There's no explicit way to convert between signed <-> unsigned values

[nmigen-issue-migration]

Issue by Maykeye
Friday Jan 03, 2020 at 07:19 GMT
Originally opened as m-labs/nmigen#292

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I have an unsigned signal. I want to compare it as signed for a change and now there are no good explicit way to do it.

• I can make new Signal(signed(old.width)) and equate it to the old one, but in order to do so, I must place all such signals in the beginning of elaborate: if I create a copy somewhere in the middle like with m.If(en): comb+= make_signed_copy(n)<10, generator will not be able to generate wire[31:0] signed_n = n, instead it will create register because if if-branch is not executed, signed_n is not being written

• There's implicit conversion: I can use -(-n), and rely on optimizers down the road, but it feels hacky.

[nmigen-issue-migration]

Comment by whitequark
Friday Jan 03, 2020 at 07:31 GMT

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Proposed API: Value.to_signed / Value.to_unsigned.