Refactored UInt32 and UInt64 methods nextPowerOf2 #371
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adamnemecek
changed the title
Sources/NIO/ByteBuffer-int.swift
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| n += 1 | ||
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| return n | ||
| return 1 << (64 - (self - 1).leadingZeroBitCount) |
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@adamnemecek ah nice, didn't know we had leadingZeroBitCount, hope that gets lowered to the LZCNT instruction.
You can actually get the number of bits a type has from Self.bitWidth. Then the code for all unsigned integer types will actually be the same. You can probably just put the extension on UnsignedInteger and you'll get it for all.
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It uses bsr https://godbolt.org/g/A9RjhW
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@adamnemecek awesome, thank you! TIL that godbolt supports Swift, how cool's that!
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You can guess who added the support. His name starts with A and ends with dam Nemecek.
Sources/NIO/ByteBuffer-int.swift
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| @@ -97,22 +97,10 @@ extension ByteBuffer { | |||
| extension UInt64 { | |||
| /// Returns the next power of two. | |||
| public func nextPowerOf2() -> UInt64 { | |||
| guard self > 0 else { | |||
| if self == 0 { | |||
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I don't think we should take this change. Happy to make it guard self != 0 else { ... } though. But the guard tells/should tell the compiler that this is the less likely case and it can optimise for that.
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@swift-nio-bot test this please |
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@swift-nio-bot test this please |
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@swift-nio-bot test this please |
Refactored nextPowerOf2 methods.
Motivation:
Make them shorter and somewhat faster.
Modifications:
Changed the implementations of nextPowerOf2
Result:
Methods are shorter.