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Separate jump target calculation from jump_in_id

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Sven Stucki 2015-09-03 02:08:48 +02:00
parent 2c2ad21c85
commit 77ef44a82f
2 changed files with 39 additions and 32 deletions
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65
controller.sv
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@ -120,6 +120,7 @@ module controller
output logic [1:0] operand_c_fw_mux_sel_o, // regfile rc data selector form ID stage
// Jump target calcuation done decision
output logic [1:0] jump_target_mux_sel_o, // jump target selection
input logic [1:0] jump_in_ex_i, // jump is being calculated in ALU
output logic [1:0] jump_in_id_o, // jump is being calculated in ALU
input logic branch_decision_i,
@ -191,6 +192,7 @@ module controller
always_comb
begin
jump_in_id = `BRANCH_NONE;
jump_target_mux_sel_o = `BRANCH_NONE;
alu_operator = `ALU_NOP;
alu_op_a_mux_sel_o = `OP_A_REGA_OR_FWD;
@ -249,43 +251,44 @@ module controller
//////////////////////////////////////
`OPCODE_JAL: begin // Jump and Link
if (instr_rdata_i ==? `INSTR_JAL) begin
jump_in_id = `BRANCH_JAL;
// Calculate and store PC+4
alu_op_a_mux_sel_o = `OP_A_CURRPC;
alu_op_b_mux_sel_o = `OP_B_IMM;
immediate_mux_sel_o = `IMM_PCINCR;
alu_operator = `ALU_ADD;
regfile_alu_we = 1'b1;
// Calculate jump target (= PC + UJ imm)
alu_op_c_mux_sel_o = `OP_C_JT;
end else begin
illegal_insn_int = 1'b1;
end
jump_target_mux_sel_o = `BRANCH_JAL;
jump_in_id = `BRANCH_JAL;
// Calculate and store PC+4
alu_op_a_mux_sel_o = `OP_A_CURRPC;
alu_op_b_mux_sel_o = `OP_B_IMM;
immediate_mux_sel_o = `IMM_PCINCR;
alu_operator = `ALU_ADD;
regfile_alu_we = 1'b1;
// Calculate jump target (= PC + UJ imm)
alu_op_c_mux_sel_o = `OP_C_JT;
end
`OPCODE_JALR: begin // Jump and Link Register
if (instr_rdata_i ==? `INSTR_JALR) begin
jump_in_id = `BRANCH_JALR;
// Calculate and store PC+4
alu_op_a_mux_sel_o = `OP_A_CURRPC;
alu_op_b_mux_sel_o = `OP_B_IMM;
immediate_mux_sel_o = `IMM_PCINCR;
alu_operator = `ALU_ADD;
regfile_alu_we = 1'b1;
// Calculate jump target (= RS1 + I imm)
rega_used = 1'b1;
alu_op_c_mux_sel_o = `OP_C_JT;
end else begin
illegal_insn_int = 1'b1;
jump_target_mux_sel_o = `BRANCH_JALR;
jump_in_id = `BRANCH_JALR;
// Calculate and store PC+4
alu_op_a_mux_sel_o = `OP_A_CURRPC;
alu_op_b_mux_sel_o = `OP_B_IMM;
immediate_mux_sel_o = `IMM_PCINCR;
alu_operator = `ALU_ADD;
regfile_alu_we = 1'b1;
// Calculate jump target (= RS1 + I imm)
rega_used = 1'b1;
alu_op_c_mux_sel_o = `OP_C_JT;
if (instr_rdata_i[14:12] != 3'b0) begin
jump_in_id = `BRANCH_NONE;
regfile_alu_we = 1'b0;
illegal_insn_int = 1'b0;
end
end
`OPCODE_BRANCH: begin // Branch
jump_in_id = `BRANCH_COND;
alu_op_c_mux_sel_o = `OP_C_JT;
rega_used = 1'b1;
regb_used = 1'b1;
jump_target_mux_sel_o = `BRANCH_COND;
jump_in_id = `BRANCH_COND;
alu_op_c_mux_sel_o = `OP_C_JT;
rega_used = 1'b1;
regb_used = 1'b1;
unique case (instr_rdata_i[14:12])
3'b000: alu_operator = `ALU_EQ;
@ -829,6 +832,8 @@ module controller
///////////////////////////////////////////////
`OPCODE_HWLOOP: begin // hardware loop instructions
jump_target_mux_sel_o = `BRANCH_JALR; // reuse jump target adder to calculate PC + I imm
unique case (instr_rdata_i[14:12])
3'b000: begin
// lp.starti set start address

6
id_stage.sv
View file

@ -215,6 +215,8 @@ module id_stage
logic [2:0] immediate_mux_sel;
logic [1:0] jump_target_mux_sel;
// Multiplier Control
logic mult_en; // multiplication is used instead of ALU
logic [1:0] mult_sel_subword; // Select a subword when doing multiplications
@ -348,8 +350,8 @@ module id_stage
//////////////////////////////////////////////////////////////////
always_comb
begin
unique case (jump_in_id_o)
begin : jump_target_mux
unique case (jump_target_mux_sel)
`BRANCH_JAL: jump_target = current_pc_id_i + imm_uj_type;
`BRANCH_JALR: jump_target = regfile_data_ra_id + imm_i_type; // cannot forward rs1 as path is too long
`BRANCH_COND: jump_target = current_pc_id_i + imm_sb_type;