ASIC: Register file updates

The register file is down from 96 entries to 64, and reads
are synchronous.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>

asic/behavioural/Microwatt_FP_DFFRFile.v

@@ -3,22 +3,21 @@ module Microwatt_FP_DFFRFile (
     inout VPWR,
     inout VGND,
 `endif
-    input [6:0]   R1, R2, R3, RW,
+    input [5:0]   R1, R2, R3, RW,
     input [63:0]  DW,
-    output [63:0] D1, D2, D3,
+    output reg [63:0] D1, D2, D3,
     input CLK,
     input WE
 );
 
-    reg [63:0] registers[0:95];
+    reg [63:0] registers[0:63];
-
-    assign D1 = registers[R1];
-    assign D2 = registers[R2];
-    assign D3 = registers[R3];
 
     always @(posedge CLK) begin
         if (WE)
             registers[RW] <= DW;
+        D1 <= registers[R1];
+        D2 <= registers[R2];
+        D3 <= registers[R3];
     end
 
 endmodule

asic/register_file.vhdl

@@ -7,13 +7,16 @@ use work.common.all;
 
 entity register_file is
     generic (
-        SIM        : boolean := false;
+        SIM : boolean := false;
-        HAS_FPU    : boolean := true;
+        HAS_FPU : boolean := true;
+        -- Non-zero to enable log data collection
         LOG_LENGTH : natural := 0
         );
     port(
         clk           : in std_logic;
+        stall         : in std_ulogic;
 
+        d1_in         : in Decode1ToRegisterFileType;
         d_in          : in Decode2ToRegisterFileType;
         d_out         : out RegisterFileToDecode2Type;
 
@@ -24,6 +27,7 @@ entity register_file is
         dbg_gpr_addr  : in gspr_index_t;
         dbg_gpr_data  : out std_ulogic_vector(63 downto 0);
 
+        -- debug
         sim_dump      : in std_ulogic;
         sim_dump_done : out std_ulogic;
 
@@ -35,69 +39,142 @@ architecture behaviour of register_file is
     component Microwatt_FP_DFFRFile port (
         CLK : in std_ulogic;
 
-        R1  : in std_ulogic_vector(6 downto 0);
+        R1  : in std_ulogic_vector(5 downto 0);
-        R2  : in std_ulogic_vector(6 downto 0);
+        R2  : in std_ulogic_vector(5 downto 0);
-        R3  : in std_ulogic_vector(6 downto 0);
+        R3  : in std_ulogic_vector(5 downto 0);
 
         D1  : out std_ulogic_vector(63 downto 0);
         D2  : out std_ulogic_vector(63 downto 0);
         D3  : out std_ulogic_vector(63 downto 0);
 
         WE  : in std_ulogic;
-        RW  : in std_ulogic_vector(6 downto 0);
+        RW  : in std_ulogic_vector(5 downto 0);
         DW  : in std_ulogic_vector(63 downto 0)
     );
     end component;
 
-    signal d1: std_ulogic_vector(63 downto 0);
+    signal addr_1_reg : gspr_index_t;
-    signal d2: std_ulogic_vector(63 downto 0);
+    signal addr_2_reg : gspr_index_t;
-    signal d3: std_ulogic_vector(63 downto 0);
+    signal addr_3_reg : gspr_index_t;
-begin
+    signal addr_1_stalled: gspr_index_t;
+    signal addr_2_stalled: gspr_index_t;
+    signal addr_3_stalled: gspr_index_t;
+    signal fwd_1 : std_ulogic;
+    signal fwd_2 : std_ulogic;
+    signal fwd_3 : std_ulogic;
+    signal data_1 : std_ulogic_vector(63 downto 0);
+    signal data_2 : std_ulogic_vector(63 downto 0);
+    signal data_3 : std_ulogic_vector(63 downto 0);
+    signal prev_write_data : std_ulogic_vector(63 downto 0);
 
+begin
     register_file_0 : Microwatt_FP_DFFRFile
         port map (
             CLK => clk,
 
-            R1  => d_in.read1_reg,
+            R1  => addr_1_stalled,
-            R2  => d_in.read2_reg,
+            R2  => addr_2_stalled,
-            R3  => d_in.read3_reg,
+            R3  => addr_3_stalled,
 
-            D1  => d1,
+            D1  => data_1,
-            D2  => d2,
+            D2  => data_2,
-            D3  => d3,
+            D3  => data_3,
 
             WE  => w_in.write_enable,
             RW  => w_in.write_reg,
             DW  => w_in.write_data
             );
 
-    x_state_check: process(clk)
+    -- asynchronous handling of stall signal
+     addr_1_stalled <= addr_1_reg when stall = '1' else d1_in.reg_1_addr;
+     addr_2_stalled <= addr_2_reg when stall = '1' else d1_in.reg_2_addr;
+     addr_3_stalled <= addr_3_reg when stall = '1' else d1_in.reg_3_addr;
+
+    -- synchronous reads and writes
+    register_write_0: process(clk)
+        variable a_addr, b_addr, c_addr : gspr_index_t;
+        variable w_addr : gspr_index_t;
     begin
         if rising_edge(clk) then
             if w_in.write_enable = '1' then
+                w_addr := w_in.write_reg;
+                if w_addr(5) = '1' then
+                    report "Writing FPR " & to_hstring(w_addr(4 downto 0)) & " " & to_hstring(w_in.write_data);
+                else
+                    report "Writing GPR " & to_hstring(w_addr) & " " & to_hstring(w_in.write_data);
+                end if;
                 assert not(is_x(w_in.write_data)) and not(is_x(w_in.write_reg)) severity failure;
             end if;
+
+            a_addr := d1_in.reg_1_addr;
+            b_addr := d1_in.reg_2_addr;
+            c_addr := d1_in.reg_3_addr;
+            if stall = '1' then
+                a_addr := addr_1_reg;
+                b_addr := addr_2_reg;
+                c_addr := addr_3_reg;
+            else
+                addr_1_reg <= a_addr;
+                addr_2_reg <= b_addr;
+                addr_3_reg <= c_addr;
+            end if;
+
+            fwd_1 <= '0';
+            fwd_2 <= '0';
+            fwd_3 <= '0';
+            if w_in.write_enable = '1' then
+                if w_addr = a_addr then
+                    fwd_1 <= '1';
+                end if;
+                if w_addr = b_addr then
+                    fwd_2 <= '1';
+                end if;
+                if w_addr = c_addr then
+                    fwd_3 <= '1';
+                end if;
+            end if;
+
+            prev_write_data <= w_in.write_data;
         end if;
-    end process x_state_check;
+    end process register_write_0;
 
-    -- Forward any written data
+    -- asynchronous forwarding of write data
     register_read_0: process(all)
+        variable out_data_1 : std_ulogic_vector(63 downto 0);
+        variable out_data_2 : std_ulogic_vector(63 downto 0);
+        variable out_data_3 : std_ulogic_vector(63 downto 0);
     begin
-        d_out.read1_data <= d1;
+        out_data_1 := data_1;
-        d_out.read2_data <= d2;
+        out_data_2 := data_2;
-        d_out.read3_data <= d3;
+        out_data_3 := data_3;
+        if fwd_1 = '1' then
+            out_data_1 := prev_write_data;
+        end if;
+        if fwd_2 = '1' then
+            out_data_2 := prev_write_data;
+        end if;
+        if fwd_3 = '1' then
+            out_data_3 := prev_write_data;
+        end if;
 
-        if w_in.write_enable = '1' then
+        if d_in.read1_enable = '1' then
-            if d_in.read1_reg = w_in.write_reg then
+            report "Reading GPR " & to_hstring(addr_1_reg) & " " & to_hstring(out_data_1);
-                d_out.read1_data <= w_in.write_data;
-            end if;
-            if d_in.read2_reg = w_in.write_reg then
-                d_out.read2_data <= w_in.write_data;
-            end if;
-            if d_in.read3_reg = w_in.write_reg then
-                d_out.read3_data <= w_in.write_data;
-            end if;
         end if;
+        if d_in.read2_enable = '1' then
+            report "Reading GPR " & to_hstring(addr_2_reg) & " " & to_hstring(out_data_2);
+        end if;
+        if d_in.read3_enable = '1' then
+            report "Reading GPR " & to_hstring(addr_3_reg) & " " & to_hstring(out_data_3);
+        end if;
+
+        d_out.read1_data <= out_data_1;
+        d_out.read2_data <= out_data_2;
+        d_out.read3_data <= out_data_3;
     end process register_read_0;
 
+    dbg_gpr_ack <= '0';
+    dbg_gpr_data <= (others => '0');
+    sim_dump_done <= '0';
+    log_out <= (others => '0');
+
 end architecture behaviour;