[Help-smalltalk] Re: Error while trying to write numbers in words

[Paolo Bonzini]

Paolo Bonzini wrote:
> Olivier Blanc wrote:
> > Hi Paolo,
> >
> > I couldn't find a way to point out where the bug is appearing.
> > How do you trace it down ?
>
> I modified a little the code (just to make it more similar to my 
> Smalltalk coding style), and got a "stack height mismatch", which hints 
> to a bug in the compiler.

In the bytecode optimizer, more precisely.  The optimization of 
jumps-to-jumps was causing a jump with a small range (<256 bytes) to 
become a jump with a large range (>256 bytes), and the optimizer was 
truncating the jump.

I fixed this in 43baff3b8586cae9cb505e8d3bc43c7915d4aa28 by more or less 
rewriting the bytecode optimizer (_gst_optimize_bytecodes).

Then I noticed a speedup opportunity, because the optimizer was not 
generating a few bytecodes that are in the bytecode set.  These are 
"compound" bytecodes such as this one

  101 = bytecode bc101 {
    PREFETCH ();
    DUP_STACK_TOP ();
    POP_JUMP_FALSE (arg);
  }

(used in compiling #and: and #or: messages), this one

  165 = bytecode bc165 {
    PREFETCH ();
    NOT_NIL_SPECIAL ();
    POP_JUMP_FALSE (arg);
  }

(resulting from "a notNil ifTrue: [...]"), and this one

  134 = bytecode bc134 {
    ADVANCE ();
    POP_STACK_TOP ();
    JUMP_BACK (arg);
  }

(used in compiling #whileTrue: and #whileFalse: messages).  Generation 
of these bytecodes is now done, after these three commits:

- 9bc2bf594fd75b4bbc02f4a13b421f545d507880 (a bug fix in the printing of 
CompiledMethods)

- 18c63d0a2fcb677f176c30dd933366172f81a328 (bugs in the implementation 
of the bytecodes that went unnoticed until now)

- 5aa9ebc511af8bd0615d3fb9e10198d145c22098 (actual generation of the 
bytecodes in the optimizer)

I applied all four patches to the 3.0 branch too.  Should there be 
problems, on the branch I might revert the last one or two.

Paolo