> Compiler Control (https://openjdk.org/jeps/165) provides method-context > dependent control of the JVM compilers (C1 and C2). The active directive > stack is built from the directive files passed with the > `-XX:CompilerDirectivesFile` diagnostic command-line option and the > Compiler.add_directives diagnostic command. It is also possible to clear all > directives or remove the top from the stack. > > A matching directive will be applied at method compilation time when such > compilation is started. If directives are added or changed, but compilation > does not start, then the state of compiled methods doesn't correspond to the > rules. This is not an error, and it happens in long running applications when > directives are added or removed after compilation of methods that could be > matched. For example, the user decides that C2 compilation needs to be > disabled for some method due to a compiler bug, issues such a directive but > this does not affect the application behavior. In such case, the target > application needs to be restarted, and such an operation can have high costs > and risks. Another goal is testing/debugging compilers. > > It would be convenient to optionally reconcile at least existing matching > nmethods to the current stack of compiler directives. Methods in general are > often inlined, and this information is hard to track down. > > Natural way to eliminate the discrepancy between the result of compilation > and the broken rule is to discard the compilation result, i.e. > deoptimization. Obviously there is a performance penalty, so it should be > applied with care. Hot code will most likely be recompiled soon, as nothing > happens to its hotness. > > A new flag '`-d`' has beed introduced for some directives related to compile > commands: `Compiler.add_directives`, `Compiler.remove_directives`, > `Compiler.clear_directives`. The default behavior has not changed (no flag). > If the new flag is present, the command scans already compiled methods and > marks for deoptimization those methods that have any active non-default > matching compiler directives. There is currently no distinction which > directives are found. In particular, this means that if there are rules for > inlining into some method, it will be deoptimized. On the other hand, if > there are rules for a method and it was inlined, top-level methods won't be > deoptimized, but this can be achieved by having rules for them. > > In addition, a new diagnistic command `Compiler.replace_directives`, has been > added for convenience. It's like a combinatio...
Dmitry Chuyko has updated the pull request incrementally with one additional commit since the last revision: jcheck fix ------------- Changes: - all: https://git.openjdk.org/jdk/pull/14111/files - new: https://git.openjdk.org/jdk/pull/14111/files/40de84af..2d8cf4e9 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=14111&range=03 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14111&range=02-03 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/14111.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/14111/head:pull/14111 PR: https://git.openjdk.org/jdk/pull/14111
