Reading the compiler's mind
-XX:+LogCompilation flag produces a low-level XML file about compiler and runtime decisions, which may be interesting to some. The
-XX:+UnlockDiagnosticVMOptions must come first. The dump is to
hotspot.log in the current directory; use
-XX:LogFile=foo.log to change this.
The format of this file is complex and subject to change. Here is an overview of the syntax, and a tool for parsing the files.
The XML file is also line-oriented, so simple greps or text editing scans are sometimes useful.