[WIP] [stdlib] Implement more efficient DoubleWidth division and fix division-related bugs #13784
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| /// | ||
| /// The resulting quotient must be representable within the bounds of the | ||
| /// type. If the quotient of dividing `dividend` by this value is too large | ||
| /// to represent in the type, a runtime error may occur. | ||
| /// | ||
| /// - Parameter dividend: A tuple containing the high and low parts of a | ||
| /// double-width integer. The `high` component of the value carries the | ||
| /// sign, if the type is signed. |
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This is a potentially confusing remark because it is not found anywhere else, even though a similar tuple is accepted as an argument or returned in many other places.
The two's complement value will differ from its magnitude in both the high and low parts, and it's highly doubtful that anyone will wonder if it's the low component that carries the actual sign bit itself.
xwu
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Still missing tests, but let's see how this does. |
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@swift-ci Please smoke test OS X platform |
| @_inlineable // FIXME(sil-serialize-all) | ||
| public // @testable |
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Although it appears that this initializer was originally not intended for public consumption, the documentation tells users to use it. In fact, this initializer is promoted as part of the main use case for DoubleWidth (and I would agree with that characterization).
xwu
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@swift-ci Please smoke benchmark |
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@swift-ci Please smoke benchmark |
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!!! Couldn't read commit file !!! |
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@shahmishal What does it mean when swift-ci says "!!! Couldn't read commit file !!!" and refuses to benchmark? Or, more to the point, what can I do about it? |
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@swift-ci Please smoke benchmark |
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@swift-ci Please smoke test OS X platform |
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@swift-ci Please smoke test OS X platform |
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Yikes, why is CI failing... |
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@swift-ci Please clean smoke test OS X platform |
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!!! Couldn't read commit file !!! |
This PR implements more efficient
DoubleWidthdivision using full-width division primitives available onBase.Also in this PR:
DoubleWidth.swift.gyb.DoubleWidthdocumentation.DoubleWidthmasking shifts.remainderReportingOverflowanddividedReportingOverflow.remainderReportingOverflowfor builtin types when dividing by-1.{U}Int64.dividingFullWidthin terms ofDoubleWidth<{U}Int32>.dividingFullWidth.DoubleWidth.dividingFullWidthandDoubleWidth.quotientAndRemainder.Not in this PR:
dividingFullWidthoverflow by using_checked_trunc_instead of_truncOrBitCast_operations, and add tests for overflow.