1 files changed, 76 insertions, 0 deletions
diff --git a/chapter16/src/test/java/com/seaofnodes/simple/IntegerIdentityTest.java b/chapter16/src/test/java/com/seaofnodes/simple/IntegerIdentityTest.java
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+++ b/chapter16/src/test/java/com/seaofnodes/simple/IntegerIdentityTest.java
@@ -0,0 +1,76 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.type.*;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class IntegerIdentityTest {
+    private static final String[] OPS = {"And","Or","Xor","Shl","Sar","Shr","Add","Mul","Div"};
+
+    @Test public void testIdentityWaitsForIntegerInput() {
+        new Parser("return 0;").parse();
+        for( String name : OPS ) {
+            Node lhs = input(Type.BOTTOM);
+            Node rhs = input(TypeInteger.constant(identity(name)));
+            Node op = op(name,lhs,rhs);
+            assertFalse(name,lhs._type.isa(op.compute()));
+            assertNull(name,op.idealize());
+            // Model a provisional input lifting to int. The same fold can now fire.
+            lhs._type = TypeInteger.BOT;
+            assertSame(name,lhs,op.idealize());
+            assertTrue(name,lhs._type.isa(op.compute()));
+        }
+    }
+
+    @Test public void testNonIntegerIdentityCannotEraseTheOperator() {
+        new Parser("return 0;").parse();
+        for( Type type : new Type[]{TypeFloat.constant(3.5)} )
+            for( String name : OPS ) {
+                Node lhs=input(type);
+                Node op=op(name,lhs,input(TypeInteger.constant(identity(name))));
+                assertNull(name,op.idealize());
+            }
+    }
+
+    @Test public void testIntegerIdentitiesAndMaskedShiftsStillFold() {
+        new Parser("return 0;").parse();
+        for( String name : OPS )
+            for( Type type : new Type[]{TypeInteger.BOT,TypeInteger.make(2,7),TypeInteger.constant(5)} ) {
+                Node lhs=input(type);
+                long[] identities = name.equals("And") ? new long[]{-1} :
+                    name.equals("Shl") || name.equals("Sar") || name.equals("Shr") ? new long[]{0,64,-64} : new long[]{identity(name)};
+                for( long identity : identities ) {
+                    Node op=op(name,lhs,input(TypeInteger.constant(identity)));
+                    assertSame(name,lhs,op.idealize());
+                    assertTrue(name,lhs._type.isa(op.compute()));
+                }
+            }
+    }
+
+    // These tests exercise idealize directly, before GVN or constant folding.
+    private static Node input(Type type) {
+        Node n = new ConstantNode(type);
+        n._type=type;
+        return n;
+    }
+
+    private static long identity(String name) {
+        return name.equals("And") ? -1 : name.equals("Mul") || name.equals("Div") ? 1 : 0;
+    }
+
+    private static Node op(String name, Node lhs, Node rhs) {
+        return switch(name) {
+            case "And" -> new AndNode(lhs,rhs);
+            case "Or" -> new OrNode(lhs,rhs);
+            case "Xor" -> new XorNode(lhs,rhs);
+            case "Shl" -> new ShlNode(lhs,rhs);
+            case "Sar" -> new SarNode(lhs,rhs);
+            case "Shr" -> new ShrNode(lhs,rhs);
+            case "Add" -> new AddNode(lhs,rhs);
+            case "Mul" -> new MulNode(lhs,rhs);
+            case "Div" -> new DivNode(lhs,rhs);
+            default -> throw new AssertionError(name);
+        };
+    }
+}