https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97605
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2020-10-28
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. This is partial dead code elimination which we do not perform.
You can think of partial dead code elimination as sinking & duplicating code
to N places where dataflow determines that in M < N places the sunk code
is dead (it's usually done for stores, but calls work as well of course).
For malloc/free pairs it actually requires eliding the whole pair while
classically for stores only the sunk store is. Thus
int g;
void f (int i)
{
g = 1;
if (i)
g = 2;
}
becomes
int g;
void f (int i)
{
if (i)
g = 2;
else
g = 1;
}
in your case you'd sink the malloc and elide the malloc/free pair.
It might be tempting to implement this in two-steps and only do the
sinking, relying on followup DCE/DSE but that will likely run into
cases where we just ended up duplicating code.
