[PATCH] D147866: ValueTracking: Implement computeKnownFPClass for minnum/maxnum

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D147866#4272135 <https://reviews.llvm.org/D147866#4272135>, @arsenm wrote:

> In D147866#4269440 <https://reviews.llvm.org/D147866#4269440>, @jcranmer-intel wrote:
>
>> In D147866#4269363 <https://reviews.llvm.org/D147866#4269363>, @arsenm wrote:
>>
>>> In D147866#4269348 <https://reviews.llvm.org/D147866#4269348>, @jcranmer-intel wrote:
>>>
>>>> `minnum(0.0, 0.0)` can return `-0.0`, so the handling around positive/negative zero isn't correct.
>
> The sign is of zero is not indeterminate. minnum(0.0, 0.0) cannot choose to introduce a signed zero. The ordering of a positive zero and negative zero is undetermined.

Section 11 states "Do not depend on the sign of a zero result or the quantum of a decimal result for minNum(x, y), maxNum(x, y), minNumMag(x, y), or maxNumMag(x, y) when x and y are equal.". But the definition for minNum and maxNum state it returns x or y. Returning -0 would be returning a value that is neither x nor y, so I maintain the handling here is correct as-is


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