Most programming languages does have 128-bit of type except Swift.
I don't think there is huge demand for a full-blown Int128 type in the standard library, but it would be nice to have double-width multiplication & division methods in Swift's existing integer types. I assume LLVM has intrinsics for this that compile down to single instructions on x86_64.
This would speed up some 64-bit fixed-point operations with 128-bit temporaries (such as Mach timestamp scaling arithmetic) and allow pure Swift arbitrary-precision integer packages to provide faster operations.
I currently need to emulate full-width multiplication/division with code such as this:
https://github.com/lorentey/BigInt/blob/master/Sources/BigDigit.swift#L102-L177
A 128/64=64 full-width division done this way requires 2 single-width divisions and 6 multiplications. I'd love to replace this with a single full-width x86 DIV instruction.
···
On 2016-05-17 14:30:36 +0000, Muse M via swift-evolution said:
Most programming languages does have 128-bit of type except Swift.
--
Károly
@lorentey
One reason we don't have Int128 everywhere is that we don't currently
have the necessary primitives on 32-bit systems.
However, when the integers protocol proposal that Max Moiseev is working on
comes out, it will include an implementation of a
DoublePrecision<T:Integer>
either as public API or in the tests (I forget which). The intention is
that on 32-bit platforms we can eventually define Int128 as a typealias
for DoublePrecision<Int64>. We can also introduce Int256, for which I
know there is an audience.
···
on Sat May 21 2016, Károly Lőrentey <swift-evolution@swift.org> wrote:
On 2016-05-17 14:30:36 +0000, Muse M via swift-evolution said:
Most programming languages does have 128-bit of type except Swift.
I don't think there is huge demand for a full-blown Int128 type in the
standard library, but it would be nice to have double-width
multiplication & division methods in Swift's existing integer types. I
assume LLVM has intrinsics for this that compile down to single
instructions on x86_64.This would speed up some 64-bit fixed-point operations with 128-bit
temporaries (such as Mach timestamp scaling arithmetic) and allow pure
Swift arbitrary-precision integer packages to provide faster
operations.I currently need to emulate full-width multiplication/division with
code such as this:https://github.com/lorentey/BigInt/blob/master/Sources/BigDigit.swift#L102-L177
A 128/64=64 full-width division done this way requires 2 single-width
divisions and 6 multiplications. I'd love to replace this with a
single full-width x86 DIV instruction.
--
-Dave
FWIW: here is the link to the prototype https://github.com/apple/swift/blob/master/test/Prototypes/Integers.swift.gyb
Max
···
On May 25, 2016, at 3:53 PM, Dave Abrahams via swift-evolution <swift-evolution@swift.org> wrote:
on Sat May 21 2016, Károly Lőrentey <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
On 2016-05-17 14:30:36 +0000, Muse M via swift-evolution said:
Most programming languages does have 128-bit of type except Swift.
I don't think there is huge demand for a full-blown Int128 type in the
standard library, but it would be nice to have double-width
multiplication & division methods in Swift's existing integer types. I
assume LLVM has intrinsics for this that compile down to single
instructions on x86_64.This would speed up some 64-bit fixed-point operations with 128-bit
temporaries (such as Mach timestamp scaling arithmetic) and allow pure
Swift arbitrary-precision integer packages to provide faster
operations.I currently need to emulate full-width multiplication/division with
code such as this:https://github.com/lorentey/BigInt/blob/master/Sources/BigDigit.swift#L102-L177
A 128/64=64 full-width division done this way requires 2 single-width
divisions and 6 multiplications. I'd love to replace this with a
single full-width x86 DIV instruction.One reason we don't have Int128 everywhere is that we don't currently
have the necessary primitives on 32-bit systems.However, when the integers protocol proposal that Max Moiseev is working on
comes out, it will include an implementation of aDoublePrecision<T:Integer>
either as public API or in the tests (I forget which). The intention is
that on 32-bit platforms we can eventually define Int128 as a typealias
for DoublePrecision<Int64>. We can also introduce Int256, for which I
know there is an audience.--
-Dave_______________________________________________
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