/*

 * Copyright (c) 2013, 2015, 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

 * questions.

 */

package org.graalvm.compiler.lir.amd64;

import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.ILLEGAL;

import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.REG;

import static jdk.vm.ci.code.ValueUtil.asRegister;

import java.lang.reflect.Array;

import java.lang.reflect.Field;

import org.graalvm.compiler.asm.Label;

import org.graalvm.compiler.asm.amd64.AMD64Address;

import org.graalvm.compiler.asm.amd64.AMD64Address.Scale;

import org.graalvm.compiler.asm.amd64.AMD64Assembler.ConditionFlag;

import org.graalvm.compiler.asm.amd64.AMD64MacroAssembler;

import org.graalvm.compiler.core.common.LIRKind;

import org.graalvm.compiler.lir.LIRInstructionClass;

import org.graalvm.compiler.lir.Opcode;

import org.graalvm.compiler.lir.asm.CompilationResultBuilder;

import org.graalvm.compiler.lir.gen.LIRGeneratorTool;

import jdk.vm.ci.amd64.AMD64;

import jdk.vm.ci.amd64.AMD64.CPUFeature;

import jdk.vm.ci.amd64.AMD64Kind;

import jdk.vm.ci.code.Register;

import jdk.vm.ci.code.TargetDescription;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.Value;

import sun.misc.Unsafe;

/**

 * Emits code which compares two arrays of the same length. If the CPU supports any vector

 * instructions specialized code is emitted to leverage these instructions.

 */

@Opcode("ARRAY_EQUALS")

public final class AMD64ArrayEqualsOp extends AMD64LIRInstruction {

    public static final LIRInstructionClass<AMD64ArrayEqualsOp> TYPE = LIRInstructionClass.create(AMD64ArrayEqualsOp.class);

    private final JavaKind kind;

    private final int arrayBaseOffset;

    private final int arrayIndexScale;

    @Def({REG}) protected Value resultValue;

    @Alive({REG}) protected Value array1Value;

    @Alive({REG}) protected Value array2Value;

    @Alive({REG}) protected Value lengthValue;

    @Temp({REG}) protected Value temp1;

    @Temp({REG}) protected Value temp2;

    @Temp({REG}) protected Value temp3;

    @Temp({REG}) protected Value temp4;

    @Temp({REG, ILLEGAL}) protected Value vectorTemp1;

    @Temp({REG, ILLEGAL}) protected Value vectorTemp2;

    public AMD64ArrayEqualsOp(LIRGeneratorTool tool, JavaKind kind, Value result, Value array1, Value array2, Value length) {

        super(TYPE);

        this.kind = kind;

        Class<?> arrayClass = Array.newInstance(kind.toJavaClass(), 0).getClass();

        this.arrayBaseOffset = UNSAFE.arrayBaseOffset(arrayClass);

        this.arrayIndexScale = UNSAFE.arrayIndexScale(arrayClass);

        this.resultValue = result;

        this.array1Value = array1;

        this.array2Value = array2;

        this.lengthValue = length;

        // Allocate some temporaries.

        this.temp1 = tool.newVariable(LIRKind.unknownReference(tool.target().arch.getWordKind()));

        this.temp2 = tool.newVariable(LIRKind.unknownReference(tool.target().arch.getWordKind()));

        this.temp3 = tool.newVariable(LIRKind.value(tool.target().arch.getWordKind()));

        this.temp4 = tool.newVariable(LIRKind.value(tool.target().arch.getWordKind()));

        // We only need the vector temporaries if we generate SSE code.

        if (supportsSSE41(tool.target())) {

            this.vectorTemp1 = tool.newVariable(LIRKind.value(AMD64Kind.DOUBLE));

            this.vectorTemp2 = tool.newVariable(LIRKind.value(AMD64Kind.DOUBLE));

        } else {

            this.vectorTemp1 = Value.ILLEGAL;

            this.vectorTemp2 = Value.ILLEGAL;

        }

    }

    @Override

    public void emitCode(CompilationResultBuilder crb, AMD64MacroAssembler masm) {

        Register result = asRegister(resultValue);

        Register array1 = asRegister(temp1);

        Register array2 = asRegister(temp2);

        Register length = asRegister(temp3);

        Label trueLabel = new Label();

        Label falseLabel = new Label();

        Label done = new Label();

        // Load array base addresses.

        masm.leaq(array1, new AMD64Address(asRegister(array1Value), arrayBaseOffset));

        masm.leaq(array2, new AMD64Address(asRegister(array2Value), arrayBaseOffset));

        // Get array length in bytes.

        masm.imull(length, asRegister(lengthValue), arrayIndexScale);

        masm.movl(result, length); // copy

        if (supportsAVX2(crb.target)) {

            emitAVXCompare(crb, masm, result, array1, array2, length, trueLabel, falseLabel);

        } else if (supportsSSE41(crb.target)) {

            emitSSE41Compare(crb, masm, result, array1, array2, length, trueLabel, falseLabel);

        }

        emit8ByteCompare(crb, masm, result, array1, array2, length, trueLabel, falseLabel);

        emitTailCompares(masm, result, array1, array2, length, trueLabel, falseLabel);

        // Return true

        masm.bind(trueLabel);

        masm.movl(result, 1);

        masm.jmpb(done);

        // Return false

        masm.bind(falseLabel);

        masm.xorl(result, result);

        // That's it

        masm.bind(done);

    }

    /**

     * Returns if the underlying AMD64 architecture supports SSE 4.1 instructions.

     *

     * @param target target description of the underlying architecture

     * @return true if the underlying architecture supports SSE 4.1

     */

    private static boolean supportsSSE41(TargetDescription target) {

        AMD64 arch = (AMD64) target.arch;

        return arch.getFeatures().contains(CPUFeature.SSE4_1);

    }

    /**

     * Vector size used in {@link #emitSSE41Compare}.

     */

    private static final int SSE4_1_VECTOR_SIZE = 16;

    /**

     * Emits code that uses SSE4.1 128-bit (16-byte) vector compares.

     */

    private void emitSSE41Compare(CompilationResultBuilder crb, AMD64MacroAssembler masm, Register result, Register array1, Register array2, Register length, Label trueLabel, Label falseLabel) {

        assert supportsSSE41(crb.target);

        Register vector1 = asRegister(vectorTemp1, AMD64Kind.DOUBLE);

        Register vector2 = asRegister(vectorTemp2, AMD64Kind.DOUBLE);

        Label loop = new Label();

        Label compareTail = new Label();

        // Compare 16-byte vectors

        masm.andl(result, SSE4_1_VECTOR_SIZE - 1); // tail count (in bytes)

        masm.andl(length, ~(SSE4_1_VECTOR_SIZE - 1)); // vector count (in bytes)

        masm.jccb(ConditionFlag.Zero, compareTail);

        masm.leaq(array1, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.leaq(array2, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.negq(length);

        // Align the main loop

        masm.align(crb.target.wordSize * 2);

        masm.bind(loop);

        masm.movdqu(vector1, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.movdqu(vector2, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.pxor(vector1, vector2);

        masm.ptest(vector1, vector1);

        masm.jcc(ConditionFlag.NotZero, falseLabel);

        masm.addq(length, SSE4_1_VECTOR_SIZE);

        masm.jcc(ConditionFlag.NotZero, loop);

        masm.testl(result, result);

        masm.jcc(ConditionFlag.Zero, trueLabel);

        /*

         * Compare the remaining bytes with an unaligned memory load aligned to the end of the

         * array.

         */

        masm.movdqu(vector1, new AMD64Address(array1, result, Scale.Times1, -SSE4_1_VECTOR_SIZE));

        masm.movdqu(vector2, new AMD64Address(array2, result, Scale.Times1, -SSE4_1_VECTOR_SIZE));

        masm.pxor(vector1, vector2);

        masm.ptest(vector1, vector1);

        masm.jcc(ConditionFlag.NotZero, falseLabel);

        masm.jmp(trueLabel);

        masm.bind(compareTail);

        masm.movl(length, result);

    }

    /**

     * Returns if the underlying AMD64 architecture supports AVX instructions.

     *

     * @param target target description of the underlying architecture

     * @return true if the underlying architecture supports AVX

     */

    private static boolean supportsAVX2(TargetDescription target) {

        AMD64 arch = (AMD64) target.arch;

        return arch.getFeatures().contains(CPUFeature.AVX2);

    }

    /**

     * Vector size used in {@link #emitAVXCompare}.

     */

    private static final int AVX_VECTOR_SIZE = 32;

    private void emitAVXCompare(CompilationResultBuilder crb, AMD64MacroAssembler masm, Register result, Register array1, Register array2, Register length, Label trueLabel, Label falseLabel) {

        assert supportsAVX2(crb.target);

        Register vector1 = asRegister(vectorTemp1, AMD64Kind.DOUBLE);

        Register vector2 = asRegister(vectorTemp2, AMD64Kind.DOUBLE);

        Label loop = new Label();

        Label compareTail = new Label();

        // Compare 16-byte vectors

        masm.andl(result, AVX_VECTOR_SIZE - 1); // tail count (in bytes)

        masm.andl(length, ~(AVX_VECTOR_SIZE - 1)); // vector count (in bytes)

        masm.jccb(ConditionFlag.Zero, compareTail);

        masm.leaq(array1, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.leaq(array2, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.negq(length);

        // Align the main loop

        masm.align(crb.target.wordSize * 2);

        masm.bind(loop);

        masm.vmovdqu(vector1, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.vmovdqu(vector2, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.vpxor(vector1, vector1, vector2);

        masm.vptest(vector1, vector1);

        masm.jcc(ConditionFlag.NotZero, falseLabel);

        masm.addq(length, AVX_VECTOR_SIZE);

        masm.jcc(ConditionFlag.NotZero, loop);

        masm.testl(result, result);

        masm.jcc(ConditionFlag.Zero, trueLabel);

        /*

         * Compare the remaining bytes with an unaligned memory load aligned to the end of the

         * array.

         */

        masm.vmovdqu(vector1, new AMD64Address(array1, result, Scale.Times1, -AVX_VECTOR_SIZE));

        masm.vmovdqu(vector2, new AMD64Address(array2, result, Scale.Times1, -AVX_VECTOR_SIZE));

        masm.vpxor(vector1, vector1, vector2);

        masm.vptest(vector1, vector1);

        masm.jcc(ConditionFlag.NotZero, falseLabel);

        masm.jmp(trueLabel);

        masm.bind(compareTail);

        masm.movl(length, result);

    }

    /**

     * Vector size used in {@link #emit8ByteCompare}.

     */

    private static final int VECTOR_SIZE = 8;

    /**

     * Emits code that uses 8-byte vector compares.

     */

    private void emit8ByteCompare(CompilationResultBuilder crb, AMD64MacroAssembler masm, Register result, Register array1, Register array2, Register length, Label trueLabel, Label falseLabel) {

        Label loop = new Label();

        Label compareTail = new Label();

        Register temp = asRegister(temp4);

        masm.andl(result, VECTOR_SIZE - 1); // tail count (in bytes)

        masm.andl(length, ~(VECTOR_SIZE - 1));  // vector count (in bytes)

        masm.jccb(ConditionFlag.Zero, compareTail);

        masm.leaq(array1, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.leaq(array2, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.negq(length);

        // Align the main loop

        masm.align(crb.target.wordSize * 2);

        masm.bind(loop);

        masm.movq(temp, new AMD64Address(array1, length, Scale.Times1, 0));

        masm.cmpq(temp, new AMD64Address(array2, length, Scale.Times1, 0));

        masm.jccb(ConditionFlag.NotEqual, falseLabel);

        masm.addq(length, VECTOR_SIZE);

        masm.jccb(ConditionFlag.NotZero, loop);

        masm.testl(result, result);

        masm.jccb(ConditionFlag.Zero, trueLabel);

        /*

         * Compare the remaining bytes with an unaligned memory load aligned to the end of the

         * array.

         */

        masm.movq(temp, new AMD64Address(array1, result, Scale.Times1, -VECTOR_SIZE));

        masm.cmpq(temp, new AMD64Address(array2, result, Scale.Times1, -VECTOR_SIZE));

        masm.jccb(ConditionFlag.NotEqual, falseLabel);

        masm.jmpb(trueLabel);

        masm.bind(compareTail);

        masm.movl(length, result);

    }

    /**

     * Emits code to compare the remaining 1 to 4 bytes.

     */

    private void emitTailCompares(AMD64MacroAssembler masm, Register result, Register array1, Register array2, Register length, Label trueLabel, Label falseLabel) {

        Label compare2Bytes = new Label();

        Label compare1Byte = new Label();

        Register temp = asRegister(temp4);

        if (kind.getByteCount() <= 4) {

            // Compare trailing 4 bytes, if any.

            masm.testl(result, 4);

            masm.jccb(ConditionFlag.Zero, compare2Bytes);

            masm.movl(temp, new AMD64Address(array1, 0));

            masm.cmpl(temp, new AMD64Address(array2, 0));

            masm.jccb(ConditionFlag.NotEqual, falseLabel);

            if (kind.getByteCount() <= 2) {

                // Move array pointers forward.

                masm.leaq(array1, new AMD64Address(array1, 4));

                masm.leaq(array2, new AMD64Address(array2, 4));

                // Compare trailing 2 bytes, if any.

                masm.bind(compare2Bytes);

                masm.testl(result, 2);

                masm.jccb(ConditionFlag.Zero, compare1Byte);

                masm.movzwl(temp, new AMD64Address(array1, 0));

                masm.movzwl(length, new AMD64Address(array2, 0));

                masm.cmpl(temp, length);

                masm.jccb(ConditionFlag.NotEqual, falseLabel);

                // The one-byte tail compare is only required for boolean and byte arrays.

                if (kind.getByteCount() <= 1) {

                    // Move array pointers forward before we compare the last trailing byte.

                    masm.leaq(array1, new AMD64Address(array1, 2));

                    masm.leaq(array2, new AMD64Address(array2, 2));

                    // Compare trailing byte, if any.

                    masm.bind(compare1Byte);

                    masm.testl(result, 1);

                    masm.jccb(ConditionFlag.Zero, trueLabel);

                    masm.movzbl(temp, new AMD64Address(array1, 0));

                    masm.movzbl(length, new AMD64Address(array2, 0));

                    masm.cmpl(temp, length);

                    masm.jccb(ConditionFlag.NotEqual, falseLabel);

                } else {

                    masm.bind(compare1Byte);

                }

            } else {

                masm.bind(compare2Bytes);

            }

        }

    }

    private static final Unsafe UNSAFE = initUnsafe();

    private static Unsafe initUnsafe() {

        try {

            return Unsafe.getUnsafe();

        } catch (SecurityException se) {

            try {

                Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");

                theUnsafe.setAccessible(true);

                return (Unsafe) theUnsafe.get(Unsafe.class);

            } catch (Exception e) {

                throw new RuntimeException("exception while trying to get Unsafe", e);

            }

        }

    }

}