RFR(M): 8031754: Type speculation should favor profile data from outermost inlined method

Vladimir Kozlov vladimir.kozlov at oracle.com
Thu Feb 6 09:18:49 PST 2014

On 2/6/14 8:45 AM, Roland Westrelin wrote:
> Hi Vladimir,
>>>> In general I am comfortable to have inline_depth as additional type's attribute. But only for speculative types when it make sense.
>>>> So why you keep _inline_depth in remove_speculative()?
>>> Because it’s never used in practice with non speculative types (it should always be InlineDepthBottom for a non speculative type). The only place where it changes the behavior of compilation is in GraphKit::record_profile_for_speculation() where it’s used only for speculative types. Anyway, I can reset it to InlineDepthBottom in remove_speculative() if you like.
>> Yes, please, set to InlineDepthBottom. It will be consistent with types without speculative types.
> Actually, that’s not possible. Because then, that code:
> 2589     if (res_oopptr->remove_speculative() == res_oopptr->speculative()) {
> 2590       return res_oopptr->remove_speculative();
> in TypeOopPtr::xmeet()
> doesn’t trigger if res_oopptr has an inline depth of InlineDepthTop. remove_speculative() transforms it to InlineDepthBottom. And the type system is no longer symmetric.

Do you know why it is top? The default value is InlineDepthBottom, how it is converted to top?

> Instead shouldn’t I assert in remove_speculative() that if _speculative is non NULL then _inline_depth is InlineDepthTop or InlineDepthBottom?

To have assert is good but we need to understand why in such case inline_depth could be top.


> Roland.

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