analysis
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package Global
A full type-flow analysis on a method computes in- and out-flows for each basic block (that's what MethodTFA does).
A full type-flow analysis on a method computes in- and out-flows for each basic block (that's what MethodTFA does).
For the purposes of Inliner, doing so guarantees that an abstract typestack-slot is available by the time an inlining candidate (a CALL_METHOD instruction) is visited. This subclass (MTFAGrowable) of MethodTFA also aims at performing such analysis on CALL_METHOD instructions, with some differences:
(a) early screening is performed while the type-flow is being computed (in an override of blockTransfer) by testing a subset of the conditions that Inliner checks later.
The reasoning here is: if the early check fails at some iteration, there's no chance a follow-up iteration (with a yet more lub-ed typestack-slot) will succeed.
Failure is sufficient to remove that particular CALL_METHOD from the typeflow's remainingCALLs.
A forward note: in case inlining occurs at some basic block B, all blocks reachable from B get their CALL_METHOD instructions considered again as candidates
(because of the more precise types that -- perhaps -- can be computed).
(b) in case the early check does not fail, no conclusive decision can be made, thus the CALL_METHOD stays isOnwatchlist.
In other words, remainingCALLs tracks those callsites that still remain as candidates for inlining, so that Inliner can focus on those.
remainingCALLs also caches info about the typestack just before the callsite, so as to spare computing them again at inlining time.
Besides caching, a further optimization involves skipping those basic blocks whose in-flow and out-flow isn't needed anyway (as explained next).
A basic block lacking a callsite in remainingCALLs, when visited by the standard algorithm, won't cause any inlining.
But as we know from the way type-flows are computed, computing the in- and out-flow for a basic block relies in general on those of other basic blocks.
In detail, we want to focus on that sub-graph of the CFG such that control flow may reach a remaining candidate callsite.
Those basic blocks not in that subgraph can be skipped altogether. That's why:
forwardAnalysis() in MTFAGrowable now checks for inclusion of a basic block in relevantBBs The rest of the story takes place in Inliner, which does not visit all of the method's basic blocks but only on those represented in remainingCALLs.
A map which returns the bottom type for unfound elements
A map which returns the bottom type for unfound elements
Test two objects for inequality.
Test two objects for inequality.
true if !(this == that), false otherwise.
Equivalent to x.hashCode except for boxed numeric types and null.
Equivalent to x.hashCode except for boxed numeric types and null.
For numerics, it returns a hash value which is consistent
with value equality: if two value type instances compare
as true, then ## will produce the same hash value for each
of them.
For null returns a hashcode where null.hashCode throws a
NullPointerException.
a hash value consistent with ==
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
true if the receiver object is equivalent to the argument; false otherwise.
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics.
Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at
runtime, while the expression List(1).asInstanceOf[List[String]] will not.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the requested type.
the receiver object.
ClassCastException if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
a copy of the receiver object.
not specified by SLS as a member of AnyRef
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on
non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.x of type AnyRef, x.eq(null) and null.eq(x) returns false.null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equality method for reference types.
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as
well as the interaction between finalize and non-local returns
and exceptions, are all platform dependent.
not specified by SLS as a member of AnyRef
A representation that corresponds to the dynamic class of the receiver object.
A representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
not specified by SLS as a member of AnyRef
The hashCode method for reference types.
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics.
Therefore the expression 1.isInstanceOf[String] will return false, while the
expression List(1).isInstanceOf[List[String]] will return true.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the specified type.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Equivalent to !(this eq that).
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
The type flow lattice contains a binding from local variable names to types and a type stack.
The type flow lattice contains a binding from local variable names to types and a type stack.
The lattice of ICode types.
The lattice of ICode types.
The lattice of type stacks.
The lattice of type stacks. It is a straight forward extension of the type lattice (lub is pairwise lub of the list elements).
ICode analysis for optimization