Re: [Tinycc-devel] Compiling qemu-0.8.2 with tcc (yes, I am insane).

[Rob Landley]

On Friday 13 October 2006 12:41 am, Daniel Glöckner wrote:
> On 12 Oct 06 17:11, Rob Landley wrote:
> > and teaching it about dead code elimination are higher priority for me
> > than most other things.
> 
> Isn't that easy to do.
> Think about
> 
> if(0) {
>  ...
> label:
>  ...
> }
> ...
> goto label;
> 
> You may not discard the contents of the "if" until you are shure that the
> label won't be called.

Or until you're sure it hasn't got any labels in it.

> If C had no "goto" or "switch", setting nocode_wanted would have sufficed.

First approximation is to switch nocode_wanted back on when you hit your first 
label.  Anything else requires two passes, but there's stuff we're already 
doing two passes for anyway (according to the notes, haven't made it that far 
in the code yet.  Printed out it's 205 pages for tcc.c, I've read maybe 25 of 
those so far...)

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery