http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57361
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-05-22
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Assignment expansion makes this optimization:
/* Optimize away no-op moves without side-effects. */
if (operand_equal_p (to, from, 0))
return;
The operand_equal_p implementation looks safe at the moment (even in terms
of type-based aliasing rules).
I'd have done a more aggressive optimization in DSE, doing
if (stmt_kills_ref_p (stmt, gimple_assign_rhs1 (stmt)))
... must be a self-assignment ...
which would definitely need extra care for self-assignments that change
the effective type of a memory location. Though I have a hard time
creating a testcase that would exhibit sth like
MEM[(struct X *)q_1] = MEM[(struct Y *)q_1];
which would change the dynamic type of *q_1 to X from Y.
