fold_builtin changes tree

[Ian Lance Taylor]

"Paulo J. Matos" <paulo@matos-sorge.com> writes:

> I have builtin __function_size(foobar) that is applied to functions.
> This should be folded to a symbol foobar@size.
>
> The problem comes when I mark in the fold_builtin function in my backend 
> that DECL_PRESERVE(foobar) = 1;
>
> The reason I need to do this is so that foobar is not removed if we 
> happen to use __function_size(foobar) since I will need foobar during 
> linking phase to do some calculations with regards to its size.
>
> As a consequence of DECL_PRESERVE(foobar) I cannot build GCC with --
> enable-checking because it fails the check in: fold-const.c and shows the 
> message:
> internal compiler error: fold check: original tree changed by fold
>
> This is really annoying since I like to run my tests with --enable-
> checking=full to get the most of the checks in GCC but I can't with this 
> issue lying around. I am open to suggestions on how to mark the function 
> as preserve is the function name is referred to by a function builtin.

I'm not sure what you are folding the builtin to, but perhaps you could
retain a reference to the function.

Or, you could write a tiny pass which set DECL_PRESERVED_P for each
function passed to __function_size.

Or, perhaps you could handle it in expand_builtin rather than
fold_builtin.

Ian