[squeak-dev] How to find a CompiledBlock's parse node in a CompiledMethod's parse tree?

Eliot Miranda eliot.miranda at gmail.com
Tue Dec 14 22:27:34 UTC 2021

On Tue, Dec 14, 2021 at 5:19 AM Marcel Taeumel <marcel.taeumel at hpi.de>

> Hi all --
> Decompilation for instances of CompiledBlock is currently wrong. It just
> treats the CompiledMethod where the CompiledBlock is embedded.

Well, it's been that way for a long time and there's something to do with
method wrappers (see methodForDecompile) that I don't understand that makes
me leery of just changing this.

> Compare the following two examples:
> [3+4] method "i.e., compiledCode" decompile decompileString.
> [3+4] decompile decompileString.
> Well, first, the message #method on FullBlockClosure  is misleading
> because we are looking for the compiled-code object, which is an instance
> of CompiledBlock here.
> Anyway, I then tried to understand how to make Decompiler >>
> decompileBlock: work for CompiledBlock and not just FullBlockClosure. It
> turns out, that there is no #pc set in any decompiled parse node.
> How to find a CompiledBlock's parse node in a CompiledMethod's parse tree?

See Decompiler>>decompileBlock:

| block |
block := [3+4].
block method decompileWithTemps nodesDo:
   [:node| (node pc isVariableBinding and: [node pc key = block method])
ifTrue: [^node]]

=>  {[3 + 4]}

i.e. the decompiler carefully sets the pc of a full block node to an
association so you can find the thing.

Now, as far as changing things to work the way you expect, I don't object,
provided you check out MethodWrappers, etc.
CompiledMethod>>methodForDecompile has my initials on it, but I didn't
write it.  So what its comment means I don't know but we shoud find out
before we break things.

    "This is a hook to allow recursive methods like MwMethodWrapper to
avoid infinite recursion."

I *really* don't like this method, but presumably it's there for a reason.

best, Eliot
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