https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67886
Yuri Gribov <tetra2005 at gmail dot com> changed:
What |Removed |Added
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CC| |hubicka at gcc dot gnu.org,
| |tetra2005 at gmail dot com
--- Comment #2 from Yuri Gribov <tetra2005 at gmail dot com> ---
There is a more important optimization hiding here.
Standard suggests (in 3.8.7, in n3690.pdf) that when the same source variable
is used for the instance pointer, it's dynamic type should not change. This
allows code like
Base *p = new Derived;
p->foo();
p->foo();
to be optimized to
Derived::foo(p);
Derived::foo(p);
(which would also allow to optimize Simon's original case).
Clang currently performs this sort of optimization (see old discussion in
https://groups.google.com/forum/#!topic/llvm-dev/XPxvsEauirM and recent blog
post in http://blog.llvm.org/2017/03/devirtualization-in-llvm-and-clang.html).
This sort of optimization requires frontend knowledge so probly can't be done
solely in GIMPLE? Summon Honza to comment.
