines 2629 to 2639 in 776ff7e

	// We canonicalize commutative operations.
	// (Perhaps should eventually handle associative/commutative [AC] ops -- but that gets complicated...)
	if (VNFuncIsCommutative(func))
	{
	// Order arg0 arg1 by numerical VN value.
	if (arg0VN > arg1VN)
	{
	std::swap(arg0VN, arg1VN);
	}
	}

Namely, oper is compare and op1 is IsVNConstant (but not handle!) -> swap

I think if we want to canonicalize constants we should do it consistently, not just to target this one specific transformation on relops. But it sounds like that takes some more work, so I will leave it for another time.

[AndyAyersMS]

LGTM too