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

Marcel Taeumel marcel.taeumel at hpi.de
Wed Dec 15 08:39:36 UTC 2021

Hi Eliot --

(Full)BlockClosure works fine. I am talking about CompiledBlock.

Am 14.12.2021 23:29:42 schrieb Eliot Miranda <eliot.miranda at gmail.com>:

On Tue, Dec 14, 2021 at 2:27 PM Eliot Miranda <eliot.miranda at gmail.com [mailto:eliot.miranda at gmail.com]> wrote:

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

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.

and #== works the same/is to be preferred:

| block |
block := [3+4].
block method decompileWithTemps nodesDo:

    [:node| (node pc isVariableBinding and: [node pc key == block method]) ifTrue: [^node]]

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



best, Eliot
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