github.com/olofk.serv
1
0
Fork 0
mirror of https://github.com/olofk/serv.git synced 2026-04-15 15:39:47 +00:00
Code Issues Releases Wiki Activity

Separate decode and state

Browse Source
This commit is contained in:
Olof Kindgren
2019-09-14 23:55:27 +02:00
parent 7289a68f6e
commit 9575eb4fef
4 changed files with 274 additions and 215 deletions
Download Patch File Download Diff File Expand all files Collapse all files

217
rtl/serv_decode.v
View File

@@ -2,79 +2,62 @@
module serv_decode
(
input wire clk,
input wire i_rst,
input wire i_new_irq,
//Input
input wire i_cnt_en,
input wire [31:0] i_wb_rdt,
input wire i_wb_en,
input wire i_rf_ready,
output wire o_init,
output wire o_run,
output wire o_cnt_en,
output reg [4:0] o_cnt,
output reg [3:0] o_cnt_r,
output wire o_cnt_done,
output reg o_bufreg_hold,
input wire i_alu_cmp,
//To state
output wire o_take_branch,
output wire o_e_op,
output wire o_ebreak,
output wire o_branch_op,
output wire o_mem_op,
output wire o_shift_op,
output wire o_slt_op,
//To bufreg
output wire o_bufreg_loop,
output wire o_bufreg_rs1_en,
output wire o_bufreg_imm_en,
output wire o_bufreg_loop,
output wire o_ctrl_pc_en,
output reg o_ctrl_jump,
//To ctrl
output wire o_ctrl_jalr,
output wire o_ctrl_jal_or_jalr,
output wire o_ctrl_utype,
output wire o_ctrl_pc_rel,
output wire o_ctrl_trap,
output reg o_ctrl_mret,
input wire i_ctrl_misalign,
output wire o_rf_rs_en,
//To alu
output wire o_alu_sub,
output wire [1:0] o_alu_bool_op,
output wire o_alu_cmp_eq,
output wire o_alu_cmp_uns,
output wire o_alu_sh_signed,
output wire o_alu_sh_right,
output reg [1:0] o_alu_rd_sel,
//To RF
output wire o_rf_rd_en,
output reg [4:0] o_rf_rd_addr,
output reg [4:0] o_rf_rs1_addr,
output reg [4:0] o_rf_rs2_addr,
output wire o_alu_sub,
output wire [1:0] o_alu_bool_op,
output wire o_alu_cmp_eq,
output wire o_alu_cmp_uns,
input wire i_alu_cmp,
output wire o_alu_shamt_en,
output wire o_alu_sh_signed,
output wire o_alu_sh_right,
input wire i_alu_sh_done,
output reg [1:0] o_alu_rd_sel,
output wire o_dbus_cyc,
output wire o_mem_op,
//To mem IF
output reg [2:0] o_funct3,
output wire o_mem_cmd,
output wire [1:0] o_mem_bytecnt,
input wire i_mem_misalign,
output wire o_rd_csr_en,
//To CSR
output wire o_csr_en,
output reg [1:0] o_csr_addr,
output wire o_csr_mstatus_en,
output wire o_csr_mie_en,
output wire o_csr_mcause_en,
output wire [1:0] o_csr_source,
output reg [3:0] o_csr_mcause,
output wire o_csr_imm,
output wire o_csr_d_sel,
output reg [2:0] o_funct3,
//To top
output wire o_imm,
output wire o_op_b_source,
output wire o_rd_csr_en,
output wire o_rd_alu_en,
output wire o_rd_mem_en);
`include "serv_params.vh"
localparam [1:0]
IDLE = 2'd0,
INIT = 2'd1,
RUN = 2'd2,
TRAP = 2'd3;
reg [1:0] state;
reg cnt_done;
wire cnt_en;
reg [4:0] opcode;
reg [31:0] imm;
reg op20;
@@ -82,28 +65,20 @@ module serv_decode
reg op22;
reg op26;
wire running;
wire mem_op;
wire shift_op;
wire slt_op;
wire branch_op;
wire e_op;
reg imm30;
assign o_cnt_done = cnt_done;
assign mem_op = !opcode[4] & !opcode[2] & !opcode[0];
assign o_mem_op = mem_op;
wire op_or_opimm = (!opcode[4] & opcode[2] & !opcode[0]);
assign shift_op = op_or_opimm & (o_funct3[1:0] == 2'b01);
assign slt_op = op_or_opimm & (o_funct3[2:1] == 2'b01);
assign o_mem_op = !opcode[4] & !opcode[2] & !opcode[0];
assign o_shift_op = op_or_opimm & (o_funct3[1:0] == 2'b01);
assign o_slt_op = op_or_opimm & (o_funct3[2:1] == 2'b01);
assign o_branch_op = opcode[4] & !opcode[2];
//Matches system opcodes except CSR accesses (o_funct3 == 0)
//No idea anymore why the !op21 condition is needed here
assign e_op = opcode[4] & opcode[2] & !op21 & !(|o_funct3);
assign o_e_op = opcode[4] & opcode[2] & !op21 & !(|o_funct3);
assign o_ebreak = op20;
//jal,branch = imm
//jalr = rs1+imm
@@ -112,21 +87,19 @@ module serv_decode
assign o_bufreg_rs1_en = !opcode[4] | (!opcode[1] & opcode[0]);
assign o_bufreg_imm_en = !opcode[2];
//Set loop mode for shift operations
//Loop bufreg contents for shift operations
assign o_bufreg_loop = op_or_opimm;
assign o_ctrl_pc_en = running | o_ctrl_trap;
//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 (o_funct3[0] == 0) and ALU compare is true
//c) It's a conditional branch (opcode[0] == 0) of type bne,bge,bgeu (o_funct3[0] == 1) and ALU compare is false
wire take_branch = (opcode[4] & !opcode[2]) & (opcode[0] | (i_alu_cmp^o_funct3[0]));
//Only valid during the last cycle of INIT, when the branch condition has
//been calculated.
wire o_take_branch = opcode[4] & !opcode[2] & (opcode[0] | (i_alu_cmp^o_funct3[0]));
assign o_ctrl_jalr = opcode[4] & (opcode[1:0] == 2'b01);
assign o_ctrl_utype = !opcode[4] & opcode[2] & opcode[0];
assign o_ctrl_utype = !opcode[4] & opcode[2] & opcode[0];
assign o_ctrl_jalr = opcode[4] & (opcode[1:0] == 2'b01);
assign o_ctrl_jal_or_jalr = opcode[4] & opcode[0];
//True for jal, b* auipc
@@ -141,11 +114,7 @@ module serv_decode
(!opcode[2] & opcode[4] & opcode[0]) |
(!opcode[2] & !opcode[3] & !opcode[0]));
reg alu_sub_r;
assign o_alu_sub = alu_sub_r;
always @(posedge clk)
alu_sub_r <= opcode[3] & imm30;
assign o_alu_sub = opcode[3] & imm30/*alu_sub_r*/;
/*
300 0_000 mstatus RWSC
@@ -174,19 +143,14 @@ module serv_decode
assign o_csr_source = o_funct3[1:0];
assign o_csr_d_sel = o_funct3[2];
assign o_csr_imm = (o_cnt < 5) ? o_rf_rs1_addr[o_cnt[2:0]] : 1'b0;
assign o_alu_cmp_eq = o_funct3[2:1] == 2'b00;
assign o_alu_cmp_uns = (o_funct3[0] & o_funct3[1]) | (o_funct3[1] & o_funct3[2]);
assign o_alu_shamt_en = (o_cnt < 5) & (state == INIT);
assign o_alu_sh_signed = imm30;
assign o_alu_sh_right = o_funct3[2];
assign o_mem_cmd = opcode[3];
assign o_mem_bytecnt = o_cnt[4:3];
assign o_alu_bool_op = o_funct3[1:0];
wire sign_bit = i_wb_rdt[31];
@@ -246,7 +210,7 @@ module serv_decode
stype ? i_wb_rdt[7] :
1'b0;
end
if (cnt_en)
if (i_cnt_en)
imm <= {imm[0], imm[31:1]};
end
@@ -260,100 +224,5 @@ module serv_decode
assign o_rd_alu_en = !opcode[0] & opcode[2] & !opcode[4];
assign o_rd_mem_en = !opcode[2] & !opcode[4];
assign cnt_en = (state != IDLE);
assign o_cnt_en = cnt_en;
assign o_init = (state == INIT);
assign running = (state == RUN);
assign o_run = running;
assign o_ctrl_trap = (state == TRAP);
wire mem_misalign = mem_op & i_mem_misalign;
always @(posedge clk) begin
o_csr_mcause[3:0] <= 4'd0;
if (mem_misalign)
o_csr_mcause[3:0] <= {2'b01, o_mem_cmd, 1'b0};
if (e_op)
o_csr_mcause <= {!op20,3'b011};
end
//slt*, branch/jump, shift, load/store
wire two_stage_op =
slt_op | (opcode[4:2] == 3'b110) | (opcode[2:1] == 2'b00) |
shift_op;
reg stage_one_done;
reg pending_irq;
assign o_rf_rs_en = two_stage_op ? (state == INIT) : o_ctrl_pc_en;
assign o_dbus_cyc = (state == IDLE) & stage_one_done & mem_op & !mem_misalign;
always @(posedge clk) begin
if (state == INIT)
o_ctrl_jump <= take_branch;
if (state == IDLE)
o_ctrl_jump <= 1'b0;
if (i_new_irq)
pending_irq <= 1'b1;
cnt_done <= (o_cnt[4:2] == 3'b111) & o_cnt_r[2];
o_bufreg_hold <= 1'b0;
case (state)
IDLE : begin
if (i_rf_ready) begin
state <= RUN;
if (two_stage_op & !stage_one_done)
state <= INIT;
if (e_op | pending_irq)
state <= TRAP;
end else if (i_alu_sh_done & shift_op & stage_one_done)
state <= RUN;
end
INIT : begin
stage_one_done <= 1'b1;
if (cnt_done)
if (mem_misalign | (take_branch & i_ctrl_misalign))
state <= TRAP;
else if (mem_op | shift_op ) begin
state <= IDLE;
o_bufreg_hold <= 1'b1;
end
else
state <= RUN;
end
RUN : begin
stage_one_done <= 1'b0;
if (cnt_done)
state <= IDLE;
end
TRAP : begin
pending_irq <= 1'b0;
if (cnt_done)
state <= IDLE;
end
default : state <= IDLE;
endcase
o_cnt <= o_cnt + {4'd0,cnt_en};
if (cnt_en)
o_cnt_r <= {o_cnt_r[2:0],o_cnt_r[3]};
if (i_rst) begin
state <= IDLE;
o_cnt <= 5'd0;
pending_irq <= 1'b0;
stage_one_done <= 1'b0;
o_ctrl_jump <= 1'b0;
o_cnt_r <= 4'b0001;
end
end
endmodule