add Math.signbit #333
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add Math.signbit #333
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dcodeIO
reviewed
Nov 17, 2018
dcodeIO
reviewed
Nov 17, 2018
std/assembly/math.ts
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| @@ -2046,6 +2053,11 @@ export namespace NativeMathf { | |||
| } | |||
| } | |||
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| @inline | |||
| export function signbit(x: f32): bool { | |||
| return <bool>((reinterpret<u32>(x) >>> 31) & <i32>(x == x)); | |||
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This looks like it might result in an unnecessary & 1 to convert from i32 to bool. A better way to write it is: <bool>(reinterpret<u32>(x) >>> 31) & (x == x), as it keeps type conversions to a minimum.
dcodeIO
reviewed
Nov 17, 2018
std/assembly/math.ts
Outdated
| export function signbit(x: f64): bool { | ||
| // In ECMAScript all NaN values are indistinguishable from each other | ||
| // so we need handle NaN and negative NaN in similar way | ||
| return <bool>(<i32>(reinterpret<u64>(x) >>> 63 != 0) & <i32>(x == x)); |
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Similar to the f32 version, the != 0 instruction can be saved here as well.
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I'm not sure. Because without != 0 u64 will be cast (extend op code) to i32 anyway
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Oh, actually != 0 doesn't matter because it has to convert from 64 to 32 bits anyway.
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Thank you! |
willemneal
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to willemneal/assemblyscript
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Dec 26, 2018
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