Status and rationale for toplevel bootstrap (was Re: Example of debugging GCC with toplevel bootstrap)

[Daniel Jacobowitz]

On Mon, Jan 16, 2006 at 12:43:13PM -0500, Richard Kenner wrote:
>     Only if you assume a "cross" compiler and a true native compiler
>     generate different code. I certainly hope that isn't the case.
> 
> Why not?  It's a pretty strong statement to assume they generate *exactly* the
> same code under all circumstances and it seems unnecessary.  All we require
> is that they both generate *correct* code.  It's perfectly reasonable for the
> optimizers to behave slightly differently in host and cross configurations,
> such as in what they fold.  Clearly, it's advantageous to minimize these
> differences, and we do that, but I think having to reduce them to zero
> is too strong a requirement, especially since it's so easy to avoid
> starting a bootstrap with a cross-compiler.

As a heavy debugger of cross compilers I strongly disagree with this
sentiment.  Host dependencies of any sort are a bug.

-- 
Daniel Jacobowitz
CodeSourcery