Fix Float/Double .nextUp/.nextDown on arm(v7). #2879
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On armv7, leastNonzeroMagnitude is defined to be leastNormalMagnitude. This seems wrong to me from a language point of view, because it's possible to have a nonzero float that compares less than the leastNonzero float. However, it must have been done to gloss over hardware rounding errors. This is not a problem on arm64. As a result, nextUp/Down methods were not self-consistent. I fixed this by skipping over subnormal representations, following the precedent set by leastNonZeroMagnitude. This fixes the FloatingPoint floatNextUpDownTests on armv7.
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@swift-ci Please smoke test and merge. |
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Not sure what the linux package manager failure is about, but it's not from this change. |
MaxDesiatov
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Apr 19, 2021
[pull] swiftwasm from main
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On armv7, leastNonzeroMagnitude is defined to be leastNormalMagnitude.
This seems wrong to me from a language point of view, because it's
possible to have a nonzero float that compares less than the leastNonzero float.
However, it must have been done to gloss over hardware rounding errors.
This is not a problem on arm64.
As a result, nextUp/Down methods were not self-consistent. I fixed
this by skipping over subnormal representations, following the
precedent set by leastNonZeroMagnitude.
This fixes the FloatingPoint floatNextUpDownTests on armv7.