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Removed mux in PCNextF logic. Minor IFU improvements.

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This commit is contained in:
Ross Thompson 2022-01-26 22:33:26 -06:00
parent 23c4ba2777
commit c3a78553be
1 changed files with 12 additions and 19 deletions
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31
pipelined/src/ifu/ifu.sv
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@ -96,7 +96,6 @@ module ifu (
logic [`XLEN-1:0] PCD; logic [`XLEN-1:0] PCD;
localparam [31:0] nop = 32'h00000013; // instruction for NOP localparam [31:0] nop = 32'h00000013; // instruction for NOP
logic reset_q; // see comment below about PCNextF and icache.
logic [`XLEN-1:0] PCBPWrongInvalidate; logic [`XLEN-1:0] PCBPWrongInvalidate;
logic BPPredWrongM; logic BPPredWrongM;
@ -106,8 +105,8 @@ module ifu (
logic [`XLEN+1:0] PCFExt; logic [`XLEN+1:0] PCFExt;
logic CacheableF; logic CacheableF;
logic [`XLEN-1:0] PCNextFMux; logic [`XLEN-1:0] PCNextFSpill;
logic [`XLEN-1:0] PCFMux; logic [`XLEN-1:0] PCFSpill;
logic SelNextSpill; logic SelNextSpill;
logic ICacheFetchLine; logic ICacheFetchLine;
logic BusStall; logic BusStall;
@ -127,8 +126,8 @@ module ifu (
// this exists only if there are compressed instructions. // this exists only if there are compressed instructions.
assign PCFp2 = PCF + `XLEN'b10; assign PCFp2 = PCF + `XLEN'b10;
assign PCNextFMux = SelNextSpill ? PCFp2 : PCNextF; assign PCNextFSpill = SelNextSpill ? PCFp2 : PCNextF;
assign PCFMux = SelSpill ? PCFp2 : PCF; assign PCFSpill = SelSpill ? PCFp2 : PCF;
assign Spill = &PCF[$clog2(SPILLTHRESHOLD)+1:1]; assign Spill = &PCF[$clog2(SPILLTHRESHOLD)+1:1];
@ -167,18 +166,18 @@ module ifu (
// end of spill support // end of spill support
end else begin : NoSpillSupport // line: SpillSupport end else begin : NoSpillSupport // line: SpillSupport
assign PCNextFMux = PCNextF; assign PCNextFSpill = PCNextF;
assign PCFMux = PCF; assign PCFSpill = PCF;
assign SelNextSpill = 0; assign SelNextSpill = 0;
assign PostSpillInstrRawF = InstrRawF; assign PostSpillInstrRawF = InstrRawF;
end end
assign PCFExt = {2'b00, PCFMux}; assign PCFExt = {2'b00, PCFSpill};
mmu #(.TLB_ENTRIES(`ITLB_ENTRIES), .IMMU(1)) mmu #(.TLB_ENTRIES(`ITLB_ENTRIES), .IMMU(1))
immu(.PAdr(PCFExt[`PA_BITS-1:0]), immu(.PAdr(PCFExt[`PA_BITS-1:0]),
.VAdr(PCFMux), .VAdr(PCFSpill),
.Size(2'b10), .Size(2'b10),
.PTE(PTE), .PTE(PTE),
.PageTypeWriteVal(PageType), .PageTypeWriteVal(PageType),
@ -235,7 +234,7 @@ module ifu (
simpleram #( simpleram #(
.BASE(`RAM_BASE), .RANGE(`RAM_RANGE)) ram ( .BASE(`RAM_BASE), .RANGE(`RAM_RANGE)) ram (
.clk, .clk,
.a(CPUBusy | reset ? PCPF[31:0] : PCNextFMux[31:0]), // mux is also inside $, have to replay address if CPU is stalled. .a(CPUBusy | reset ? PCPF[31:0] : PCNextFSpill[31:0]), // mux is also inside $, have to replay address if CPU is stalled.
.we(1'b0), .we(1'b0),
.wd(0), .rd(FinalInstrRawF_FIXME)); .wd(0), .rd(FinalInstrRawF_FIXME));
assign FinalInstrRawF = FinalInstrRawF_FIXME[31:0]; assign FinalInstrRawF = FinalInstrRawF_FIXME[31:0];
@ -286,7 +285,7 @@ module ifu (
.RW(IFURWF), .RW(IFURWF),
.Atomic(2'b00), .Atomic(2'b00),
.FlushCache(1'b0), .FlushCache(1'b0),
.NextAdr(PCNextFMux[11:0]), .NextAdr(PCNextFSpill[11:0]),
.PAdr(PCPF), .PAdr(PCPF),
.CacheCommitted(), .CacheCommitted(),
.InvalidateCacheM(InvalidateICacheM)); .InvalidateCacheM(InvalidateICacheM));
@ -303,7 +302,7 @@ module ifu (
// branch predictor signal // branch predictor signal
logic SelBPPredF; logic SelBPPredF;
logic [`XLEN-1:0] BPPredPCF, PCNext0F, PCNext1F, PCNext2F, PCNext3F; logic [`XLEN-1:0] BPPredPCF, PCNext0F, PCNext1F, PCNext2F;
logic [4:0] InstrClassD, InstrClassE; logic [4:0] InstrClassD, InstrClassE;
@ -333,13 +332,7 @@ module ifu (
mux2 #(`XLEN) pcmux2(.d0(PCNext1F), .d1(PCBPWrongInvalidate), .s(InvalidateICacheM), .y(PCNext2F)); mux2 #(`XLEN) pcmux2(.d0(PCNext1F), .d1(PCBPWrongInvalidate), .s(InvalidateICacheM), .y(PCNext2F));
// Mux only required on instruction class miss prediction. // Mux only required on instruction class miss prediction.
mux2 #(`XLEN) pcmuxBPWrongInvalidateFlush(.d0(PCE), .d1(PCF), .s(BPPredWrongM), .y(PCBPWrongInvalidate)); mux2 #(`XLEN) pcmuxBPWrongInvalidateFlush(.d0(PCE), .d1(PCF), .s(BPPredWrongM), .y(PCBPWrongInvalidate));
mux2 #(`XLEN) pcmux3(.d0(PCNext2F), .d1(PrivilegedNextPCM), .s(PrivilegedChangePCM), .y(PCNext3F)); mux2 #(`XLEN) pcmux3(.d0(PCNext2F), .d1(PrivilegedNextPCM), .s(PrivilegedChangePCM), .y(UnalignedPCNextF));
// This mux is required as PCNextF needs to be the valid reset vector during reset.
// Reseting PCF does not accomplish this as PCNextF will be +2/4 more than PCF.
//mux2 #(`XLEN) pcmux4(.d0(PCNext3F), .d1(`RESET_VECTOR), .s(`MEM_IROM ? reset : reset_q), .y(UnalignedPCNextF));
// mux2 #(`XLEN) pcmux4(.d0(PCNext3F), .d1(`RESET_VECTOR), .s(reset), .y(UnalignedPCNextF)); // ******* probably can get rid of by making reset SelAdr = 01
assign UnalignedPCNextF = PCNext3F;
flopenrc #(1) BPPredWrongMReg(.clk, .reset, .en(~StallM), .clear(FlushM), .d(BPPredWrongE), .q(BPPredWrongM)); flopenrc #(1) BPPredWrongMReg(.clk, .reset, .en(~StallM), .clear(FlushM), .d(BPPredWrongE), .q(BPPredWrongM));