/*
 * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
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 */
package jdk.vm.ci.hotspot;

import static jdk.vm.ci.hotspot.CompilerToVM.compilerToVM;
import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime;
import static jdk.vm.ci.hotspot.HotSpotVMConfig.config;
import static jdk.vm.ci.hotspot.UnsafeAccess.UNSAFE;

import jdk.vm.ci.common.JVMCIError;
import jdk.vm.ci.common.NativeImageReinitialize;
import jdk.vm.ci.meta.ConstantPool;
import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.JavaField;
import jdk.vm.ci.meta.JavaMethod;
import jdk.vm.ci.meta.JavaType;
import jdk.vm.ci.meta.ResolvedJavaMethod;
import jdk.vm.ci.meta.ResolvedJavaType;
import jdk.vm.ci.meta.Signature;
import jdk.vm.ci.meta.UnresolvedJavaField;
import jdk.vm.ci.meta.UnresolvedJavaMethod;
import jdk.vm.ci.meta.UnresolvedJavaType;

Implementation of ConstantPool for HotSpot. /**
 * Implementation of {@link ConstantPool} for HotSpot.
 */
public final class HotSpotConstantPool implements ConstantPool, MetaspaceHandleObject {

    
Subset of JVM bytecode opcodes used by HotSpotConstantPool. /**
     * Subset of JVM bytecode opcodes used by {@link HotSpotConstantPool}.
     */
    public static class Bytecodes {
        public static final int LDC = 18; // 0x12
        public static final int LDC_W = 19; // 0x13
        public static final int LDC2_W = 20; // 0x14
        public static final int GETSTATIC = 178; // 0xB2
        public static final int PUTSTATIC = 179; // 0xB3
        public static final int GETFIELD = 180; // 0xB4
        public static final int PUTFIELD = 181; // 0xB5
        public static final int INVOKEVIRTUAL = 182; // 0xB6
        public static final int INVOKESPECIAL = 183; // 0xB7
        public static final int INVOKESTATIC = 184; // 0xB8
        public static final int INVOKEINTERFACE = 185; // 0xB9
        public static final int INVOKEDYNAMIC = 186; // 0xBA
        public static final int NEW = 187; // 0xBB
        public static final int NEWARRAY = 188; // 0xBC
        public static final int ANEWARRAY = 189; // 0xBD
        public static final int CHECKCAST = 192; // 0xC0
        public static final int INSTANCEOF = 193; // 0xC1
        public static final int MULTIANEWARRAY = 197; // 0xC5

        static boolean isInvoke(int opcode) {
            switch (opcode) {
                case INVOKEVIRTUAL:
                case INVOKESPECIAL:
                case INVOKESTATIC:
                case INVOKEINTERFACE:
                case INVOKEDYNAMIC:
                    return true;
                default:
                    return false;
            }
        }

        
See: Rewriter::maybe_rewrite_invokehandle. /**
         * See: {@code Rewriter::maybe_rewrite_invokehandle}.
         */
        static boolean isInvokeHandleAlias(int opcode) {
            switch (opcode) {
                case INVOKEVIRTUAL:
                case INVOKESPECIAL:
                    return true;
                default:
                    return false;
            }
        }
    }

    static final class JvmConstant {
        private final int tag;
        private final String name;

        JvmConstant(int tag, String name) {
            this.tag = tag;
            this.name = name;
        }

        @Override
        public String toString() {
            return name;
        }
    }

    
JVM_CONSTANT constants used in the VM including both public and internal ones. /**
     * {@code JVM_CONSTANT} constants used in the VM including both public and internal ones.
     */
    static final class JvmConstants {

        private final HotSpotVMConfig c = config();
        private final int externalMax = c.jvmConstantExternalMax;
        private final int internalMax = c.jvmConstantInternalMax;
        private final int internalMin = c.jvmConstantInternalMin;
        private final JvmConstant[] table = new JvmConstant[externalMax + 1 + (internalMax - internalMin) + 1];

        final JvmConstant jvmUtf8 = add(new JvmConstant(c.jvmConstantUtf8, "Utf8"));
        final JvmConstant jvmInteger = add(new JvmConstant(c.jvmConstantInteger, "Integer"));
        final JvmConstant jvmLong = add(new JvmConstant(c.jvmConstantLong, "Long"));
        final JvmConstant jvmFloat = add(new JvmConstant(c.jvmConstantFloat, "Float"));
        final JvmConstant jvmDouble = add(new JvmConstant(c.jvmConstantDouble, "Double"));
        final JvmConstant jvmClass = add(new JvmConstant(c.jvmConstantClass, "Class"));
        final JvmConstant jvmUnresolvedClass = add(new JvmConstant(c.jvmConstantUnresolvedClass, "UnresolvedClass"));
        final JvmConstant jvmUnresolvedClassInError = add(new JvmConstant(c.jvmConstantUnresolvedClassInError, "UnresolvedClassInError"));
        final JvmConstant jvmString = add(new JvmConstant(c.jvmConstantString, "String"));
        final JvmConstant jvmFieldref = add(new JvmConstant(c.jvmConstantFieldref, "Fieldref"));
        final JvmConstant jvmMethodref = add(new JvmConstant(c.jvmConstantMethodref, "Methodref"));
        final JvmConstant jvmInterfaceMethodref = add(new JvmConstant(c.jvmConstantInterfaceMethodref, "InterfaceMethodref"));
        final JvmConstant jvmNameAndType = add(new JvmConstant(c.jvmConstantNameAndType, "NameAndType"));
        final JvmConstant jvmMethodHandle = add(new JvmConstant(c.jvmConstantMethodHandle, "MethodHandle"));
        final JvmConstant jvmMethodHandleInError = add(new JvmConstant(c.jvmConstantMethodHandleInError, "MethodHandleInError"));
        final JvmConstant jvmMethodType = add(new JvmConstant(c.jvmConstantMethodType, "MethodType"));
        final JvmConstant jvmMethodTypeInError = add(new JvmConstant(c.jvmConstantMethodTypeInError, "MethodTypeInError"));
        final JvmConstant jvmInvokeDynamic = add(new JvmConstant(c.jvmConstantInvokeDynamic, "InvokeDynamic"));

        private JvmConstant add(JvmConstant constant) {
            table[indexOf(constant.tag)] = constant;
            return constant;
        }

        private int indexOf(int tag) {
            if (tag >= internalMin) {
                return tag - internalMin + externalMax + 1;
            } else {
                assert tag <= externalMax;
            }
            return tag;
        }

        JvmConstant get(int tag) {
            JvmConstant res = table[indexOf(tag)];
            if (res != null) {
                return res;
            }
            throw new JVMCIError("Unknown JvmConstant tag %s", tag);
        }

        @NativeImageReinitialize private static volatile JvmConstants instance;

        static JvmConstants instance() {
            JvmConstants result = instance;
            if (result == null) {
                synchronized (JvmConstants.class) {
                    result = instance;
                    if (result == null) {
                        instance = result = new JvmConstants();
                    }
                }
            }
            return result;
        }
    }

    private static class LookupTypeCacheElement {
        int lastCpi = Integer.MIN_VALUE;
        JavaType javaType;

        LookupTypeCacheElement(int lastCpi, JavaType javaType) {
            super();
            this.lastCpi = lastCpi;
            this.javaType = javaType;
        }
    }

    
Handle to the ConstantPool VM object. The handle is in JVMCI::_metadata_handles. /**
     * Handle to the {@code ConstantPool} VM object. The handle is in
     * {@code JVMCI::_metadata_handles}.
     */
    private final long metadataHandle;

    private volatile LookupTypeCacheElement lastLookupType;
    private final JvmConstants constants;

    
Gets the JVMCI mirror from a HotSpot constant pool.The VM is responsible for ensuring that the ConstantPool is kept alive for the duration of this call and the HotSpotJVMCIRuntime keeps it alive after that. Called from the VM. 
Params:
metaspaceConstantPool – a metaspace ConstantPool object
Returns:
the HotSpotConstantPool corresponding to metaspaceConstantPool/**
     * Gets the JVMCI mirror from a HotSpot constant pool.The VM is responsible for ensuring that
     * the ConstantPool is kept alive for the duration of this call and the
     * {@link HotSpotJVMCIRuntime} keeps it alive after that.
     *
     * Called from the VM.
     *
     * @param metaspaceConstantPool a metaspace ConstantPool object
     * @return the {@link HotSpotConstantPool} corresponding to {@code metaspaceConstantPool}
     */
    @SuppressWarnings("unused")
    @VMEntryPoint
    private static HotSpotConstantPool fromMetaspace(long metaspaceConstantPool) {
        return new HotSpotConstantPool(metaspaceConstantPool);
    }

    private HotSpotConstantPool(long metadataHandle) {
        this.metadataHandle = metadataHandle;
        this.constants = JvmConstants.instance();
        HandleCleaner.create(this, metadataHandle);
    }

    
Gets the holder for this constant pool as HotSpotResolvedObjectTypeImpl. 
Returns:
holder for this constant pool/**
     * Gets the holder for this constant pool as {@link HotSpotResolvedObjectTypeImpl}.
     *
     * @return holder for this constant pool
     */
    private HotSpotResolvedObjectType getHolder() {
        return compilerToVM().getResolvedJavaType(this, config().constantPoolHolderOffset, false);
    }

    
Converts a raw index from the bytecodes to a constant pool cache index by adding a constant. 
Params:
rawIndex – index from the bytecode
opcode – bytecode to convert the index for
Returns:
constant pool cache index/**
     * Converts a raw index from the bytecodes to a constant pool cache index by adding a
     * {@link HotSpotVMConfig#constantPoolCpCacheIndexTag constant}.
     *
     * @param rawIndex index from the bytecode
     * @param opcode bytecode to convert the index for
     * @return constant pool cache index
     */
    private static int rawIndexToConstantPoolCacheIndex(int rawIndex, int opcode) {
        int index;
        if (opcode == Bytecodes.INVOKEDYNAMIC) {
            index = rawIndex;
            // See: ConstantPool::is_invokedynamic_index
            assert index < 0 : "not an invokedynamic constant pool index " + index;
        } else {
            assert opcode == Bytecodes.GETFIELD || opcode == Bytecodes.PUTFIELD || opcode == Bytecodes.GETSTATIC || opcode == Bytecodes.PUTSTATIC || opcode == Bytecodes.INVOKEINTERFACE ||
                            opcode == Bytecodes.INVOKEVIRTUAL || opcode == Bytecodes.INVOKESPECIAL || opcode == Bytecodes.INVOKESTATIC : "unexpected invoke opcode " + opcode;
            index = rawIndex + config().constantPoolCpCacheIndexTag;
        }
        return index;
    }

    
Decode a constant pool cache index to a constant pool index. See ConstantPool::decode_cpcache_index. 
Params:
index – constant pool cache index
Returns:
decoded index/**
     * Decode a constant pool cache index to a constant pool index.
     *
     * See {@code ConstantPool::decode_cpcache_index}.
     *
     * @param index constant pool cache index
     * @return decoded index
     */
    private static int decodeConstantPoolCacheIndex(int index) {
        if (isInvokedynamicIndex(index)) {
            return decodeInvokedynamicIndex(index);
        } else {
            return index - config().constantPoolCpCacheIndexTag;
        }
    }

    
See ConstantPool::is_invokedynamic_index. /**
     * See {@code ConstantPool::is_invokedynamic_index}.
     */
    private static boolean isInvokedynamicIndex(int index) {
        return index < 0;
    }

    
See ConstantPool::decode_invokedynamic_index. /**
     * See {@code ConstantPool::decode_invokedynamic_index}.
     */
    private static int decodeInvokedynamicIndex(int i) {
        assert isInvokedynamicIndex(i) : i;
        return ~i;
    }

    long getMetaspaceConstantPool() {
        return getMetaspacePointer();
    }

    @Override
    public long getMetadataHandle() {
        return metadataHandle;
    }

    
Gets the constant pool tag at index index. 
Params:
index – constant pool index
Returns:
constant pool tag/**
     * Gets the constant pool tag at index {@code index}.
     *
     * @param index constant pool index
     * @return constant pool tag
     */
    private JvmConstant getTagAt(int index) {
        assert checkBounds(index);
        HotSpotVMConfig config = config();
        final long metaspaceConstantPoolTags = UNSAFE.getAddress(getMetaspaceConstantPool() + config.constantPoolTagsOffset);
        final int tag = UNSAFE.getByteVolatile(null, metaspaceConstantPoolTags + config.arrayU1DataOffset + index);
        if (tag == 0) {
            return null;
        }
        return constants.get(tag);
    }

    
Gets the constant pool entry at index index. 
Params:
index – constant pool index
Returns:
constant pool entry/**
     * Gets the constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return constant pool entry
     */
    long getEntryAt(int index) {
        assert checkBounds(index);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getAddress(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the integer constant pool entry at index index. 
Params:
index – constant pool index
Returns:
integer constant pool entry at index/**
     * Gets the integer constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return integer constant pool entry at index
     */
    private int getIntAt(int index) {
        assert checkTag(index, constants.jvmInteger);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getInt(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the long constant pool entry at index index. 
Params:
index – constant pool index
Returns:
long constant pool entry/**
     * Gets the long constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return long constant pool entry
     */
    private long getLongAt(int index) {
        assert checkTag(index, constants.jvmLong);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getLong(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the float constant pool entry at index index. 
Params:
index – constant pool index
Returns:
float constant pool entry/**
     * Gets the float constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return float constant pool entry
     */
    private float getFloatAt(int index) {
        assert checkTag(index, constants.jvmFloat);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getFloat(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the double constant pool entry at index index. 
Params:
index – constant pool index
Returns:
float constant pool entry/**
     * Gets the double constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return float constant pool entry
     */
    private double getDoubleAt(int index) {
        assert checkTag(index, constants.jvmDouble);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getDouble(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the JVM_CONSTANT_NameAndType constant pool entry at index index. 
Params:
index – constant pool index
Returns:
JVM_CONSTANT_NameAndType constant pool entry/**
     * Gets the {@code JVM_CONSTANT_NameAndType} constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return {@code JVM_CONSTANT_NameAndType} constant pool entry
     */
    private int getNameAndTypeAt(int index) {
        assert checkTag(index, constants.jvmNameAndType);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        return UNSAFE.getInt(getMetaspaceConstantPool() + config().constantPoolSize + offset);
    }

    
Gets the JVM_CONSTANT_NameAndType reference index constant pool entry at index index. 
Params:
index – constant pool index
Returns:
JVM_CONSTANT_NameAndType reference constant pool entry/**
     * Gets the {@code JVM_CONSTANT_NameAndType} reference index constant pool entry at index
     * {@code index}.
     *
     * @param index constant pool index
     * @return {@code JVM_CONSTANT_NameAndType} reference constant pool entry
     */
    private int getNameAndTypeRefIndexAt(int index) {
        return compilerToVM().lookupNameAndTypeRefIndexInPool(this, index);
    }

    
Gets the name of a JVM_CONSTANT_NameAndType constant pool entry referenced by another entry denoted by which. 
Params:
which – constant pool index or constant pool cache index
Returns:
name as String/**
     * Gets the name of a {@code JVM_CONSTANT_NameAndType} constant pool entry referenced by another
     * entry denoted by {@code which}.
     *
     * @param which constant pool index or constant pool cache index
     * @return name as {@link String}
     */
    private String getNameOf(int which) {
        return compilerToVM().lookupNameInPool(this, which);
    }

    
Gets the name reference index of a JVM_CONSTANT_NameAndType constant pool entry at index index. 
Params:
index – constant pool index
Returns:
name reference index/**
     * Gets the name reference index of a {@code JVM_CONSTANT_NameAndType} constant pool entry at
     * index {@code index}.
     *
     * @param index constant pool index
     * @return name reference index
     */
    private int getNameRefIndexAt(int index) {
        final int refIndex = getNameAndTypeAt(index);
        // name ref index is in the low 16-bits.
        return refIndex & 0xFFFF;
    }

    
Gets the signature of a JVM_CONSTANT_NameAndType constant pool entry referenced by another entry denoted by which. 
Params:
which – constant pool index or constant pool cache index
Returns:
signature as String/**
     * Gets the signature of a {@code JVM_CONSTANT_NameAndType} constant pool entry referenced by
     * another entry denoted by {@code which}.
     *
     * @param which constant pool index or constant pool cache index
     * @return signature as {@link String}
     */
    private String getSignatureOf(int which) {
        return compilerToVM().lookupSignatureInPool(this, which);
    }

    
Gets the signature reference index of a JVM_CONSTANT_NameAndType constant pool entry at index index. 
Params:
index – constant pool index
Returns:
signature reference index/**
     * Gets the signature reference index of a {@code JVM_CONSTANT_NameAndType} constant pool entry
     * at index {@code index}.
     *
     * @param index constant pool index
     * @return signature reference index
     */
    private int getSignatureRefIndexAt(int index) {
        final int refIndex = getNameAndTypeAt(index);
        // signature ref index is in the high 16-bits.
        return refIndex >>> 16;
    }

    
Gets the klass reference index constant pool entry at index index. 
Params:
index – constant pool index
Returns:
klass reference index/**
     * Gets the klass reference index constant pool entry at index {@code index}.
     *
     * @param index constant pool index
     * @return klass reference index
     */
    private int getKlassRefIndexAt(int index) {
        return compilerToVM().lookupKlassRefIndexInPool(this, index);
    }

    
Gets the uncached klass reference index constant pool entry at index index. See: ConstantPool::uncached_klass_ref_index_at. 
Params:
index – constant pool index
Returns:
klass reference index/**
     * Gets the uncached klass reference index constant pool entry at index {@code index}. See:
     * {@code ConstantPool::uncached_klass_ref_index_at}.
     *
     * @param index constant pool index
     * @return klass reference index
     */
    private int getUncachedKlassRefIndexAt(int index) {
        assert checkTagIsFieldOrMethod(index);
        int offset = index * runtime().getHostJVMCIBackend().getTarget().wordSize;
        final int refIndex = UNSAFE.getInt(getMetaspaceConstantPool() + config().constantPoolSize + offset);
        // klass ref index is in the low 16-bits.
        return refIndex & 0xFFFF;
    }

    
Checks that the constant pool index index is in the bounds of the constant pool. 
Params:
index – constant pool index
Throws:
AssertionError – if the check fails/**
     * Checks that the constant pool index {@code index} is in the bounds of the constant pool.
     *
     * @param index constant pool index
     * @throws AssertionError if the check fails
     */
    private boolean checkBounds(int index) {
        assert 0 <= index && index < length() : "index " + index + " not between 0 and " + length();
        return true;
    }

    
Checks that the constant pool tag at index index is equal to tag. 
Params:
index – constant pool index
tag – expected tag
Throws:
AssertionError – if the check fails/**
     * Checks that the constant pool tag at index {@code index} is equal to {@code tag}.
     *
     * @param index constant pool index
     * @param tag expected tag
     * @throws AssertionError if the check fails
     */
    private boolean checkTag(int index, JvmConstant tag) {
        final JvmConstant tagAt = getTagAt(index);
        assert tagAt == tag : "constant pool tag at index " + index + " is " + tagAt + " but expected " + tag;
        return true;
    }

    
Asserts that the constant pool tag at index index is a JvmConstants.jvmFieldref, or a JvmConstants.jvmMethodref, or a JvmConstants.jvmInterfaceMethodref. 
Params:
index – constant pool index
Throws:
AssertionError – if the check fails/**
     * Asserts that the constant pool tag at index {@code index} is a
     * {@link JvmConstants#jvmFieldref}, or a {@link JvmConstants#jvmMethodref}, or a
     * {@link JvmConstants#jvmInterfaceMethodref}.
     *
     * @param index constant pool index
     * @throws AssertionError if the check fails
     */
    private boolean checkTagIsFieldOrMethod(int index) {
        final JvmConstant tagAt = getTagAt(index);
        assert tagAt == constants.jvmFieldref || tagAt == constants.jvmMethodref || tagAt == constants.jvmInterfaceMethodref : tagAt;
        return true;
    }

    @Override
    public int length() {
        return UNSAFE.getInt(getMetaspaceConstantPool() + config().constantPoolLengthOffset);
    }

    public boolean hasDynamicConstant() {
        return (flags() & config().constantPoolHasDynamicConstant) != 0;
    }

    private int flags() {
        return UNSAFE.getInt(getMetaspaceConstantPool() + config().constantPoolFlagsOffset);
    }

    @Override
    public Object lookupConstant(int cpi) {
        assert cpi != 0;
        final JvmConstant tag = getTagAt(cpi);
        switch (tag.name) {
            case "Integer":
                return JavaConstant.forInt(getIntAt(cpi));
            case "Long":
                return JavaConstant.forLong(getLongAt(cpi));
            case "Float":
                return JavaConstant.forFloat(getFloatAt(cpi));
            case "Double":
                return JavaConstant.forDouble(getDoubleAt(cpi));
            case "Class":
            case "UnresolvedClass":
            case "UnresolvedClassInError":
                final int opcode = -1;  // opcode is not used
                return lookupType(cpi, opcode);
            case "String":
                /*
                 * Normally, we would expect a String here, but unsafe anonymous classes can have
                 * "pseudo strings" (arbitrary live objects) patched into a String entry. Such
                 * entries do not have a symbol in the constant pool slot.
                 */
                return compilerToVM().resolvePossiblyCachedConstantInPool(this, cpi);
            case "MethodHandle":
            case "MethodHandleInError":
            case "MethodType":
            case "MethodTypeInError":
                return compilerToVM().resolvePossiblyCachedConstantInPool(this, cpi);
            default:
                throw new JVMCIError("Unknown constant pool tag %s", tag);
        }
    }

    @Override
    public String lookupUtf8(int cpi) {
        assert checkTag(cpi, constants.jvmUtf8);
        return compilerToVM().getSymbol(getEntryAt(cpi));
    }

    @Override
    public Signature lookupSignature(int cpi) {
        return new HotSpotSignature(runtime(), lookupUtf8(cpi));
    }

    @Override
    public JavaConstant lookupAppendix(int cpi, int opcode) {
        assert Bytecodes.isInvoke(opcode);
        final int index = rawIndexToConstantPoolCacheIndex(cpi, opcode);
        return compilerToVM().lookupAppendixInPool(this, index);
    }

    
Gets a JavaType corresponding a given resolved or unresolved type. 
Params:
type – either a ResolvedJavaType or a String naming a unresolved type./**
     * Gets a {@link JavaType} corresponding a given resolved or unresolved type.
     *
     * @param type either a ResolvedJavaType or a String naming a unresolved type.
     */
    private static JavaType getJavaType(final Object type) {
        if (type instanceof String) {
            String name = (String) type;
            return UnresolvedJavaType.create("L" + name + ";");
        } else {
            return (JavaType) type;
        }
    }

    @Override
    public JavaMethod lookupMethod(int cpi, int opcode) {
        final int index = rawIndexToConstantPoolCacheIndex(cpi, opcode);
        final HotSpotResolvedJavaMethod method = compilerToVM().lookupMethodInPool(this, index, (byte) opcode);
        if (method != null) {
            return method;
        } else {
            // Get the method's name and signature.
            String name = getNameOf(index);
            HotSpotSignature signature = new HotSpotSignature(runtime(), getSignatureOf(index));
            if (opcode == Bytecodes.INVOKEDYNAMIC) {
                HotSpotResolvedObjectType holder = runtime().getMethodHandleClass();
                return new UnresolvedJavaMethod(name, signature, holder);
            } else {
                final int klassIndex = getKlassRefIndexAt(index);
                final Object type = compilerToVM().lookupKlassInPool(this, klassIndex);
                JavaType holder = getJavaType(type);
                return new UnresolvedJavaMethod(name, signature, holder);
            }
        }
    }

    @Override
    public JavaType lookupType(int cpi, int opcode) {
        final LookupTypeCacheElement elem = this.lastLookupType;
        if (elem != null && elem.lastCpi == cpi) {
            return elem.javaType;
        } else {
            final Object type = compilerToVM().lookupKlassInPool(this, cpi);
            JavaType result = getJavaType(type);
            if (result instanceof ResolvedJavaType) {
                this.lastLookupType = new LookupTypeCacheElement(cpi, result);
            }
            return result;
        }
    }

    @Override
    public JavaType lookupReferencedType(int cpi, int opcode) {
        int index;
        switch (opcode) {
            case Bytecodes.CHECKCAST:
            case Bytecodes.INSTANCEOF:
            case Bytecodes.NEW:
            case Bytecodes.ANEWARRAY:
            case Bytecodes.MULTIANEWARRAY:
            case Bytecodes.LDC:
            case Bytecodes.LDC_W:
            case Bytecodes.LDC2_W:
                index = cpi;
                break;
            case Bytecodes.GETSTATIC:
            case Bytecodes.PUTSTATIC:
            case Bytecodes.GETFIELD:
            case Bytecodes.PUTFIELD:
            case Bytecodes.INVOKEVIRTUAL:
            case Bytecodes.INVOKESPECIAL:
            case Bytecodes.INVOKESTATIC:
            case Bytecodes.INVOKEINTERFACE: {
                index = rawIndexToConstantPoolCacheIndex(cpi, opcode);
                index = getKlassRefIndexAt(index);
                break;
            }
            default:
                throw JVMCIError.shouldNotReachHere("Unexpected opcode " + opcode);
        }
        final Object type = compilerToVM().lookupKlassInPool(this, index);
        return getJavaType(type);
    }

    @Override
    public JavaField lookupField(int cpi, ResolvedJavaMethod method, int opcode) {
        final int index = rawIndexToConstantPoolCacheIndex(cpi, opcode);
        final int nameAndTypeIndex = getNameAndTypeRefIndexAt(index);
        final int typeIndex = getSignatureRefIndexAt(nameAndTypeIndex);
        String typeName = lookupUtf8(typeIndex);
        JavaType type = runtime().lookupType(typeName, getHolder(), false);

        final int holderIndex = getKlassRefIndexAt(index);
        JavaType holder = lookupType(holderIndex, opcode);

        if (holder instanceof HotSpotResolvedObjectTypeImpl) {
            int[] info = new int[3];
            HotSpotResolvedObjectTypeImpl resolvedHolder;
            try {
                resolvedHolder = compilerToVM().resolveFieldInPool(this, index, (HotSpotResolvedJavaMethodImpl) method, (byte) opcode, info);
            } catch (Throwable t) {
                /*
                 * If there was an exception resolving the field we give up and return an unresolved
                 * field.
                 */
                return new UnresolvedJavaField(holder, lookupUtf8(getNameRefIndexAt(nameAndTypeIndex)), type);
            }
            final int flags = info[0];
            final int offset = info[1];
            final int fieldIndex = info[2];
            HotSpotResolvedJavaField result = resolvedHolder.createField(type, offset, flags, fieldIndex);
            return result;
        } else {
            return new UnresolvedJavaField(holder, lookupUtf8(getNameRefIndexAt(nameAndTypeIndex)), type);
        }
    }

    
Converts a raw index from the bytecodes to a constant pool index (not a cache index).
Params:
rawIndex – index from the bytecode
opcode – bytecode to convert the index for
Returns:
constant pool index/**
     * Converts a raw index from the bytecodes to a constant pool index (not a cache index).
     *
     * @param rawIndex index from the bytecode
     *
     * @param opcode bytecode to convert the index for
     *
     * @return constant pool index
     */
    public int rawIndexToConstantPoolIndex(int rawIndex, int opcode) {
        int index;
        if (isInvokedynamicIndex(rawIndex)) {
            assert opcode == Bytecodes.INVOKEDYNAMIC;
            index = decodeInvokedynamicIndex(rawIndex) + config().constantPoolCpCacheIndexTag;
        } else {
            assert opcode != Bytecodes.INVOKEDYNAMIC;
            index = rawIndexToConstantPoolCacheIndex(rawIndex, opcode);
        }
        return compilerToVM().constantPoolRemapInstructionOperandFromCache(this, index);
    }

    @Override
    public void loadReferencedType(int cpi, int opcode) {
        loadReferencedType(cpi, opcode, true /* initialize */);
    }

    @SuppressWarnings("fallthrough")
    public void loadReferencedType(int cpi, int opcode, boolean initialize) {
        int index;
        switch (opcode) {
            case Bytecodes.CHECKCAST:
            case Bytecodes.INSTANCEOF:
            case Bytecodes.NEW:
            case Bytecodes.ANEWARRAY:
            case Bytecodes.MULTIANEWARRAY:
            case Bytecodes.LDC:
            case Bytecodes.LDC_W:
            case Bytecodes.LDC2_W:
                index = cpi;
                break;
            case Bytecodes.INVOKEDYNAMIC: {
                // invokedynamic instructions point to a constant pool cache entry.
                index = decodeConstantPoolCacheIndex(cpi) + config().constantPoolCpCacheIndexTag;
                index = compilerToVM().constantPoolRemapInstructionOperandFromCache(this, index);
                break;
            }
            case Bytecodes.GETSTATIC:
            case Bytecodes.PUTSTATIC:
            case Bytecodes.GETFIELD:
            case Bytecodes.PUTFIELD:
            case Bytecodes.INVOKEVIRTUAL:
            case Bytecodes.INVOKESPECIAL:
            case Bytecodes.INVOKESTATIC:
            case Bytecodes.INVOKEINTERFACE: {
                // invoke and field instructions point to a constant pool cache entry.
                index = rawIndexToConstantPoolCacheIndex(cpi, opcode);
                index = compilerToVM().constantPoolRemapInstructionOperandFromCache(this, index);
                break;
            }
            default:
                throw JVMCIError.shouldNotReachHere("Unexpected opcode " + opcode);
        }

        final JvmConstant tag = getTagAt(index);
        if (tag == null) {
            assert getTagAt(index - 1) == constants.jvmDouble || getTagAt(index - 1) == constants.jvmLong;
            return;
        }
        switch (tag.name) {
            case "Methodref":
            case "Fieldref":
            case "InterfaceMethodref":
                index = getUncachedKlassRefIndexAt(index);
                // Read the tag only once because it could change between multiple reads.
                final JvmConstant klassTag = getTagAt(index);
                assert klassTag == constants.jvmClass || klassTag == constants.jvmUnresolvedClass || klassTag == constants.jvmUnresolvedClassInError : klassTag;
                // fall through
            case "Class":
            case "UnresolvedClass":
            case "UnresolvedClassInError":
                final HotSpotResolvedObjectTypeImpl type = compilerToVM().resolveTypeInPool(this, index);
                if (initialize && !type.isPrimitive() && !type.isArray()) {
                    type.ensureInitialized();
                }
                if (tag == constants.jvmMethodref) {
                    if (Bytecodes.isInvokeHandleAlias(opcode) && isSignaturePolymorphicHolder(type)) {
                        final int methodRefCacheIndex = rawIndexToConstantPoolCacheIndex(cpi, opcode);
                        assert checkTag(compilerToVM().constantPoolRemapInstructionOperandFromCache(this, methodRefCacheIndex), constants.jvmMethodref);
                        compilerToVM().resolveInvokeHandleInPool(this, methodRefCacheIndex);
                    }
                }

                break;
            case "InvokeDynamic":
                if (isInvokedynamicIndex(cpi)) {
                    compilerToVM().resolveInvokeDynamicInPool(this, cpi);
                }
                break;
            default:
                // nothing
                break;
        }

    }

    // Lazily initialized.
    private static String[] signaturePolymorphicHolders;

    
Determines if type contains signature polymorphic methods. /**
     * Determines if {@code type} contains signature polymorphic methods.
     */
    @SuppressFBWarnings(value = "LI_LAZY_INIT_STATIC", justification = "signaturePolymorphicHolders is a cache, not a singleton that must be constructed exactly once" +
                    "and compiler re-ordering is not an issue due to the VM call")
    static boolean isSignaturePolymorphicHolder(final ResolvedJavaType type) {
        String name = type.getName();
        if (signaturePolymorphicHolders == null) {
            signaturePolymorphicHolders = compilerToVM().getSignaturePolymorphicHolders();
        }
        for (String holder : signaturePolymorphicHolders) {
            if (name.equals(holder)) {
                return true;
            }
        }
        return false;
    }

    
Check for a resolved dynamic adapter method at the specified index, resulting from either a
resolved invokedynamic or invokevirtual on a signature polymorphic MethodHandle method
(HotSpot invokehandle).
Params:
cpi – the constant pool index
opcode – the opcode of the instruction for which the lookup is being performed
Returns:
true if a signature polymorphic method reference was found, otherwise false/**
     * Check for a resolved dynamic adapter method at the specified index, resulting from either a
     * resolved invokedynamic or invokevirtual on a signature polymorphic MethodHandle method
     * (HotSpot invokehandle).
     *
     * @param cpi the constant pool index
     * @param opcode the opcode of the instruction for which the lookup is being performed
     * @return {@code true} if a signature polymorphic method reference was found, otherwise
     *         {@code false}
     */
    public boolean isResolvedDynamicInvoke(int cpi, int opcode) {
        if (Bytecodes.isInvokeHandleAlias(opcode)) {
            final int methodRefCacheIndex = rawIndexToConstantPoolCacheIndex(cpi, opcode);
            assert checkTag(compilerToVM().constantPoolRemapInstructionOperandFromCache(this, methodRefCacheIndex), constants.jvmMethodref);
            int op = compilerToVM().isResolvedInvokeHandleInPool(this, methodRefCacheIndex);
            return op == opcode;
        }
        return false;
    }

    public String getSourceFileName() {
        final int sourceFileNameIndex = UNSAFE.getChar(getMetaspaceConstantPool() + config().constantPoolSourceFileNameIndexOffset);
        if (sourceFileNameIndex == 0) {
            return null;
        }
        return lookupUtf8(sourceFileNameIndex);
    }

    @Override
    public String toString() {
        HotSpotResolvedObjectType holder = getHolder();
        return "HotSpotConstantPool<" + holder.toJavaName() + ">";
    }
}