synthesis optimizations

hw/rtl/libs/VX_priority_encoder.v

@@ -48,7 +48,7 @@ module VX_priority_encoder #(
         VX_onehot_encoder #(
             .N (N),
             .REVERSE (REVERSE)
-        ) b (
+        ) onehot_encoder (
             .data_in  (onehot),
             .data_out (index),        
             `UNUSED_PIN (valid)

hw/rtl/libs/VX_rr_arbiter.v

@@ -3,7 +3,8 @@
 module VX_rr_arbiter #(
     parameter NUM_REQS     = 1,
     parameter LOCK_ENABLE  = 0,
-    parameter LOG_NUM_REQS = $clog2(NUM_REQS)
+    parameter LOG_NUM_REQS = $clog2(NUM_REQS),
+    parameter FAST         = 1
 ) (
     input  wire                     clk,
     input  wire                     reset,          
@@ -23,6 +24,58 @@ module VX_rr_arbiter #(
         assign grant_onehot = requests;
         assign grant_valid  = requests[0];
 
+    end else if (FAST == 1)  begin
+    
+        wire [NUM_REQS-1:0] req_masked;
+        wire [NUM_REQS-1:0] grant, grant_masked, grant_unmasked;
+    /* verilator lint_off UNOPTFLAT */
+        wire [NUM_REQS-1:0] mask_higher_pri_reqs;
+    /* verilator lint_off UNOPTFLAT */
+        wire [NUM_REQS-1:0] unmask_higher_pri_reqs;
+        wire no_req_masked;
+        reg [NUM_REQS-1:0] pointer_reg;
+
+        // Simple priority arbitration for masked portion
+        assign req_masked = requests & pointer_reg;
+        assign mask_higher_pri_reqs[NUM_REQS-1:1] = mask_higher_pri_reqs[NUM_REQS-2:0] | req_masked[NUM_REQS-2:0];
+        assign mask_higher_pri_reqs[0] = 1'b0;
+        assign grant_masked[NUM_REQS-1:0] = req_masked[NUM_REQS-1:0] & ~mask_higher_pri_reqs[NUM_REQS-1:0];
+
+        // Simple priority arbitration for unmasked portion
+        assign unmask_higher_pri_reqs[NUM_REQS-1:1] = unmask_higher_pri_reqs[NUM_REQS-2:0] | requests[NUM_REQS-2:0];
+        assign unmask_higher_pri_reqs[0] = 1'b0;
+        assign grant_unmasked[NUM_REQS-1:0] = requests[NUM_REQS-1:0] & ~unmask_higher_pri_reqs[NUM_REQS-1:0];
+        
+        // Use grant_masked if there is any there, otherwise use grant_unmasked.
+        assign no_req_masked = ~(| req_masked);
+        assign grant = ({NUM_REQS{no_req_masked}} & grant_unmasked) | grant_masked;
+
+        // Generate arbiter pointer update
+        wire mask_ptr_sel = (| req_masked) & (!LOCK_ENABLE || enable);
+        wire unmask_ptr_sel = (| requests) & (!LOCK_ENABLE || enable);
+        
+        // Pointer update
+        always @(posedge clk) begin
+            if (reset) begin
+                pointer_reg <= {NUM_REQS{1'b1}};
+            end else if (mask_ptr_sel) begin // select if masked arbiter used
+                pointer_reg <= mask_higher_pri_reqs;
+            end else if (unmask_ptr_sel) begin // select if unmasked arbiter used
+                pointer_reg <= unmask_higher_pri_reqs;
+            end
+        end
+
+        VX_onehot_encoder #(
+            .N (NUM_REQS)
+        ) onehot_encoder (
+            .data_in  (grant),
+            .data_out (grant_index),        
+            `UNUSED_PIN (valid)
+        );
+
+        assign grant_onehot = grant;
+        assign grant_valid  = (| requests);
+
     end else begin
 
         reg [LOG_NUM_REQS-1:0] grant_table [NUM_REQS-1:0];

hw/rtl/libs/VX_skid_buffer.v

@@ -83,7 +83,7 @@ module VX_skid_buffer #(
                 end                
                 if (pop && !use_buffer) begin
                     data_out_r <= data_in;                    
-                end else if (pop) begin
+                end else if (ready_out) begin
                     data_out_r <= buffer;
                 end
             end