TruffleConstantFieldProvider.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.graalvm.compiler.truffle;

import java.lang.annotation.Annotation;

import org.graalvm.compiler.core.common.spi.ConstantFieldProvider;
import org.graalvm.util.EconomicMap;

import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.nodes.Node.Child;
import com.oracle.truffle.api.nodes.Node.Children;

import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.JavaType;
import jdk.vm.ci.meta.MetaAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaField;

public class TruffleConstantFieldProvider implements ConstantFieldProvider {
    private final ConstantFieldProvider graalConstantFieldProvider;
    private final MetaAccessProvider metaAccess;
    private final EconomicMap<ResolvedJavaField, Annotation[]> cachedAnnotations;

    public TruffleConstantFieldProvider(ConstantFieldProvider graalConstantFieldProvider, MetaAccessProvider metaAccess) {
        this.graalConstantFieldProvider = graalConstantFieldProvider;
        this.metaAccess = metaAccess;
        this.cachedAnnotations = EconomicMap.create();
    }

    @Override
    public <T> T readConstantField(ResolvedJavaField field, ConstantFieldTool<T> tool) {
        boolean isStaticField = field.isStatic();
        if (!isStaticField && tool.getReceiver().isNull()) {
            // can't be optimized
            return null;
        }

        boolean isArrayField = field.getType().isArray();
        if (!isArrayField) {
            // The fast way does not require any annotation processing but only covers the most
            // frequent cases. It must not be used for array fields as it might return an incorrect
            // value for the number of stable dimensions.
            T ret = readConstantFieldFast(field, tool);
            if (ret != null) {
                return ret;
            }
        }

        boolean hasObjectKind = field.getType().getJavaKind() == JavaKind.Object;
        Annotation[] annotations = getAnnotations(field);
        if (annotations.length > 0) {
            if (!isStaticField && hasObjectKind && getAnnotation(annotations, Child.class) != null) {
                return tool.foldConstant(verifyFieldValue(field, tool.readValue(), annotations));
            }

            CompilationFinal compilationFinal = getAnnotation(annotations, CompilationFinal.class);
            if (compilationFinal != null) {
                if (isArrayField) {
                    int stableDimensions = actualStableDimensions(field, compilationFinal.dimensions());
                    return tool.foldStableArray(tool.readValue(), stableDimensions, true);
                } else {
                    return tool.foldConstant(tool.readValue());
                }
            }

            if (!isStaticField && hasObjectKind && getAnnotation(annotations, Children.class) != null) {
                int stableDimensions = isArrayField ? 1 : 0;
                return tool.foldStableArray(verifyFieldValue(field, tool.readValue(), annotations), stableDimensions, true);
            }
        }

        if (isArrayField) {
            return readConstantFieldFast(field, tool);
        }
        return null;
    }

    private Annotation[] getAnnotations(ResolvedJavaField field) {
        Annotation[] annotations = cachedAnnotations.get(field);
        if (annotations == null) {
            annotations = field.getAnnotations();
            cachedAnnotations.put(field, annotations);
        }
        return annotations;
    }

    private static <T extends Annotation> T getAnnotation(Annotation[] annotations, Class<T> annotationClass) {
        // hardly any fields have more than one annotation, so a simple loop works best
        for (int i = 0; i < annotations.length; i++) {
            if (annotations[i].annotationType() == annotationClass) {
                return annotationClass.cast(annotations[i]);
            }
        }
        return null;
    }

    private <T> T readConstantFieldFast(ResolvedJavaField field, ConstantFieldTool<T> tool) {
        T ret = graalConstantFieldProvider.readConstantField(field, tool);
        if (ret == null && field.isFinal()) {
            ret = tool.foldConstant(tool.readValue());
        }
        return ret;
    }

    private static int actualStableDimensions(ResolvedJavaField field, int dimensions) {
        if (dimensions == 0) {
            return 0;
        }
        int arrayDim = getArrayDimensions(field.getType());
        if (dimensions < 0) {
            if (dimensions != -1) {
                throw new IllegalArgumentException("Negative @CompilationFinal dimensions");
            }
            return arrayDim;
        }
        if (dimensions > arrayDim) {
            throw new IllegalArgumentException(String.format("@CompilationFinal(dimensions=%d) exceeds declared array dimensions (%d) of field %s", dimensions, arrayDim, field));
        }
        return dimensions;
    }

    private static int getArrayDimensions(JavaType type) {
        int dimensions = 0;
        for (JavaType componentType = type; componentType.isArray(); componentType = componentType.getComponentType()) {
            dimensions++;
        }
        return dimensions;
    }

    private JavaConstant verifyFieldValue(ResolvedJavaField field, JavaConstant constant, Annotation[] annotations) {
        assert getAnnotation(annotations, Child.class) == null || constant.isNull() ||
                        metaAccess.lookupJavaType(com.oracle.truffle.api.nodes.Node.class).isAssignableFrom(metaAccess.lookupJavaType(constant)) : String.format(
                                        "@Child field value must be a Node: %s, but was: %s", field, constant);
        assert getAnnotation(annotations, Children.class) == null || constant.isNull() ||
                        metaAccess.lookupJavaType(constant).isArray() : String.format("@Children field value must be an array: %s, but was: %s", field, constant);
        return constant;
    }
}