[Laszlo-dev] For Review: Change 20070919-dda-V Summary: script compiler refactoring

[Donald Anderson]

Change 20070919-dda-V by dda at freddie.local on 2007-09-19 17:35:41 EDT
     in /Users/dda/laszlo/src/svn/openlaszlo/trunk/WEB-INF/lps/server/ 
src/org/openlaszlo/sc
     for http://svn.openlaszlo.org/openlaszlo/trunk/WEB-INF/lps/ 
server/src/org/openlaszlo/sc

Summary: script compiler refactoring

New Features:
   No externally visible changes.  A rearrangement of source code to  
allow for better
   sharing between modules, and separation of most of the platform  
independent parts of the compiler.
   This more easily allows various future work (e.g. SWF9) to proceed  
in parallel with
   general maintenance changes.

Bugs Fixed:

Technical Reviewer: ptw
QA Reviewer: (pending)
Doc Reviewer: (pending)

Documentation:

Release Notes:

Details:
     Added a new class CommonGenerator that is the base class of
     JavascriptGenerator and CodeGenerator.  Methods from the two
     subclasses that are textually the same, or can be easily coerced
     to be the same are now only in CommonGenerator.
     Data members and internal classes that are identical are
     also now in the base class.

     To get even greater sharing, many methods (like virtually all the
     visit* methods) that had signature changes in JavascriptGenerator
     (that is, they return 'SimpleNode' rather than void), have changed
     across the board to return SimpleNode.  That is, these functions  
return
     the possibly modified node that is visited.  In the  
CodeGenerator class, this
     concept is generally not used, so even though this class plays  
by the
     same rules, return values from such methods are ultimately ignored.
     But this gives a lot more code sharing and many more functions  
could be moved
     to CommonGenerator.

     Likewise, methods that visit expressions that used to be declared
     returning boolean in CodeGenerator now must return SimpleNode.
     The backwards-seeming translation is that 'true' corresponds to  
null,
     and false corresponds to the existing node.  Doing it this way
     gets the maximum code sharing, it clearly reflects the way that
     the code was originally transformed after splitting.

     CommonGenerator also implements a new interface: ASTVisitor,  
which is
     the union of all the visit* methods (returning a SimpleNode, of
     course).  This allows methods in CommonGenerator (esp.  
visitStatement)
     to freely call any other visit* method, whether or not it is  
actually
     defined in CommonGenerator.

     Most of these changes listed above are almost mechanical using the
     indicated strategy; only occasionally were small (equivalent)  
coding
     changes introduced, and then only if a method was otherwise  
identical.
     More elaborate code sharing is possible, and was attempted, but
     such changes tended to inhibit overall readability and  
maintainability.

Tests:
     built all files in lps/includes/lfc with the previous compiler  
(without
     these changes) using the flags "--option  
generatePredictableTemps=true".
     built the same files with the new compiler (with these changes).
     All *.js files compare exactly, all *.lzl files were disassembled,
     and the output from that compares exactly.

Files:
M      JavascriptGenerator.java
A      CommonGenerator.java
A      ASTVisitor.java
M      CodeGenerator.java

Changeset: http://svn.openlaszlo.org/openlaszlo/patches/20070919-dda- 
V.tar



--

Don Anderson
Java/C/C++, Berkeley DB, systems consultant

Voice:  617-547-7881
Email:  dda at ddanderson.com
WWW:    http://www.ddanderson.com