Merge pull request #3516 from dehekkendekrekker/subcircuit_fix

Fixes #3515

libs/subcircuit/subcircuit.cc

@@ -912,6 +912,10 @@ class SubCircuit::SolverWorker
 	bool pruneEnumerationMatrix(std::vector<std::set<int>> &enumerationMatrix, const GraphData &needle, const GraphData &haystack, int &nextRow, bool allowOverlap)
 	{
 		bool didSomething = true;
+
+		// Map of j:[i where j is used]
+		std::map<int, std::set<int>> usedNodes;
+
 		while (didSomething)
 		{
 			nextRow = -1;
@@ -923,13 +927,23 @@ class SubCircuit::SolverWorker
 						didSomething = true;
 					else if (!allowOverlap && haystack.usedNodes[j])
 						didSomething = true;
-					else
+					else {
 						newRow.insert(j);
+						usedNodes[j].insert(i); // Store the needle index by haystack node index
 					}
+				}
+
+				// This indicates there are no available haystack nodes to assign to the needle
 				if (newRow.size() == 0)
 					return false;
+
+				// If there are multiple needles assigned to the haystack node, the solution is invalid
+				if (newRow.size() == 1 && usedNodes[*newRow.begin()].size() > 1)
+					return false;
+
 				if (newRow.size() >= 2 && (nextRow < 0 || needle.adjMatrix.at(nextRow).size() < needle.adjMatrix.at(i).size()))
 					nextRow = i;
+
 				enumerationMatrix[i].swap(newRow);
 			}
 		}

tests/various/bug3515.v

@@ -0,0 +1,26 @@
+// Triple AND GATE
+module mod_74x08_3 (
+    input A_1,
+    input B_1,
+    input A_2,
+    input B_2,
+    input A_3,
+    input B_3,
+    output Y_1,
+    output Y_2,
+    output Y_3);
+
+assign Y_1 = A_1 & B_1;
+assign Y_2 = A_2 & B_2;
+assign Y_3 = A_3 & B_3;
+
+endmodule
+
+// OR GATE
+module mod_74x32_1 (
+    input A_1,
+    input B_1,
+    output Y_1);
+
+assign Y_1 = A_1 | B_1;
+endmodule

tests/various/bug3515.ys

@@ -0,0 +1,31 @@
+# base case is able to map
+read_verilog << EOF
+module and_x3 (
+    input a, b, c, d,
+    output reg y
+);
+
+assign y = (a&b)&(c&d);
+endmodule
+EOF
+hierarchy -top and_x3
+opt
+extract -map ./bug3515.v
+select -assert-count 1 t:mod_74x08_3
+
+# more needles than haystacks; not able to map
+design -reset
+read_verilog << EOF
+module mod_and_or (
+    input a, b, c, d,
+    output reg y
+);
+
+assign y = (a&b)|(c&d);
+endmodule
+EOF
+hierarchy -top mod_and_or
+opt
+extract -map ./bug3515.v
+select -assert-count 2 t:$and
+