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Debug support: Make single-stepping work again

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This commit is contained in:
Andreas Traber 2015-08-31 17:00:26 +02:00
parent d5802e5e62
commit 116b5f4641
1 changed files with 45 additions and 9 deletions
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54
controller.sv
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@ -1091,8 +1091,7 @@ module controller
// take care of debug
// branches take two cycles, jumps just one
// everything else can be done immediately
// TODO: there is a bug here, I'm sure of it
if(trap_hit_i == 1'b1 && stall_ex_o == 1'b0 && jump_in_id == 2'b0 && jump_in_ex_i == 2'b0)
if(trap_hit_i == 1'b1 && stall_ex_o == 1'b0 && jump_in_id == `BRANCH_NONE)
begin
halt_if = 1'b1;
halt_id = 1'b1;
@ -1100,26 +1099,61 @@ module controller
end
end
// handle branches
BRANCH:
begin
// assume branch instruction is in EX
if (jump_in_ex_i == `BRANCH_COND && ~branch_decision_i) begin
// not taken
pc_mux_sel_o = `PC_INCR;
if (~stall_id_o)
ctrl_fsm_ns = DECODE;
// if we want to debug, flush the pipeline
// the current_pc_if will take the value of the next instruction to
// be executed (NPC)
if (trap_hit_i)
begin
halt_if = 1'b1;
halt_id = 1'b1;
ctrl_fsm_ns = DBG_FLUSH_EX;
end else begin
if (~stall_id_o)
ctrl_fsm_ns = DECODE;
end
end else begin
// branch taken or jump
// branch taken
pc_mux_sel_o = `PC_BRANCH;
if (~stall_id_o)
ctrl_fsm_ns = BRANCH_DELAY;
// if we want to debug, flush the pipeline
// the current_pc_if will take the value of the next instruction to
// be executed (NPC)
if (trap_hit_i)
begin
ctrl_fsm_ns = DBG_FLUSH_EX;
end else begin
if (~stall_id_o)
ctrl_fsm_ns = BRANCH_DELAY;
end
end
end
// "delay slot" of jump and branch
// inserts a nop by not decoding the instruction
BRANCH_DELAY:
begin
if (~stall_id_o)
ctrl_fsm_ns = DECODE;
// if we want to debug, flush the pipeline
// the current_pc_if will take the value of the next instruction to
// be executed (NPC)
if (trap_hit_i)
begin
halt_if = 1'b1;
halt_id = 1'b1;
ctrl_fsm_ns = DBG_FLUSH_EX;
end else begin
if (~stall_id_o)
ctrl_fsm_ns = DECODE;
end
end
DBG_FLUSH_EX:
@ -1220,6 +1254,8 @@ module controller
// Stall because of jr path
// - always stall if a result is to be forwarded to the PC
// we don't care about in which state the ctrl_fsm is as we deassert_we
// anyway when we are not in DECODE
if ((jump_in_id == `BRANCH_JALR) &&
(((regfile_we_wb_i == 1'b1) && (reg_d_wb_is_reg_a_id == 1'b1)) ||
((regfile_we_ex_i == 1'b1) && (reg_d_ex_is_reg_a_id == 1'b1)) ||