From 48239128c368abeddf1dfd1912854b6f6284dfce Mon Sep 17 00:00:00 2001
From: Alban Gruin <alban.gruin@irit.fr>
Date: Wed, 9 Feb 2022 16:07:24 +0100
Subject: [PATCH] scoreboard: size and timing improvements
Signed-off-by: Alban Gruin <alban.gruin@irit.fr>
---
src/scoreboard.sv | 184 +++++++++++++++++-----------------------------
1 file changed, 66 insertions(+), 118 deletions(-)
diff --git a/src/scoreboard.sv b/src/scoreboard.sv
index 92254af9..a53aacbb 100644
--- a/src/scoreboard.sv
+++ b/src/scoreboard.sv
@@ -239,70 +239,45 @@ module scoreboard #(
// RD clobber process
// -------------------
// rd_clobber output: output currently clobbered destination registers
- logic [2**ariane_pkg::REG_ADDR_SIZE-1:0][NR_ENTRIES:0] gpr_clobber_vld;
- logic [2**ariane_pkg::REG_ADDR_SIZE-1:0][NR_ENTRIES:0] fpr_clobber_vld;
- ariane_pkg::fu_t [NR_ENTRIES:0] clobber_fu;
-
- always_comb begin : clobber_assign
- gpr_clobber_vld = '0;
- fpr_clobber_vld = '0;
-
- // default (highest entry hast lowest prio in arbiter tree below)
- clobber_fu[NR_ENTRIES] = ariane_pkg::NONE;
- for (int unsigned i = 0; i < 2**ariane_pkg::REG_ADDR_SIZE; i++) begin
- gpr_clobber_vld[i][NR_ENTRIES] = 1'b1;
- fpr_clobber_vld[i][NR_ENTRIES] = 1'b1;
- end
-
- // check for all valid entries and set the clobber accordingly
- for (int unsigned i = 0; i < NR_ENTRIES; i++) begin
- gpr_clobber_vld[mem_q[i].sbe.rd][i] = ~mem_q[i].pending & mem_q[i].issued & ~mem_q[i].is_rd_fpr_flag;
- fpr_clobber_vld[mem_q[i].sbe.rd][i] = ~mem_q[i].pending & mem_q[i].issued & mem_q[i].is_rd_fpr_flag;
- clobber_fu[i] = mem_q[i].sbe.fu;
+ logic [2**ariane_pkg::REG_ADDR_SIZE-1:0][NR_ENTRIES-1:0] gpr_clobber_vld;
+ logic [2**ariane_pkg::REG_ADDR_SIZE-1:0][NR_ENTRIES-1:0] fpr_clobber_vld;
+ ariane_pkg::fu_t [NR_ENTRIES-1:0] clobber_fu;
+
+ for (genvar i = 0; i < 2**ariane_pkg::REG_ADDR_SIZE; i++) begin
+ for (genvar j = 0; j < NR_ENTRIES; j++) begin
+ assign gpr_clobber_vld[i][j] = mem_q[j].sbe.rd == i & ~mem_q[j].pending & mem_q[j].issued & ~mem_q[j].is_rd_fpr_flag & i != 0;
+ assign fpr_clobber_vld[i][j] = mem_q[j].sbe.rd == i & ~mem_q[j].pending & mem_q[j].issued & mem_q[j].is_rd_fpr_flag;
end
+ end
- // GPR[0] is always free
- gpr_clobber_vld[0] = '0;
+ for (genvar k = 0; k < NR_ENTRIES; k++) begin
+ assign clobber_fu[k] = mem_q[k].sbe.fu;
end
- for (genvar k = 0; k < 2**ariane_pkg::REG_ADDR_SIZE; k++) begin : gen_sel_clobbers
- // get fu that is going to clobber this register (there should be only one)
- rr_arb_tree #(
- .NumIn(NR_ENTRIES+1),
- .DataType(ariane_pkg::fu_t),
- .ExtPrio(1'b1),
- .AxiVldRdy(1'b1)
- ) i_sel_gpr_clobbers (
- .clk_i ( clk_i ),
- .rst_ni ( rst_ni ),
- .flush_i ( 1'b0 ),
- .rr_i ( '0 ),
- .req_i ( gpr_clobber_vld[k] ),
- .gnt_o ( ),
- .data_i ( clobber_fu ),
- .gnt_i ( 1'b1 ),
- .req_o ( ),
- .data_o ( rd_clobber_gpr_o[k] ),
- .idx_o ( )
+ for (genvar k = 0; k < 2**ariane_pkg::REG_ADDR_SIZE; k++) begin
+ logic [$clog2(NR_ENTRIES)-1:0] gpr_clobber_idx, fpr_clobber_idx;
+ logic gpr_no_clobber, fpr_no_clobber;
+
+ lzc #(
+ .WIDTH ( NR_ENTRIES ),
+ .MODE ( 0 )
+ ) lzc_gpr_clobbers (
+ .in_i ( gpr_clobber_vld[k] ),
+ .cnt_o ( gpr_clobber_idx ),
+ .empty_o ( gpr_no_clobber )
);
- rr_arb_tree #(
- .NumIn(NR_ENTRIES+1),
- .DataType(ariane_pkg::fu_t),
- .ExtPrio(1'b1),
- .AxiVldRdy(1'b1)
- ) i_sel_fpr_clobbers (
- .clk_i ( clk_i ),
- .rst_ni ( rst_ni ),
- .flush_i ( 1'b0 ),
- .rr_i ( '0 ),
- .req_i ( fpr_clobber_vld[k] ),
- .gnt_o ( ),
- .data_i ( clobber_fu ),
- .gnt_i ( 1'b1 ),
- .req_o ( ),
- .data_o ( rd_clobber_fpr_o[k] ),
- .idx_o ( )
+
+ lzc #(
+ .WIDTH ( NR_ENTRIES ),
+ .MODE ( 0 )
+ ) lzc_fpr_clobbers (
+ .in_i ( fpr_clobber_vld[k] ),
+ .cnt_o ( fpr_clobber_idx ),
+ .empty_o ( fpr_no_clobber )
);
+
+ assign rd_clobber_gpr_o[k] = (gpr_no_clobber) ? ariane_pkg::NONE : clobber_fu[gpr_clobber_idx];
+ assign rd_clobber_fpr_o[k] = (fpr_no_clobber) ? ariane_pkg::NONE : clobber_fu[fpr_clobber_idx];
end
// ----------------------------------
@@ -310,6 +285,7 @@ module scoreboard #(
// ----------------------------------
// read operand interface: same logic as register file
logic [NR_ENTRIES+NR_WB_PORTS-1:0] rs1_fwd_req, rs2_fwd_req, rs3_fwd_req;
+ logic [$clog2(NR_WB_PORTS+NR_ENTRIES)-1:0] rs1_fwd_idx, rs2_fwd_idx, rs3_fwd_idx;
logic [NR_ENTRIES+NR_WB_PORTS-1:0][riscv::XLEN-1:0] rs_data;
logic rs1_valid, rs2_valid;
@@ -327,72 +303,44 @@ module scoreboard #(
assign rs_data[k+NR_WB_PORTS] = mem_q[k].sbe.result;
end
- // check whether we are accessing GPR[0], rs3 is only used with the FPR!
- assign rs1_valid_o = rs1_valid & ((|rs1_i) | ariane_pkg::is_rs1_fpr(issue_instr_o.op));
- assign rs2_valid_o = rs2_valid & ((|rs2_i) | ariane_pkg::is_rs2_fpr(issue_instr_o.op));
-
- // use fixed prio here
- // this implicitly gives higher prio to WB ports
- rr_arb_tree #(
- .NumIn(NR_ENTRIES+NR_WB_PORTS),
- .DataWidth(riscv::XLEN),
- .ExtPrio(1'b1),
- .AxiVldRdy(1'b1)
- ) i_sel_rs1 (
- .clk_i ( clk_i ),
- .rst_ni ( rst_ni ),
- .flush_i ( 1'b0 ),
- .rr_i ( '0 ),
- .req_i ( rs1_fwd_req ),
- .gnt_o ( ),
- .data_i ( rs_data ),
- .gnt_i ( 1'b1 ),
- .req_o ( rs1_valid ),
- .data_o ( rs1_o ),
- .idx_o ( )
+ lzc #(
+ .WIDTH ( NR_WB_PORTS+NR_ENTRIES ),
+ .MODE ( 0 )
+ ) i_lzc_rs1_wb (
+ .in_i ( rs1_fwd_req ),
+ .cnt_o ( rs1_fwd_idx ),
+ .empty_o ( )
);
- rr_arb_tree #(
- .NumIn(NR_ENTRIES+NR_WB_PORTS),
- .DataWidth(riscv::XLEN),
- .ExtPrio(1'b1),
- .AxiVldRdy(1'b1)
- ) i_sel_rs2 (
- .clk_i ( clk_i ),
- .rst_ni ( rst_ni ),
- .flush_i ( 1'b0 ),
- .rr_i ( '0 ),
- .req_i ( rs2_fwd_req ),
- .gnt_o ( ),
- .data_i ( rs_data ),
- .gnt_i ( 1'b1 ),
- .req_o ( rs2_valid ),
- .data_o ( rs2_o ),
- .idx_o ( )
+ lzc #(
+ .WIDTH ( NR_WB_PORTS+NR_ENTRIES ),
+ .MODE ( 0 )
+ ) i_lzc_rs2_wb (
+ .in_i ( rs2_fwd_req ),
+ .cnt_o ( rs2_fwd_idx ),
+ .empty_o ( )
);
- riscv::xlen_t rs3;
-
- rr_arb_tree #(
- .NumIn(NR_ENTRIES+NR_WB_PORTS),
- .DataWidth(riscv::XLEN),
- .ExtPrio(1'b1),
- .AxiVldRdy(1'b1)
- ) i_sel_rs3 (
- .clk_i ( clk_i ),
- .rst_ni ( rst_ni ),
- .flush_i ( 1'b0 ),
- .rr_i ( '0 ),
- .req_i ( rs3_fwd_req ),
- .gnt_o ( ),
- .data_i ( rs_data ),
- .gnt_i ( 1'b1 ),
- .req_o ( rs3_valid_o ),
- .data_o ( rs3 ),
- .idx_o ( )
+ lzc #(
+ .WIDTH ( NR_WB_PORTS+NR_ENTRIES ),
+ .MODE ( 0 )
+ ) i_lzc_rs3_wb (
+ .in_i ( rs3_fwd_req ),
+ .cnt_o ( rs3_fwd_idx ),
+ .empty_o ( )
);
- assign rs3_o = rs3[ariane_pkg::FLEN-1:0];
+ assign rs1_valid = |rs1_fwd_req;
+ assign rs2_valid = |rs2_fwd_req;
+ assign rs3_valid_o = |rs3_fwd_req;
+
+ assign rs1_o = (rs1_valid) ? rs_data[rs1_fwd_idx] : '0;
+ assign rs2_o = (rs2_valid) ? rs_data[rs2_fwd_idx] : '0;
+ assign rs3_o = (rs3_valid_o) ? rs_data[rs3_fwd_idx] : '0;
+
+ // check whether we are accessing GPR[0], rs3 is only used with the FPR!
+ assign rs1_valid_o = rs1_valid & ((|rs1_i) | ariane_pkg::is_rs1_fpr(issue_instr_o.op));
+ assign rs2_valid_o = rs2_valid & ((|rs2_i) | ariane_pkg::is_rs2_fpr(issue_instr_o.op));
// sequential process
always_ff @(posedge clk_i or negedge rst_ni) begin : regs
--
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