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Fix basic incr PC flow, ID PC miscalculation

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Sven Stucki 2015-08-17 05:13:38 +02:00
parent 0addc4f1bd
commit a08f53928a
1 changed files with 49 additions and 34 deletions
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83
if_stage.sv
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@ -97,8 +97,6 @@ module if_stage
logic force_nop_int;
logic handle_branch;
logic do_fetch;
logic [31:0] instr_rdata_int;
@ -137,12 +135,11 @@ module if_stage
assign compressed_instr = instr_rdata_int[1:0] != 2'b11;
assign do_fetch = req_i;
always_comb
begin
if (pc_if_offset) begin
incr_pc = fetch_addr + (is_compressed[1] ? 32'd2 : 32'd4);
incr_pc = fetch_addr + (is_compressed[1] ? 32'd4 : 32'd6);
end else begin
incr_pc = fetch_addr + (is_compressed[0] ? 32'd2 : 32'd4);
end
@ -186,8 +183,18 @@ module if_stage
instr_rdata_int = {25'b0, `OPCODE_OPIMM};
end
assign is_compressed[0] = data_arr[0][1:0] != 2'b11;
assign is_compressed[1] = data_arr[0][17:16] != 2'b11;
always_comb
begin
if (fetch_fsm_cs == WAIT_ACK) begin
is_compressed[0] = rdata_int[1:0] != 2'b11;
is_compressed[1] = rdata_int[17:16] != 2'b11;
end else begin
is_compressed[0] = data_arr[0][1:0] != 2'b11;
is_compressed[1] = data_arr[0][17:16] != 2'b11;
end
end
//assign is_compressed[0] = data_arr[0][1:0] != 2'b11;
//assign is_compressed[1] = data_arr[0][17:16] != 2'b11;
//assign is_compressed[0] = rdata_int[1:0] != 2'b11;
//assign is_compressed[1] = rdata_int[17:16] != 2'b11;
@ -204,18 +211,15 @@ module if_stage
always_comb
begin
fetch_fsm_ns = fetch_fsm_cs;
fetch_fsm_ns = fetch_fsm_cs;
pc_if_offset_n = pc_if_offset;
force_nop_int = 1'b0;
bypass_data_reg = 1'b1;
sample_addr = 1'b1;
//ack_o = ack_int;
//req_int = req_i;
ack_o = 1'b0;
req_int = 1'b0;
fetch_addr_n = {next_pc[31:2], 2'b0};
pc_if_offset_n = pc_if_offset;
sample_addr = 1'b0;
ack_o = 1'b0;
req_int = 1'b0;
fetch_addr_n = {next_pc[31:2], 2'b0};
case (fetch_fsm_cs)
IDLE:
@ -225,19 +229,30 @@ module if_stage
fetch_fsm_ns = WAIT_REQ;
end
WAIT_REQ:
WAIT_REQ,
WAIT_ACK:
begin
if (fetch_fsm_cs == WAIT_ACK) begin
fetch_fsm_ns = WAIT_ACK;
sample_addr = 1'b0;
if (ack_int) begin
ack_o = 1'b1;
fetch_fsm_ns = WAIT_REQ;
// TODO: Already handle request here
end
end
if (req_i) begin
fetch_fsm_ns = WAIT_ACK;
req_int = 1'b1;
if (pc_if_offset) begin
if (is_compressed[1]) begin
// serve second part of already fetched instruction
// serve second part of fetched instruction and request next
pc_if_offset_n = 1'b0;
ack_o = 1'b1;
req_int = 1'b1;
fetch_fsm_ns = WAIT_REQ;
sample_addr = 1'b1;
fetch_fsm_ns = WAIT_ACK;
end else begin
// cross line access
// .. need to fetch next word here and delay everything till then
@ -246,30 +261,26 @@ module if_stage
end
end else begin
if (is_compressed[0]) begin
// compressed instruction, increase PC by two bytes
sample_addr = 1'b0;
ack_o = 1'b1;
pc_if_offset_n = 1'b1;
fetch_fsm_ns = WAIT_REQ;
end else begin
// regular fetch
sample_addr = 1'b1;
end
end
end
end
WAIT_ACK:
begin
sample_addr = 1'b0;
if (ack_int) begin
ack_o = 1'b1;
fetch_fsm_ns = WAIT_REQ;
// TODO: Already handle request here
end
end
FETCH_NEXT:
begin
sample_addr = 1'b0;
if (ack_int) begin
//sample_addr = 1'b1;
ack_o = 1'b1;
bypass_data_reg = 1'b0;
fetch_fsm_ns = WAIT_REQ;
end
end
@ -383,10 +394,10 @@ module if_stage
always_comb
begin : EXC_PC_MUX
unique case (exc_pc_mux_i)
`EXC_PC_NO_INCR: begin exc_pc = current_pc_if_o; end
`EXC_PC_ILLINSN: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_ILLINSN }; end
`EXC_PC_IRQ: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_IRQ }; end
`EXC_PC_IRQ_NM: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_IRQ_NM }; end
`EXC_PC_NO_INCR: begin exc_pc = current_pc_if_o; end
`EXC_PC_ILLINSN: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_ILLINSN }; end
`EXC_PC_IRQ: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_IRQ }; end
`EXC_PC_IRQ_NM: begin exc_pc = {boot_addr_i[31:5], `EXC_OFF_IRQ_NM }; end
endcase
end
@ -490,7 +501,11 @@ module if_stage
if (stall_id_i == 1'b0)
begin : ENABLED_PIPE
instr_rdata_id_o <= instr_rdata_int;
current_pc_id_o <= last_fetch_addr + (pc_if_offset? 32'd2 : '0);
if (pc_if_offset)
current_pc_id_o <= last_fetch_addr + (bypass_data_reg? 32'd2 : -2); // TODO: Cleanup
else
current_pc_id_o <= last_fetch_addr;
//current_pc_id_o <= last_fetch_addr + (pc_if_offset? 32'd2 : '0);
//current_pc_id_o <= current_pc_if_o;
end
end