PrettyGoodRISCV/E-Series
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This commit is contained in:
John Terrell 2023-03-17 08:50:28 -07:00
parent 2d5e8fddd7
commit 4d9aa3063c
Signed by untrusted user who does not match committer: johnt
GPG Key ID: 2E424258DD3731F4
1 changed files with 19 additions and 1 deletions
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20
src/Cpu/FetchStage.bsv
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@ -18,11 +18,17 @@ interface FetchStage_Ifc#(numeric type xlen);
interface Get#(IF_ID#(xlen)) getIF_ID;
interface ReadOnlyMemoryClient#(xlen, 32) memoryClient;
interface Get#(Bit#(xlen)) getNPC;
interface Put#(Bool) putStall;
endinterface
module mkFetchStage#(FetchStage_Cfg#(xlen) cfg)(FetchStage_Ifc#(xlen));
Wire#(PC_IF#(xlen)) pc_if <- mkWire;
Wire#(IF_ID#(xlen)) if_id <- mkWire;
Wire#(Bit#(xlen)) npc <- mkWire;
Reg#(Bool) stall <- mkReg(False);
Reg#(Bool) externalStall <- mkReg(False);
// Memory request output
Reg#(Bool) memoryRequestInFlight <- mkReg(False);
@ -31,6 +37,11 @@ module mkFetchStage#(FetchStage_Cfg#(xlen) cfg)(FetchStage_Ifc#(xlen));
// Memory response input (FIFO)
FIFOF#(ReadOnlyMemoryResponse#(32)) memoryResponses <- mkFIFOF;
//
// processMemoryResponse - takes a memory response and returns an IF_ID containing
// the encoded instruction (or a trap if the original request
// was denied by the memory system)
//
function IF_ID#(xlen) processMemoryResponse(ReadOnlyMemoryResponse#(32) response);
IF_ID#(xlen) if_id_ = defaultValue;
if_id_.common.pc = pc_if.common.pc;
@ -56,7 +67,9 @@ module mkFetchStage#(FetchStage_Cfg#(xlen) cfg)(FetchStage_Ifc#(xlen));
if_id_.common.pc = pc_if.common.pc;
if_id_.common.isBubble = True;
if (!pc_if.common.isBubble) begin
npc <= pc_if.common.pc + 4;
if (!pc_if.common.isBubble && !stall) begin
// If there's an active request, handle it if it's returned
if (memoryRequestInFlight) begin
if (memoryResponses.notEmpty) begin
@ -92,10 +105,15 @@ module mkFetchStage#(FetchStage_Cfg#(xlen) cfg)(FetchStage_Ifc#(xlen));
end
end
// Determine if fetching should stall on the next cycle.
stall <= externalStall; // || ichache_miss || itlb_busy;
if_id <= if_id_;
endrule
interface Put putPC_IF = toPut(asIfc(pc_if));
interface Get getIF_ID = toGet(if_id);
interface ReadOnlyMemoryClient memoryClient = toGPClient(memoryRequest, memoryResponses);
interface Get getNPC = toGet(npc);
interface Put putStall = toPut(asIfc(externalStall));
endmodule