Add back support for delay slot, but with writing PC+4 when linking and using delay...

[fpga/lx-cpu1/tumbl.git] / hw / decode.vhd

diff --git a/hw/decode.vhd b/hw/decode.vhd
index cf681e0e33fbad900a932280ce02f7e9da9877b1..67e207c5c02f0cc8e5df70a13d36362a0d093c3f 100644 (file)
--- a/hw/decode.vhd
+++ b/hw/decode.vhd
@@ -38,9 +38,7 @@ ENTITY decode IS
                ID2EX_o     : OUT ID2EX_Type;
                --
                INT_CTRL_i  :  IN INT_CTRL_Type;
-               ID2CTRL_o   : OUT ID2CTRL_Type;
-               --
-               noLiteOpc_o : OUT STD_LOGIC
+               ID2CTRL_o   : OUT ID2CTRL_Type
        );
 END ENTITY decode;
 
@@ -87,9 +85,8 @@ p_decode:
                rB_v            := instruction_v (15 DOWNTO 11);
                IMM16_v         := instruction_v (15 DOWNTO  0);
                IMM_Lock_v      := '0';
-               IF (COMPATIBILITY_MODE_g = TRUE) THEN
-                       delayBit_v    := '0';
-               ELSE
+               delayBit_v      := '0';
+               IF (COMPATIBILITY_MODE_g = FALSE) THEN
                        it_Action_v   :=  NO_IT;
                END IF;
                condition_raw_v := (others => '1');
@@ -104,8 +101,6 @@ p_decode:
                -- for decoding SEXT16, SEXT8, SRC, SRC or SRL
                code_x26_v      := instruction_v(6) & instruction_v(5) & instruction_v(0);
                int_busy_v      := INT_CTRL_i.int_busy;
-               -- for debugging purposes
-               noLiteOpc_o     <= '0';
 
                IF (INT_CTRL_i.setup_int = '1') THEN
 
@@ -164,8 +159,6 @@ p_decode:
                                                WHEN "000" =>                                     -- MUL
                                                        IF (USE_HW_MUL_g = TRUE) THEN
                                                                alu_Action_v := A_MUL;
-                                                       ELSE
-                                                               noLiteOpc_o <= '1';
                                                        END IF;
 
                                                WHEN "001" =>                                     -- BS
@@ -177,8 +170,6 @@ p_decode:
                                                                ELSE
                                                                        alu_Action_v := A_BSRL;
                                                                END IF;
-                                                       ELSE
-                                                               noLiteOpc_o <= '1';
                                                        END IF;
 
                                                WHEN "010" | "011" =>                             -- CMP(U)
@@ -188,8 +179,6 @@ p_decode:
                                                                ELSE
                                                                        alu_Action_v := A_CMP;
                                                                END IF;
-                                                       ELSE
-                                                               noLiteOpc_o <= '1';
                                                        END IF;
 
                                                WHEN "100" | "101" =>                             -- IT(U) / ITT(U) / ITE(U)
@@ -201,24 +190,18 @@ p_decode:
                                                                END IF;
 
                                                                CASE rD_v(4 downto 3) IS
-                                                                       WHEN "00"   =>
-                                                                               it_Action_v := IT;
-                                                                       WHEN "01"   =>
-                                                                               it_Action_v := ITT;
-                                                                       WHEN "10"   =>
-                                                                               it_Action_v := ITE;
-                                                                       WHEN OTHERS =>
-                                                                               noLiteOpc_o <= '1';
+                                                                       WHEN "00"   =>  it_Action_v := IT;
+                                                                       WHEN "01"   =>  it_Action_v := ITT;
+                                                                       WHEN "10"   =>  it_Action_v := ITE;
+                                                                       WHEN OTHERS =>  NULL;
                                                                END CASE;
                                                                condition_raw_v := rD_v(2 downto 0);
                                                                -- IT instruction isn't writing to anything
                                                                wrb_Action_v := NO_WRB;
-                                                       ELSE
-                                                               noLiteOpc_o <= '1';
                                                        END IF;
 
                                                WHEN OTHERS =>
-                                                               noLiteOpc_o <= '1';
+                                                               NULL;
                                        END CASE;
 
                                WHEN "10" =>
@@ -234,7 +217,7 @@ p_decode:
                                                                        WHEN "10" =>                                -- SRL
                                                                                alu_Cin_v := CIN_ZERO;
                                                                        WHEN OTHERS =>
-                                                                               noLiteOpc_o <= '1';
+                                                                               NULL;
                                                                        END CASE;
                                                                alu_Action_v := A_SHIFT;
                                                                msr_Action_v := UPDATE_CARRY;
@@ -244,7 +227,7 @@ p_decode:
                                                        WHEN "111" =>                                   -- SEXT16
                                                                alu_Action_v := A_SEXT16;
                                                        WHEN OTHERS  =>
-                                                               noLiteOpc_o  <= '1';
+                                                               NULL;
                                                END CASE;
 
                                        ELSIF (opcIx_v (3 DOWNTO 0) = "1100") THEN          -- IMM
@@ -257,17 +240,14 @@ p_decode:
                                                CASE rD_v (3 DOWNTO 0) IS
                                                        WHEN "0001" =>                                  -- RTI(D)
                                                                int_busy_v := '0';
-                                                       WHEN "0000" =>                                  -- RTS(D)
-                                                               WHEN OTHERS  =>
-                                                       noLiteOpc_o <= '1';
+                                                       WHEN OTHERS =>                                  -- RTS(D)
+                                                               NULL;
                                                END CASE;
 
                                                alu_Action_v    := A_ADD;
                                                branch_Action_v := BR;
                                                wrb_Action_v    := NO_WRB;
-                                               IF (COMPATIBILITY_MODE_g = TRUE) THEN
-                                                       delayBit_v  := rD_v(4);
-                                               END IF;
+                                               delayBit_v      := rD_v(4);
 
                                        ELSIF (opcIx_v (3 DOWNTO 0) = "0101") THEN
 
@@ -278,7 +258,7 @@ p_decode:
                                                                alu_Action_v := A_MTS;
                                                                wrb_Action_v := NO_WRB;
                                                        WHEN OTHERS  =>
-                                                               noLiteOpc_o  <= '1';
+                                                               NULL;
                                                END CASE;
                                                rB_v := (OTHERS => '0');    -- in order to prevent occasional hazards (r16, r24)
 
@@ -300,35 +280,31 @@ p_decode:
                                                                END IF;
 
                                                        WHEN "110" =>                                                                             -- BR(I)(D)
-                                                               IF (rA_v(2) = '1') THEN
-                                                                       branch_Action_v := BRL;
-                                                               ELSE
-                                                                       branch_Action_v := BR;
-                                                                       wrb_Action_v    := NO_WRB;
-                                                               END IF;
-
                                                                IF (rA_v(3) = '1') THEN
                                                                        alu_Op1_v := ALU_IN_ZERO;
                                                                ELSE
                                                                        alu_Op1_v := ALU_IN_PC;
                                                                END IF;
-                                                               alu_Action_v    := A_ADD;
-                                                               IF (COMPATIBILITY_MODE_g = TRUE) THEN
-                                                                       delayBit_v  := rA_v(4);
+
+                                                               IF (rA_v(2) = '1') THEN
+                                                                       branch_Action_v := BRL;
+                                                               ELSE
+                                                                       branch_Action_v := BR;
+                                                                       wrb_Action_v    := NO_WRB;
                                                                END IF;
+                                                               alu_Action_v := A_ADD;
+                                                               delayBit_v   := rA_v(4);
 
                                                        WHEN "111" =>
                                                                condition_raw_v := rD_v(2 downto 0);          -- Conditional branching
                                                                branch_Action_v := BR;
-                                                               alu_Action_v := A_ADD;
-                                                               alu_Op1_v    := ALU_IN_PC;
-                                                               IF (COMPATIBILITY_MODE_g = TRUE) THEN
-                                                                       delayBit_v := rD_v(4);
-                                                               END IF;
-                                                               wrb_Action_v := NO_WRB;     -- evaluate and update/overwrite in exeq
+                                                               alu_Action_v    := A_ADD;
+                                                               alu_Op1_v       := ALU_IN_PC;
+                                                               delayBit_v      := rD_v(4);
+                                                               wrb_Action_v    := NO_WRB;     -- evaluate and update/overwrite in exeq
 
                                                        WHEN OTHERS =>
-                                                               noLiteOpc_o  <= '1';
+                                                               NULL;
                                                END CASE;
                                        END IF;
 
@@ -343,8 +319,7 @@ p_decode:
                                                        WHEN "00"   => transfer_Size_v := BYTE;
                                                        WHEN "01"   => transfer_Size_v := HALFWORD;
                                                        WHEN "10"   => transfer_Size_v := WORD;
-                                                       WHEN OTHERS =>
-                                                               noLiteOpc_o <= '1';
+                                                       WHEN OTHERS => NULL;
                                                END CASE;
                                                IF (opcIx_v(2) = '0') THEN
                                                        mem_Action_v := RD_MEM;
@@ -356,7 +331,7 @@ p_decode:
                                        END IF;
 
                                WHEN OTHERS =>
-                                       noLiteOpc_o  <= '1';
+                                       NULL;
 
                        END CASE;
 
@@ -401,13 +376,10 @@ p_decode:
                                ID2EX_o.condition    <= COND_ALL;
                        WHEN OTHERS =>
                                ID2EX_o.condition    <= COND_ALL;
-                               noLiteOpc_o            <= '1';
                END CASE;
                --
-               IF (COMPATIBILITY_MODE_g = TRUE) THEN
-                       ID2CTRL_o.delayBit   <= delayBit_v;
-               END IF;
-               ID2CTRL_o.int_busy     <= int_busy_v;
+               ID2CTRL_o.delayBit       <= delayBit_v;
+               ID2CTRL_o.int_busy       <= int_busy_v;
 
        END PROCESS;