From 39be4f29bde53331c60d669c1f3d6ae73aa2b38a Mon Sep 17 00:00:00 2001
From: williamzhu17 <williammzhu@gmail.com>
Date: Sun, 11 May 2025 10:58:29 -0700
Subject: [PATCH] opt_balance_tree test cases

---
 passes/silimate/opt_balance_tree.cc |  25 ++++++-
 tests/silimate/opt_balance_tree.ys  | 107 ++++++++++++++++++++++++----
 2 files changed, 114 insertions(+), 18 deletions(-)

diff --git a/passes/silimate/opt_balance_tree.cc b/passes/silimate/opt_balance_tree.cc
index da308e582..b575b9172 100644
--- a/passes/silimate/opt_balance_tree.cc
+++ b/passes/silimate/opt_balance_tree.cc
@@ -202,10 +202,10 @@ struct OptBalanceTreeWorker {
 		cell->fixup_parameters();
 	}
 
-	void process_chain(vector<Cell*> &chain) {
+	bool process_chain(vector<Cell*> &chain) {
 		// If chain size is less than 3, no balancing needed
 		if (GetSize(chain) < 3)
-			return;
+			return false;
 
 		// Get mid, midnext (at index mid+1) and end of chain
 		Cell *mid_cell = chain[GetSize(chain) / 2];
@@ -262,6 +262,8 @@ struct OptBalanceTreeWorker {
 
 		// Width reduce mid cell
 		wreduce(mid_cell);
+
+		return true;
 	}
 
 	void cleanup() {
@@ -291,7 +293,24 @@ struct OptBalanceTreeWorker {
 			// For each chain, if len >= 3, convert to tree via "rotation" and recurse on subtrees
 			for (auto c : chain_start_cells) {
 				vector<Cell*> chain = create_chain(c);
-				process_chain(chain);
+				bool processed = process_chain(chain);
+
+				if (processed) {
+					// Rename cells and wires for formal check to pass as cells signals have changed functionalities post rotation
+					for (Cell *cell : chain) {
+						module->rename(cell, NEW_ID2_SUFFIX("rot_cell"));
+					}
+					for (Cell *cell : chain) {
+						SigSpec y_sig = sigmap(cell->getPort(ID::Y));
+						if (y_sig.is_wire()) {
+							Wire *wire = y_sig.as_wire();
+							if (wire && !wire->port_input && !wire->port_output) {
+								module->rename(y_sig.as_wire(), NEW_ID2_SUFFIX("rot_wire"));
+							}
+						}
+					}
+				}
+
 				cell_count[cell_type] += GetSize(chain);
 			}
 
diff --git a/tests/silimate/opt_balance_tree.ys b/tests/silimate/opt_balance_tree.ys
index 8427d25cb..29b16b627 100644
--- a/tests/silimate/opt_balance_tree.ys
+++ b/tests/silimate/opt_balance_tree.ys
@@ -14,27 +14,31 @@ endmodule
 EOF
 check -assert
 
-autoname
-write_json pre.json
-exec -- netlistsvg pre.json -o pre.svg
-
 # Check equivalence after opt_balance_tree
 equiv_opt -assert opt_balance_tree
 
 design -load postopt
-# opt_balance_tree
 
-autoname
-write_json post.json
-exec -- netlistsvg post.json -o post.svg
+# Checks if inputs to and gates has been rewired
+select -set a_wires i:a %co
+select -set driven_by_a @a_wires %co
+select -set and_a_cell t:$and @driven_by_a %i
 
-# Checks if y is still wired up to the correct gate
-# select -set y_wires o:y %ci
-# select -set y_driver @y_wires %ci
-# select -set and_y_cell t:$and @y_driver %i
-# select @and_y_cell -assert-count 1
-# select -set inputs @and_y_cell %ci
-# select -assert-count 1 @inputs i:c %i
+select -set b_wires i:b %co
+select -set driven_by_b @b_wires %co
+select -set and_b_cell t:$and @driven_by_b %i
+
+select -assert-none @and_a_cell @and_b_cell %d
+
+select -set c_wires i:c %co
+select -set driven_by_c @c_wires %co
+select -set and_c_cell t:$and @driven_by_c %i
+
+select -set d_wires i:d %co
+select -set driven_by_d @d_wires %co
+select -set and_d_cell t:$and @driven_by_d %i
+
+select -assert-none @and_c_cell @and_d_cell %d
 
 design -reset
 log -pop
@@ -188,5 +192,78 @@ equiv_opt -assert opt_balance_tree
 design -load postopt
 select -assert-count 3 t:$and
 
+design -reset
+log -pop
+
+log -header "Interesting tree situation"
+log -push
+design -reset
+read_verilog <<EOF
+module top (
+  input wire a, b, c, d,
+  input wire e, f, g, h,
+  output wire x,
+);
+  wire i, j;
+
+  assign i = a & b & c & d;
+  assign j = e & f & g & h & i;
+
+  assign x = i & j;
+endmodule
+EOF
+check -assert
+
+# Check equivalence after opt_balance_tree
+equiv_opt -assert opt_balance_tree
+
+design -load postopt
+
+# Checks if inputs to and gates has been rewired
+
+# a and b
+select -set a_wires i:a %co
+select -set driven_by_a @a_wires %co
+select -set and_a_cell t:$and @driven_by_a %i
+
+select -set b_wires i:b %co
+select -set driven_by_b @b_wires %co
+select -set and_b_cell t:$and @driven_by_b %i
+
+select -assert-none @and_a_cell @and_b_cell %d
+
+# c and d
+select -set c_wires i:c %co
+select -set driven_by_c @c_wires %co
+select -set and_c_cell t:$and @driven_by_c %i
+
+select -set d_wires i:d %co
+select -set driven_by_d @d_wires %co
+select -set and_d_cell t:$and @driven_by_d %i
+
+select -assert-none @and_c_cell @and_d_cell %d
+
+# e and f
+select -set e_wires i:e %co
+select -set driven_by_e @e_wires %co
+select -set and_e_cell t:$and @driven_by_e %i
+
+select -set f_wires i:f %co
+select -set driven_by_f @f_wires %co
+select -set and_f_cell t:$and @driven_by_f %i
+
+select -assert-none @and_e_cell @and_f_cell %d
+
+# g and h
+select -set g_wires i:g %co
+select -set driven_by_g @g_wires %co
+select -set and_g_cell t:$and @driven_by_g %i
+
+select -set h_wires i:h %co
+select -set driven_by_h @h_wires %co
+select -set and_h_cell t:$and @driven_by_h %i
+
+select -assert-none @and_g_cell @and_h_cell %d
+
 design -reset
 log -pop
\ No newline at end of file