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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8" />
<title>HotSpot Intrinsics</title>
<meta name="description" content="A short introduction to HotSpot Intrinsics" />
<meta name="author" content="Volker H. Simonis" />
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<section>
<h1>HotSpot Intrinsics<br/></h1>
<p>
<small>Volker Simonis [Фолкер Симонис], SAP / <a href="mailto:volker.simonis@gmail.com">volker.simonis@gmail.com</a></small>
</p>
</section>
<section>
<h2>Intrinsics</h2>
<blockquote>
<p style="text-align:justify">
“ ..an <span class="bold">intrinsic</span> function (a.k.a.
<span class="bold">builtin</span> function) is a function
available for use in a given programming language whose
implementation is handled specially by the compiler. Typically, it
substitutes a sequence of automatically generated instructions for
the original function call.. ”
</p>
</blockquote>
<blockquote>
<p style="text-align:justify">
“ ..the compiler has an intimate knowledge of the intrinsic
function and can therefore better integrate it and optimize it for
the situation.. ”
</p>
<footer>
<cite><a href="https://en.wikipedia.org/wiki/Intrinsic_function">Intrinsic function - Wikipedia</a></cite>
</footer>
</blockquote>
</section>
<section>
<h2>Intrinsics</h2>
<ul>
<li>Improve performance:<br/>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
GCC: bzero(), snprintf(), strndup(), log2(), ..
Java: Math.sqrt(), System.arraycopy(), ..
]]>
</code>
</pre>
</li>
<li>Expose functionality not expressable in the language itself:<br/>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
GCC: _xbegin(), _xend(), .. // Transactional Memory
Java: Unsafe.allocateInstance(),
Thread.onSpinWait() // JEP 285
]]>
</code>
</pre>
</li>
<li>Direct access to CPU instructions (assembler):<br/>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
MSVC: __movsq(), __mul128()
Java: Unsafe.loadFence()
]]>
</code>
</pre>
<br/>
<a href="https://software.intel.com/sites/landingpage/IntrinsicsGuide">https://software.intel.com/sites/landingpage/IntrinsicsGuide</a>
</li>
</ul>
</section>
<section>
<section>
<h2>The “<code>HelloWorld</code>” Intrinsic</h2>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
public class HelloWorld {
public static void sayHello() {
System.out.println("Hello JETConf!");
}
public static void main(String ... args) {
long start = System.nanoTime();
sayHello();
long stop = System.nanoTime();
System.out.format("%,9d%s%n", stop - start, "ns");
}
}
]]>
</code>
</pre>
</section>
<section>
<h2>The “<code>HelloWorld</code>” Intrinsic - DEMO</h2>
<pre class="big noshadow" data-trim="true">
<code class="terminal" data-trim="true" data-noescape="true">
$ java -Xint org.simonis.HelloWorld
<span class="fragment">Hello JETConf!
6,968,398ns</span>
<span class="fragment">$ java -Xint -XX:+JETConf org.simonis.HelloWorld</span>
<span class="fragment">Hello JETConf!
153,191ns</span>
</code>
</pre>
</section>
</section>
<section style="height: 100%;">
<section>
<h2>Observability - Bytecode Instrumentation</h2>
<ul>
<li>Allows dynamic changes of Java Bytecodes at runtime</li>
<li>Only addition of bytecodes to Java methods</li>
<li>Used by monitoring agents, profilers, coverage tools and event loggers</li>
<li>Implemented in <code>java.lang.instrument</code></li>
<li>Loaded into the VM with <code>-javaagent:jarpath[=options]</code></li>
<li>The agent implements "<code>premain(String args, Instrumentation inst)</code>"</li>
</ul>
</section>
<section style="height: 100%;">
<h2>The Java Instrumentation Agent</h2>
<pre class="big noshadow scrollable" style="height: 80%;" data-trim="true">
<code class="java" text-trim="true" data-noescape="true">
<![CDATA[
package org.simonis;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import jdk.internal.org.objectweb.asm.ClassReader;
import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
public class MethodInstrumentationAgent {
static String pattern;
public static void premain(String args, Instrumentation inst) {
inst.addTransformer(new MethodInstrumentorTransformer());
pattern = args;
}
static class MethodInstrumentorTransformer implements ClassFileTransformer {
@Override
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
MethodInstrumentorClassVisitor cv = new MethodInstrumentorClassVisitor(cw);
ClassReader cr = new ClassReader(classfileBuffer);
cr.accept(cv, 0);
return cw.toByteArray();
}
}
static class MethodInstrumentorClassVisitor extends ClassVisitor {
private String className;
public MethodInstrumentorClassVisitor(ClassVisitor cv) {
super(Opcodes.ASM5, cv);
}
@Override
public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
cv.visit(version, access, name, signature, superName, interfaces);
className = name;
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions);
if (className.startsWith(pattern)) {
mv = new MethodInstrumentorMethodVisitor(mv, name + desc);
}
return mv;
}
}
static class MethodInstrumentorMethodVisitor extends MethodVisitor implements Opcodes {
private String methodName;
public MethodInstrumentorMethodVisitor(MethodVisitor mv, String name) {
super(Opcodes.ASM5, mv);
methodName = name;
}
@Override
public void visitCode() {
mv.visitCode();
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitLdcInsn("-> " + methodName);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
}
@Override
public void visitInsn(int opcode) {
if ((opcode >= IRETURN && opcode <= RETURN) || opcode == ATHROW) {
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitLdcInsn("<- " + methodName);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
}
mv.visitInsn(opcode);
}
}
}
]]>
</code>
</pre>
</section>
<section>
<p>The Manifest file:</p>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
Manifest-VErsion: 1.0
Premain-Class: org.simonis.MethodInstrumentationAgent
]]>
</code>
</pre>
<p>Compile and create with:</p>
<pre class="big noshadow" data-trim="true">
<code class="terminal" data-trim="true" data-noescape="true">
$ javac -XDignore.symbol.file=true org/simonis/MethodInstrumentationAgent.java
$ jar cvfm MethodInstrumentationAgent.jar manifest.mf \
org/simonis/MethodInstrumentationAgent*.class
</code>
</pre>
</section>
<section>
<h2>Observability - Bytecode Instrumentation</h2>
<pre class="big noshadow" data-trim="true">
<code class="terminal" data-trim="true" data-noescape="true">
$ java -javaagent:MethodInstrumentationAgent.jar=org/simonis \
org.simonis.HelloWorld
<span class="fragment">-> main([Ljava/lang/String;)V
-> sayHello()V
Hello JETConf!
<- sayHello()V
651,538ns
<- main([Ljava/lang/String;)V</span>
<span class="fragment">$ java -XX:+JETConf -javaagent:MethodInstrumentationAgent.jar=org/simonis \
org.simonis.HelloWorld</span>
<span class="fragment">-> main([Ljava/lang/String;)V
Hello JETConf!
51,750ns
<- main([Ljava/lang/String;)V</span>
</code>
</pre>
</section>
</section>
<section style="height: 100%;">
<section>
<h2>Observability - JVMTI Agents</h2>
<ul>
<li>JVMTI is the Java Virtual Machine Tool Interface</li>
<li>Allows programs to inspect the state and control the execution of the VM</li>
<li>Used by debuggers and profilers</li>
<li>A native interface to the Java VM</li>
<li>JVMTI agents are loaded during VM initialization</li>
<li>They access the VM by calling JVMTI and JNI functions</li>
</ul>
</section>
<section style="height: 100%;">
<h2>A simple tracing JVMTI Agent</h2>
<pre class="big noshadow scrollable" style="height: 80%;" data-trim="true">
<code class="cpp" text-trim="true" data-noescape="true">
<![CDATA[
// Build as follows:
// g++ -fPIC -shared -I <JDK>/include/ -I <JDK>/include/linux/ -o traceMethodAgent.so traceMethodAgent.cpp
#include <jvmti.h>
#include <stdio.h>
#include <string.h>
const char* pattern = "";
static void printMethod(jvmtiEnv* jvmti, jmethodID method, const char* prefix) {
char *name, *sig, *cl;
jclass javaClass;
jvmti->GetMethodDeclaringClass(method, &javaClass);
jvmti->GetClassSignature(javaClass, &cl, NULL);
++cl; // Ignore leading 'L'
if (strstr(cl, pattern) == cl) {
jvmti->GetMethodName(method, &name, &sig, NULL);
cl[strlen(cl) - 1] = '\0'; // Strip trailing ';'
fprintf(stdout, "%s %s::%s%s\n", prefix, cl, name, sig);
fflush (NULL);
jvmti->Deallocate((unsigned char*) name);
jvmti->Deallocate((unsigned char*) sig);
}
jvmti->Deallocate((unsigned char*) --cl);
}
void JNICALL methodEntryCallback(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread, jmethodID method) {
printMethod(jvmti, method, "->");
}
void JNICALL methodExitCallback(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread, jmethodID method, jboolean except, jvalue ret_val) {
printMethod(jvmti, method, "<-");
}
extern "C"
JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
jvmtiEnv* jvmti = NULL;
jvmtiCapabilities capa;
jvmtiError error;
if (options) pattern = strdup(options); // Options may contain the pattern
jint result = jvm->GetEnv((void**) &jvmti, JVMTI_VERSION_1_1);
if (result != JNI_OK) {
fprintf(stderr, "Can't access JVMTI!\n");
return JNI_ERR;
}
memset(&capa, 0, sizeof(jvmtiCapabilities));
capa.can_generate_method_entry_events = 1;
capa.can_generate_method_exit_events = 1;
if (jvmti->AddCapabilities(&capa) != JVMTI_ERROR_NONE) {
fprintf(stderr, "Can't set capabilities!\n");
return JNI_ERR;
}
jvmtiEventCallbacks callbacks;
memset(&callbacks, 0, sizeof(jvmtiEventCallbacks));
callbacks.MethodEntry = methodEntryCallback;
callbacks.MethodExit = methodExitCallback;
if (jvmti->SetEventCallbacks(&callbacks, sizeof(jvmtiEventCallbacks)) != JVMTI_ERROR_NONE) {
fprintf(stderr, "Can't set event callbacks!\n");
return JNI_ERR;
}
if (jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_METHOD_ENTRY, NULL) != JVMTI_ERROR_NONE) {
fprintf(stderr, "Can't enable JVMTI_EVENT_METHOD_ENTRY!\n");
return JNI_ERR;
}
if (jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_METHOD_EXIT, NULL) != JVMTI_ERROR_NONE) {
fprintf(stderr, "Can't enable JVMTI_EVENT_METHOD_EXIT!\n");
return JNI_ERR;
}
}
]]>
</code>
</pre>
</section>
<section>
<h2>Observability - JVMTI Agents</h2>
<pre class="big noshadow" data-trim="true">
<code class="terminal" data-trim="true" data-noescape="true">
$ java -XX:-JETConf -agentpath:traceMethodAgent.so=org/simonis \
org.simonis.HelloWorld
<span class="fragment">-> org/simonis/HelloWorld::main([Ljava/lang/String;)V
-> org/simonis/HelloWorld::sayHello()V
Hello JETConf!
<- org/simonis/HelloWorld::sayHello()V
24,256,161ns
<- org/simonis/HelloWorld::main([Ljava/lang/String;)V</span>
<span class="fragment">$ java -XX:+JETConf -agentpath:traceMethodAgent.so=org/simonis \
org.simonis.HelloWorld</span>
<span class="fragment">-> org/simonis/HelloWorld::main([Ljava/lang/String;)V
Hello JETConf!
171,417ns
<- org/simonis/HelloWorld::main([Ljava/lang/String;)V</span>
</code>
</pre>
</section>
</section>
<section>
<h3 style="text-transform: none;"><a href="https://bugs.openjdk.java.net/browse/JDK-8013579">https://bugs.openjdk.java.net/browse/JDK-8013579</a></h3>
<img class="plain" data-src="images/8013579_intrinsics_class_redef.png" alt="JDK-8013579: Intrinsics for Java methods don't take class redefinition into account"/>
</section>
<section style="height: 100%;">
<section>
<h2>DEMO - Math Intrinsics</h2>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
static double compute(int count, double d) {
for (int i = 0; i < count; i++) {
d += Math.pow(Math.sin(d), Math.sqrt(d)); // d += sin(d) ^ sqrt(d)
}
return d;
}
public static void main(String[] args) throws Exception {
double seed = args.length; // Avoid constant folding
int count = Integer.parseInt(args[0]); // Iteration count for compute()
for (int i = 0; i < 20_000; i++) {
compute(1, seed); // JIT-compile compute()
}
compute(count, seed); // Call compute() with huge count
}
]]>
</code>
</pre>
</section>
</section>
<section style="height: 100%;">
<section>
<h2>Math Intrinsics & Time To Safepoint (TTS)</h2>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
public static void main(String[] args) throws Exception {
... // Same as before ...
new Thread() { // Create a new thread..
{ setDaemon(true); } // ..and make it a daemon thread.
public void run() {
while (true) {
try {
Thread.sleep(1_000); // Every second..
} catch (InterruptedException e) {}
System.gc(); // ..we trigger a GC.
}
}
}.start(); // Let it run concurrently.
compute(count, seed); // Call compute() with huge count
]]>
</code>
</pre>
</section>
<section>
<h3 style="text-transform: none;"><code>-XX:+UseCountedLoopSafepoints</code><a href="https://bugs.openjdk.java.net/browse/JDK-6869327"> (JDK-6869327)</a></h3>
<img class="plain" data-src="images/6869327_counted_loop_safep.png" alt="JDK-6869327: Add new C2 flag to keep safepoints in counted loops"/>
</section>
<!--
6869327: Add new C2 flag to keep safepoints in counted loops.
-XX:+UseCountedLoopSafepoints
6869327_counted_loop_safep.png
-->
</section>
<section style="height: 100%;">
<h2>HotSpot Intrinsics</h2>
<p style="text-align:left">Defined in: <code>src/share/vm/classfile/vmSymbols.hpp</code></p>
<ul>
<li>Library intrinsics (~260)
<ul>
<li>Library methods replaced by assembly, IR or both</li>
</ul>
</li>
<li>Bytecode intrinsics (~40)
<ul>
<li>Late/always inlining candidates (e.g. <code>StringBuffer::*</code>, boxing/unboxing methods)</li>
<li>See: <code>Compile::should_delay_string_inlining()</code> in <code>doCall.cpp</code></li>
<li>See: <code>InlineTree::should_inline()</code> in <code>bytecodeInfo.cpp</code></li>
</ul>
</li>
<li><em>Only for system classes</em></li>
<li>Must be annotated with <code>jdk.internal.HotSpotIntrinsicCandidate</code> (since Java 9)
<ul>
<li>Checked by <code>-XX:+CheckIntrinsics</code></li>
</ul>
</li>
</ul>
</section>
<section style="height: 100%;">
<h2>Library Intrinsics</h2>
<ul>
<li>Interpreter:
<ul>
<li>Implements only few intrinsics (notably <code>Math</code> and <code>CRC32</code>)</li>
<li>Generates special entry points (see: <code>AbstractInterpreter::MethodKind()</code>)</li>
</ul>
</li>
<li>C1 (aka "client") JIT:
<ul>
<li>Mostly <code>Unsafe</code> and <code>Math</code> intrinsics (see <code>Compiler::is_intrinsic_supported()</code>)</li>
<li>See: <code>GraphBuilder::build_graph_for_intrinsic()</code></li>
</ul>
</li>
<li>C2 (aka "server") JIT:<ul>
<li>See <code>C2Compiler::is_intrinsic_supported()</code> for a complete list</li>
<li>See <code>LibraryCallKit::try_to_inline()</code> in <code>library_call.cpp</code></li>
<li>Create new "Intermediate Representation" (i.e. IR) nodes..<br/>
..and match these nodes with corresponding "Machine Nodes" in <code>.ad</code> file</li>
<li>Use <code>IdealKit</code>/<code>GraphKit</code> to mimic the functionality directly in IR<br/>
(see <code>PhaseStringOpts</code> methods in <code>stringopts.hpp</code></li>
</ul>
</li>
</ul>
</section>
<section style="height: 100%;">
<h2>Controlling Intrinsics</h2>
<ul>
<li><code>-XX:+PrintCompilation -XX:+PrintInlining</code><br/>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
613 1 b org.simonis.Loop::compute (29 bytes)
@ 9 java.lang.Math::sin (5 bytes) (intrinsic)
@ 13 java.lang.Math::sqrt (5 bytes) (intrinsic)
]]>
</code>
</pre>
</li>
<li><code>-XX:+CheckIntrinsics</code> (together with <code>@HotSpotIntrinsicCandidate</code>)><br/>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
Compiler intrinsic is defined for method [org.simonis.HelloWorld.sayHello()V],
but the method is not annotated with @HotSpotIntrinsicCandidate. Exiting.
]]>
</code>
</pre>
</li>
<li><code>-XX:DisableIntrinsic={_dsqrt, ...}</code> (use id from <code>vmSymbols.hpp</code>)</li>
<li><code>-XX:+PrintIntrinsics</code></li>
<li><code>-XX:+Use{AES,CRC32,GHASH,MathExact,...}Intrinsics</code></li>
<li><code>-XX:-InlineNatives</code>, <code>-XX:-Inline{Math, Class, Thread, ...}Natives</code><br/>
<code>-XX:-Inline{UnsafeOps, ArrayCopy, ObjectHash}</code></li>
</ul>
</section>
<section>
<h2>Native vs. Intrinsic methods</h2>
<ul>
<li>JVM state (safepoints)</li>
<li>Java vs. native calling conventions</li>
<li>Platform dependent (native implementation required!)</li>
<li>OK for 'expensive' calls like I/O</li>
</ul>
</section>
<section style="height: 100%;">
<section>
<h2>Implementing an Interpreter Intrinsics</h2>
<p style="text-align:left">Define in: <code>src/share/vm/classfile/vmSymbols.hpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
do_class( helloWorld, "org/simonis/HelloWorld") \
do_intrinsic(_sayHello, helloWorld, sayHello_name, sayHello_sign, F_S) \
do_name( sayHello_name, "sayHello") \
do_signature(sayHello_sign, "()V") \
]]>
</code>
</pre>
<p style="text-align:left">Define in: <code>src/share/vm/interpreter/abstractInterpreter.hpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
class AbstractInterpreter: AllStatic {
enum MethodKind {
zerolocals, // normal method (needs locals initialization)
java_lang_math_sin, // implementation of java.lang.Math.sin(x)
...
HelloWorld_sayHello, // implementation of org.simonis.HelloWorld.sayHello()
]]>
</code>
</pre>
</section>
<section>
<h2>Implementing an Interpreter Intrinsics</h2>
<p style="text-align:left">Map in: <code>src/share/vm/interpreter/abstractInterpreter.cpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
MethodKind AbstractInterpreter::method_kind(methodHandle m) {
...
if (JETConf) {
if (m->intrinsic_id() == vmIntrinsics::_sayHello) {
return HelloWorld_sayHello;
]]>
</code>
</pre>
<p style="text-align:left">Generate in: <code>src/share/vm/interpreter/templateInterpreterGenerator.cpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
address TemplateInterpreterGenerator::generate_method_entry(MethodKind kind) {
switch (kind) {
case Interpreter::HelloWorld_sayHello: entry_point = generate_sayHello();
...
return entry_point;
]]>
</code>
</pre>
</section>
<section>
<h2>Implementing an Interpreter Intrinsics</h2>
<p style="text-align:left">Implement in: <code>src/cpu/x86/vm/templateInterpreterGenerator_x86_64.cpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
#define __ _masm->
address TemplateInterpreterGenerator::generate_sayHello() {
// r13: sender sp
// stack: [ ret adr ] <-- rsp
address entry_point = __ pc();
const char *msg = "Hello JETConf!\n";
__ mov64(c_rarg1, (long)stdout);
__ mov64(c_rarg0, (long)msg);
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, fputs)));
__ pop(rax);
__ mov(rsp, r13);
__ jmp(rax);
return entry_point;
}
]]>
</code>
</pre>
</section>
<section>
<h2>Implementing an Interpreter Intrinsics</h2>
<p style="text-align:left">Enable in: <code>src/share/vm/oops/method.cpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
vmSymbols::SID Method::klass_id_for_intrinsics(const Klass* holder) {
// if loader is not the default loader (i.e., != NULL), we can't know the
// intrinsics because we are not loading from core libraries
const InstanceKlass* ik = InstanceKlass::cast(holder);
if (JETConf && ik->name()->equals("org/simonis/HelloWorld")) { // <----
// check for org.simonis.HelloWorld // <----
return vmSymbols::find_sid(ik->name()); // <----
}
if ((ik->class_loader() != NULL)) {
return vmSymbols::NO_SID; // regardless of name, no intrinsics here
}
// see if the klass name is well-known:
Symbol* klass_name = ik->name();
return vmSymbols::find_sid(klass_name);
}
]]>
</code>
</pre>
</section>
</section>
<section style="height: 100%;">
<section>
<h2>Implementing a C2-JIT Intrinsic</h2>
<p style="text-align:left">Intrinsify: <code>java.util.Random.nextInt()</code></p>
<pre class="big noshadow" data-trim="true">
<code class="java" text-trim="true">
<![CDATA[
public class Random implements java.io.Serializable {
...
@HotSpotIntrinsicCandidate
public int nextInt() {
return next(32);
}
]]>
</code>
</pre>
<p style="text-align:left">Define in: <code>src/share/vm/classfile/vmSymbols.hpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
do_class( java_util_Random, "java/util/Random") \
do_intrinsic(_nextInt, java_util_Random, nextInt_name, ni_sign, F_R)\
do_name( nextInt_name, "nextInt") \
do_signature(ni_sign, "()I") \
]]>
</code>
</pre>
</section>
<section>
<h2>Implementing a C2-JIT Intrinsic</h2>
<p style="text-align:left">Detect <code>rdrand</code> instruction in: <code>src/cpu/x86/vm/vm_version_x86.hpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
class VM_Version {
static uint64_t feature_flags() {
if (_cpuid_info.std_cpuid1_ecx.bits.rdrand != 0)
result |= CPU_RDRAND;
static bool supports_rdrand() { return (_features & CPU_RDRAND) != 0; }
]]>
</code>
</pre>
<p style="text-align:left">Implement <code>rdrand</code> in: <code>src/cpu/x86/vm/assembler_x86.hpp</code></p>
<pre class="big noshadow" data-trim="true">
<code class="cpp" text-trim="true">
<![CDATA[
void Assembler::rdrandl(Register dst) {
int encode = prefix_and_encode(dst->encoding());
emit_int8(0x0F);
emit_int8((unsigned char)0xC7);
emit_int8((unsigned char)(0xF0 | encode));