[Laszlo-dev] For Review: Change 20080724-dda-2 Summary: minor cleanup of SWF6 compiler transforms

[Donald Anderson]

Change 20080724-dda-2 by dda at lester.local on 2008-07-24 16:43:04 EDT
     in /Users/dda/laszlo/src/svn/openlaszlo/trunk-a
     for http://svn.openlaszlo.org/openlaszlo/trunk

Summary: minor cleanup of SWF6 compiler transforms

New Features:

Bugs Fixed: LPP-6669 (Remove swf6 byte-code kludges from  
CodeGenerator.java)

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

Documentation:

Release Notes:

Details:
Most of the issues implied by the LPP-6669 cannot be fixed - but  
details are listed here.

0)  Removed some code specific to swf6 involving using lower case for  
variable and register names

Examined and tested the various transforms in question:

1)
     // swf6 returns undefined for comparisons with NaN, it
     // is supposed to return false (note that you cannot
     // eliminate one NOT by inverting the sense of the
     // comparison
     BinopInstrs.put(ParserConstants.LT, new Instruction[]  
{Instructions.LessThan, Instructions.NOT, Instructions.NOT});

Tried setting this to just Instructions.LesThan, but smokecheck gives  
errors on NaN comparisons.

2)
     // swf6 does not have GE or LE, but inverting the
     // complement operator does not work for NaN ordering
     // Luckily, LogicalOr coerces undefined to false, so we
     // don't have to play the NOT NOT trick above
     BinopInstrs.put(ParserConstants.LE, new Instruction[]

Tried setting LE to { Instructions.GT, Instructions.NOT }
    smokecheck also gives errors on NaN comparisons.
For kicks, also tried setting LE to { Instructions.GT,  
Instructions.NOT , Instructions.NOT , Instructions.NOT }
    to see if the 'double NOT' trick might work, but also gives the  
same smokecheck errors.

Also examined flasm source to see if GE or LE has been added (they  
have not).

3)
     // swf6 does not have NE or SNE either, but inverting
     // the complement is correct for NaN

There are no new opcodes for NE or SNE (at least as known to flasm)

4)
     // Approximate a in b as b.a =! void 0

No new opcodes for 'in'

5)  Special case of 'is' in translateBinaryExpression.

No new opcodes for 'is'

6)  Special case of 'cast' in translateBinaryExpression.

There is a SWF 'CAST' operator that leaves a 'null' on the stack in  
case of error.
This is not being utilized, and there's already a separate TODO for  
this item.
It didn't seem to be under the purvue of this Jira bug.


Tests:
    regression: smokecheck swf8/dhtml

Files:
M      WEB-INF/lps/server/src/org/openlaszlo/sc/CodeGenerator.java

Changeset: http://svn.openlaszlo.org/openlaszlo/patches/20080724-dda-2.tar



--

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

voice: 617-547-7881
email: dda at ddanderson.com
www: http://www.ddanderson.com



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