# Eliminating Array Bounds Checks

DevFeed: [Eliminating Array Bounds Checks](<https://devfeed.tech/articles/eliminating-array-bounds-checks-25610.md>)

Original publisher: [Read original article](<https://www.romainguy.dev/posts/2025/eliminating-array-bounds-checks/>)

Author: Romain Guy

Published: 2025-05-13T00:00:00Z

Content type: tutorial

Language: en

Sources: [Posts on Romain Guy](<https://devfeed.tech/sources/posts-on-romain-guy.md>)

Topics: [Android](<https://devfeed.tech/topics/android.md>), [Kotlin](<https://devfeed.tech/topics/kotlin.md>), [Memory Safety](<https://devfeed.tech/topics/memory-safety.md>), [Compiler](<https://devfeed.tech/topics/compiler.md>), [Exception](<https://devfeed.tech/topics/exception.md>), [toolchain](<https://devfeed.tech/topics/toolchain.md>), [inlining](<https://devfeed.tech/topics/inlining.md>)

Tags: [android](<https://devfeed.tech/tags/android.md>), [assembly](<https://devfeed.tech/tags/assembly.md>), [code](<https://devfeed.tech/tags/code.md>), [compiler](<https://devfeed.tech/tags/compiler.md>), [developer](<https://devfeed.tech/tags/developer.md>), [exception](<https://devfeed.tech/tags/exception.md>), [graphics](<https://devfeed.tech/tags/graphics.md>), [inlining](<https://devfeed.tech/tags/inlining.md>), [kotlin](<https://devfeed.tech/tags/kotlin.md>), [memory-safety](<https://devfeed.tech/tags/memory-safety.md>), [performance](<https://devfeed.tech/tags/performance.md>), [toolchain](<https://devfeed.tech/tags/toolchain.md>)

## AI overview

This tutorial explains how Android Runtime array bounds checks protect memory safety but can add unnecessary instructions. It shows how a simple explicit check can help the compiler eliminate those checks in a fixed-size array, reducing the example from 136 to 60 arm64 instructions.

## Source excerpt

The Android Runtime (ART) offers a nice memory safety feature when accessing the content of an array. The indices you use are automatically checked against the bounds of the array to prevent unsafe memory accesses. To achieve this, ART generates extra machine instructions to throw an ArrayIndexOutOfBoundsException when the index is invalid. Here is a simple Kotlin example: 1fun scaleZ(values: FloatArray, scale: Float) = values[2] * scale After translation to arm64 assembly, we obtain the following result: