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[rocketv] Interlock vector .vf ops against an in-flight scalar FP producer #1227

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[rocketv] Interlock vector .vf ops against an in-flight scalar FP producer #1227

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17 changes: 14 additions & 3 deletions rocketv/src/RocketCore.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1342,8 +1342,19 @@ class Rocket(val parameter: RocketParameter)
Option.when(usingVector)(exRegDecodeOutput(parameter.decoderParameter.vector)).getOrElse(false.B)
val dataHazardEx: Bool =
exRegDecodeOutput(parameter.decoderParameter.wxd) && checkHazards(hazardTargets, _ === exWaddr)
// A vector `.vf` instruction reads its scalar operand from the F register file
// (decoded as vectorReadFRs1). Exactly like a scalar FP consumer it must interlock
// against an in-flight FP-register producer (fmv.w.x, flw, ...) that is still in
// EX/MEM/WB; otherwise it issues to the vector unit with a stale frs1. The
// scoreboard-based idStallFpu below already covers vectorReadFRs1, but these
// EX/MEM/WB checks did not, leaving a 1-2 cycle window of stale scalar reads.
val idReadFRs1: Bool =
idDecodeOutput(parameter.decoderParameter.fp) ||
Option
.when(usingVector)(idDecodeOutput(parameter.decoderParameter.vectorReadFRs1))
.getOrElse(false.B)
val fpDataHazardEx: Option[Bool] = fpHazardTargets.map(fpHazardTargets =>
idDecodeOutput(parameter.decoderParameter.fp) && exRegDecodeOutput(
idReadFRs1 && exRegDecodeOutput(
parameter.decoderParameter.wfd
) && checkHazards(fpHazardTargets, _ === exWaddr)
)
Expand All @@ -1366,7 +1377,7 @@ class Rocket(val parameter: RocketParameter)
val dataHazardMem: Bool =
memRegDecodeOutput(parameter.decoderParameter.wxd) && checkHazards(hazardTargets, _ === memWaddr)
val fpDataHazardMem: Option[Bool] = fpHazardTargets.map(fpHazardTargets =>
idDecodeOutput(parameter.decoderParameter.fp) &&
idReadFRs1 &&
memRegDecodeOutput(parameter.decoderParameter.wfd) &&
checkHazards(fpHazardTargets, _ === memWaddr)
)
Expand All @@ -1377,7 +1388,7 @@ class Rocket(val parameter: RocketParameter)
wbRegDecodeOutput(parameter.decoderParameter.wxd) && checkHazards(hazardTargets, _ === wbWaddr)
val fpDataHazardWb: Bool = fpHazardTargets
.map(fpHazardTargets =>
idDecodeOutput(parameter.decoderParameter.fp) &&
idReadFRs1 &&
wbRegDecodeOutput(parameter.decoderParameter.wfd) &&
checkHazards(fpHazardTargets, _ === wbWaddr)
)
Expand Down