Fix a Diamond issue in decode2

By using a temporary we avoid a build issue in Diamond.

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

decode2.vhdl

@@ -79,32 +79,33 @@ architecture behaviour of decode2 is
 	function decode_input_reg_b (t : input_reg_b_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
+		variable ret : decode_input_reg_t;
 	begin
 		case t is
 		when RB =>
 		    assert is_fast_spr(ispr) = '0' report "Decode B says GPR but ISPR says SPR:" &
 			to_hstring(ispr) severity failure;
-		    return ('1', gpr_to_gspr(insn_rb(insn_in)), reg_data);
+		    ret := ('1', gpr_to_gspr(insn_rb(insn_in)), reg_data);
 		when CONST_UI =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(unsigned(insn_ui(insn_in)), 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(unsigned(insn_ui(insn_in)), 64)));
 		when CONST_SI =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_si(insn_in)), 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_si(insn_in)), 64)));
 		when CONST_SI_HI =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_si(insn_in)) & x"0000", 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_si(insn_in)) & x"0000", 64)));
 		when CONST_UI_HI =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(unsigned(insn_si(insn_in)) & x"0000", 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(unsigned(insn_si(insn_in)) & x"0000", 64)));
 		when CONST_LI =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_li(insn_in)) & "00", 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_li(insn_in)) & "00", 64)));
 		when CONST_BD =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_bd(insn_in)) & "00", 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_bd(insn_in)) & "00", 64)));
 		when CONST_DS =>
-			return ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_ds(insn_in)) & "00", 64)));
+			ret := ('0', (others => '0'), std_ulogic_vector(resize(signed(insn_ds(insn_in)) & "00", 64)));
                 when CONST_M1 =>
-			return ('0', (others => '0'), x"FFFFFFFFFFFFFFFF");
+			ret := ('0', (others => '0'), x"FFFFFFFFFFFFFFFF");
 		when CONST_SH =>
-			return ('0', (others => '0'), x"00000000000000" & "00" & insn_in(1) & insn_in(15 downto 11));
+			ret := ('0', (others => '0'), x"00000000000000" & "00" & insn_in(1) & insn_in(15 downto 11));
 		when CONST_SH32 =>
-			return ('0', (others => '0'), x"00000000000000" & "000" & insn_in(15 downto 11));
+			ret := ('0', (others => '0'), x"00000000000000" & "000" & insn_in(15 downto 11));
 		when SPR =>
 		    -- ISPR must be either a valid fast SPR number or all 0 for a slow SPR.
 		    -- If it's all 0, we don't treat it as a dependency as slow SPRs
@@ -112,10 +113,12 @@ architecture behaviour of decode2 is
 		    assert is_fast_spr(ispr) = '1' or ispr = "000000"
 			report "Decode B says SPR but ISPR is invalid:" &
 			to_hstring(ispr) severity failure;
-		    return (is_fast_spr(ispr), ispr, reg_data);
+		    ret := (is_fast_spr(ispr), ispr, reg_data);
 		when NONE =>
-			return ('0', (others => '0'), (others => '0'));
+			ret := ('0', (others => '0'), (others => '0'));
 		end case;
+
+		return ret;
 	end;
 
 	function decode_input_reg_c (t : input_reg_c_t; insn_in : std_ulogic_vector(31 downto 0);