Homework B (benchmarks)

src/cd/transform/optimizers/WriteOnlyVarRemoval.java

@@ -0,0 +1,58 @@
+package cd.transform.optimizers;
+
+import cd.ir.Ast;
+import cd.ir.Ast.*;
+import cd.ir.BasicBlock;
+import cd.ir.ControlFlowGraph;
+import cd.ir.ExprVisitor;
+import cd.ir.Symbol.VariableSymbol;
+import cd.transform.analysis.LiveVarAnalysis;
+
+import java.util.*;
+
+public class WriteOnlyVarRemoval extends OptimizerVisitor<Set<VariableSymbol>> {
+	@Override
+	public boolean go(ControlFlowGraph cfg) {
+		LiveVarAnalysis analysis = new LiveVarAnalysis(cfg);
+		for (BasicBlock block : cfg.allBlocks) {
+			Set<VariableSymbol> state = new HashSet<>(analysis.outStateOf(block));
+			if (block.condition != null)
+				new LiveVarAnalysis.Visitor().visit(block.condition, state);
+			for (ListIterator<Stmt> iterator = block.stmts.listIterator(block.stmts.size()); iterator.hasPrevious(); ) {
+				Stmt stmt = iterator.previous();
+				Ast res = visit(stmt, state);
+				// TODO: this code should work? even if we iterate through the newly created Stmt nodes
+				if (stmt != res) {
+					iterator.remove();
+					assert res instanceof Seq;
+					Seq seq = (Seq) res;
+					for (Ast ast : seq.rwChildren) {
+						assert ast instanceof Stmt;
+						iterator.add((Stmt) ast);
+					}
+					nodeReplaced(stmt, res);
+				}
+			}
+		}
+		return hasChanged();
+	}
+
+	@Override
+	public Ast assign(Assign ast, Set<VariableSymbol> arg) {
+		if (ast.left() instanceof Var && !arg.contains(((Var) ast.left()).sym)) {
+			List<Ast> methodCalls = new ArrayList<>();
+			new MethodCallFinder().visit(ast.right(), methodCalls);
+			return new Seq(methodCalls);
+		} else {
+			return ast;
+		}
+	}
+
+	private class MethodCallFinder extends ExprVisitor<Void, List<Ast>> {
+		@Override
+		public Void methodCall(Ast.MethodCallExpr ast, List<Ast> arg) {
+			arg.add(new MethodCall(ast));
+			return null;
+		}
+	}
+}