Add the StringSwitch and EnumSwitch constructs

src/main/java/io/quarkus/gizmo/AbstractSwitch.java

@@ -0,0 +1,34 @@
+package io.quarkus.gizmo;
+
+import java.util.Objects;
+import java.util.function.Consumer;
+
+abstract class AbstractSwitch<T> extends BytecodeCreatorImpl implements Switch<T> {
+
+    protected static final Consumer<BytecodeCreator> EMPTY_BLOCK = bc -> {
+    };
+
+    protected boolean fallThrough;
+    protected Consumer<BytecodeCreator> defaultBlockConsumer;
+
+    AbstractSwitch(BytecodeCreatorImpl enclosing) {
+        super(enclosing);
+    }
+
+    @Override
+    public void fallThrough() {
+        fallThrough = true;
+    }
+
+    @Override
+    public void defaultCase(Consumer<BytecodeCreator> defatultBlockConsumer) {
+        Objects.requireNonNull(defatultBlockConsumer);
+        this.defaultBlockConsumer = defatultBlockConsumer;
+    }
+
+    @Override
+    public void doBreak(BytecodeCreator creator) {
+        creator.breakScope(this);
+    }
+
+}

src/main/java/io/quarkus/gizmo/BytecodeCreator.java

@@ -1033,6 +1033,24 @@ default ResultHandle increment(ResultHandle toIncrement) {
         return add(toIncrement, load(1));
     }
 
+    /**
+     * Create a new switch construct for a string value.
+     * 
+     * @param value The string value to switch on
+     * @return the switch construct
+     */
+    Switch.StringSwitch stringSwitch(ResultHandle value);
+
+    /**
+     * Create a new switch construct for an enum constant.
+     * 
+     * @param <E>
+     * @param value The enum constant to switch on
+     * @param enumClass
+     * @return the switch construct
+     */
+    <E extends Enum<E>> Switch.EnumSwitch<E> enumSwitch(ResultHandle value, Class<E> enumClass);
+
     /**
      * Indicate that the scope is no longer in use. The scope may refuse additional instructions after this method
      * is called.

src/main/java/io/quarkus/gizmo/BytecodeCreatorImpl.java

@@ -801,6 +801,16 @@ public BytecodeCreator createScope() {
         operations.add(new BlockOperation(enclosed));
         return enclosed;
     }
+
+    /**
+     * Go the the top of the given scope. Unlike {@link #continueScope(BytecodeCreator)} this method does not verify if this
+     * bytecode creator is scoped within the given bytecode creator.
+     * 
+     * @param scope
+     */
+    void jumpTo(BytecodeCreator scope) {
+        operations.add(new JumpOperation(((BytecodeCreatorImpl) scope).top));
+    }
 
     static void storeResultHandle(MethodVisitor methodVisitor, ResultHandle handle) {
         if (handle.getResultType() == ResultHandle.ResultType.UNUSED) {
@@ -1318,6 +1328,23 @@ public ResultHandle bitwiseXor(ResultHandle a1, ResultHandle a2) {
         return emitBinaryArithmetic(Opcodes.IXOR, a1, a2);
     }
 
+    @Override
+    public Switch.StringSwitch stringSwitch(ResultHandle value) {
+        Objects.requireNonNull(value);
+        StringSwitchImpl stringSwitch = new StringSwitchImpl(value, this);
+        operations.add(new BlockOperation(stringSwitch));
+        return stringSwitch;
+    }
+
+    @Override
+    public <E extends Enum<E>> Switch.EnumSwitch<E> enumSwitch(ResultHandle value, Class<E> enumClass) {
+        Objects.requireNonNull(value);
+        Objects.requireNonNull(enumClass);
+        EnumSwitchImpl<E> enumSwitch = new EnumSwitchImpl<>(value, enumClass, this);
+        operations.add(new BlockOperation(enumSwitch));
+        return enumSwitch;
+    }
+
     private ResultHandle emitBinaryArithmetic(int intOpcode, ResultHandle a1, ResultHandle a2) {
         Objects.requireNonNull(a1);
         Objects.requireNonNull(a2);

src/main/java/io/quarkus/gizmo/EnumSwitchImpl.java

@@ -0,0 +1,193 @@
+package io.quarkus.gizmo;
+
+import static org.objectweb.asm.Opcodes.ACC_PRIVATE;
+import static org.objectweb.asm.Opcodes.ACC_STATIC;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.function.Consumer;
+
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+
+class EnumSwitchImpl<E extends Enum<E>> extends AbstractSwitch<E> implements Switch.EnumSwitch<E> {
+
+    private final Map<Integer, Consumer<BytecodeCreator>> ordinalToCaseBlocks;
+
+    public EnumSwitchImpl(ResultHandle value, Class<E> enumClass, BytecodeCreatorImpl enclosing) {
+        super(enclosing);
+        this.ordinalToCaseBlocks = new LinkedHashMap<>();
+
+        MethodDescriptor enumOrdinal = MethodDescriptor.ofMethod(enumClass, "ordinal", int.class);
+        ResultHandle ordinal = invokeVirtualMethod(enumOrdinal, value);
+
+        // Generate the int[] switch table needed for binary compatibility
+        ResultHandle switchTable;
+        MethodCreatorImpl methodCreator = findMethodCreator(enclosing);
+        if (methodCreator != null) {
+            // Generate a static method that returns the switch table 
+            char sep = '$';
+            ClassCreator classCreator = methodCreator.getClassCreator();
+            // $GIZMO_SWITCH_TABLE$org$acme$MyEnum()
+            StringBuilder methodName = new StringBuilder();
+            methodName.append(sep).append("GIZMO_SWITCH_TABLE");
+            for (String part : enumClass.getName().split("\\.")) {
+                methodName.append(sep).append(part);
+            }
+            MethodDescriptor gizmoSwitchTableDescriptor = MethodDescriptor.ofMethod(classCreator.getClassName(),
+                    methodName.toString(), int[].class);
+            if (!classCreator.getExistingMethods()
+                    .contains(gizmoSwitchTableDescriptor)) {
+                MethodCreator gizmoSwitchTable = classCreator.getMethodCreator(gizmoSwitchTableDescriptor)
+                        .setModifiers(ACC_PRIVATE | ACC_STATIC);
+                gizmoSwitchTable.returnValue(generateSwitchTable(enumClass, gizmoSwitchTable, enumOrdinal));
+            }
+            switchTable = invokeStaticMethod(gizmoSwitchTableDescriptor);
+        } else {
+            // This is suboptimal - the switch table is generated for each switch construct 
+            switchTable = generateSwitchTable(enumClass, methodCreator, enumOrdinal);
+        }
+        ResultHandle effectiveOrdinal = readArrayValue(switchTable, ordinal);
+
+        Set<ResultHandle> inputHandles = new HashSet<>();
+        inputHandles.add(effectiveOrdinal);
+
+        operations.add(new Operation() {
+
+            @Override
+            void writeBytecode(MethodVisitor methodVisitor) {
+                E[] constants = enumClass.getEnumConstants();
+                Map<Integer, Label> ordinalToLabel = new HashMap<>();
+                List<BytecodeCreatorImpl> caseBlocks = new ArrayList<>();
+
+                BytecodeCreatorImpl defaultBlock = new BytecodeCreatorImpl(EnumSwitchImpl.this);
+                if (defaultBlockConsumer != null) {
+                    defaultBlockConsumer.accept(defaultBlock);
+                }
+
+                // Initialize the case blocks
+                for (Entry<Integer, Consumer<BytecodeCreator>> caseEntry : ordinalToCaseBlocks.entrySet()) {
+                    BytecodeCreatorImpl caseBlock = new BytecodeCreatorImpl(EnumSwitchImpl.this);
+                    Consumer<BytecodeCreator> blockConsumer = caseEntry.getValue();
+                    blockConsumer.accept(caseBlock);
+                    if (blockConsumer != EMPTY_BLOCK && !fallThrough) {
+                        caseBlock.breakScope(EnumSwitchImpl.this);
+                    }
+                    caseBlock.findActiveResultHandles(inputHandles);
+                    caseBlocks.add(caseBlock);
+                    ordinalToLabel.put(caseEntry.getKey(), caseBlock.getTop());
+                }
+
+                int min = ordinalToLabel.keySet().stream().mapToInt(Integer::intValue).min().orElse(0);
+                int max = ordinalToLabel.keySet().stream().mapToInt(Integer::intValue).max().orElse(0);
+
+                // Add empty blocks for missing ordinals
+                // This would be suboptimal for cases if there is a large number of missing ordinals 
+                for (int i = 0; i < constants.length; i++) {
+                    if (i >= min && i <= max) {
+                        if (ordinalToLabel.get(i) == null) {
+                            BytecodeCreatorImpl emptyCaseBlock = new BytecodeCreatorImpl(EnumSwitchImpl.this);
+                            caseBlocks.add(emptyCaseBlock);
+                            ordinalToLabel.put(i, emptyCaseBlock.getTop());
+                        }
+                    }
+                }
+
+                // Load the ordinal of the tested value
+                loadResultHandle(methodVisitor, effectiveOrdinal, EnumSwitchImpl.this, "I");
+
+                int[] ordinals = ordinalToLabel.keySet().stream().mapToInt(Integer::intValue).sorted().toArray();
+                Label[] labels = new Label[ordinals.length];
+                for (int i = 0; i < ordinals.length; i++) {
+                    labels[i] = ordinalToLabel.get(ordinals[i]);
+                }
+                methodVisitor.visitTableSwitchInsn(min, max, defaultBlock.getTop(), labels);
+
+                // Write the case blocks
+                for (BytecodeCreatorImpl caseBlock : caseBlocks) {
+                    caseBlock.writeOperations(methodVisitor);
+                }
+
+                // Write the default block
+                defaultBlock.writeOperations(methodVisitor);
+            }
+
+            @Override
+            ResultHandle getTopResultHandle() {
+                return null;
+            }
+
+            @Override
+            ResultHandle getOutgoingResultHandle() {
+                return null;
+            }
+
+            @Override
+            Set<ResultHandle> getInputResultHandles() {
+                return inputHandles;
+            }
+
+        });
+    }
+
+    @Override
+    public void caseOf(E value, Consumer<BytecodeCreator> caseBlockConsumer) {
+        Objects.requireNonNull(value);
+        Objects.requireNonNull(caseBlockConsumer);
+        addCaseBlock(value, caseBlockConsumer);
+    }
+
+    @Override
+    public void caseOf(List<E> values, Consumer<BytecodeCreator> caseBlockConsumer) {
+        Objects.requireNonNull(values);
+        Objects.requireNonNull(caseBlockConsumer);
+        for (Iterator<E> it = values.iterator(); it.hasNext();) {
+            E e = it.next();
+            if (it.hasNext()) {
+                addCaseBlock(e, EMPTY_BLOCK);
+            } else {
+                addCaseBlock(e, caseBlockConsumer);
+            }
+        }
+    }
+
+    private void addCaseBlock(E value, Consumer<BytecodeCreator> caseBlockConsumer) {
+        int ordinal = value.ordinal();
+        if (ordinalToCaseBlocks.containsKey(ordinal)) {
+            throw new IllegalArgumentException("A case block for the enum value " + value + " already exists");
+        }
+        ordinalToCaseBlocks.put(ordinal, caseBlockConsumer);
+    }
+
+    private MethodCreatorImpl findMethodCreator(BytecodeCreatorImpl enclosing) {
+        if (enclosing instanceof MethodCreatorImpl) {
+            return (MethodCreatorImpl) enclosing;
+        }
+        if (enclosing.getOwner() != null) {
+            return findMethodCreator(enclosing.getOwner());
+        }
+        return null;
+    }
+
+    private ResultHandle generateSwitchTable(Class<E> enumClass, BytecodeCreator bytecodeCreator,
+            MethodDescriptor enumOrdinal) {
+        E[] constants = enumClass.getEnumConstants();
+        ResultHandle switchTable = bytecodeCreator.newArray(int.class, constants.length);
+        for (int i = 0; i < constants.length; i++) {
+            ResultHandle currentConstant = bytecodeCreator
+                    .readStaticField(FieldDescriptor.of(enumClass, constants[i].name(), enumClass));
+            ResultHandle currentOrdinal = bytecodeCreator.invokeVirtualMethod(enumOrdinal, currentConstant);
+            bytecodeCreator.writeArrayValue(switchTable, i, currentOrdinal);
+        }
+        return switchTable;
+    }
+
+}