The Trunk: Compiler-eem.252.mcz

Eliot Miranda uploaded a new version of Compiler to project The Trunk:
http://source.squeak.org/trunk/Compiler-eem.252.mcz

==================== Summary ====================

Name: Compiler-eem.252
Author: eem
Time: 11 February 2013, 1:35:53.482 pm
UUID: eb0dde9d-1648-4b12-88ca-44c46fda0e9e
Ancestors: Compiler-eem.251

Yet another fix for decompilation of to:do: loops compiled
with Compiler-nice.224 or later.  If the stack is non-empty
when convertDoDoLoop is invoked, the stack must be left
non-empty.  This really does fix decompilation of e.g.
        ^nil to: 3 do: [:i| i class]
and not just
        true ifTrue: [^thisContext method decompile].
        ^nil to: 3 do: [:i| i class]

=============== Diff against Compiler-eem.251 ===============

Item was changed:
  ----- Method: Decompiler>>convertToDoLoop (in category 'private') -----
  convertToDoLoop
  "If statements contains the pattern
  var := startExpr.
  [var <= limit] whileTrue: [...statements... var := var + incConst]
  then replace this by
  startExpr to: limit by: incConst do: [:var | ...statements...]"
  | leaveOnStack initStmt toDoStmt limitStmt |
  leaveOnStack := false.
  (stack notEmpty
  and: [stack last isAssignmentNode])
  ifTrue:
  [initStmt := stack last.
  (toDoStmt := statements last toDoFromWhileWithInit: initStmt) ifNil:
  [^self].
  stack removeLast.
  statements removeLast; addLast: toDoStmt.
  leaveOnStack := true]
  ifFalse:
  [statements size < 2 ifTrue:
  [^self].
  initStmt := statements at: statements size-1.
  (toDoStmt := statements last toDoFromWhileWithInit: initStmt) ifNil:
  [^self].
  statements removeLast; removeLast; addLast: toDoStmt].
  initStmt variable scope: -1.  "Flag arg as block temp"
 
  "Attempt further conversion of the pattern
  limitVar := limitExpr.
  startExpr to: limitVar by: incConst do: [:var | ...statements...]
  to
  startExpr to: limitExpr by: incConst do: [:var | ...statements...].
  The complication here is that limitVar := limitExpr's value may be used, in which case it'll
  be statements last, or may not be used, in which case it'll be statements nextToLast."
  statements size < 2 ifTrue:
+ [leaveOnStack ifTrue:
+ [stack addLast: statements removeLast].
+ ^self].
- [^self].
  limitStmt := statements last.
  ((limitStmt isMemberOf: AssignmentNode)
  and: [limitStmt variable isTemp
  and: [limitStmt variable == toDoStmt arguments first]]) ifFalse:
  [limitStmt := statements at: statements size-1.
  ((limitStmt isMemberOf: AssignmentNode)
  and: [limitStmt variable isTemp
  and: [limitStmt variable == toDoStmt arguments first]]) ifFalse:
  [leaveOnStack ifTrue:
  [stack addLast: statements removeLast].
  ^self]].
 
  (self blockScopeRefersOnlyOnceToTemp: limitStmt variable fieldOffset) ifFalse:
  [^self].
  toDoStmt arguments at: 1 put: limitStmt value.
  limitStmt variable scope: -2.  "Flag limit var so it won't print"
  statements last == limitStmt
  ifTrue: [statements removeLast]
  ifFalse: [statements removeLast; removeLast; addLast: toDoStmt]!