Make multiplier hang off the side of execute1

With this, the multiplier isn't a separate pipe that decode2 issues
instructions to, but rather is a unit that execute1 sends operands
to and which sends the result back to execute1, which then sends it
to writeback.  Execute1 now sends a stall signal when it gets a
multiply instruction until it gets a valid signal back from the
multiplier.

This all means that we no longer need to mark the multiply
instructions as single-issue.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Makefile

@@ -17,7 +17,7 @@ common.o: decode_types.o
 control.o: gpr_hazard.o cr_hazard.o common.o
 sim_jtag.o: sim_jtag_socket.o
 core_tb.o: common.o wishbone_types.o core.o soc.o sim_jtag.o
-core.o: common.o wishbone_types.o fetch1.o fetch2.o icache.o decode1.o decode2.o register_file.o cr_file.o execute1.o loadstore1.o dcache.o multiply.o writeback.o core_debug.o divider.o
+core.o: common.o wishbone_types.o fetch1.o fetch2.o icache.o decode1.o decode2.o register_file.o cr_file.o execute1.o loadstore1.o dcache.o writeback.o core_debug.o divider.o
 core_debug.o: common.o
 countzero.o:
 countzero_tb.o: common.o glibc_random.o countzero.o
@@ -26,7 +26,7 @@ crhelpers.o: common.o
 decode1.o: common.o decode_types.o
 decode2.o: decode_types.o common.o helpers.o insn_helpers.o control.o
 decode_types.o:
-execute1.o: decode_types.o common.o helpers.o crhelpers.o insn_helpers.o ppc_fx_insns.o rotator.o logical.o countzero.o
+execute1.o: decode_types.o common.o helpers.o crhelpers.o insn_helpers.o ppc_fx_insns.o rotator.o logical.o countzero.o multiply.o
 fetch1.o: common.o
 fetch2.o: common.o wishbone_types.o
 glibc_random_helpers.o:

common.vhdl

@@ -130,7 +130,7 @@ package common is
 	 invert_out => '0', input_carry => ZERO, output_carry => '0', input_cr => '0', output_cr => '0',
 	 is_32bit => '0', is_signed => '0', xerc => xerc_init, others => (others => '0'));
 
-    type Decode2ToMultiplyType is record
+    type Execute1ToMultiplyType is record
 	valid: std_ulogic;
 	insn_type: insn_type_t;
 	write_reg: gpr_index_t;
@@ -141,7 +141,7 @@ package common is
 	is_32bit: std_ulogic;
 	xerc: xer_common_t;
     end record;
-    constant Decode2ToMultiplyInit : Decode2ToMultiplyType := (valid => '0', insn_type => OP_ILLEGAL, rc => '0',
+    constant Execute1ToMultiplyInit : Execute1ToMultiplyType := (valid => '0', insn_type => OP_ILLEGAL, rc => '0',
 								 oe => '0', is_32bit => '0', xerc => xerc_init,
 								 others => (others => '0'));
 
@@ -261,17 +261,16 @@ package common is
 								   write_xerc_enable => '0', xerc => xerc_init,
 								   others => (others => '0'));
 
-    type MultiplyToWritebackType is record
+    type MultiplyToExecute1Type is record
 	valid: std_ulogic;
 
-	write_reg_enable : std_ulogic;
 	write_reg_nr: gpr_index_t;
 	write_reg_data: std_ulogic_vector(63 downto 0);
 	write_xerc_enable : std_ulogic;
 	xerc : xer_common_t;
 	rc: std_ulogic;
     end record;
-    constant MultiplyToWritebackInit : MultiplyToWritebackType := (valid => '0', write_reg_enable => '0',
+    constant MultiplyToExecute1Init : MultiplyToExecute1Type := (valid => '0',
 								 rc => '0', write_xerc_enable => '0',
 								 xerc => xerc_init,
 								 others => (others => '0'));

core.vhdl

@@ -63,10 +63,6 @@ architecture behave of core is
     signal loadstore1_to_dcache: Loadstore1ToDcacheType;
     signal dcache_to_writeback: DcacheToWritebackType;
 
-    -- multiply signals
-    signal decode2_to_multiply: Decode2ToMultiplyType;
-    signal multiply_to_writeback: MultiplyToWritebackType;
-
     -- divider signals
     signal decode2_to_divider: Decode2ToDividerType;
     signal divider_to_writeback: DividerToWritebackType;
@@ -115,7 +111,6 @@ architecture behave of core is
     attribute keep_hierarchy of register_file_0 : label is keep_h(DISABLE_FLATTEN);
     attribute keep_hierarchy of cr_file_0 : label is keep_h(DISABLE_FLATTEN);
     attribute keep_hierarchy of execute1_0 : label is keep_h(DISABLE_FLATTEN);
-    attribute keep_hierarchy of multiply_0 : label is keep_h(DISABLE_FLATTEN);
     attribute keep_hierarchy of divider_0 : label is keep_h(DISABLE_FLATTEN);
     attribute keep_hierarchy of loadstore1_0 : label is keep_h(DISABLE_FLATTEN);
     attribute keep_hierarchy of dcache_0 : label is keep_h(DISABLE_FLATTEN);
@@ -197,7 +192,6 @@ begin
             d_in => decode1_to_decode2,
             e_out => decode2_to_execute1,
             l_out => decode2_to_loadstore1,
-            m_out => decode2_to_multiply,
             d_out => decode2_to_divider,
             r_in => register_file_to_decode2,
             r_out => decode2_to_register_file,
@@ -265,13 +259,6 @@ begin
             wishbone_out => wishbone_data_out
             );
 
-    multiply_0: entity work.multiply
-        port map (
-            clk => clk,
-            m_in => decode2_to_multiply,
-            m_out => multiply_to_writeback
-            );
-
     divider_0: entity work.divider
         port map (
             clk => clk,
@@ -285,7 +272,6 @@ begin
             clk => clk,
             e_in => execute1_to_writeback,
             l_in => dcache_to_writeback,
-            m_in => multiply_to_writeback,
             d_in => divider_to_writeback,
             w_out => writeback_to_register_file,
             c_out => writeback_to_cr_file,

decode1.vhdl

@@ -54,7 +54,7 @@ architecture behaviour of decode1 is
 		41 =>       (LDST,   OP_LOAD,      RA_OR_ZERO, CONST_SI,    NONE, RT,   '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '1', '0', '0', '0', NONE, '0', '1'), -- lhzu
 		32 =>       (LDST,   OP_LOAD,      RA_OR_ZERO, CONST_SI,    NONE, RT,   '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '0', '0', '0', '0', NONE, '0', '1'), -- lwz
                 33 =>       (LDST,   OP_LOAD,      RA_OR_ZERO, CONST_SI,    NONE, RT,   '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '1', '0', '0', '0', NONE, '0', '1'), -- lwzu
-		 7 =>       (MUL,    OP_MUL_L64,   RA,         CONST_SI,    NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', NONE, '0', '1'), -- mulli
+		 7 =>       (ALU,    OP_MUL_L64,   RA,         CONST_SI,    NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', NONE, '0', '0'), -- mulli
 		24 =>       (ALU,    OP_OR,        NONE,       CONST_UI,    RS,   RA,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- ori
 		25 =>       (ALU,    OP_OR,        NONE,       CONST_UI_HI, RS,   RA,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- oris
 		20 =>       (ALU,    OP_RLC,       RA,         CONST_SH32,  RS,   RA,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC,   '0', '0'), -- rlwimi
@@ -244,19 +244,19 @@ architecture behaviour of decode1 is
 		2#1100001011#  =>       (DIV,    OP_MOD,       RA,         RB,          NONE, RT,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1'), -- modsw
 		2#0010010000#  =>       (ALU,    OP_MTCRF,     NONE,       NONE,        RS,   NONE, '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- mtcrf/mtocrf
 		2#0111010011#  =>       (ALU,    OP_MTSPR,     NONE,       NONE,        RS,   SPR,  '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- mtspr
-		2#0001001001#  =>       (MUL,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '1'), -- mulhd
+		2#0001001001#  =>       (ALU,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '0'), -- mulhd
-		2#0000001001#  =>       (MUL,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '1'), -- mulhdu
+		2#0000001001#  =>       (ALU,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'), -- mulhdu
-		2#0001001011#  =>       (MUL,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '1'), -- mulhw
+		2#0001001011#  =>       (ALU,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '0'), -- mulhw
-		2#0000001011#  =>       (MUL,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC,   '0', '1'), -- mulhwu
+		2#0000001011#  =>       (ALU,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC,   '0', '0'), -- mulhwu
                 -- next 4 have reserved bit set
-		2#1001001001#  =>       (MUL,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '1'), -- mulhd
+		2#1001001001#  =>       (ALU,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '0'), -- mulhd
-		2#1000001001#  =>       (MUL,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '1'), -- mulhdu
+		2#1000001001#  =>       (ALU,    OP_MUL_H64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'), -- mulhdu
-		2#1001001011#  =>       (MUL,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '1'), -- mulhw
+		2#1001001011#  =>       (ALU,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '0'), -- mulhw
-		2#1000001011#  =>       (MUL,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC,   '0', '1'), -- mulhwu
+		2#1000001011#  =>       (ALU,    OP_MUL_H32,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC,   '0', '0'), -- mulhwu
-		2#0011101001#  =>       (MUL,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '1'), -- mulld
+		2#0011101001#  =>       (ALU,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '0'), -- mulld
-		2#1011101001#  =>       (MUL,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '1'), -- mulldo
+		2#1011101001#  =>       (ALU,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '1', RC,   '0', '0'), -- mulldo
-		2#0011101011#  =>       (MUL,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '1'), -- mullw
+		2#0011101011#  =>       (ALU,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '0'), -- mullw
-		2#1011101011#  =>       (MUL,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '1'), -- mullwo
+		2#1011101011#  =>       (ALU,    OP_MUL_L64,   RA,         RB,          NONE, RT,   '0', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '1', RC,   '0', '0'), -- mullwo
 		2#0111011100#  =>       (ALU,    OP_AND,       NONE,       RB,          RS,   RA,   '0', '0', '0', '1', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'), -- nand
 		2#0001101000#  =>       (ALU,    OP_ADD,       RA,         NONE,        NONE, RT,   '0', '0', '1', '0', ONE,  '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'), -- neg
 		2#1001101000#  =>       (ALU,    OP_ADD,       RA,         NONE,        NONE, RT,   '0', '0', '1', '0', ONE,  '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'), -- nego

decode2.vhdl

@@ -24,7 +24,6 @@ entity decode2 is
 		d_in  : in Decode1ToDecode2Type;
 
 		e_out : out Decode2ToExecute1Type;
-		m_out : out Decode2ToMultiplyType;
                 d_out : out Decode2ToDividerType;
 		l_out : out Decode2ToLoadstore1Type;
 
@@ -39,7 +38,6 @@ end entity decode2;
 architecture behaviour of decode2 is
 	type reg_type is record
 		e : Decode2ToExecute1Type;
-		m : Decode2ToMultiplyType;
                 d : Decode2ToDividerType;
 		l : Decode2ToLoadstore1Type;
 	end record;
@@ -238,7 +236,7 @@ begin
 	decode2_0: process(clk)
 	begin
 		if rising_edge(clk) then
-			if rin.e.valid = '1' or rin.l.valid = '1' or rin.m.valid = '1' or rin.d.valid = '1' then
+			if rin.e.valid = '1' or rin.l.valid = '1' or rin.d.valid = '1' then
 				report "execute " & to_hstring(rin.e.nia);
 			end if;
 			r <= rin;
@@ -266,14 +264,12 @@ begin
 
 		v.e := Decode2ToExecute1Init;
 		v.l := Decode2ToLoadStore1Init;
-		v.m := Decode2ToMultiplyInit;
                 v.d := Decode2ToDividerInit;
 
 		mul_a := (others => '0');
 		mul_b := (others => '0');
 
 		--v.e.input_cr := d_in.decode.input_cr;
-		--v.m.input_cr := d_in.decode.input_cr;
 		--v.e.output_cr := d_in.decode.output_cr;
     
 		decoded_reg_a := decode_input_reg_a (d_in.decode.input_reg_a, d_in.insn, r_in.read1_data, d_in.ispr1);
@@ -323,38 +319,6 @@ begin
                 v.e.insn := d_in.insn;
                 v.e.data_len := length;
 
-		-- multiply unit
-		v.m.insn_type := d_in.decode.insn_type;
-		mul_a := decoded_reg_a.data;
-		mul_b := decoded_reg_b.data;
-		v.m.write_reg := gspr_to_gpr(decoded_reg_o.reg);
-		v.m.rc := decode_rc(d_in.decode.rc, d_in.insn);
-		v.m.xerc := c_in.read_xerc_data;
-		if v.m.insn_type = OP_MUL_L64 then
-		  v.m.oe := decode_oe(d_in.decode.rc, d_in.insn);
-		end if;
-		v.m.is_32bit := d_in.decode.is_32bit;
-
-		if d_in.decode.is_32bit = '1' then
-			if d_in.decode.is_signed = '1' then
-				v.m.data1 := (others => mul_a(31));
-				v.m.data1(31 downto 0) := mul_a(31 downto 0);
-				v.m.data2 := (others => mul_b(31));
-				v.m.data2(31 downto 0) := mul_b(31 downto 0);
-			else
-				v.m.data1 := '0' & x"00000000" & mul_a(31 downto 0);
-				v.m.data2 := '0' & x"00000000" & mul_b(31 downto 0);
-			end if;
-		else
-			if d_in.decode.is_signed = '1' then
-				v.m.data1 := mul_a(63) & mul_a;
-				v.m.data2 := mul_b(63) & mul_b;
-			else
-				v.m.data1 := '0' & mul_a;
-				v.m.data2 := '0' & mul_b;
-			end if;
-		end if;
-
                 -- divide unit
                 -- PPC divide and modulus instruction words have these bits in
                 -- the bottom 11 bits: o1dns 010t1 r
@@ -438,7 +402,6 @@ begin
                 cr_write_valid <= d_in.decode.output_cr or decode_rc(d_in.decode.rc, d_in.insn);
 
 		v.e.valid := '0';
-		v.m.valid := '0';
                 v.d.valid := '0';
 		v.l.valid := '0';
 		case d_in.decode.unit is
@@ -446,8 +409,6 @@ begin
 			v.e.valid := control_valid_out;
 		when LDST =>
 			v.l.valid := control_valid_out;
-		when MUL =>
-			v.m.valid := control_valid_out;
                 when DIV =>
                         v.d.valid := control_valid_out;
 		when NONE =>
@@ -458,7 +419,6 @@ begin
 		if rst = '1' then
 			v.e := Decode2ToExecute1Init;
 			v.l := Decode2ToLoadStore1Init;
-			v.m := Decode2ToMultiplyInit;
                         v.d := Decode2ToDividerInit;
 		end if;
 
@@ -468,7 +428,6 @@ begin
 		-- Update outputs
 		e_out <= r.e;
 		l_out <= r.l;
-		m_out <= r.m;
                 d_out <= r.d;
 	end process;
 end architecture behaviour;

decode_types.vhdl

@@ -46,7 +46,7 @@ package decode_types is
 
     constant TOO_OFFSET : integer := 0;
 
-    type unit_t is (NONE, ALU, LDST, MUL, DIV);
+    type unit_t is (NONE, ALU, LDST, DIV);
     type length_t is (NONE, is1B, is2B, is4B, is8B);
 
     type decode_rom_t is record

execute1.vhdl

@@ -35,6 +35,7 @@ architecture behaviour of execute1 is
 	e : Execute1ToWritebackType;
 	lr_update : std_ulogic;
 	next_lr : std_ulogic_vector(63 downto 0);
+	mul_in_progress : std_ulogic;
     end record;
 
     signal r, rin : reg_type;
@@ -48,6 +49,10 @@ architecture behaviour of execute1 is
     signal logical_result: std_ulogic_vector(63 downto 0);
     signal countzero_result: std_ulogic_vector(63 downto 0);
 
+    -- multiply signals
+    signal x_to_multiply: Execute1ToMultiplyType;
+    signal multiply_to_x: MultiplyToExecute1Type;
+
     procedure set_carry(e: inout Execute1ToWritebackType;
 			carry32 : in std_ulogic;
 			carry : in std_ulogic) is
@@ -123,6 +128,13 @@ begin
 	    result => countzero_result
 	    );
 
+    multiply_0: entity work.multiply
+        port map (
+            clk => clk,
+            m_in => x_to_multiply,
+            m_out => multiply_to_x
+            );
+
     execute1_0: process(clk)
     begin
 	if rising_edge(clk) then
@@ -204,6 +216,38 @@ begin
 	end if;
 
 	v.lr_update := '0';
+	v.mul_in_progress := '0';
+
+	-- signals to multiply unit
+	x_to_multiply <= Execute1ToMultiplyInit;
+	x_to_multiply.insn_type <= e_in.insn_type;
+	x_to_multiply.write_reg <= gspr_to_gpr(e_in.write_reg);
+	x_to_multiply.rc <= e_in.rc;
+	x_to_multiply.xerc <= v.e.xerc;
+	if e_in.insn_type = OP_MUL_L64 then
+	    x_to_multiply.oe <= e_in.oe;
+	end if;
+	x_to_multiply.is_32bit <= e_in.is_32bit;
+
+	if e_in.is_32bit = '1' then
+	    if e_in.is_signed = '1' then
+		x_to_multiply.data1 <= (others => e_in.read_data1(31));
+		x_to_multiply.data1(31 downto 0) <= e_in.read_data1(31 downto 0);
+		x_to_multiply.data2 <= (others => e_in.read_data2(31));
+		x_to_multiply.data2(31 downto 0) <= e_in.read_data2(31 downto 0);
+	    else
+		x_to_multiply.data1 <= '0' & x"00000000" & e_in.read_data1(31 downto 0);
+		x_to_multiply.data2 <= '0' & x"00000000" & e_in.read_data2(31 downto 0);
+	    end if;
+	else
+	    if e_in.is_signed = '1' then
+		x_to_multiply.data1 <= e_in.read_data1(63) & e_in.read_data1;
+		x_to_multiply.data2 <= e_in.read_data2(63) & e_in.read_data2;
+	    else
+		x_to_multiply.data1 <= '0' & e_in.read_data1;
+		x_to_multiply.data2 <= '0' & e_in.read_data2;
+	    end if;
+	end if;
 
 	ctrl_tmp <= ctrl;
 	-- FIXME: run at 512MHz not core freq
@@ -506,11 +550,19 @@ begin
 	    when OP_ICBI =>
 		icache_inval <= '1';
 
+		when OP_MUL_L64 | OP_MUL_H64 | OP_MUL_H32 =>
+		v.e.valid := '0';
+		v.mul_in_progress := '1';
+		stall_out <= '1';
+		x_to_multiply.valid <= '1';
+
 	    when others =>
 		terminate_out <= '1';
 		report "illegal";
 	    end case;
 
+	    v.e.rc := e_in.rc and e_in.valid;
+
 	    -- Update LR on the next cycle after a branch link
 	    --
 	    -- WARNING: The LR update isn't tracked by our hazard tracker. This
@@ -536,11 +588,25 @@ begin
 	    v.e.write_len := x"8";
 	    v.e.sign_extend := '0';
 	    v.e.valid := '1';
+	elsif r.mul_in_progress = '1' then
+	    if multiply_to_x.valid = '1' then
+		v.e.write_reg := gpr_to_gspr(multiply_to_x.write_reg_nr);
+		result := multiply_to_x.write_reg_data;
+		result_en := '1';
+		v.e.rc := multiply_to_x.rc;
+		v.e.xerc := multiply_to_x.xerc;
+		v.e.write_xerc_enable := multiply_to_x.write_xerc_enable;
+		v.e.valid := '1';
+		v.e.write_len := x"8";
+		v.e.sign_extend := '0';
+	    else
+		stall_out <= '1';
+		v.mul_in_progress := '1';
+	    end if;
 	end if;
 
 	v.e.write_data := result;
 	v.e.write_enable := result_en;
-	v.e.rc := e_in.rc and e_in.valid;
 
 	-- Update registers
 	rin <= v;

multiply.vhdl

@@ -13,13 +13,13 @@ entity multiply is
     port (
         clk   : in std_logic;
 
-        m_in  : in Decode2ToMultiplyType;
+        m_in  : in Execute1ToMultiplyType;
-        m_out : out MultiplyToWritebackType
+        m_out : out MultiplyToExecute1Type
         );
 end entity multiply;
 
 architecture behaviour of multiply is
-    signal m: Decode2ToMultiplyType;
+    signal m: Execute1ToMultiplyType;
 
     type multiply_pipeline_stage is record
         valid     : std_ulogic;
@@ -64,7 +64,7 @@ begin
     begin
         v := r;
 
-        m_out <= MultiplyToWritebackInit;
+        m_out <= MultiplyToExecute1Init;
 
         v.multiply_pipeline(0).valid := m.valid;
         v.multiply_pipeline(0).insn_type := m.insn_type;
@@ -107,7 +107,6 @@ begin
 	-- Generate OV/OV32/SO when OE=1
         if v.multiply_pipeline(PIPELINE_DEPTH-1).valid = '1' then
             m_out.valid <= '1';
-            m_out.write_reg_enable <= '1';
             m_out.rc <= v.multiply_pipeline(PIPELINE_DEPTH-1).rc;
             m_out.write_xerc_enable <= v.multiply_pipeline(PIPELINE_DEPTH-1).oe;
 

multiply_tb.vhdl

@@ -17,8 +17,8 @@ architecture behave of multiply_tb is
 
     constant pipeline_depth : integer := 4;
 
-    signal m1               : Decode2ToMultiplyType;
+    signal m1               : Execute1ToMultiplyType;
-    signal m2               : MultiplyToWritebackType;
+    signal m2               : MultiplyToExecute1Type;
 begin
     multiply_0: entity work.multiply
         generic map (PIPELINE_DEPTH => pipeline_depth)
@@ -58,7 +58,6 @@ begin
 
         wait for clk_period;
         assert m2.valid = '1';
-        assert m2.write_reg_enable = '1';
         assert m2.write_reg_nr = "10001";
         assert m2.write_reg_data = x"0000000001111000";
         assert m2.rc = '0';
@@ -76,7 +75,6 @@ begin
 
         wait for clk_period * (pipeline_depth-1);
         assert m2.valid = '1';
-        assert m2.write_reg_enable = '1';
         assert m2.write_reg_nr = "10001";
         assert m2.write_reg_data = x"0000000001111000";
         assert m2.rc = '1';

writeback.vhdl

@@ -12,7 +12,6 @@ entity writeback is
 
         e_in         : in Execute1ToWritebackType;
         l_in         : in DcacheToWritebackType;
-        m_in         : in MultiplyToWritebackType;
         d_in         : in DividerToWritebackType;
 
         w_out        : out WritebackToRegisterFileType;
@@ -67,32 +66,28 @@ begin
     begin
         x := "" & e_in.valid;
         y := "" & l_in.valid;
-        z := "" & m_in.valid;
+        z := "" & d_in.valid;
-        w := "" & d_in.valid;
+        assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1 severity failure;
-        assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z)) + to_integer(unsigned(w))) <= 1 severity failure;
 
         x := "" & e_in.write_enable;
         y := "" & l_in.write_enable;
-        z := "" & m_in.write_reg_enable;
+        z := "" & d_in.write_reg_enable;
-        w := "" & d_in.write_reg_enable;
+        assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1 severity failure;
-        assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z)) + to_integer(unsigned(w))) <= 1 severity failure;
 
         w := "" & e_in.write_cr_enable;
         x := "" & (e_in.write_enable and e_in.rc);
-        y := "" & (m_in.valid and m_in.rc);
         z := "" & (d_in.valid and d_in.rc);
-        assert (to_integer(unsigned(w)) + to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1 severity failure;
+        assert (to_integer(unsigned(w)) + to_integer(unsigned(x)) + to_integer(unsigned(z))) <= 1 severity failure;
 
         x := "" & e_in.write_xerc_enable;
-        y := "" & m_in.write_xerc_enable;
         z := "" & D_in.write_xerc_enable;
-        assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1 severity failure;
+        assert (to_integer(unsigned(x)) + to_integer(unsigned(z))) <= 1 severity failure;
 
         w_out <= WritebackToRegisterFileInit;
         c_out <= WritebackToCrFileInit;
 
         complete_out <= '0';
-        if e_in.valid = '1' or l_in.valid = '1' or m_in.valid = '1' or d_in.valid = '1' then
+        if e_in.valid = '1' or l_in.valid = '1' or d_in.valid = '1' then
             complete_out <= '1';
         end if;
 
@@ -143,19 +138,6 @@ begin
 	    xe := l_in.xerc;
         end if;
 
-        if m_in.write_reg_enable = '1' then
-            w_out.write_enable <= '1';
-            w_out.write_reg <= gpr_to_gspr(m_in.write_reg_nr);
-            data_in <= m_in.write_reg_data;
-            rc <= m_in.rc;
-	    xe := m_in.xerc;
-        end if;
-
-	if m_in.write_xerc_enable = '1' then
-            c_out.write_xerc_enable <= '1';
-            c_out.write_xerc_data <= m_in.xerc;
-	end if;
-
         if d_in.write_reg_enable = '1' then
             w_out.write_enable <= '1';
             w_out.write_reg <= gpr_to_gspr(d_in.write_reg_nr);