sras: size improvements

Signed-off-by: Alban Gruin <alban.gruin@irit.fr>

src/frontend/sras.sv

@@ -54,38 +54,44 @@ module sras #(
     assign overflow = |ovf_counter_q[ptr_spec_q];
 
     always_comb begin
-        tos_d = tos_q;
         ovf_counter_d = ovf_counter_q;
 
         if (flush_i) begin
-            tos_d = '0;
             ovf_counter_d = '0;
         end else if (!bad_spec_i) begin
             if (push_i && !pop_i) begin
                 if (overflow) begin
                     ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q] + 1'b1;
-                end else begin
-                    if (prev_plus_one == '0 || pp_plus_one == '0) begin
-                        ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q] + 1'b1;
-                        if (begin_spec_i) begin
-                            ovf_counter_d[ptr_spec_q] = ovf_counter_q[ptr_spec_q] + 1'b1;
-                        end
-                    end else begin
-                        tos_d[ptr_spec_d] = prev_plus_one;
-                        if (begin_spec_i) begin
-                            tos_d[ptr_spec_q] = pp_plus_one;
-                        end
+                end else if (prev_plus_one == '0 || pp_plus_one == '0) begin
+                    ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q] + 1'b1;
+                    if (begin_spec_i) begin
+                        ovf_counter_d[ptr_spec_q] = ovf_counter_q[ptr_spec_q] + 1'b1;
                     end
                 end
-            end else if (!push_i && pop_i) begin
-                if (ovf_counter_q[ptr_spec_q] != '0) begin
-                    ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q] - 1'b1;
-                end else begin
-                    tos_d[ptr_spec_d] = prev_minus_one;
+            end else if (!push_i && pop_i && ovf_counter_q[ptr_spec_q] != '0) begin
+                ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q] - 1'b1;
+            end else if (!bad_spec_i && begin_spec_i) begin
+                ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q];
+            end
+        end
+    end
+
+    always_comb begin
+        tos_d = tos_q;
+
+        if (flush_i) begin
+            tos_d = '0;
+        end else if (!bad_spec_i) begin
+            if (push_i && !pop_i && !overflow && prev_plus_one != '0 && pp_plus_one != '0) begin
+                tos_d[ptr_spec_d] = prev_plus_one;
+
+                if (begin_spec_i) begin
+                    tos_d[ptr_spec_q] = pp_plus_one;
                 end
+            end else if (!push_i && pop_i && ovf_counter_q[ptr_spec_q] == '0) begin
+                tos_d[ptr_spec_d] = prev_minus_one;
             end else if (!bad_spec_i && begin_spec_i) begin
                 tos_d[ptr_spec_d] = tos_q[ptr_spec_q];
-                ovf_counter_d[ptr_spec_d] = ovf_counter_q[ptr_spec_q];
             end
         end
     end
@@ -133,15 +139,16 @@ module sras #(
                             stack_q[i];
     end
 
+    initial stack_q = '0;
     always_ff @(posedge clk_i or negedge rst_ni) begin
+        stack_q <= stack_d;
+
         if (~rst_ni) begin
-            stack_q       <= '0;
             ptr_spec_q    <= '0;
             ptr_backup_q  <= '0;
             tos_q         <= '0;
             ovf_counter_q <= '0;
         end else begin
-            stack_q       <= stack_d;
             ptr_spec_q    <= ptr_spec_d;
             ptr_backup_q  <= ptr_backup_d;
             tos_q         <= tos_d;