https://www.graalvm.org/ 
/*
 * Copyright (c) 2016, 2020, Oracle and/or its affiliates.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 * conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided
 * with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.oracle.truffle.llvm.runtime.nodes.op;

import com.oracle.truffle.api.dsl.Cached;
import com.oracle.truffle.api.dsl.NodeChild;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.interop.UnsupportedMessageException;
import com.oracle.truffle.api.library.CachedLibrary;
import com.oracle.truffle.llvm.runtime.library.internal.LLVMNativeLibrary;
import com.oracle.truffle.llvm.runtime.nodes.api.LLVMExpressionNode;
import com.oracle.truffle.llvm.runtime.nodes.api.LLVMNode;
import com.oracle.truffle.llvm.runtime.nodes.op.LLVMPointerCompareNodeGen.LLVMNegateNodeGen;
import com.oracle.truffle.llvm.runtime.nodes.op.ToComparableValue.ManagedToComparableValue;
import com.oracle.truffle.llvm.runtime.nodes.util.LLVMSameObjectNode;
import com.oracle.truffle.llvm.runtime.pointer.LLVMManagedPointer;
import com.oracle.truffle.llvm.runtime.pointer.LLVMNativePointer;

@NodeChild(type = LLVMExpressionNode.class)
@NodeChild(type = LLVMExpressionNode.class)
public abstract class LLVMPointerCompareNode extends LLVMAbstractCompareNode {
    private final NativePointerCompare op;

    public LLVMPointerCompareNode(NativePointerCompare op) {
        this.op = op;
    }

    // the first two cases are redundant but much more efficient than the ones below

    @Specialization
    boolean doCompare(long a, long b) {
        return op.compare(a, b);
    }

    @Specialization
    boolean doCompare(LLVMNativePointer a, LLVMNativePointer b) {
        return op.compare(a.asNative(), b.asNative());
    }

    @Specialization(guards = {"libA.isPointer(a)", "libB.isPointer(b)"}, limit = "3", rewriteOn = UnsupportedMessageException.class)
    protected boolean doPointerPointer(Object a, Object b,
                    @CachedLibrary("a") LLVMNativeLibrary libA,
                    @CachedLibrary("b") LLVMNativeLibrary libB) throws UnsupportedMessageException {
        return op.compare(libA.asPointer(a), libB.asPointer(b));
    }

    @Specialization(guards = {"libA.isPointer(a)", "libB.isPointer(b)"}, limit = "3")
    protected boolean doPointerPointerException(Object a, Object b,
                    @CachedLibrary("a") LLVMNativeLibrary libA,
                    @CachedLibrary("b") LLVMNativeLibrary libB,
                    @Cached LLVMManagedCompareNode managedCompare) {
        try {
            return doPointerPointer(a, b, libA, libB);
        } catch (UnsupportedMessageException ex) {
            // even though both say isPointer == true, one of them threw an exception in asPointer
            // this is the same as if one of the objects has isPointer == false
            return doOther(a, b, libA, libB, managedCompare);
        }
    }

    @Specialization(guards = "!libA.isPointer(a) || !libB.isPointer(b)", limit = "3")
    protected boolean doOther(Object a, Object b,
                    @CachedLibrary("a") LLVMNativeLibrary libA,
                    @CachedLibrary("b") LLVMNativeLibrary libB,
                    @Cached LLVMManagedCompareNode managedCompare) {
        return managedCompare.execute(a, libA, b, libB, op);
    }

    public static LLVMAbstractCompareNode create(Kind kind, LLVMExpressionNode l, LLVMExpressionNode r) {
        switch (kind) {
            case SLT:
                return LLVMPointerCompareNodeGen.create(new NativePointerCompare() {

                    @Override
                    public boolean compare(long a, long b) {
                        return a < b;
                    }
                }, l, r);
            case SLE:
                return LLVMPointerCompareNodeGen.create(new NativePointerCompare() {

                    @Override
                    public boolean compare(long a, long b) {
                        return a <= b;
                    }
                }, l, r);
            case ULE:
                return LLVMPointerCompareNodeGen.create(new NativePointerCompare() {

                    @Override
                    public boolean compare(long a, long b) {
                        return Long.compareUnsigned(a, b) <= 0;
                    }
                }, l, r);
            case ULT:
                return LLVMPointerCompareNodeGen.create(new NativePointerCompare() {

                    @Override
                    public boolean compare(long a, long b) {
                        return Long.compareUnsigned(a, b) < 0;
                    }
                }, l, r);
            case EQ:
                return LLVMAddressEqualsNodeGen.create(l, r);
            case NEQ:
                return LLVMNegateNode.create(LLVMAddressEqualsNodeGen.create(l, r));
            default:
                throw new AssertionError();

        }
    }

    public enum Kind {
        ULT,
        ULE,
        SLT,
        SLE,
        EQ,
        NEQ,
    }

    protected abstract static class NativePointerCompare {
        abstract boolean compare(long a, long b);
    }

    
Whenever we used ManagedToComparableValue in this class, we only convert the managed object to a long value and ignore the pointer offset (including the offset would increase the probability of collisions). However, we can only ignore the offset safely when we know that both pointers do not point to the same object. 
/**
     * Whenever we used {@link ManagedToComparableValue} in this class, we only convert the managed
     * object to a long value and ignore the pointer offset (including the offset would increase the
     * probability of collisions). However, we can only ignore the offset safely when we know that
     * both pointers do not point to the same object.
     */
    abstract static class LLVMManagedCompareNode extends LLVMNode {
        private static final long TYPICAL_POINTER = 0x00007f0000000000L;

        abstract boolean execute(Object a, LLVMNativeLibrary libA, Object b, LLVMNativeLibrary libB, NativePointerCompare op);

        @Specialization(guards = {"pointToSameObject.execute(a.getObject(), b.getObject())"})
        protected boolean doForeign(LLVMManagedPointer a, @SuppressWarnings("unused") LLVMNativeLibrary libA,
                        LLVMManagedPointer b, @SuppressWarnings("unused") LLVMNativeLibrary libB, NativePointerCompare op,
                        @SuppressWarnings("unused") @Cached LLVMSameObjectNode pointToSameObject) {
            // when comparing pointers to the same object, it is not sufficient to simply compare
            // the offsets if we have an unsigned comparison and one of the offsets is negative. So,
            // we add a "typical" pointer value to both offsets and compare the resulting values.
            return op.compare(TYPICAL_POINTER + a.getOffset(), TYPICAL_POINTER + b.getOffset());
        }

        @Specialization(guards = "!pointToSameObject.execute(a.getObject(), b.getObject())")
        protected boolean doForeign(LLVMManagedPointer a, @SuppressWarnings("unused") LLVMNativeLibrary libA,
                        LLVMManagedPointer b, @SuppressWarnings("unused") LLVMNativeLibrary libB, NativePointerCompare op,
                        @SuppressWarnings("unused") @Cached LLVMSameObjectNode pointToSameObject,
                        @Cached("createIgnoreOffset()") ManagedToComparableValue convertA,
                        @Cached("createIgnoreOffset()") ManagedToComparableValue convertB) {
            return op.compare(convertA.executeWithTarget(a), convertB.executeWithTarget(b));
        }

        
Params:
  • a – 
  • libA – 
  • b – 
  • libB – 
  • op – 
See Also:
/**
         * @param a
         * @param libA
         * @param b
         * @param libB
         * @param op
         * @see #execute(Object, LLVMNativeLibrary, Object, LLVMNativeLibrary, NativePointerCompare)
         */
        @Specialization(guards = "libA.isPointer(a)", rewriteOn = UnsupportedMessageException.class)
        protected boolean doNativeManaged(Object a, LLVMNativeLibrary libA, Object b, LLVMNativeLibrary libB, NativePointerCompare op,
                        @Cached("createIgnoreOffset()") ManagedToComparableValue convert) throws UnsupportedMessageException {
            return op.compare(libA.asPointer(a), convert.executeWithTarget(b));
        }

        
Params:
  • a – 
  • libA – 
  • b – 
  • libB – 
  • op – 
See Also:
/**
         * @param a
         * @param libA
         * @param b
         * @param libB
         * @param op
         * @see #execute(Object, LLVMNativeLibrary, Object, LLVMNativeLibrary, NativePointerCompare)
         */
        @Specialization(guards = "libB.isPointer(b)", rewriteOn = UnsupportedMessageException.class)
        protected boolean doManagedNative(Object a, LLVMNativeLibrary libA, Object b, LLVMNativeLibrary libB, NativePointerCompare op,
                        @Cached("createIgnoreOffset()") ManagedToComparableValue convert) throws UnsupportedMessageException {
            return op.compare(convert.executeWithTarget(a), libB.asPointer(b));
        }

        @Specialization(guards = "libA.isPointer(a) || libB.isPointer(b)")
        protected boolean doManagedNativeException(Object a, LLVMNativeLibrary libA, Object b, LLVMNativeLibrary libB, NativePointerCompare op,
                        @Cached("createIgnoreOffset()") ManagedToComparableValue convert) {
            try {
                return op.compare(libA.asPointer(a), convert.executeWithTarget(b));
            } catch (UnsupportedMessageException e) {
                try {
                    return op.compare(convert.executeWithTarget(a), libB.asPointer(b));
                } catch (UnsupportedMessageException ex) {
                    return op.compare(convert.executeWithTarget(a), convert.executeWithTarget(b));
                }
            }
        }
    }

    public abstract static class LLVMNegateNode extends LLVMAbstractCompareNode {
        @Child private LLVMAbstractCompareNode booleanExpression;

        LLVMNegateNode(LLVMAbstractCompareNode booleanExpression) {
            this.booleanExpression = booleanExpression;
        }

        public static LLVMAbstractCompareNode create(LLVMAbstractCompareNode booleanExpression) {
            return LLVMNegateNodeGen.create(booleanExpression);
        }

        @Override
        public final boolean executeWithTarget(Object a, Object b) {
            return !booleanExpression.executeWithTarget(a, b);
        }

        @Specialization
        public boolean doNegate(VirtualFrame frame) {
            return !booleanExpression.executeGenericBoolean(frame);
        }
    }
}