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Commented WFI non-flush in writeback stage of hazard unit

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David Harris 2023-04-07 21:27:13 -07:00
parent a9b7bd101e
commit 5119222c2f
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src/hazard/hazard.sv
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@ -71,6 +71,7 @@ module hazard (
// Similarly, CSR writes and fences flush all subsequent instructions and refetch them in light of the new operating modes and cache/TLB contents // Similarly, CSR writes and fences flush all subsequent instructions and refetch them in light of the new operating modes and cache/TLB contents
// Branch misprediction is found in the Execute stage and must flush the next two instructions. // Branch misprediction is found in the Execute stage and must flush the next two instructions.
// However, an active division operation resides in the Execute stage, and when the BP incorrectly mispredicts the divide as a taken branch, the divde must still complete // However, an active division operation resides in the Execute stage, and when the BP incorrectly mispredicts the divide as a taken branch, the divde must still complete
// When a WFI is interrupted and causes a trap, it flushes the rest of the pipeline but not the W stage, because the WFI needs to commit
assign FlushDCause = TrapM | RetM | CSRWriteFenceM | BPWrongE; assign FlushDCause = TrapM | RetM | CSRWriteFenceM | BPWrongE;
assign FlushECause = TrapM | RetM | CSRWriteFenceM |(BPWrongE & ~(DivBusyE | FDivBusyE)); assign FlushECause = TrapM | RetM | CSRWriteFenceM |(BPWrongE & ~(DivBusyE | FDivBusyE));
assign FlushMCause = TrapM | RetM | CSRWriteFenceM; assign FlushMCause = TrapM | RetM | CSRWriteFenceM;