On Tue, 27 Dec 2022 20:12:51 GMT, Christian Wimmer <[email protected]> wrote:
> The method `String.split` contains a fast-path when the regular expression
> parameter is not really a regular expression, but just a single split
> character.
> This fast path vs. slow path check can be constant folded when the regular
> expression parameter is a literal constant - a quite frequent pattern (for
> example, all JDK usages of `String.split` have a constant expression
> parameter). But method inlining in JIT and AOT compilers can usually not
> inline `String.split` because the method body is too large. Factoring out the
> actual fast-path splitting logic into a separate method solves this problem:
> the JIT or AOT compiler can inline `String.split`, constant-fold the
> fast/slow path check, and then only the invoke of either the fast path or the
> slow path remains.
src/java.base/share/classes/java/lang/String.java line 3133:
> 3131: {
> 3132: // All the checks above can potentially be constant folded
> by
> 3133: // a JIT/AOT compiler when the regex is a constant string.
Probably worth mentioning explicitly that the private `split` was extracted to
help with inlining (to reduce the probability of future regressions).
-------------
PR: https://git.openjdk.org/jdk/pull/11791
