Homework B (benchmarks)

src/cd/transform/analysis/ConstantAnalysis.java

@@ -0,0 +1,50 @@
+package cd.transform.analysis;
+
+
+import cd.ir.Ast;
+import cd.ir.Ast.Assign;
+import cd.ir.Ast.Var;
+import cd.ir.ControlFlowGraph;
+import cd.ir.Symbol.VariableSymbol;
+
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * This class implements constant propagation:
+ * remember variables that have constant values
+ * no need evaluate them at runtime, save movl instruction
+ */
+public class ConstantAnalysis extends MaybeFlowAnalysis<Integer> {
+	public ConstantAnalysis(ControlFlowGraph cfg) {
+		super(cfg, true, false);
+	}
+
+	@Override
+	protected MaybeC<Integer> defaultInit(VariableSymbol varSym) {
+		if (varSym.kind == VariableSymbol.Kind.LOCAL)
+			return MaybeC.value(0);
+		else
+			return MaybeC.notConstant();
+	}
+
+	@Override
+	public void transferStmt(Ast.Stmt stmt, Map<VariableSymbol, MaybeC<Integer>> state) {
+		if (stmt instanceof Assign) {
+			Assign ast = (Assign) stmt;
+			if (ast.left() instanceof Var) {
+				VariableSymbol symbol = ((Var) ast.left()).sym;
+				if (!state.containsKey(symbol)) return;
+
+				// Obtain value and previous MaybeConstant
+				Optional<Integer> valueOpt = cte.calc(ast.right());
+				MaybeC<Integer> mc = state.get(symbol);
+				if (valueOpt.isPresent()) {
+					state.put(symbol, MaybeC.value(valueOpt.get()));
+				} else {
+					mc.setNotConstant();
+				}
+			}
+		}
+	}
+}