/*

 * Copyright (c) 2013, 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

 * questions.

 */

package org.graalvm.compiler.lir.amd64;

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

import static org.graalvm.compiler.asm.amd64.AMD64Assembler.AMD64BinaryArithmetic.XOR;

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

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

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

import java.util.Objects;

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;

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

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

import org.graalvm.compiler.asm.amd64.AMD64BaseAssembler.OperandSize;

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

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

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

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.lir.LIRInstructionClass;

import org.graalvm.compiler.lir.LIRValueUtil;

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;

/**

 * 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.

 *

 * This op can also compare arrays of different integer types (e.g. {@code byte[]} and

 * {@code char[]}) with on-the-fly sign- or zero-extension. If one of the given arrays is a

 * {@code char[]} array, the smaller elements are zero-extended, otherwise they are sign-extended.

 */

@Opcode("ARRAY_EQUALS")

public final class AMD64ArrayEqualsOp extends AMD64LIRInstruction {

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

    private final JavaKind kind1;

    private final JavaKind kind2;

    private final int arrayBaseOffset1;

    private final int arrayBaseOffset2;

    private final Scale arrayIndexScale1;

    private final Scale arrayIndexScale2;

    private final AVXKind.AVXSize vectorSize;

    private final boolean signExtend;

    @Def({REG}) private Value resultValue;

    @Alive({REG}) private Value array1Value;

    @Alive({REG}) private Value array2Value;

    @Alive({REG, CONST}) private Value lengthValue;

    @Temp({REG, ILLEGAL}) private Value temp1;

    @Temp({REG, ILLEGAL}) private Value temp2;

    @Temp({REG}) private Value temp3;

    @Temp({REG, ILLEGAL}) private Value temp4;

    @Temp({REG, ILLEGAL}) private Value temp5;

    @Temp({REG, ILLEGAL}) private Value tempXMM;

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

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

    @Temp({REG, ILLEGAL}) private Value vectorTemp3;

    @Temp({REG, ILLEGAL}) private Value vectorTemp4;

    public AMD64ArrayEqualsOp(LIRGeneratorTool tool, JavaKind kind1, JavaKind kind2, Value result, Value array1, Value array2, Value length,

                    boolean directPointers, int maxVectorSize) {

        super(TYPE);

        this.kind1 = kind1;

        this.kind2 = kind2;

        this.signExtend = kind1 != JavaKind.Char && kind2 != JavaKind.Char;

        assert kind1.isNumericInteger() && kind2.isNumericInteger() || kind1 == kind2;

        this.arrayBaseOffset1 = directPointers ? 0 : tool.getProviders().getMetaAccess().getArrayBaseOffset(kind1);

        this.arrayBaseOffset2 = directPointers ? 0 : tool.getProviders().getMetaAccess().getArrayBaseOffset(kind2);

        this.arrayIndexScale1 = Objects.requireNonNull(Scale.fromInt(tool.getProviders().getMetaAccess().getArrayIndexScale(kind1)));

        this.arrayIndexScale2 = Objects.requireNonNull(Scale.fromInt(tool.getProviders().getMetaAccess().getArrayIndexScale(kind2)));

        this.vectorSize = ((AMD64) tool.target().arch).getFeatures().contains(CPUFeature.AVX2) && (maxVectorSize < 0 || maxVectorSize >= 32) ? AVXKind.AVXSize.YMM : AVXKind.AVXSize.XMM;

        this.resultValue = result;

        this.array1Value = array1;

        this.array2Value = array2;

        this.lengthValue = length;

        // Allocate some temporaries.

        if (supportsSSE41(tool.target()) && canGenerateConstantLengthCompare(tool.target()) && !constantLengthCompareNeedsTmpArrayPointers()) {

            this.temp1 = Value.ILLEGAL;

            this.temp2 = Value.ILLEGAL;

        } else {

            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()));

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

            this.temp4 = Value.ILLEGAL;

            this.temp5 = Value.ILLEGAL;

        } else {

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

            this.temp5 = kind1.isNumericFloat() || kind1 != kind2 ? tool.newVariable(LIRKind.value(tool.target().arch.getWordKind())) : Value.ILLEGAL;

        }

        if (kind1 == JavaKind.Float) {

            this.tempXMM = tool.newVariable(LIRKind.value(AMD64Kind.SINGLE));

        } else if (kind1 == JavaKind.Double) {

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

        } else {

            this.tempXMM = Value.ILLEGAL;

        }

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

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

            if (canGenerateConstantLengthCompare(tool.target())) {

                LIRKind lirKind = LIRKind.value(vectorSize == AVXKind.AVXSize.YMM ? AMD64Kind.V256_BYTE : AMD64Kind.V128_BYTE);

                this.vectorTemp1 = tool.newVariable(lirKind);

                this.vectorTemp2 = tool.newVariable(lirKind);

                this.vectorTemp3 = tool.newVariable(lirKind);

                this.vectorTemp4 = tool.newVariable(lirKind);

            } else {

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

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

                this.vectorTemp3 = Value.ILLEGAL;

                this.vectorTemp4 = Value.ILLEGAL;

            }

        } else {

            this.vectorTemp1 = Value.ILLEGAL;

            this.vectorTemp2 = Value.ILLEGAL;

            this.vectorTemp3 = Value.ILLEGAL;

            this.vectorTemp4 = Value.ILLEGAL;

        }

    }

    private boolean canGenerateConstantLengthCompare(TargetDescription target) {

        return LIRValueUtil.isJavaConstant(lengthValue) && kind1.isNumericInteger() && (kind1 == kind2 || getElementsPerVector(AVXKind.AVXSize.XMM) <= constantLength()) && supportsSSE41(target);

    }

    private int constantLength() {

        return LIRValueUtil.asJavaConstant(lengthValue).asInt();

    }

    @Override

    public void emitCode(CompilationResultBuilder crb, AMD64MacroAssembler masm) {

        Register result = asRegister(resultValue);

        Label trueLabel = new Label();

        Label falseLabel = new Label();

        Label done = new Label();

        if (canGenerateConstantLengthCompare(crb.target)) {

            emitConstantLengthArrayCompareBytes(crb, masm, new Register[]{asRegister(vectorTemp1), asRegister(vectorTemp2), asRegister(vectorTemp3), asRegister(vectorTemp4)}, falseLabel);

        } else {

            Register array1 = asRegister(temp1);

            Register array2 = asRegister(temp2);

            // Load array base addresses.

            masm.leaq(array1, new AMD64Address(asRegister(array1Value), arrayBaseOffset1));

            masm.leaq(array2, new AMD64Address(asRegister(array2Value), arrayBaseOffset2));

            Register length = asRegister(temp3);

            // Get array length.

            if (LIRValueUtil.isJavaConstant(lengthValue)) {

                masm.movl(length, constantLength());

            } else {

                masm.movl(length, asRegister(lengthValue));

            }

            // copy

            masm.movl(result, length);

            emitArrayCompare(crb, 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);

    }

    private void emitArrayCompare(CompilationResultBuilder crb, AMD64MacroAssembler masm,

                    Register result, Register array1, Register array2, Register length,

                    Label trueLabel, Label falseLabel) {

        if (supportsSSE41(crb.target)) {

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

        }

        if (kind1 == kind2) {

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

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

        } else {

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

        }

    }

    /**

     * 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);

    }

    /**

     * Emits code that uses SSE4.1/AVX1 128-bit (16-byte) or AVX2 256-bit (32-byte) vector compares.

     */

    private void emitVectorCompare(CompilationResultBuilder crb, AMD64MacroAssembler masm,

                    Register result, Register array1, Register array2, Register length,

                    Label trueLabel, Label falseLabel) {

        assert supportsSSE41(crb.target);

        Register vector1 = asRegister(vectorTemp1);

        Register vector2 = asRegister(vectorTemp2);

        int elementsPerVector = getElementsPerVector(vectorSize);

        Label loop = new Label();

        Label compareTail = new Label();

        boolean requiresNaNCheck = kind1.isNumericFloat();

        Label loopCheck = new Label();

        Label nanCheck = new Label();

        // Compare 16-byte vectors

        masm.andl(result, elementsPerVector - 1); // tail count

        masm.andl(length, ~(elementsPerVector - 1)); // vector count

        masm.jcc(ConditionFlag.Zero, compareTail);

        masm.leaq(array1, new AMD64Address(array1, length, arrayIndexScale1, 0));

        masm.leaq(array2, new AMD64Address(array2, length, arrayIndexScale2, 0));

        masm.negq(length);

        // Align the main loop

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

        masm.bind(loop);

        emitVectorLoad1(masm, vector1, array1, length, 0, vectorSize);

        emitVectorLoad2(masm, vector2, array2, length, 0, vectorSize);

        emitVectorCmp(masm, vector1, vector2, vectorSize);

        masm.jcc(ConditionFlag.NotZero, requiresNaNCheck ? nanCheck : falseLabel);

        masm.bind(loopCheck);

        masm.addq(length, elementsPerVector);

        masm.jcc(ConditionFlag.NotZero, loop);

        masm.testl(result, result);

        masm.jcc(ConditionFlag.Zero, trueLabel);

        if (requiresNaNCheck) {

            Label unalignedCheck = new Label();

            masm.jmpb(unalignedCheck);

            masm.bind(nanCheck);

            emitFloatCompareWithinRange(crb, masm, array1, array2, length, 0, falseLabel, elementsPerVector);

            masm.jmpb(loopCheck);

            masm.bind(unalignedCheck);

        }

        /*

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

         * array.

         */

        emitVectorLoad1(masm, vector1, array1, result, scaleDisplacement1(-vectorSize.getBytes()), vectorSize);

        emitVectorLoad2(masm, vector2, array2, result, scaleDisplacement2(-vectorSize.getBytes()), vectorSize);

        emitVectorCmp(masm, vector1, vector2, vectorSize);

        if (requiresNaNCheck) {

            masm.jcc(ConditionFlag.Zero, trueLabel);

            emitFloatCompareWithinRange(crb, masm, array1, array2, result, -vectorSize.getBytes(), falseLabel, elementsPerVector);

        } else {

            masm.jcc(ConditionFlag.NotZero, falseLabel);

        }

        masm.jmp(trueLabel);

        masm.bind(compareTail);

        masm.movl(length, result);

    }

    private int getElementsPerVector(AVXKind.AVXSize vSize) {

        return vSize.getBytes() >> Math.max(arrayIndexScale1.log2, arrayIndexScale2.log2);

    }

    private void emitVectorLoad1(AMD64MacroAssembler asm, Register dst, Register src, int displacement, AVXKind.AVXSize size) {

        emitVectorLoad1(asm, dst, src, Register.None, displacement, size);

    }

    private void emitVectorLoad2(AMD64MacroAssembler asm, Register dst, Register src, int displacement, AVXKind.AVXSize size) {

        emitVectorLoad2(asm, dst, src, Register.None, displacement, size);

    }

    private void emitVectorLoad1(AMD64MacroAssembler asm, Register dst, Register src, Register index, int displacement, AVXKind.AVXSize size) {

        emitVectorLoad(asm, dst, src, index, displacement, arrayIndexScale1, arrayIndexScale2, size);

    }

    private void emitVectorLoad2(AMD64MacroAssembler asm, Register dst, Register src, Register index, int displacement, AVXKind.AVXSize size) {

        emitVectorLoad(asm, dst, src, index, displacement, arrayIndexScale2, arrayIndexScale1, size);

    }

    private void emitVectorLoad(AMD64MacroAssembler asm, Register dst, Register src, Register index, int displacement, Scale ownScale, Scale otherScale, AVXKind.AVXSize size) {

        AMD64Address address = new AMD64Address(src, index, ownScale, displacement);

        if (ownScale.value < otherScale.value) {

            if (size == AVXKind.AVXSize.YMM) {

                getAVX2LoadAndExtendOp(ownScale, otherScale, signExtend).emit(asm, size, dst, address);

            } else {

                loadAndExtendSSE(asm, dst, address, ownScale, otherScale, signExtend);

            }

        } else {

            if (size == AVXKind.AVXSize.YMM) {

                asm.vmovdqu(dst, address);

            } else {

                asm.movdqu(dst, address);

            }

        }

    }

    private int scaleDisplacement1(int displacement) {

        return scaleDisplacement(displacement, arrayIndexScale1, arrayIndexScale2);

    }

    private int scaleDisplacement2(int displacement) {

        return scaleDisplacement(displacement, arrayIndexScale2, arrayIndexScale1);

    }

    private static int scaleDisplacement(int displacement, Scale ownScale, Scale otherScale) {

        if (ownScale.value < otherScale.value) {

            return displacement >> (otherScale.log2 - ownScale.log2);

        }

        return displacement;

    }

    private static AMD64Assembler.VexRMOp getAVX2LoadAndExtendOp(Scale ownScale, Scale otherScale, boolean signExtend) {

        switch (ownScale) {

            case Times1:

                switch (otherScale) {

                    case Times2:

                        return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXBW : AMD64Assembler.VexRMOp.VPMOVZXBW;

                    case Times4:

                        return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXBD : AMD64Assembler.VexRMOp.VPMOVZXBD;

                    case Times8:

                        return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXBQ : AMD64Assembler.VexRMOp.VPMOVZXBQ;

                }

                throw GraalError.shouldNotReachHere();

            case Times2:

                switch (otherScale) {

                    case Times4:

                        return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXWD : AMD64Assembler.VexRMOp.VPMOVZXWD;

                    case Times8:

                        return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXWQ : AMD64Assembler.VexRMOp.VPMOVZXWQ;

                }

                throw GraalError.shouldNotReachHere();

            case Times4:

                return signExtend ? AMD64Assembler.VexRMOp.VPMOVSXDQ : AMD64Assembler.VexRMOp.VPMOVZXDQ;

        }

        throw GraalError.shouldNotReachHere();

    }

    private static void loadAndExtendSSE(AMD64MacroAssembler asm, Register dst, AMD64Address src, Scale ownScale, Scale otherScale, boolean signExtend) {

        switch (ownScale) {

            case Times1:

                switch (otherScale) {

                    case Times2:

                        if (signExtend) {

                            asm.pmovsxbw(dst, src);

                        } else {

                            asm.pmovzxbw(dst, src);

                        }

                        return;

                    case Times4:

                        if (signExtend) {

                            asm.pmovsxbd(dst, src);

                        } else {

                            asm.pmovzxbd(dst, src);

                        }

                        return;

                    case Times8:

                        if (signExtend) {

                            asm.pmovsxbq(dst, src);

                        } else {

                            asm.pmovzxbq(dst, src);

                        }

                        return;

                }

                throw GraalError.shouldNotReachHere();

            case Times2:

                switch (otherScale) {

                    case Times4:

                        if (signExtend) {

                            asm.pmovsxwd(dst, src);

                        } else {

                            asm.pmovzxwd(dst, src);

                        }

                        return;

                    case Times8:

                        if (signExtend) {

                            asm.pmovsxwq(dst, src);

                        } else {

                            asm.pmovzxwq(dst, src);

                        }

                        return;

                }

                throw GraalError.shouldNotReachHere();

            case Times4:

                if (signExtend) {

                    asm.pmovsxdq(dst, src);

                } else {

                    asm.pmovzxdq(dst, src);

                }

                return;

        }

        throw GraalError.shouldNotReachHere();

    }

    private static void emitVectorCmp(AMD64MacroAssembler masm, Register vector1, Register vector2, AVXKind.AVXSize size) {

        emitVectorXor(masm, vector1, vector2, size);

        emitVectorTest(masm, vector1, size);

    }

    private static void emitVectorXor(AMD64MacroAssembler masm, Register vector1, Register vector2, AVXKind.AVXSize size) {

        if (size == AVXKind.AVXSize.YMM) {

            masm.vpxor(vector1, vector1, vector2);

        } else {

            masm.pxor(vector1, vector2);

        }

    }

    private static void emitVectorTest(AMD64MacroAssembler masm, Register vector1, AVXKind.AVXSize size) {

        if (size == AVXKind.AVXSize.YMM) {

            masm.vptest(vector1, vector1);

        } else {

            masm.ptest(vector1, vector1);

        }

    }

    /**

     * 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) {

        assert kind1 == kind2;

        Label loop = new Label();

        Label compareTail = new Label();

        int elementsPerVector = 8 >> arrayIndexScale1.log2;

        boolean requiresNaNCheck = kind1.isNumericFloat();

        Label loopCheck = new Label();

        Label nanCheck = new Label();

        Register temp = asRegister(temp4);

        masm.andl(result, elementsPerVector - 1); // tail count

        masm.andl(length, ~(elementsPerVector - 1));  // vector count

        masm.jcc(ConditionFlag.Zero, compareTail);

        masm.leaq(array1, new AMD64Address(array1, length, arrayIndexScale1, 0));

        masm.leaq(array2, new AMD64Address(array2, length, arrayIndexScale2, 0));

        masm.negq(length);

        // Align the main loop

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