JIT Fun Part 4: Intrinsics and Inlining

Definition: Intrinsic

Intrinsic methods in Java are ones that have a native implementation by default in the JDK. They will have a Java version but most of the time it will get inlined and and the intrinsic implementation will be called instead.

Note that what methods are made intrinsic may depend on the platform.

Examples of Intrinsic methods include Math functions (sin, cos, min, max). The full list is here.

Example

Code:

	public static void main(String... args) {
	int[] data = new int[100_000];
	Random random = new Random();
	for (int i = 0; i< 100_000; i++) {
	data[i] = random.nextInt();
	}
	int max = Integer.MIN_VALUE;
	for (int x : data) {
	max = Math.max(max, x);
	}
	System.out.println(max);
	}

view raw mathMaxIntrinsic.java hosted with ❤ by GitHub

We run this method with the following jvm flags:

-XX:+UnlockDiagnosticVMOptions -XX:+PrintInlining

In the output we see the following:

 @ 97   java.lang.Math::max (11 bytes)   (intrinsic)

Woohoo! It got inlined with the intrinsic code.