Re:If Java Is Dying, It Sure Looks Awfully Healthy
by astral303 on Thursday October 10, 2013 @09:32AM
(#6527513)
There's far more than branch prediction optimization, which AFAIK, is bread and butter of profile-guided optimization.
Even that assumes that your program does not significantly shift its behavior mid-execution--in fact, you're optimizing for the average, not the current case.
One of the coolest JIT things is ability to inline virtual calls. Think about that, I could have my code calling a 3rd party library calling another 3rd party library thru 10 levels of stack and if all that call ever returns is "false", then JIT will optimize right through all that.
I don't believe PGO does virtual call inlining. That's a C++ nonstarter. In C, the equivalent would be inlining for function pointer calls.
Even that assumes that your program does not significantly shift its behavior mid-execution--in fact, you're optimizing for the average, not the current case.
One of the coolest JIT things is ability to inline virtual calls. Think about that, I could have my code calling a 3rd party library calling another 3rd party library thru 10 levels of stack and if all that call ever returns is "false", then JIT will optimize right through all that.
I don't believe PGO does virtual call inlining. That's a C++ nonstarter. In C, the equivalent would be inlining for function pointer calls.