Tim, you asked even more questions.
>So my first question is why you couldn't simply ask the question in  
>email.

For historical reasons. When I've started the article, I didn't know that
I'll end up with three questions and GCC's optimizer bug.

>
>Second question is why you are spending effort on the 1.18 vm,  
>something so old and obsolete it practically smells of mold.

Since it is the smallest Squeak I could get. I like to study programs that
I can comprehend. Squeak 1.18 is much closer to it than contemporary Squeaks.

>
>Third, the shift/xor trick for determining a valid smallInt value is  
>one I came up with in 1987 and it was put into the Squeak vm  in  
>probably 1.2 or thereabouts, when nobody was considering anything  
>other than 32 bit cpus and so the comment was perfectly reasonable.

Reasonable yes, but still wrong. I've found that out, when trying to prove
that both expressions are equivalent.
  
>In what way is the comment 'rather useless'? I think it explains the  
>point quite adequately and it's sure as hell better than the complete  
>lack of comments in 90% or more of the methods in the system..

It sure is! But most of it simply rephrases the code. And that is what
I consider useless. 

>Fourth, the code generator changes quite a lot of things in the  
>process of transliterating from the VM code to the C code so you  
>shouldn't be at all surprised when one formulation is used in the  
>image and another in the generated code.

I am not surprised! I've noticed that inLining-flag. I am not at all
mourning at it.

>
>Fifth - you're surely not surprised to find bugs in gcc?

Hmm. Kind of. I was using gcc quite a lot in the FreeBSD/NetBSD project. And
never found a bug. But as I learned today this is because the default flags in 
those projects did carefully avoid calling the optimizer.

Greetings,
Wolfgang