ADDITIONAL SYSTEM INFORMATION :
Java 17.0.7 and Java 21.ea.29 on Linux, tested on a Lenovo T14s and Google Cloud c2-computer-8

A DESCRIPTION OF THE PROBLEM :
Significant performance change for a simple parser implementation. The implementation itself already challenges JDK 17 and leads to strange runtime behavior, but when going to 21, it seems to produce even more elevated runtimes.

It is about the runtimes of B03a (70 --> 100 ns) and B05f (1,000 --> 1,837 ns)

REGRESSION : Last worked in version 17.0.7

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See this public repo and execute JMH benchmarks org.xceptance.B03* and org.xceptance.B05f_QuotedWarmupAndUnquotedTest

There are other test cases, which belong to another defect that will be opened soon.

https://github.com/rschwietzke/jmh-C2-compile

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JDK 17.0.7 provides these runtimes:

B03a: 70 ns
B03b: 447 ns
B03c: 669 ns
B05f: 1,000 ns
ACTUAL -
JDK 21.ea.20 provides these runtimes:

B03a: 100 ns
B03b: 430 ns
B03c: 690 ns
B05f: 1,837 ns

---------- BEGIN SOURCE ----------
https://github.com/rschwietzke/jmh-C2-compile

https://github.com/rschwietzke/jmh-C2-compile/blob/main/src/main/java/org/xceptance/B03a_ShortWarmupAndTest.java
https://github.com/rschwietzke/jmh-C2-compile/blob/main/src/main/java/org/xceptance/B03b_UnquotedWarmupAndTest.java
https://github.com/rschwietzke/jmh-C2-compile/blob/main/src/main/java/org/xceptance/B03c_QuotedWarmupAndTest.java
https://github.com/rschwietzke/jmh-C2-compile/blob/main/src/main/java/org/xceptance/B05f_QuotedWarmupAndUnquotedTest.java
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Rewrite the code under tests change the runtime behavior.

FREQUENCY : always