memory: fix up slightly

[firearm.git] / Memory.v

diff --git a/Memory.v b/Memory.v
index 2b4b2a40b69e9f455c427879a045d288d8558d2b..409b282f3cad4cb34325201dfcbf5fe7421441a3 100644 (file)
--- a/Memory.v
+++ b/Memory.v
@@ -27,18 +27,19 @@ module Memory(
 
        /* pc stuff */
        output reg [31:0] outpc,
-       output reg [31:0] newpc,
 
        /* stall */
        output outstall,
-       output reg outbubble,
-       output reg flush
+       output reg outbubble
 );
 
-       reg [31:0] addr, raddr;
+       reg [31:0] addr, raddr, next_regdata;
+       reg [3:0] next_regsel;
+       reg next_writeback, next_notdone, next_inc_next;
+       reg [31:0] align_s1, align_s2, align_rddata;
+
        reg notdone = 1'b0;
        reg inc_next = 1'b0;
-       wire [31:0] align_s1, align_s2, align_rddata;
        assign outstall = rw_wait | notdone;
 
        always @(*)
@@ -50,6 +51,10 @@ module Memory(
                wr_data = 32'hxxxxxxxx;
                busaddr = 32'hxxxxxxxx;
                outstall = 1'b0;
+               next_notdone = 1'b0;
+               next_regsel = 4'hx;
+               next_regdata = 32'hxxxxxxxx;
+               next_inc_next = 1'b0;
                casez(insn)
                `DECODE_LDRSTR_UNDEFINED: begin end
                `DECODE_LDRSTR: begin
@@ -58,12 +63,29 @@ module Memory(
                        busaddr = {raddr[31:2], 2'b0}; /* pre/post increment */
                        rd_req = insn[20];
                        wr_req = ~insn[20];
-                       if(!insn[20]) begin /* store */
+
+                       /* rotate to correct position */
+                       align_s1 = raddr[1] ? {rd_data[15:0], rd_data[31:16]} : rd_data;
+                       align_s2 = raddr[0] ? {align_s1[7:0], align_s1[31:8]} : align_s1;
+                       /* select byte or word */
+                       align_rddata = insn[22] ? {24'b0, align_s2[7:0]} : align_s2;
+
+                       if(!insn[20]) begin
                                st_read = insn[15:12];
-                               wr_data = insn[22] ? {4{st_data[7:0]}} : st_data;
+                               wr_data = insn[22] ? {4{st_data[7:0]}} : st_data; /* XXX need to actually store just a byte */
+                       end
+                       else if(!inc_next) begin
+                               next_writeback = 1'b1;
+                               next_regsel = insn[15:12];
+                               next_regdata = align_rddata;
+                               next_inc_next = 1'b1;
                        end
-                       else if(insn[15:12] == 4'hF)
-                               flush = 1'b1;
+                       else if(insn[21]) begin
+                               next_writeback = 1'b1;
+                               next_regsel = insn[19:16];
+                               next_regdata = addr;
+                       end
+                       next_notdone = rw_wait & insn[20] & insn[21];
                end
                `DECODE_LDMSTM: begin
                end
@@ -71,55 +93,16 @@ module Memory(
                endcase
        end
 
-       assign align_s1 = raddr[1] ? {rd_data[15:0], rd_data[31:16]} : rd_data;
-       assign align_s2 = raddr[0] ? {align_s1[7:0], align_s1[31:8]} : align_s1;
-       assign align_rddata = insn[22] ? {24'b0, align_s2[7:0]} : align_s2;
 
        always @(posedge clk)
        begin
                outpc <= pc;
                outbubble <= rw_wait;
-               casez(insn)
-               `DECODE_LDRSTR_UNDEFINED: begin
-                       writeback <= 1'b0;
-                       regsel <= 4'hx;
-                       regdata <= 32'hxxxxxxxx;
-                       notdone <= 1'b0;
-               end
-               `DECODE_LDRSTR: begin
-                       if(insn[20] && !inc_next) begin /* load - delegate regfile write to writeback stage */
-                               if(insn[15:12] == 4'hF) begin
-                                       newpc <= align_rddata;
-                               end
-                               else begin
-                                       writeback <= 1'b1;
-                                       regsel <= insn[15:12];
-                                       regdata <= align_rddata;
-                               end
-                               inc_next <= 1'b1;
-                       end
-                       else if(insn[21]) begin /* write back */
-                               writeback <= 1'b1;
-                               regsel <= insn[19:16];
-                               regdata <= addr;
-                               inc_next <= 1'b0;
-                       end else begin
-                               writeback <= 1'b0;
-                               inc_next <= 1'b0;
-                               regsel <= 4'hx;
-                               regdata <= 32'hxxxxxxxx;
-                       end
-                       notdone <= rw_wait & insn[20] & insn[21];
-               end
-               `DECODE_LDMSTM: begin
-               end
-               default: begin
-                       writeback <= 1'b0;
-                       regsel <= 4'hx;
-                       regdata <= 32'hxxxxxxxx;
-                       notdone <= 1'b0;
-               end
-               endcase
+               writeback <= next_writeback;
+               regsel <= next_regsel;
+               regdata <= next_regdata;
+               notdone <= next_notdone;
+               inc_next <= next_inc_next;
        end
 
 endmodule