RFR: 8361842: Move input validation checks to Java for String-related intrinsics [v8]

[Raffaello Giulietti]

On Thu, 17 Jul 2025 14:29:08 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

> What is the thinking when an `@IntrinsicCandidate` method invokes another `@IntrinsicCandidate` method? Which part is responsible for the checks?
> 
> For example, the Java code of `StringCoding.encodeISOArray0()` invokes `StringUTF16.getChar()`, another `@IntrinsicCandidate` method. The latter does not check its arguments (OK, there's an `assert`, but this is a weak check). The invocation from `encodeISOArray0()` is fine and safe, but `getChar()` is invoked by other parts of the code.
> 
> So what is the general strategy? Add checks to `getChar()` and rely on the runtime to eliminate redundant checks?

To reformulate my confusing question for the above example, there are apparently around 75-80 invocations of `getChar()`. How to make sure that they are all safe? Some are easy to verify, but others are not.

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PR Comment: https://git.openjdk.org/jdk/pull/25998#issuecomment-3084525709