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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
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package org.graalvm.compiler.lir.aarch64;

import static jdk.vm.ci.aarch64.AArch64.zr;
import static jdk.vm.ci.code.ValueUtil.asRegister;
import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.REG;

import java.lang.reflect.Array;
import java.lang.reflect.Field;

import org.graalvm.compiler.asm.Label;
import org.graalvm.compiler.asm.aarch64.AArch64Address;
import org.graalvm.compiler.asm.aarch64.AArch64MacroAssembler;
import org.graalvm.compiler.asm.aarch64.AArch64Assembler.ConditionFlag;
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.code.Register;
import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.Value;
import sun.misc.Unsafe;

Emits code which compares two arrays lexicographically. If the CPU supports any vector instructions specialized code is emitted to leverage these instructions.
/** * Emits code which compares two arrays lexicographically. If the CPU supports any vector * instructions specialized code is emitted to leverage these instructions. */
@Opcode("ARRAY_COMPARE_TO") public final class AArch64ArrayCompareToOp extends AArch64LIRInstruction { public static final LIRInstructionClass<AArch64ArrayCompareToOp> TYPE = LIRInstructionClass.create(AArch64ArrayCompareToOp.class); private final JavaKind kind1; private final JavaKind kind2; private final int array1BaseOffset; private final int array2BaseOffset; @Def({REG}) protected Value resultValue; @Alive({REG}) protected Value array1Value; @Alive({REG}) protected Value array2Value; @Use({REG}) protected Value length1Value; @Use({REG}) protected Value length2Value; @Temp({REG}) protected Value length1ValueTemp; @Temp({REG}) protected Value length2ValueTemp; @Temp({REG}) protected Value temp1; @Temp({REG}) protected Value temp2; @Temp({REG}) protected Value temp3; @Temp({REG}) protected Value temp4; @Temp({REG}) protected Value temp5; @Temp({REG}) protected Value temp6; public AArch64ArrayCompareToOp(LIRGeneratorTool tool, JavaKind kind1, JavaKind kind2, Value result, Value array1, Value array2, Value length1, Value length2) { super(TYPE); this.kind1 = kind1; this.kind2 = kind2; // Both offsets should be the same but better be safe than sorry. Class<?> array1Class = Array.newInstance(kind1.toJavaClass(), 0).getClass(); Class<?> array2Class = Array.newInstance(kind2.toJavaClass(), 0).getClass(); this.array1BaseOffset = UNSAFE.arrayBaseOffset(array1Class); this.array2BaseOffset = UNSAFE.arrayBaseOffset(array2Class); this.resultValue = result; this.array1Value = array1; this.array2Value = array2; /* * The length values are inputs but are also killed like temporaries so need both Use and * Temp annotations, which will only work with fixed registers. */ this.length1Value = length1; this.length2Value = length2; this.length1ValueTemp = length1; this.length2ValueTemp = length2; // 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.unknownReference(tool.target().arch.getWordKind())); this.temp4 = tool.newVariable(LIRKind.unknownReference(tool.target().arch.getWordKind())); this.temp5 = tool.newVariable(LIRKind.unknownReference(tool.target().arch.getWordKind())); this.temp6 = tool.newVariable(LIRKind.unknownReference(tool.target().arch.getWordKind())); } 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); } } } @Override protected void emitCode(CompilationResultBuilder crb, AArch64MacroAssembler masm) { Register result = asRegister(resultValue); Register length1 = asRegister(length1Value); Register length2 = asRegister(length2Value); Register array1 = asRegister(temp1); Register array2 = asRegister(temp2); Register length = asRegister(temp3); Register temp = asRegister(temp4); Register tailCount = asRegister(temp5); Register vecCount = asRegister(temp6); // Checkstyle: stop final Label BREAK_LABEL = new Label(); final Label STRING_DIFFER_LABEL = new Label(); final Label LENGTH_DIFFER_LABEL = new Label(); final Label MAIN_LOOP_LABEL = new Label(); final Label COMPARE_SHORT_LABEL = new Label(); // Checkstyle: resume // Checkstyle: stop int CHAR_SIZE_BYTES = 1; int VECTOR_SIZE_BYTES = 8; int VECTOR_COUNT_BYTES = 8; // Checkstyle: resume // Byte is expanded to short if we compare strings with different encoding if (kind1 != kind2 || kind1 == JavaKind.Char) { CHAR_SIZE_BYTES = 2; } if (kind1 != kind2) { VECTOR_COUNT_BYTES = 4; } // Load array base addresses. masm.lea(array1, AArch64Address.createUnscaledImmediateAddress(asRegister(array1Value), array1BaseOffset)); masm.lea(array2, AArch64Address.createUnscaledImmediateAddress(asRegister(array2Value), array2BaseOffset)); // Calculate minimal length in chars for different kind case // Conditions could be squashed but lets keep it readable if (kind1 != kind2) { masm.lshr(64, length2, length2, 1); } if (kind1 == kind2 && kind1 == JavaKind.Char) { masm.lshr(64, length1, length1, 1); masm.lshr(64, length2, length2, 1); } masm.cmp(64, length1, length2); masm.cmov(64, length, length1, length2, ConditionFlag.LT); // One of strings is empty masm.cbz(64, length, LENGTH_DIFFER_LABEL); // Go back to bytes if necessary if (kind1 != kind2 || kind1 == JavaKind.Char) { masm.shl(64, length, length, 1); } masm.mov(64, vecCount, zr); masm.and(64, tailCount, length, VECTOR_SIZE_BYTES - 1); // tail count (in bytes) masm.ands(64, length, length, ~(VECTOR_SIZE_BYTES - 1)); // vector count (in bytes) // Length of string is less than VECTOR_SIZE, go to simple compare masm.branchConditionally(ConditionFlag.EQ, COMPARE_SHORT_LABEL); // MAIN_LOOP - read strings by 8 byte. masm.bind(MAIN_LOOP_LABEL); if (kind1 != kind2) { // Load 32 bits ad unpack it to entire 64bit register masm.ldr(32, result, AArch64Address.createRegisterOffsetAddress(array1, vecCount, false)); masm.ubfm(64, temp, result, 0, 7); masm.lshr(64, result, result, 8); masm.bfm(64, temp, result, 48, 7); masm.lshr(64, result, result, 8); masm.bfm(64, temp, result, 32, 7); masm.lshr(64, result, result, 8); masm.bfm(64, temp, result, 16, 7); // Unpacked value placed in temp now masm.shl(64, result, vecCount, 1); masm.ldr(64, result, AArch64Address.createRegisterOffsetAddress(array2, result, false)); } else { masm.ldr(64, temp, AArch64Address.createRegisterOffsetAddress(array1, vecCount, false)); masm.ldr(64, result, AArch64Address.createRegisterOffsetAddress(array2, vecCount, false)); } masm.eor(64, result, temp, result); masm.cbnz(64, result, STRING_DIFFER_LABEL); masm.add(64, vecCount, vecCount, VECTOR_COUNT_BYTES); masm.cmp(64, vecCount, length); masm.branchConditionally(ConditionFlag.LT, MAIN_LOOP_LABEL); // End of MAIN_LOOP // Strings are equal and no TAIL go to END masm.cbz(64, tailCount, LENGTH_DIFFER_LABEL); // Compaire tail of long string ... masm.lea(array1, AArch64Address.createRegisterOffsetAddress(array1, length, false)); masm.lea(array2, AArch64Address.createRegisterOffsetAddress(array2, length, false)); // ... or string less than vector length masm.bind(COMPARE_SHORT_LABEL); for (int i = 0; i < VECTOR_COUNT_BYTES; i += CHAR_SIZE_BYTES) { if (kind1 != kind2) { masm.ldr(8, temp, AArch64Address.createUnscaledImmediateAddress(array1, i / 2)); } else { masm.ldr(8 * CHAR_SIZE_BYTES, temp, AArch64Address.createUnscaledImmediateAddress(array1, i)); } masm.ldr(8 * CHAR_SIZE_BYTES, result, AArch64Address.createUnscaledImmediateAddress(array2, i)); if (kind1 != kind2 && kind1 == JavaKind.Char) { // Weird swap of substraction order masm.subs(64, result, result, temp); } else { masm.subs(64, result, temp, result); } masm.branchConditionally(ConditionFlag.NE, BREAK_LABEL); masm.subs(64, tailCount, tailCount, CHAR_SIZE_BYTES); masm.branchConditionally(ConditionFlag.EQ, LENGTH_DIFFER_LABEL); } // STRING_DIFFER extract exact value of a difference masm.bind(STRING_DIFFER_LABEL); masm.rbit(64, tailCount, result); masm.clz(64, vecCount, tailCount); masm.and(64, vecCount, vecCount, ~((8 * CHAR_SIZE_BYTES) - 1)); // Round to byte or short masm.eor(64, result, temp, result); masm.ashr(64, result, result, vecCount); masm.ashr(64, temp, temp, vecCount); masm.and(64, result, result, 0xFFFF >>> (16 - (8 * CHAR_SIZE_BYTES))); // 0xFF or 0xFFFF masm.and(64, temp, temp, 0xFFFF >>> (16 - (8 * CHAR_SIZE_BYTES))); masm.sub(64, result, temp, result); masm.branchConditionally(ConditionFlag.AL, BREAK_LABEL); // End of STRING_DIFFER // Strings are equials up to length, // return length difference in chars masm.bind(LENGTH_DIFFER_LABEL); if (kind1 != kind2 && kind1 == JavaKind.Char) { // Weird swap of substraction order masm.sub(64, result, length2, length1); } else { masm.sub(64, result, length1, length2); } // We are done masm.bind(BREAK_LABEL); } } // class