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Broken dont' use.

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Ross Thompson 2022-12-11 23:24:01 -06:00
parent 0716aedbd5
commit 1ba1bed0b0
1 changed files with 18 additions and 20 deletions
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36
pipelined/src/hazard/hazard.sv
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@ -46,6 +46,7 @@ module hazard(
logic StallFCause, StallDCause, StallECause, StallMCause, StallWCause; logic StallFCause, StallDCause, StallECause, StallMCause, StallWCause;
logic FirstUnstalledD, FirstUnstalledE, FirstUnstalledM, FirstUnstalledW; logic FirstUnstalledD, FirstUnstalledE, FirstUnstalledM, FirstUnstalledW;
logic FlushDCause, FlushECause, FlushMCause, FlushWCause;
// stalls and flushes // stalls and flushes
// loads: stall for one cycle if the subsequent instruction depends on the load // loads: stall for one cycle if the subsequent instruction depends on the load
@ -59,23 +60,22 @@ module hazard(
// A stage must stall if the next stage is stalled // A stage must stall if the next stage is stalled
// If any stages are stalled, the first stage that isn't stalled must flush. // If any stages are stalled, the first stage that isn't stalled must flush.
// *** can stalls be pushed into earlier stages (e.g. no stall after Decode?) assign FlushDCause = TrapM | RetM | BPPredWrongE;
assign FlushECause = TrapM | RetM | BPPredWrongE;
assign FlushMCause = TrapM | RetM;
// on Trap the memory stage should be flushed going into the W stage,
// except if the instruction causing the Trap is an ecall or ebreak.
assign FlushWCause = TrapM & ~(BreakpointFaultM | EcallFaultM);
// *** consider replacing CSRWriteFencePendingDEM with a flush rather than a stall. // *** consider replacing CSRWriteFencePendingDEM with a flush rather than a stall.
assign StallFCause = CSRWriteFencePendingDEM & ~(TrapM | RetM | BPPredWrongE); assign StallFCause = CSRWriteFencePendingDEM & ~FlushDCause;
// stall in decode if instruction is a load/mul/csr dependent on previous // stall in decode if instruction is a load/mul/csr dependent on previous
assign StallDCause = (LoadStallD | StoreStallD | MDUStallD | CSRRdStallD | FCvtIntStallD | FStallD) & ~(TrapM | RetM | BPPredWrongE); assign StallDCause = (LoadStallD | StoreStallD | MDUStallD | CSRRdStallD | FCvtIntStallD | FStallD) & ~FlushECause;
assign StallECause = (DivBusyE | FDivBusyE) & ~(TrapM); // *** can we move to decode stage (KP?) assign StallECause = (DivBusyE | FDivBusyE) & ~FlushMCause;
// WFI terminates if any enabled interrupt is pending, even if global interrupts are disabled. It could also terminate with TW trap // WFI terminates if any enabled interrupt is pending, even if global interrupts are disabled. It could also terminate with TW trap
assign StallMCause = ((wfiM) & (~TrapM & ~IntPendingM)); assign StallMCause = wfiM & ~FlushWCause & ~IntPendingM;
assign StallWCause = ((IFUStallF | LSUStallM) & ~TrapM); // | (FDivBusyE & ~TrapM & ~IntPendingM); assign StallWCause = ((IFUStallF | LSUStallM) & ~TrapM);
//assign StallWCause = (IFUStallF | LSUStallM) & ~FlushWCause; // if the fpga fails this is likely why.
// head version
// assign StallWCause = LSUStallM | IFUStallF | (FDivBusyE & ~TrapM & ~IntPendingM); // *** FDivBusyE should look like DivBusyE
// assign StallMCause = (wfiM & (~TrapM & ~IntPendingM)); // | FDivBusyE;
// assign StallECause = (DivBusyE | FDivBusyE) & ~(TrapM); // *** can we move to decode stage (KP?)
// *** ross: my changes to cache and lsu need to disable ifu/lsu stalls on a Trap.
assign #1 StallF = StallFCause | StallD; assign #1 StallF = StallFCause | StallD;
assign #1 StallD = StallDCause | StallE; assign #1 StallD = StallDCause | StallE;
@ -89,10 +89,8 @@ module hazard(
assign FirstUnstalledW = ~StallW & StallM; assign FirstUnstalledW = ~StallW & StallM;
// Each stage flushes if the previous stage is the last one stalled (for cause) or the system has reason to flush // Each stage flushes if the previous stage is the last one stalled (for cause) or the system has reason to flush
assign #1 FlushD = FirstUnstalledD | TrapM | RetM | BPPredWrongE; assign #1 FlushD = FirstUnstalledD | FlushDCause;
assign #1 FlushE = FirstUnstalledE | TrapM | RetM | BPPredWrongE; // *** why is BPPredWrongE here, but not needed in simple processor assign #1 FlushE = FirstUnstalledE | FlushECause;
assign #1 FlushM = FirstUnstalledM | TrapM | RetM; assign #1 FlushM = FirstUnstalledM | FlushMCause;
// on Trap the memory stage should be flushed going into the W stage, assign #1 FlushW = FirstUnstalledW | FlushWCause;
// except if the instruction causing the Trap is an ecall or ebreak.
assign #1 FlushW = FirstUnstalledW | (TrapM & ~(BreakpointFaultM | EcallFaultM));
endmodule endmodule