arbiters optimization

hw/rtl/libs/VX_fair_arbiter.sv

@@ -38,17 +38,17 @@ module VX_fair_arbiter #(
 
     end else begin
 
-        reg [NUM_REQS-1:0] grant_hist;
+        reg [NUM_REQS-1:0] reqs_mask;
 
-        wire [NUM_REQS-1:0] requests_sel = requests & ~grant_hist;
-        wire rem_valid = (| requests_sel);
-        wire [NUM_REQS-1:0] requests_qual = rem_valid ? requests_sel : requests;
+        wire [NUM_REQS-1:0] requests_rem = requests & reqs_mask;
+        wire rem_valid = (| requests_rem);
+        wire [NUM_REQS-1:0] requests_qual = rem_valid ? requests_rem : requests;
 
         always @(posedge clk) begin
             if (reset) begin
-                grant_hist <= '0;
+                reqs_mask <= '1;
             end else if (grant_valid && grant_ready) begin
-                grant_hist <= rem_valid ? (grant_hist | grant_onehot) : grant_onehot;
+                reqs_mask <= rem_valid ? (reqs_mask & ~grant_onehot) : ~grant_onehot;
             end
         end
 

hw/rtl/libs/VX_onehot_mux.sv

@@ -124,6 +124,16 @@ module VX_onehot_mux #(
             assign data_out[i] = (| gather);
         end
     end else if (MODEL == 2) begin
+        VX_find_first #(
+            .N     (N),
+            .DATAW (DATAW)
+        ) find_first (
+            .valid_in (sel_in),
+            .data_in  (data_in),
+            .data_out (data_out),
+            `UNUSED_PIN (valid_out)
+        );
+    end else if (MODEL == 3) begin
         reg [DATAW-1:0] data_out_r;
         always @(*) begin
             data_out_r = 'x;

hw/rtl/libs/VX_onehot_shift.sv

@@ -0,0 +1,30 @@
+// Copyright © 2019-2023
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+`include "VX_platform.vh"
+
+module VX_onehot_shift #(
+    parameter N = 1,
+    parameter M = 1
+) (
+    input wire [N-1:0] data_in0,
+    input wire [M-1:0] data_in1,
+    output wire [N*M-1:0] data_out
+);
+    for (genvar i = 0; i < M; ++i) begin
+        for (genvar j = 0; j < N; ++j) begin
+            assign data_out[i*N + j] = data_in1[i] & data_in0[j];
+        end
+    end
+
+endmodule

hw/rtl/libs/VX_rr_arbiter.sv

@@ -426,32 +426,30 @@ module VX_rr_arbiter #(
         reg                    grant_valid_r;
         reg [LOG_NUM_REQS-1:0] grant_index_r;
         reg [NUM_REQS-1:0]     grant_onehot_r;
-        reg [LOG_NUM_REQS-1:0] next_grant_index;
-
-        wire [NUM_REQS-1:0][LOG_NUM_REQS-1:0] next_grant_index_qual;
-        for (genvar i = 0; i < NUM_REQS; ++i) begin
-            assign next_grant_index_qual[i] = LOG_NUM_REQS'(i) + next_grant_index;
-        end
+        reg [NUM_REQS-1:0][LOG_NUM_REQS-1:0] next_grant_index;
 
         always @(*) begin
             grant_index_r  = 'x;
             grant_onehot_r = 'x;
             grant_valid_r  = 0;
-            for (integer i = 0; i < NUM_REQS; ++i) begin
-                if (requests[next_grant_index_qual[i]]) begin
-                    grant_valid_r = 1;
-                    grant_index_r  = next_grant_index_qual[i];
-                    grant_onehot_r = NUM_REQS'(1) << next_grant_index_qual[i];
-                    break;
+            for (integer i = NUM_REQS-1; i >= 0; --i) begin
+                if (requests[next_grant_index[i]]) begin
+                    grant_valid_r  = 1;
+                    grant_index_r  = next_grant_index[i];
+                    grant_onehot_r = NUM_REQS'(1) << next_grant_index[i];
                 end
             end
         end
 
         always @(posedge clk) begin
             if (reset) begin
-                next_grant_index <= '0;
+                for (integer i = 0; i < NUM_REQS; ++i) begin
+                    next_grant_index[i] <= LOG_NUM_REQS'(i);
+                end
             end else if (grant_valid && grant_ready) begin
-                next_grant_index <= grant_index_r + LOG_NUM_REQS'(1);
+                for (integer i = 0; i < NUM_REQS; ++i) begin
+                    next_grant_index[i] <= grant_index_r + LOG_NUM_REQS'(i + 1);
+                end
             end
         end
 

hw/rtl/libs/VX_transpose.sv

@@ -0,0 +1,29 @@
+// Copyright © 2019-2023
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+`include "VX_platform.vh"
+
+module VX_transpose #(
+    parameter N = 1,
+    parameter M = 1
+) (
+    input wire [N-1:0][M-1:0] data_in,
+    output wire [M-1:0][N-1:0] data_out
+);
+    for (genvar i = 0; i < N; ++i) begin
+        for (genvar j = 0; j < M; ++j) begin
+            assign data_out[j][i] = data_in[i][j];
+        end
+    end
+
+endmodule