Re: [Pharo-dev] Mysteries of the compiler

Oct. 16, 2014


      
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On 16 Oct 2014, at 17:26, Marcus Denker <marcus.denker@inria.fr> wrote:
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On 16 Oct 2014, at 16:43, Marcus Denker <marcus.denker@inria.fr <mailto:marcus.denker@inria.fr>> wrote:
1. sometimes the debugger can not inspect a single tempvar (list of all temps is working)
2. number of temp vars (in method header) is wrong:
| a b c |
    a := 1.
    b := 2.
    c := 3.
    [[a asString]
        on: Error
        do: [:ex | a
                value: a
                value: b
                value: c].
    c < 0] whileTrue.
method header numtemps 1
| a b c |
    a := 1.
    b := 2.
    c := 3.
    c < 0
        ifTrue: [ 
            [ a asString ]
                on: Error
                do: [ :ex | a value: a value: b value: c ].
            c < 0 ].
    ^ a
method header numtemps 3
both methods define a block with a nested block. 
In the first method it is the receiver of #whileTrue:
the second method it is the argument to #ifTrue:
I think both blocks are optimized, but somehow the 
block receiving the whileTrue: message makes the computation
for the number of tempvars wronng
What is happening is that the variables are wrongly put in a temp vector... in the case
of loops.
the one temp is this vector.
this should be fixed.
I think the problem is that what we did is to mark a variables as escaping when it
as *read* in an optimised block.
But what we should do is to mark only all *writes* to a variable that happens in a loop as
escaping vars even in the case when they happen in the same scope.
this means the read is simpler:
visitVariableNode: aVariableNode
  | var |
  var := (self lookupVariableForRead: aVariableNode) ifNil: [(self undeclaredVariable: aVariableNode)].
  aVariableNode binding: var.
  var isUninitialized ifTrue: [self uninitializedVariable: aVariableNode].
While in the write we need to mark:
lookupVariableForWrite: aVariableNode
| var |
var := scope lookupVar: aVariableNode name.
var ifNil: [^var].
  var isSpecialVariable ifTrue: [ self storeIntoSpecialVariable: aVariableNode ].
  var isWritable ifFalse: [ self storeIntoReadOnlyVariable: aVariableNode ].
var isTemp ifTrue: [
      "when in a loop, all writes escape"
      scope outerScope isInsideOptimizedLoop ifTrue: [ var markEscapingWrite ].
      "else only escaping when they will end up in different closures"
      (var scope outerNotOptimizedScope ~= scope outerNotOptimizedScope) 
      	ifTrue: [ var markEscapingWrite]].
  ^var
I checked that all Opal tests that are failing are actually testing wrong, and I double checked
that all those methods are now compiled like with the old old compilerâ¦
Now recompilng the image.
Hmmâ¦ nopeâ¦. something wrong.

   Marcus