Hi Eliot,
Nicolas' change that we put on the tracker didn't really work as
intended (Nicolas did you see that?), but i'll let him respond to the
points he was making.
For me (point #1) It would be better for you to try and tell us the
classes/methods that are either obviously broken or need the attention
to get to a series of fixes.
e.g., ignoring the loop highlight for the moment, the pc mapping goes
wrong right at the start of this example:
toDoOutsideTemp
| temp collection |
collection := OrderedCollection new.
1 to: 5 do: [ :index |
temp := index.
collection add: [ temp ] ].
by highlighting pc=2 (IIRC) which is the assignment, but the first
highlight should be pc=3 which is the send of #new. It doesn't
correctly map/avoid the extra instructions for the array
initialisation for copying the values outside the block. is it
possible to fix that first? where do we look?
I am just wondering how this can be approached in stages if possible.
i know it is all related at some level. stepping into the code/method
that does the majority of the pc mapping is a funny experience ;-)
because the method is structured in such a way to expose a number of
these bugs.
for point #2 ideally we would not ask for a step and have nothing
happen. However i wonder if we can get the highlight areas correct,
even if we have to "step" through hidden parts. This assumes we can
suppress the highlight for the hidden bits which i think we already
have...but only if we can do one without the other. I would then
write tests for the highlights, and we would have some protection for
further changes.
thanks,
Mike
On Mon, Sep 5, 2011 at 5:14 PM, Eliot Miranda <[email protected]> wrote:
> Hi Nicolas,
> that's quite a lot to absorb. Exactly what do you want me to review?
> The first thing it seems to me is to define what we want to be highlighted
> at different bytecodes in an optimized loop. A second thing is to think
> about how the debugger can avoid stepping through the hidden sends that are
> part of a loop. What I mean is that
> 1 to: n do: [:i| ....]
> is actually
> i := 1.
> [i <= n] whileTrue: [
> and so the debugger steps through i:= 1 and i <= n, even though these aren't
> visible in the source. That's why one has to click several times to get
> into the body of the loop. The debugger could for example use the source
> ranges for the bytecodes to step until the source range changes. So if
> there is the same source range info for all the bytecodes involved in the
> loop iteration (not the loop body) the debugger will be able to respond to
> step properly. What do you think?
>
> [sorry for not having responded sooner; esug and personal issues have got in
> the way. apologies]
> On Thu, Aug 25, 2011 at 1:06 PM, Nicolas Cellier
> <[email protected]> wrote:
>>
>> A few more notes:
>>
>> - Encoder>>rawSourceRanges answer a mapping AST Node -> sourceRange
>> Gnerally, I would expect sourceRange to be an Interval, but this has
>> to be confirmed.
>> Theses ranges are constructed at source code Parse time (see senders
>> of #noteSourceRange:forNode:)
>> - The program counters are assigned to AST nodes at byte code #generate
>> time
>> - for inlined macros, like #to:do: in our case, this pc is after the
>> initialize and test statements.
>>
>> in CompiledMethod>>#rawSourceRangesAndMethodDo:
>> I just evaluated this:
>>
>> methNode encoder rawSourceRanges collect: [:ival |
>> sourceText copyFrom: ival first to: ival last]
>>
>> And what I see is that the original to:do: message (before macros
>> inlining) has the right range
>> {1
>> to: 5
>> do: [:index |
>> temp := index.
>> collection
>> add: [temp]]}->a Text for 'to: 5 do: [ :index |
>> temp := index.
>> collection add: [ temp ] ]'
>> This node is the original #to:do: and has pc=42
>>
>> There is also
>> {a LeafNode}->a Text for '[ :index |
>> temp := index.
>> collection add: [ temp ] ]'
>> which has a nil pc so it won't be taken into account in the source map.
>>
>> But one of the messages produced by the inlining has this curious range:
>> {index <= 5}->a Text for 'to: 5 do: [ :index |
>> temp := index.
>> c'
>> This node has pc = 40, so it will be selected before the correct one
>> above has a chance to be.
>> {index <= 5} is the test statement produced by inlining, and this
>> seems to be the incorrect highlighting we see.
>> Thus we know we have to concentrate on macro inlining.
>> This happens in MessageNode>>transformToDo:
>> We'll see this.
>>
>> In the interim, I played with eliminating the nodes having unitilialized
>> pc
>> Let us try to evaluate this snippet in debugger's inspector:
>> (methNode encoder rawSourceRanges keys select: [:e | e pc > 0])
>> collect: [:node |
>> | ival |
>> ival := methNode encoder rawSourceRanges at: node.
>> node -> (sourceText copyFrom: ival first to: ival last)]
>>
>> Oh god, a bug in the debugger:
>> DoItIn: homeContext
>> ^ ((homeContext namedTempAt: 2) encoder rawSourceRanges keys
>> select: [:e | e pc > 0])
>> collect: [:node |
>> | ival |
>> ival := (node namedTempAt: 2) encoder
>> rawSourceRanges at: node.
>> node
>> -> (sourceText copyFrom: ival first to:
>> ival last)]
>> (node namedTempAt: 2) does not mean a thing...
>> A confusion occurred between the homeContext (DoItIn: method argument)
>> and node (the block argument)
>> Nevermind... forget about it.
>>
>> Now let's just concentrate on MessageNode>>transformToDo:
>> We see this code:
>> test := MessageNode new
>> receiver: blockVar
>> selector: (increment key > 0 ifTrue: [#<=]
>> ifFalse: [#>=])
>> arguments: (Array with: limit)
>> precedence: precedence from: encoder
>> sourceRange: (myRange first to: blockRange
>> first).
>>
>> So the intention seems to select 'to: 5 do: '
>>
>> But we see this:
>> BlockNode>>noteSourceRangeStart:end:encoder:
>> "Note two source ranges for this node. One is for the debugger
>> and is of the last expression, the result of the block. One is
>> for
>> source analysis and is for the entire block."
>> encoder
>> noteSourceRange: (start to: end)
>> forNode: self closureCreationNode.
>> startOfLastStatement
>> ifNil:
>> [encoder
>> noteSourceRange: (start to: end)
>> forNode: self]
>> ifNotNil:
>> [encoder
>> noteSourceRange: (startOfLastStatement to:
>> end - 1)
>> forNode: self]
>>
>> So it seems intentional to select only the last instruction of the
>> block for the debugger.
>> We'd better not change this without prior asking Eliot.
>> But obviously, this is not what is expected by the #transformToDo:
>>
>> Nicolas
>>
>> 2011/8/25 Stéphane Ducasse <[email protected]>:
>> > tx nicolas this is a cool way to help :)
>> >
>> > Stef
>> >
>> > On Aug 24, 2011, at 9:54 PM, Nicolas Cellier wrote:
>> >
>> >> So the entries of interest for highlighting are
>> >>
>> >> Debugger>>contentsSelection
>> >> Debugger>>pcRange
>> >> CompiledMethod>>debuggerMap
>> >> DebuggerMethodMap class>>forMethod:
>> >> DebuggerMethodMap>>rangeForPC:contextIsActiveContext:
>> >>
>> >> Then you see the DebuggerMethodMap>>forMethod:methodNode: takes both a
>> >> CompiledMethod and its #methodNode.
>> >> CompiledMethod>>methodNode invokes the Parser to get the
>> >> AbstractSyntaxTree from method source, and if it ever fails ends up by
>> >> trying to decompile the byteCodes.
>> >>
>> >> This is the easy part. Now we to deal with #abstractPCForConcretePC:
>> >> and #abstractSourceMap.
>> >>
>> >> By reading CompiledMethod>>abstractPCForConcretePC: you should quickly
>> >> understand that a concrete PC is a byte offset of current byteCode
>> >> (the offsets displayed in the byteCode view) while the abstractPC is
>> >> just the rank of current byteCode in the list of byteCodes
>> >> instructions composing the CompiledMethod. This is just because
>> >> "byteCodes" may spread on several bytes beside their name...
>> >> This will use InstructionStream and InstructionClient which are just
>> >> an iterator and a sort of visitor on byteCode instructions.
>> >> So this is not really interesting.
>> >>
>> >> The more interesting part is #abstractSourceMap
>> >> There is a first step to obtain
>> >> CompiledMethod>>rawSourceRangesAndMethodDo:
>> >> This is the most important part.
>> >> The rest is again a mapping from concretePC (instruction byte offset)
>> >> to abstractPC (instruction rank).
>> >> And some build of a dictionary mapping instruction rank (abstractPC)
>> >> -> selected range.
>> >>
>> >> Note that the last trick seems to use a regenerated CompiledMethod
>> >> (theMethodToScan) rather than the original CompiledMethod. There is no
>> >> assertion whether these two are equivalent or not. A priori, they
>> >> should, unless the Compiler changed since last compilation or if its
>> >> behaviour is affected by some Preferences... Would we introduce some
>> >> customizable Compiler optimizations that this could become a problem
>> >> (We would then add to map decompiled AST to source code AST, probably
>> >> with guesses, unless the CompiledMethod would contain debugger
>> >> friendly hints...)
>> >> We will consider this is not a problem by now.
>> >>
>> >> So let's now concentrate on rawSourceRangesAndMethodDo:
>> >> The nice thing is that you now can just debug this
>> >>
>> >> (ClosureTests>>#testToDoOutsideTemp) methodNode
>> >> rawSourceRangesAndMethodDo: [:rs :mth | ]
>> >>
>> >> and see how it goes in Squeak. I did not look in Pharo yet, but I
>> >> would be amazed to see it much different.
>> >> It's now late, and my spare time is off, but you have clues to get
>> >> more insights. I wish you good debugging, and come back to me if it
>> >> ever goes in deeper complications.
>> >>
>> >> Cheers
>> >>
>> >> Nicolas
>> >>
>> >> 2011/8/24 Michael Roberts <[email protected]>:
>> >>>
>> >>>>
>> >>>> Ok I'm curious to know then.
>> >>>
>> >>> Here is a little trace from this example method:
>> >>>
>> >>> toDoOutsideTemp
>> >>> | temp collection |
>> >>> collection := OrderedCollection new.
>> >>> 1 to: 5 do: [ :index |
>> >>> temp := index.
>> >>> collection add: [ temp ] ]
>> >>>
>> >>> Trace is start,stop position of the highlight for each 'step over'.
>> >>>
>> >>> Whilst the numbers are hard to visualise, below you can see how they
>> >>> slightly diverge.
>> >>> Left Pharo Right Squeak
>> >>>
>> >>> 50, 73 71, 73 diff
>> >>> 71, 73 71, 73
>> >>> 50, 73 50, 73
>> >>> 108, 115 79, 121 diff
>> >>> 79, 121 79, 121
>> >>> 108, 115 108, 115
>> >>> 132, 144 132, 144
>> >>> 147, 146 146, 146 (diff negative size means no highlight)
>> >>> 146, 146 146, 146
>> >>> 79, 121 79, 121
>> >>> 108, 115 108, 115
>> >>> 132, 144 132, 144
>> >>> 147, 146 146, 146
>> >>> 146, 146 146, 146
>> >>> 79, 121 79, 121
>> >>> 108, 115 108, 115
>> >>> 132, 144 132, 144
>> >>> 147, 146 146, 146
>> >>> 146, 146 146, 146
>> >>> 79, 121 79, 121
>> >>> 108, 115 108, 115
>> >>> etc...
>> >>> For example the first difference is because Pharo shows the whole
>> >>> assignment
>> >>> of the first line as the first send, even though it is not.
>> >>> The second difference is that Pharo shows the assignment inside the
>> >>> block as
>> >>> the first highlight of the loop even though the to:do should be
>> >>> highlighted....but both Pharo & Squeak get the to:do: wrong when they
>> >>> choose
>> >>> to show it.
>> >>> hope you get the idea...
>> >>> Mike
>> >>
>> >
>> >
>> >
>>
>
>
>
> --
> best,
> Eliot
>
