abstract class CopyProp extends AnyRef
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- new CopyProp()
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- case class ProducedValue(producer: AbstractInsnNode, size: Int) extends Product with Serializable
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- abstract val postProcessor: PostProcessor
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!=(arg0: Any): Boolean
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##(): Int
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def
copyPropagation(method: MethodNode, owner: InternalName): Boolean
For every
xLOAD n, find all local variable slots that are aliases ofnusing an AliasingAnalyzer and change the instruction toxLOAD mwheremis the smallest alias.For every
xLOAD n, find all local variable slots that are aliases ofnusing an AliasingAnalyzer and change the instruction toxLOAD mwheremis the smallest alias. This leaves behind potentially stalexSTORE ninstructions, which are then eliminated by eliminateStaleStores. -
def
eliminatePushPop(method: MethodNode, owner: InternalName): Boolean
When a POP instruction has a single producer, remove the POP and eliminate the producer by bubbling up the POPs.
When a POP instruction has a single producer, remove the POP and eliminate the producer by bubbling up the POPs. For example, given ILOAD 1; ILOAD 2; IADD; POP we first eliminate the POP, then the IADD, then its inputs, so the entire sequence goes away. If a producer cannot be eliminated (need to keep side-effects), a POP is inserted.
A special case eliminates the creation of unused objects with side-effect-free constructors: NEW scala/Tuple1; DUP; ALOAD 0; INVOKESPECIAL scala/Tuple1.<init>; POP The POP has a single producer (the DUP), it's easy to eliminate these two. A special case is needed to eliminate the INVOKESPECIAL and NEW.
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def
eliminateStaleStores(method: MethodNode, owner: InternalName): Boolean
Eliminate
xSTOREinstructions that have no consumer.Eliminate
xSTOREinstructions that have no consumer. If the instruction can be completely eliminated, it is replaced by a POP. The eliminatePushPop cleans up unnecessary POPs.Note that an
ASOTREcan not always be eliminated: it removes a reference to the object that is currently stored in that local, which potentially frees it for GC (scala/bug#5313). Therefore we replace such stores byPOP; ACONST_NULL; ASTORE x. -
def
eliminateStoreLoad(method: MethodNode): Boolean
Remove
xSTORE n; xLOAD npairs ifRemove
xSTORE n; xLOAD npairs if- the local variable n is not used anywhere else in the method (1), and
- there are no executable instructions and no live labels (jump targets) between the two (2)
Note: store-load pairs that cannot be eliminated could be replaced by
DUP; xSTORE n, but that's just cosmetic and doesn't help for anything.(1) This could be made more precise by running a prodCons analysis and checking that the load is the only user of the store. Then we could eliminate the pair even if the variable is live (except for ASTORE, scala/bug#5313). Not needing an analyzer is more efficient, and catches most cases.
(2) The implementation uses a conservative estimation for liveness (if some instruction uses local n, then n is considered live in the entire method). In return, it doesn't need to run an Analyzer on the method, making it more efficient.
This method also removes
ACONST_NULL; ASTORE nif the local n is not live. This pattern is introduced by eliminateStaleStores.The implementation is a little tricky to support the following case: ISTORE 1; ISTORE 2; ILOAD 2; ACONST_NULL; ASTORE 3; ILOAD 1 The outer store-load pair can be removed if two the inner pairs can be.
- def ensuring(cond: (CopyProp) ⇒ Boolean, msg: ⇒ Any): CopyProp
- def ensuring(cond: (CopyProp) ⇒ Boolean): CopyProp
- def ensuring(cond: Boolean, msg: ⇒ Any): CopyProp
- def ensuring(cond: Boolean): CopyProp
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wait(arg0: Long): Unit
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- def →[B](y: B): (CopyProp, B)
The Scala compiler and reflection APIs.