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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.numeric_std.all;
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library work;
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use work.common.all;
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use work.wishbone_types.all;
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entity core is
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generic (
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SIM : boolean := false
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);
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port (
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clk : in std_logic;
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rst : in std_logic;
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wishbone_insn_in : in wishbone_slave_out;
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wishbone_insn_out : out wishbone_master_out;
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wishbone_data_in : in wishbone_slave_out;
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wishbone_data_out : out wishbone_master_out;
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dmi_addr : in std_ulogic_vector(3 downto 0);
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dmi_din : in std_ulogic_vector(63 downto 0);
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dmi_dout : out std_ulogic_vector(63 downto 0);
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dmi_req : in std_ulogic;
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dmi_wr : in std_ulogic;
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dmi_ack : out std_ulogic;
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terminated_out : out std_logic
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);
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end core;
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architecture behave of core is
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-- fetch signals
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signal fetch2_to_decode1: Fetch2ToDecode1Type;
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-- icache signals
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signal fetch1_to_icache : Fetch1ToIcacheType;
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signal icache_to_fetch2 : IcacheToFetch2Type;
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-- decode signals
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signal decode1_to_decode2: Decode1ToDecode2Type;
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signal decode2_to_execute1: Decode2ToExecute1Type;
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-- register file signals
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signal register_file_to_decode2: RegisterFileToDecode2Type;
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signal decode2_to_register_file: Decode2ToRegisterFileType;
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signal writeback_to_register_file: WritebackToRegisterFileType;
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-- CR file signals
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signal decode2_to_cr_file: Decode2ToCrFileType;
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signal cr_file_to_decode2: CrFileToDecode2Type;
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signal writeback_to_cr_file: WritebackToCrFileType;
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-- execute signals
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signal execute1_to_execute2: Execute1ToExecute2Type;
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signal execute2_to_writeback: Execute2ToWritebackType;
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signal execute1_to_fetch1: Execute1ToFetch1Type;
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-- load store signals
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signal decode2_to_loadstore1: Decode2ToLoadstore1Type;
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signal loadstore1_to_loadstore2: Loadstore1ToLoadstore2Type;
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signal loadstore2_to_writeback: Loadstore2ToWritebackType;
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-- multiply signals
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signal decode2_to_multiply: Decode2ToMultiplyType;
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signal multiply_to_writeback: MultiplyToWritebackType;
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-- divider signals
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signal decode2_to_divider: Decode2ToDividerType;
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signal divider_to_writeback: DividerToWritebackType;
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-- local signals
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signal fetch1_stall_in : std_ulogic;
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signal icache_stall_out : std_ulogic;
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signal fetch2_stall_in : std_ulogic;
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signal decode1_stall_in : std_ulogic;
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signal decode2_stall_out : std_ulogic;
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signal flush: std_ulogic;
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signal complete: std_ulogic;
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signal terminate: std_ulogic;
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signal core_rst: std_ulogic;
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signal icache_rst: std_ulogic;
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-- Debug actions
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signal dbg_core_stop: std_ulogic;
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signal dbg_core_rst: std_ulogic;
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signal dbg_icache_rst: std_ulogic;
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-- Debug status
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signal dbg_core_is_stopped: std_ulogic;
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begin
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core_rst <= dbg_core_rst or rst;
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fetch1_0: entity work.fetch1
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generic map (
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RESET_ADDRESS => (others => '0')
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)
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port map (
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clk => clk,
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rst => core_rst,
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stall_in => fetch1_stall_in,
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flush_in => flush,
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stop_in => dbg_core_stop,
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e_in => execute1_to_fetch1,
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i_out => fetch1_to_icache
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);
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fetch1_stall_in <= icache_stall_out or decode2_stall_out;
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icache_0: entity work.icache
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generic map(
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LINE_SIZE => 64,
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NUM_LINES => 16,
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NUM_WAYS => 2
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)
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port map(
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clk => clk,
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rst => icache_rst,
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i_in => fetch1_to_icache,
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i_out => icache_to_fetch2,
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flush_in => flush,
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stall_out => icache_stall_out,
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wishbone_out => wishbone_insn_out,
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wishbone_in => wishbone_insn_in
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);
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icache_rst <= rst or dbg_icache_rst;
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fetch2_0: entity work.fetch2
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port map (
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clk => clk,
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rst => core_rst,
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stall_in => fetch2_stall_in,
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flush_in => flush,
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i_in => icache_to_fetch2,
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f_out => fetch2_to_decode1
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);
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fetch2_stall_in <= decode2_stall_out;
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decode1_0: entity work.decode1
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port map (
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clk => clk,
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rst => core_rst,
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stall_in => decode1_stall_in,
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flush_in => flush,
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f_in => fetch2_to_decode1,
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d_out => decode1_to_decode2
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);
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decode1_stall_in <= decode2_stall_out;
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decode2_0: entity work.decode2
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port map (
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clk => clk,
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rst => core_rst,
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stall_out => decode2_stall_out,
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flush_in => flush,
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complete_in => complete,
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stopped_out => dbg_core_is_stopped,
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d_in => decode1_to_decode2,
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e_out => decode2_to_execute1,
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l_out => decode2_to_loadstore1,
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m_out => decode2_to_multiply,
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d_out => decode2_to_divider,
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r_in => register_file_to_decode2,
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r_out => decode2_to_register_file,
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c_in => cr_file_to_decode2,
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c_out => decode2_to_cr_file
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);
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register_file_0: entity work.register_file
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generic map (
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SIM => SIM
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)
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port map (
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clk => clk,
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d_in => decode2_to_register_file,
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d_out => register_file_to_decode2,
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w_in => writeback_to_register_file,
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sim_dump => terminate
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);
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cr_file_0: entity work.cr_file
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port map (
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clk => clk,
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d_in => decode2_to_cr_file,
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d_out => cr_file_to_decode2,
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w_in => writeback_to_cr_file
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);
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execute1_0: entity work.execute1
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generic map (
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SIM => SIM
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)
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port map (
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clk => clk,
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flush_out => flush,
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e_in => decode2_to_execute1,
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f_out => execute1_to_fetch1,
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e_out => execute1_to_execute2,
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terminate_out => terminate
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);
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execute2_0: entity work.execute2
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port map (
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clk => clk,
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e_in => execute1_to_execute2,
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e_out => execute2_to_writeback
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);
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loadstore1_0: entity work.loadstore1
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port map (
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clk => clk,
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l_in => decode2_to_loadstore1,
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l_out => loadstore1_to_loadstore2
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);
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loadstore2_0: entity work.loadstore2
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port map (
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clk => clk,
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l_in => loadstore1_to_loadstore2,
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w_out => loadstore2_to_writeback,
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m_in => wishbone_data_in,
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m_out => wishbone_data_out
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);
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multiply_0: entity work.multiply
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port map (
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clk => clk,
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m_in => decode2_to_multiply,
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m_out => multiply_to_writeback
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);
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divider_0: entity work.divider
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port map (
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clk => clk,
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divider: Return 0 for invalid and overflow cases, like P9 does
This adds logic to detect the cases where the quotient of the
division overflows the range of the output representation, and
return all zeroes in those cases, which is what POWER9 does.
To do this, we extend the dividend register by 1 bit and we do
an extra step in the division process to get a 2^64 bit of the
quotient, which ends up in the 'overflow' signal. This catches all
the cases where dividend >= 2^64 * divisor, including the case
where divisor = 0, and the divde/divdeu cases where |RA| >= |RB|.
Then, in the output stage, we also check that the result fits in
the representable range, which depends on whether the division is
a signed division or not, and whether it is a 32-bit or 64-bit
division. If dividend >= 2^64 or the result doesn't fit in the
representable range, write_data is set to 0 and write_cr_data to
0x20000000 (i.e. cr0.eq = 1).
POWER9 sets the top 32 bits of the result to zero for 32-bit signed
divisions, and sets CR0 when RC=1 according to the 64-bit value
(i.e. CR0.LT is always 0 for 32-bit signed divisions, even if the
32-bit result is negative). However, modsw with a negative result
sets the top 32 bits to all 1s. We follow suit.
This updates divider_tb to check the invalid cases as well as the
valid case.
This also fixes a small bug where the reset signal for the divider
was driven from rst when it should have been driven from core_rst.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
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rst => core_rst,
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d_in => decode2_to_divider,
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d_out => divider_to_writeback
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);
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writeback_0: entity work.writeback
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port map (
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clk => clk,
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e_in => execute2_to_writeback,
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l_in => loadstore2_to_writeback,
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m_in => multiply_to_writeback,
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d_in => divider_to_writeback,
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w_out => writeback_to_register_file,
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c_out => writeback_to_cr_file,
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complete_out => complete
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);
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debug_0: entity work.core_debug
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port map (
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clk => clk,
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rst => rst,
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dmi_addr => dmi_addr,
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dmi_din => dmi_din,
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dmi_dout => dmi_dout,
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dmi_req => dmi_req,
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dmi_wr => dmi_wr,
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dmi_ack => dmi_ack,
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core_stop => dbg_core_stop,
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core_rst => dbg_core_rst,
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icache_rst => dbg_icache_rst,
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terminate => terminate,
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core_stopped => dbg_core_is_stopped,
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nia => fetch1_to_icache.nia,
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terminated_out => terminated_out
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);
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end behave;
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