Given an InlineRequest(mainCallsite, post = List(postCallsite)), the postCallsite is a callsite in the method mainCallsite.callee. Once the mainCallsite is inlined into the target method (mainCallsite.callsiteMethod), we need to find the cloned callsite that corresponds to the postCallsite so we can inline that into the target method as well.

However, it is possible that there is no cloned callsite at all that corresponds to the postCallsite, for example if the corresponding callsite already inlined. Example:

def a() = 1 def b() = a() + 2 def c() = b() + 3 def d() = c() + 4

We have the following callsite objects in the call graph:

c1 = a() in b c2 = b() in c c3 = c() in d

Assume we have the following inline request r = InlineRequest(c3, post = List(InlineRequest(c2, post = List(InlineRequest(c1, post = Nil)))))

But before inlining r, assume a separate InlineRequest(c2, post = Nil) is inlined first. We get

c1' = a() in c // added to the call graph c1.inlinedClones += (c1' at c2) // remember that c1' was created when inlining c2 ~c2~ // c2 is removed from the call graph

If we now inline r, we first inline c3. We get

c1 = a() in d // added to call graph c1'.inlinedClones += (c1 at c3) // remember that c1 was created when inlining c3 ~c3~

Now we continue with the post-requests for r, i.e. c2.

• we try to find the clone of c2 that was created when inlining c3 - but there is none. c2 was already inlined before
• we continue with the post-request of c2: c1
  • we search for the callsite of c1 that was cloned when inlining c2, we find c1'
  • recursively we search for the callsite of c1' that was cloned when inlining c3, we find c1
  • so we create an inline request for c1

Check whether the body of the callee contains any instructions that prevent the callsite from being inlined. See also method earlyCanInlineCheck.

The result of this check depends on changes to the callee method's body. For example, if the callee initially invokes a private method, it cannot be inlined into a different class. If the private method is inlined into the callee, inlining the callee becomes possible. Therefore we don't query it while traversing the call graph and selecting callsites to inline - it might rule out callsites that can be inlined just fine.

Returns

• None if the callsite can be inlined
• Some((message, Nil)) if there was an issue performing the access checks, for example because of a missing classfile
• Some((message, instructions)) if inlining instructions into the callsite method would cause an IllegalAccessError

Check if a type is accessible to some class, as defined in JVMS 5.4.4. (A1) C is public (A2) C and D are members of the same run-time package

Check whether an inlining can be performed. This method performs tests that don't change even if the body of the callee is changed by the inliner / optimizer, so it can be used early (when looking at the call graph and collecting inline requests for the program).

The tests that inspect the callee's instructions are implemented in method canInlineBody, which is queried when performing an inline.

Returns

• Right(Nil) if all instructions can be safely inlined
• Right(insns) if inlining any of insns would cause a java.lang.IllegalAccessError when inlined into the destinationClass
• Left((insn, warning)) if validity of some instruction could not be checked because an error occurred

Inline the callsite of an inlining request and its post-inlining requests.

Copy and adapt the instructions of a method to a callsite.

Preconditions:

• The callsite can safely be inlined (canInlineBody is true)
• The maxLocals and maxStack values of the callsite method are correctly computed

Check if a member reference is accessible from the destinationClass, as defined in the JVMS 5.4.4. Note that the class name in a field / method reference is not necessarily the class in which the member is declared:

class A { def f = 0 }; class B extends A { f }

The INVOKEVIRTUAL instruction uses a method reference "B.f ()I". Therefore this method has two parameters:

Ordering for inline requests. Required to make the inliner deterministic:

• Always remove the same request when breaking inlining cycles
• Perform inlinings in a consistent order