Thanks that clears some of it up. It seems that java runtimes that do EA actually do this sort of crazy difficult analysis that quickly breaks down with branches and non-inlined code.
FWIW, graal has partial escape analysis, which can avoid a lot of those pitfalls by allowing allocations to escape through just some of the branches. For instance, if you have
X thing = new ...;
if (slowpath) {
unlikely_function(thing);
}
...
Even if unlikely_function isn't inlined, it can still perform scalar replacement, and push the allocation site into the branch (reconstructing the state of the allocated object as it would've been at that point), which is a big improvement.
This in turn lets the inliner be smarter about what it does and doesn't inline, vs c2 which tries to greedily inline everything, partly to assist escape analysis
