core: Do addpcis using the main adder (#189)

By adding logic to decode2 to be able to send the instruction address
down the A input, and making CONST_DX_HI (renamed to CONST_DXHI4) add
4 to the immediate value (easy since the bottom 16 bits were zero),
we can do addpcis using the main adder.  This reduces the width of the
result mux and frees up one value in insn_type_t, since we can now use
OP_ADD for addpcis.

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

decode1.vhdl

@@ -107,7 +107,7 @@ architecture behaviour of decode1 is
                 -- mcrf; and cr logical ops
 		2#000#    =>       (ALU,    OP_CROP,      NONE,       NONE,        NONE, NONE, '1', '1', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0'),
 		-- addpcis
-		2#001#    =>       (ALU,    OP_ADDPCIS,   NONE,       CONST_DX_HI, NONE, RT,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'),
+		2#001#    =>       (ALU,    OP_ADD,       CIA,        CONST_DXHI4, NONE, RT,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC,   '0', '0'),
                 -- bclr, bcctr, bctar
 		2#100#    =>       (ALU,    OP_BCREG,     SPR,        SPR,         NONE, SPR,  '1', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1', '0'),
                 -- isync

decode2.vhdl

@@ -56,7 +56,9 @@ architecture behaviour of decode2 is
 
 	function decode_input_reg_a (t : input_reg_a_t; insn_in : std_ulogic_vector(31 downto 0);
 				     reg_data : std_ulogic_vector(63 downto 0);
-				     ispr : gspr_index_t) return decode_input_reg_t is
+				     ispr : gspr_index_t;
+                                     instr_addr : std_ulogic_vector(63 downto 0))
+            return decode_input_reg_t is
 	begin
 		if t = RA or (t = RA_OR_ZERO and insn_ra(insn_in) /= "00000") then
 		    assert is_fast_spr(ispr) = '0' report "Decode A says GPR but ISPR says SPR:" &
@@ -71,6 +73,8 @@ architecture behaviour of decode2 is
 			report "Decode A says SPR but ISPR is invalid:" &
 			to_hstring(ispr) severity failure;
 		    return (is_fast_spr(ispr), ispr, reg_data);
+                elsif t = CIA then
+                    return ('0', (others => '0'), instr_addr);
 		else
 			return ('0', (others => '0'), (others => '0'));
 		end if;
@@ -100,8 +104,8 @@ architecture behaviour of decode2 is
 			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_bd(insn_in)) & "00", 64)));
 		when CONST_DS =>
 			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_ds(insn_in)) & "00", 64)));
-		when CONST_DX_HI =>
-			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_dx(insn_in)) & x"0000", 64)));
+		when CONST_DXHI4 =>
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_dx(insn_in)) & x"0004", 64)));
                 when CONST_M1 =>
 			ret := ('0', (others => '0'), x"FFFFFFFFFFFFFFFF");
 		when CONST_SH =>
@@ -282,7 +286,8 @@ begin
 		--v.e.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);
+		decoded_reg_a := decode_input_reg_a (d_in.decode.input_reg_a, d_in.insn, r_in.read1_data, d_in.ispr1,
+                                                     d_in.nia);
 		decoded_reg_b := decode_input_reg_b (d_in.decode.input_reg_b, d_in.insn, r_in.read2_data, d_in.ispr2);
 		decoded_reg_c := decode_input_reg_c (d_in.decode.input_reg_c, d_in.insn, r_in.read3_data);
 		decoded_reg_o := decode_output_reg (d_in.decode.output_reg_a, d_in.insn, d_in.ispr1);

decode_types.vhdl

@@ -3,7 +3,7 @@ use ieee.std_logic_1164.all;
 
 package decode_types is
     type insn_type_t is (OP_ILLEGAL, OP_NOP, OP_ADD,
-			 OP_ADDPCIS, OP_AND, OP_ATTN, OP_B, OP_BC, OP_BCREG,
+			 OP_AND, OP_ATTN, OP_B, OP_BC, OP_BCREG,
 			 OP_BPERM, OP_CMP, OP_CMPB, OP_CMPEQB, OP_CMPRB,
 			 OP_CNTZ, OP_CROP,
 			 OP_DARN, OP_DCBF, OP_DCBST, OP_DCBT, OP_DCBTST,
@@ -20,8 +20,9 @@ package decode_types is
 			 OP_XOR,
                          OP_FETCH_FAILED
 			 );
-    type input_reg_a_t is (NONE, RA, RA_OR_ZERO, SPR);
-    type input_reg_b_t is (NONE, RB, CONST_UI, CONST_SI, CONST_SI_HI, CONST_UI_HI, CONST_LI, CONST_BD, CONST_DX_HI, CONST_DS, CONST_M1, CONST_SH, CONST_SH32, SPR);
+    type input_reg_a_t is (NONE, RA, RA_OR_ZERO, SPR, CIA);
+    type input_reg_b_t is (NONE, RB, CONST_UI, CONST_SI, CONST_SI_HI, CONST_UI_HI, CONST_LI, CONST_BD,
+                           CONST_DXHI4, CONST_DS, CONST_M1, CONST_SH, CONST_SH32, SPR);
     type input_reg_c_t is (NONE, RS);
     type output_reg_a_t is (NONE, RT, RA, SPR);
     type rc_t is (NONE, ONE, RC);

execute1.vhdl

@@ -528,9 +528,6 @@ begin
                 end if;
 	    when OP_NOP =>
 		-- Do nothing
-	    when OP_ADDPCIS =>
-		result := ppc_adde(next_nia, b_in, '0')(63 downto 0);
-		result_en := '1';
 	    when OP_ADD | OP_CMP | OP_TRAP =>
 		if e_in.invert_a = '0' then
 		    a_inv := a_in;