Merge pull request #1000 from AnonymousVikram/fetch_buffer_vk

Distributed And-Or MUX

src/ifu/fetchbuffer.sv

@@ -29,43 +29,56 @@
 module fetchbuffer import cvw::*; #(parameter cvw_t P) (
 	input  logic        clk, reset,
 	input  logic        StallD, FlushD,
-	input  logic [31:0] writeData,
+	input  logic [31:0] WriteData,
-	output logic [31:0] readData,
+	output logic [31:0] ReadData,
 	output logic        FetchBufferStallF
 );
   localparam [31:0] nop = 32'h00000013;
-  logic      [31:0] readf0, readf1, readf2, readMuxed;
+  logic      [31:0] Readf0, Readf1, Readf2, ReadFetchBuffer;
-  logic      [2:0]  readPtr, writePtr;
+  logic      [2:0]  ReadPtr, WritePtr;
-  logic             empty, full;
+  logic             Empty, Full;
 
-  assign empty  = |(readPtr & writePtr); // Bitwise and the read&write ptr, and or the bits of the result together
+  assign Empty  = |(ReadPtr & WritePtr); // Bitwise and the read&write ptr, and or the bits of the result together
-  assign full   = |({writePtr[1:0], writePtr[2]} & readPtr); // Same as above but left rotate writePtr to "add 1"
+  assign Full   = |({WritePtr[1:0], WritePtr[2]} & ReadPtr); // Same as above but left rotate WritePtr to "add 1"
-  assign FetchBufferStallF = full;
+  assign FetchBufferStallF = Full;
 
   // will go in a generate block once this is parameterized
-  flopenr #(32) f0 (.clk, .reset(reset | FlushD), .en(writePtr[0]), .d(writeData), .q(readf0)); 
+  flopenr #(32) f0 (.clk, .reset(reset | FlushD), .en(WritePtr[0]), .d(WriteData), .q(Readf0));
-  flopenr #(32) f1 (.clk, .reset(reset | FlushD), .en(writePtr[1]), .d(writeData), .q(readf1));
+  flopenr #(32) f1 (.clk, .reset(reset | FlushD), .en(WritePtr[1]), .d(WriteData), .q(Readf1));
-  flopenr #(32) f2 (.clk, .reset(reset | FlushD), .en(writePtr[2]), .d(writeData), .q(readf2));
+  flopenr #(32) f2 (.clk, .reset(reset | FlushD), .en(WritePtr[2]), .d(WriteData), .q(Readf2));
 
-  always_comb begin : readMuxes
+  // always_comb begin : readMuxes
-    // Mux read data from the three registers
+  //   // Mux read data from the three registers
-    case (readPtr)
+  //   case (ReadPtr)
-      3'b001:  readMuxed = readf0;
+  //     3'b001:  ReadFetchBuffer = Readf0;
-      3'b010:  readMuxed = readf1;
+  //     3'b010:  ReadFetchBuffer = Readf1;
-      3'b100:  readMuxed = readf2;
+  //     3'b100:  ReadFetchBuffer = Readf2;
-      default: readMuxed = nop; // just in case?
+  //     default: ReadFetchBuffer = nop; // just in case?
-    endcase
+  //   endcase
-    // issue nop when appropriate
+  //   // issue nop when appropriate
-    readData = empty ? nop : readMuxed;
+  //   ReadData = Empty ? nop : ReadFetchBuffer;
-  end
+  // end
+
+
+  // Fetch buffer entries anded with read ptr for AO Muxing
+  logic [31:0] DaoArr [2:0];
+  //     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Make parameterizable
+  assign DaoArr[0] = ReadPtr[0] ? Readf0 : '0;
+  assign DaoArr[1] = ReadPtr[1] ? Readf1 : '0;
+  assign DaoArr[2] = ReadPtr[2] ? Readf2 : '0;
+
+  or_rows #(3, 32) ReadFBAOMux(.a(DaoArr), .y(ReadFetchBuffer));
+  //        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Make parameterizable
+
+  assign ReadData = Empty ? nop : ReadFetchBuffer;
 
   always_ff @(posedge clk) begin : shiftRegister
     if (reset) begin
-      writePtr <= 3'b001;
+      WritePtr <= 3'b001;
-      readPtr  <= 3'b001;
+      ReadPtr  <= 3'b001;
     end else begin
-      writePtr <= ~full ? {writePtr[1:0], writePtr[2]} : writePtr;
+      WritePtr <= ~Full ? {WritePtr[1:0], WritePtr[2]} : WritePtr;
-      readPtr <= ~(StallD | empty) ? {readPtr[1:0], readPtr[2]} : readPtr;
+      ReadPtr <= ~(StallD | Empty) ? {ReadPtr[1:0], ReadPtr[2]} : ReadPtr;
     end
   end
 endmodule

src/ifu/ifu.sv

@@ -305,7 +305,7 @@ module ifu import cvw::*;  #(parameter cvw_t P) (
   
   // flopenl #(32) AlignedInstrRawDFlop(clk, reset | FlushD, ~StallD, PostSpillInstrRawF, nop, InstrRawD);
   // TODO: Test this?!?!?!
-  fetchbuffer #(P) fetchbuff(.clk, .reset, .StallD, .FlushD, .writeData(PostSpillInstrRawF), .readData(InstrRawD), .FetchBufferStallF); // Figure out what TODO with StallF
+  fetchbuffer #(P) fetchbuff(.clk, .reset, .StallD, .FlushD, .WriteData(PostSpillInstrRawF), .ReadData(InstrRawD), .FetchBufferStallF); // Figure out what TODO with StallF
 
   ////////////////////////////////////////////////////////////////////////////////////////////////
   // PCNextF logic