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Move jump decision logic to serv_state

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Olof Kindgren 2020-06-12 23:03:15 +02:00
parent a614e427b8
commit 8775b321d9
3 changed files with 23 additions and 16 deletions
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15
rtl/serv_decode.v
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@ -6,9 +6,9 @@ module serv_decode
input wire i_cnt_en,
input wire [31:2] i_wb_rdt,
input wire i_wb_en,
input wire i_alu_cmp,
//To state
output wire o_take_branch,
output wire o_bne_or_bge,
output wire o_cond_branch,
output wire o_e_op,
output wire o_ebreak,
output wire o_branch_op,
@ -33,7 +33,7 @@ module serv_decode
output wire o_alu_cmp_uns,
output wire o_alu_sh_signed,
output wire o_alu_sh_right,
output wire [3:0] o_alu_rd_sel,
output wire [3:0] o_alu_rd_sel,
//To RF
output reg [4:0] o_rf_rd_addr,
output reg [4:0] o_rf_rs1_addr,
@ -97,13 +97,8 @@ module serv_decode
//False for JALR/LOAD/STORE/OP/OPIMM?
assign o_bufreg_clr_lsb = opcode[4] & ((opcode[1:0] == 2'b00) | (opcode[1:0] == 2'b11));
//Take branch for jump or branch instructions (opcode == 1x0xx) if
//a) It's an unconditional branch (opcode[0] == 1)
//b) It's a conditional branch (opcode[0] == 0) of type beq,blt,bltu (funct3[0] == 0) and ALU compare is true
//c) It's a conditional branch (opcode[0] == 0) of type bne,bge,bgeu (funct3[0] == 1) and ALU compare is false
//Only valid during the last cycle of INIT, when the branch condition has
//been calculated.
assign o_take_branch = opcode[4] & !opcode[2] & (opcode[0] | (i_alu_cmp^funct3[0]));
assign o_bne_or_bge = funct3[0];
assign o_cond_branch = !opcode[0];
assign o_ctrl_utype = !opcode[4] & opcode[2] & opcode[0];
assign o_ctrl_jal_or_jalr = opcode[4] & opcode[0];

13
rtl/serv_state.v
View file

@ -11,7 +11,9 @@ module serv_state
output wire o_rf_wreq,
input wire i_rf_ready,
output wire o_rf_rd_en,
input wire i_take_branch,
input wire i_cond_branch,
input wire i_bne_or_bge,
input wire i_alu_cmp,
input wire i_branch_op,
input wire i_mem_op,
input wire i_shift_op,
@ -65,6 +67,13 @@ module serv_state
assign o_alu_shamt_en = (o_cnt0to3 | cnt4) & o_init;
//Take branch for jump or branch instructions (opcode == 1x0xx) if
//a) It's an unconditional branch (opcode[0] == 1)
//b) It's a conditional branch (opcode[0] == 0) of type beq,blt,bltu (funct3[0] == 0) and ALU compare is true
//c) It's a conditional branch (opcode[0] == 0) of type bne,bge,bgeu (funct3[0] == 1) and ALU compare is false
//Only valid during the last cycle of INIT, when the branch condition has
//been calculated.
wire take_branch = i_branch_op & (!i_cond_branch | (i_alu_cmp^i_bne_or_bge));
//slt*, branch/jump, shift, load/store
wire two_stage_op = i_slt_op | i_mem_op | i_branch_op | i_shift_op;
@ -89,7 +98,7 @@ module serv_state
always @(posedge i_clk) begin
if (o_cnt_done)
o_ctrl_jump <= o_init & i_take_branch;
o_ctrl_jump <= o_init & take_branch;
if (o_cnt_en)
stage_two_pending <= o_init;

11
rtl/serv_top.v
View file

@ -63,7 +63,8 @@ module serv_top
wire [3:0] immdec_ctrl;
wire take_branch;
wire bne_or_bge;
wire cond_branch;
wire e_op;
wire ebreak;
wire branch_op;
@ -165,7 +166,9 @@ module serv_top
.o_rf_wreq (o_rf_wreq),
.i_rf_ready (i_rf_ready),
.o_rf_rd_en (rd_en),
.i_take_branch (take_branch),
.i_bne_or_bge (bne_or_bge),
.i_cond_branch (cond_branch),
.i_alu_cmp (alu_cmp),
.i_branch_op (branch_op),
.i_mem_op (mem_op),
.i_shift_op (shift_op),
@ -202,9 +205,9 @@ module serv_top
.i_cnt_en (cnt_en),
.i_wb_rdt (i_ibus_rdt[31:2]),
.i_wb_en (o_ibus_cyc & i_ibus_ack),
.i_alu_cmp (alu_cmp),
//To state
.o_take_branch (take_branch),
.o_bne_or_bge (bne_or_bge),
.o_cond_branch (cond_branch),
.o_e_op (e_op),
.o_ebreak (ebreak),
.o_branch_op (branch_op),