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Preserve literal value across .asSInt and .zext #4151

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merged 1 commit into from
Jun 6, 2024

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@jackkoenig jackkoenig commented Jun 6, 2024

Note that .asSInt is only defined on Bits, if you want to cast to SInt from Bundles or Vecs you already gotta go through UInt.

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@jackkoenig jackkoenig added the Feature New feature, will be included in release notes label Jun 6, 2024
@jackkoenig jackkoenig added this to the 6.x milestone Jun 6, 2024
@jackkoenig jackkoenig requested a review from seldridge June 6, 2024 21:53
@jackkoenig jackkoenig force-pushed the asSInt-literal-preservation branch from e32aedc to 37c416d Compare June 6, 2024 22:00
core/src/main/scala/chisel3/Bits.scala Outdated Show resolved Hide resolved
Comment on lines +781 to +784
def do_zext(implicit sourceInfo: SourceInfo): SInt = this.litOption match {
case Some(value) => SInt.Lit(value, this.width + 1)
case None => pushOp(DefPrim(sourceInfo, SInt(width + 1), ConvertOp, ref))
}
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It is somewhat surprising that zero extending a UInt returns an SInt. I would've thought that this took a width to zero extend to and did not change the type. This seems like it wants to be asSIntPreserveValue or something. This is what the API is, though.

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@jackkoenig jackkoenig Jun 6, 2024

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I agree the name of the API is questionable but that's what it has always been. We certain can alias it (and consider changing).

@jackkoenig jackkoenig force-pushed the asSInt-literal-preservation branch from 37c416d to bb9a996 Compare June 6, 2024 22:16
@jackkoenig jackkoenig enabled auto-merge (squash) June 6, 2024 22:19
@jackkoenig jackkoenig merged commit dbbf73a into main Jun 6, 2024
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@jackkoenig jackkoenig deleted the asSInt-literal-preservation branch June 6, 2024 22:32
@mergify mergify bot added the Backported This PR has been backported label Jun 6, 2024
mergify bot pushed a commit that referenced this pull request Jun 6, 2024
chiselbot pushed a commit that referenced this pull request Jun 6, 2024
(cherry picked from commit dbbf73a)

Co-authored-by: Jack Koenig <koenig@sifive.com>
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