Memory: Remove magic numbers from state machines.
[firearm.git] / Memory.v
index 7ca786e..40e60d7 100644 (file)
--- a/Memory.v
+++ b/Memory.v
@@ -65,7 +65,7 @@ module Memory(
        reg [3:0] next_write_num;
        reg [31:0] next_write_data;
 
-       reg [2:0] lsr_state = 3'b001, next_lsr_state;
+       reg [3:0] lsr_state = 4'b0001, next_lsr_state;
        reg [31:0] align_s1, align_s2, align_rddata;
 
        reg [2:0] lsrh_state = 3'b001, next_lsrh_state;
@@ -79,6 +79,9 @@ module Memory(
 
        reg [31:0] swp_oldval, next_swp_oldval;
        reg [1:0] swp_state = 2'b01, next_swp_state;
+       
+       reg do_rd_data_latch;
+       reg [31:0] rd_data_latch = 32'hxxxxxxxx;
 
        always @(posedge clk)
        begin
@@ -100,6 +103,8 @@ module Memory(
                lsm_state <= next_lsm_state;
                lsr_state <= next_lsr_state;
                lsrh_state <= next_lsrh_state;
+               if (do_rd_data_latch)
+                       rd_data_latch <= rd_data;
                prevaddr <= addr;
        end
        
@@ -120,6 +125,8 @@ module Memory(
                busaddr = 32'hxxxxxxxx;
                data_size = 3'bxxx;
                outstall = 1'b0;
+               st_read = 4'hx;
+               do_rd_data_latch = 0;
                next_write_reg = write_reg;
                next_write_num = write_num;
                next_write_data = write_data;
@@ -141,6 +148,23 @@ module Memory(
                next_swp_state = swp_state;
                cur_reg = prev_reg;
 
+`define SWP_READING 2'b01
+`define SWP_WRITING 2'b10
+
+`define LSRH_MEMIO     3'b001
+`define LSRH_BASEWB    3'b010
+`define LSRH_WBFLUSH   3'b100
+
+`define LSR_MEMIO      4'b0001
+`define LSR_STRB_WR    4'b0010
+`define LSR_BASEWB     4'b0100
+`define LSR_WBFLUSH    4'b1000
+
+`define LSM_SETUP      4'b0001
+`define LSM_MEMIO      4'b0010
+`define LSM_BASEWB     4'b0100
+`define LSM_WBFLUSH    4'b1000
+
                /* XXX shit not given about endianness */
                casez(insn)
                `DECODE_ALU_SWP: if(!inbubble) begin
@@ -149,23 +173,23 @@ module Memory(
                        busaddr = {op0[31:2], 2'b0};
                        data_size = insn[22] ? 3'b001 : 3'b100;
                        case(swp_state)
-                       2'b01: begin
+                       `SWP_READING: begin
                                rd_req = 1'b1;
                                outstall = 1'b1;
                                if(!rw_wait) begin
-                                       next_swp_state = 2'b10;
+                                       next_swp_state = `SWP_WRITING;
                                        next_swp_oldval = rd_data;
                                end
                                $display("SWP: read stage");
                        end
-                       2'b10: begin
+                       `SWP_WRITING: begin
                                wr_req = 1'b1;
                                wr_data = insn[22] ? {4{op1[7:0]}} : op1;
                                next_write_reg = 1'b1;
                                next_write_num = insn[15:12];
                                next_write_data = insn[22] ? {24'b0, swp_oldval[7:0]} : swp_oldval;
                                if(!rw_wait)
-                                       next_swp_state = 2'b01;
+                                       next_swp_state = `SWP_READING;
                                $display("SWP: write stage");
                        end
                        default: begin end
@@ -181,7 +205,6 @@ module Memory(
                        busaddr = raddr;
                        /* rotate to correct position */
                        case(insn[6:5])
-                       2'b00: begin end /* swp */
                        2'b01: begin /* unsigned half */
                                wr_data = {2{op2[15:0]}}; /* XXX need to store halfword */
                                data_size = 3'b010;
@@ -199,10 +222,15 @@ module Memory(
                                data_size = 3'b010;
                                lsrh_rddata = raddr[1] ? {{16{rd_data[31]}}, rd_data[31:16]} : {{16{rd_data[15]}}, rd_data[15:0]};
                        end
+                       default: begin
+                               wr_data = 32'hxxxxxxxx;
+                               data_size = 3'bxxx;
+                               lsrh_rddata = 32'hxxxxxxxx;
+                       end
                        endcase
 
                        case(lsrh_state)
-                       3'b001: begin
+                       `LSRH_MEMIO: begin
                                rd_req = insn[20];
                                wr_req = ~insn[20];
                                next_write_num = insn[15:12];
@@ -213,27 +241,27 @@ module Memory(
                                if(insn[21] | !insn[24]) begin
                                        outstall = 1'b1;
                                        if(!rw_wait)
-                                               next_lsrh_state = 3'b010;
+                                               next_lsrh_state = `LSRH_BASEWB;
                                end
                                $display("ALU_LDRSTRH: rd_req %d, wr_req %d", rd_req, wr_req);
                        end
-                       3'b010: begin
+                       `LSRH_BASEWB: begin
                                next_outbubble = 1'b0;
                                next_write_reg = 1'b1;
                                next_write_num = insn[19:16];
                                next_write_data = addr;
-                               next_lsrh_state = 3'b100;
+                               next_lsrh_state = `LSRH_WBFLUSH;
                        end
-                       3'b100: begin
+                       `LSRH_WBFLUSH: begin
                                outstall = 0;
-                               next_lsrh_state = 3'b001;
+                               next_lsrh_state = `LSRH_MEMIO;
                        end
                        default: begin end
                        endcase
                        
-                       if ((lsrh_state == 3'b001) && flush) begin      /* Reject it. */
+                       if ((lsrh_state == `LSRH_MEMIO) && flush) begin /* Reject it. */
                                outstall = 1'b0;
-                               next_lsrh_state = 3'b001;
+                               next_lsrh_state = `LSRH_MEMIO;
                        end
                end
                `DECODE_LDRSTR_UNDEFINED: begin end
@@ -248,42 +276,70 @@ module Memory(
                        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;
-                       wr_data = insn[22] ? {4{op2[7:0]}} : op2; /* XXX need to actually store just a byte */
+                       wr_data = insn[22] ? {24'h0, {op2[7:0]}} : op2;
                        data_size = insn[22] ? 3'b001 : 3'b100;
                        case(lsr_state)
-                       3'b001: begin
-                               rd_req = insn[20] /* L */;
-                               wr_req = ~insn[20] /* L */;
+
+                       `LSR_MEMIO: begin
+                               rd_req = insn[20] /* L */ || insn[22] /* B */;
+                               wr_req = !insn[20] /* L */ && !insn[22]/* B */;
                                next_write_reg = insn[20] /* L */;
                                next_write_num = insn[15:12];
                                if(insn[20] /* L */) begin
-                                       next_write_data = align_rddata;
+                                       next_write_data = insn[22] /* B */ ? {24'h0, align_rddata[7:0]} : align_rddata;
                                end
-                               if(insn[21] /* W */ | !insn[24] /* P */) begin
+                               if (insn[22] /* B */ && !insn[20] /* L */) begin
+                                       do_rd_data_latch = 1;
+                                       outstall = 1'b1;
+                                       if (!rw_wait)
+                                               next_lsr_state = `LSR_STRB_WR;
+                               end else if(insn[21] /* W */ | !insn[24] /* P */) begin
                                        outstall = 1'b1;
                                        if(!rw_wait)
-                                               next_lsr_state = 3'b010;
+                                               next_lsr_state = `LSR_BASEWB;
                                end
                                $display("LDRSTR: rd_req %d, wr_req %d, raddr %08x, wait %d", rd_req, wr_req, raddr, rw_wait);
                        end
-                       3'b010: begin
+                       `LSR_STRB_WR: begin
+                               $display("LDRSTR: Handling STRB");
+                               outstall = 1;
+                               rd_req = 0;
+                               wr_req = 1;
+                               next_write_reg = 0;
+                               case (busaddr[1:0])
+                               2'b00: wr_data = {rd_data_latch[31:8], op2[7:0]};
+                               2'b01: wr_data = {rd_data_latch[31:16], op2[7:0], rd_data_latch[7:0]};
+                               2'b10: wr_data = {rd_data_latch[31:24], op2[7:0], rd_data_latch[15:0]};
+                               2'b11: wr_data = {op2[7:0], rd_data_latch[23:0]};
+                               endcase
+                               if(insn[21] /* W */ | !insn[24] /* P */) begin
+                                       if(!rw_wait)
+                                               next_lsr_state = `LSR_BASEWB;
+                               end else if (!rw_wait)
+                                       next_lsr_state = `LSR_WBFLUSH;
+                       end
+                       `LSR_BASEWB: begin
                                outstall = 1;
+                               rd_req = 0;
+                               wr_req= 0;
                                next_outbubble = 0;
                                next_write_reg = 1'b1;
                                next_write_num = insn[19:16];
                                next_write_data = addr;
-                               next_lsr_state = 3'b100;
+                               next_lsr_state = `LSR_WBFLUSH;
                        end
-                       3'b100: begin
+                       `LSR_WBFLUSH: begin
+                               rd_req = 0;
+                               wr_req= 0;
                                outstall = 0;
-                               next_lsr_state = 3'b001;
+                               next_lsr_state = `LSR_MEMIO;
                        end
                        default: begin end
                        endcase
                        
-                       if ((lsr_state == 3'b001) && flush) begin       /* Reject it. */
+                       if ((lsr_state == `LSR_MEMIO) && flush) begin   /* Reject it. */
                                outstall = 1'b0;
-                               next_lsr_state = 3'b001;
+                               next_lsr_state = `LSR_MEMIO;
                        end
                end
                /* XXX ldm/stm incorrect in that stupid case where one of the listed regs is the base reg */
@@ -292,7 +348,7 @@ module Memory(
                        next_outbubble = rw_wait;
                        data_size = 3'b100;
                        case(lsm_state)
-                       4'b0001: begin
+                       `LSM_SETUP: begin
 //                             next_regs = insn[23] ? op1[15:0] : op1[0:15];
                                /** verilator can suck my dick */
                                $display("LDMSTM: Round 1: base register: %08x, reg list %b", op0, op1[15:0]);
@@ -300,7 +356,7 @@ module Memory(
                                                                            op1[8], op1[9], op1[10], op1[11], op1[12], op1[13], op1[14], op1[15]};
                                offset = 6'b0;
                                outstall = 1'b1;
-                               next_lsm_state = 4'b0010;
+                               next_lsm_state = `LSM_MEMIO;
                        end
                        4'b0010: begin
                                rd_req = insn[20];
@@ -403,27 +459,27 @@ module Memory(
                                outstall = 1'b1;
 
                                if(next_regs == 16'b0) begin
-                                       next_lsm_state = 4'b0100;
+                                       next_lsm_state = `LSM_BASEWB;
                                end
                        end
-                       4'b0100: begin
+                       `LSM_BASEWB: begin
                                outstall = 1;
                                next_outbubble = 0;
                                next_write_reg = insn[21] /* writeback */;
                                next_write_num = insn[19:16];
                                next_write_data = insn[23] ? op0 + {26'b0, prev_offset} : op0 - {26'b0, prev_offset};
-                               next_lsm_state = 4'b1000;
+                               next_lsm_state = `LSM_WBFLUSH;
                                $display("LDMSTM: Stage 3: Writing back");
                        end
-                       4'b1000: begin
+                       `LSM_WBFLUSH: begin
                                outstall = 0;
-                               next_lsm_state = 4'b0001;
+                               next_lsm_state = `LSM_SETUP;
                        end
                        default: $stop;
                        endcase
-                       if ((lsm_state == 4'b0001) && flush) begin      /* Reject it. */
+                       if ((lsm_state == `LSM_SETUP) && flush) begin   /* Reject it. */
                                outstall = 1'b0;
-                               next_lsm_state = 4'b0001;
+                               next_lsm_state = `LSM_SETUP;
                        end
                        $display("LDMSTM: Decoded, bubble %d, insn %08x, lsm state %b -> %b, stall %d", inbubble, insn, lsm_state, next_lsm_state, outstall);
                end
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