[Bug c++/71330] [6/7 Regression] Compile time regression

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71330

--- Comment #11 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Patrick Palka from comment #10)
> I think the problem is with cp_fold_function() which does
> 
>   cp_walk_tree (&DECL_SAVED_TREE (fndecl), cp_fold_r, NULL, NULL);
> 
> and cp_fold_r is itself recursive so the number of calls made to cp_fold_r
> via cp_fold_function() is quadratic with respect to the size of the
> function's subexpressions.  The test case features a huge subexpression
> arising from the chain of overloaded <<s.

My guess is wrong.  Removing the call to cp_fold within cp_fold_r doesn't fix
the slowdown.

But calling cp_walk_tree instead of cp_walk_tree_without_duplicates does...