https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671
--- Comment #59 from rguenther at suse dot de <rguenther at suse dot de> --- On Mon, 27 Mar 2017, redi at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671 > > --- Comment #58 from Jonathan Wakely <redi at gcc dot gnu.org> --- > But this seemingly equivalent code doesn't work: > > this->functor = static_cast<function_buffer&>(f.functor); Is function_buffer may_alias? Then it should work unless the FE messes up via folding. struct C { int i; }__attribute__((may_alias)) ; C a, b; void foo() { a = static_cast <C&> (b); } in .original (correct): <<cleanup_point <<< Unknown tree: expr_stmt (void) (a = *(const struct C & {ref-all}) &b) >>>>>; in .gimple (wrong-code): void foo() () { a = b; } caused by gimple_fold_indirect_ref_rhs doing tree gimple_fold_indirect_ref (tree t) { tree ptype = TREE_TYPE (t), type = TREE_TYPE (ptype); tree sub = t; tree subtype; STRIP_NOPS (sub); subtype = TREE_TYPE (sub); if (!POINTER_TYPE_P (subtype)) return NULL_TREE; if (TREE_CODE (sub) == ADDR_EXPR) { tree op = TREE_OPERAND (sub, 0); tree optype = TREE_TYPE (op); /* *&p => p */ if (useless_type_conversion_p (type, optype)) return op; some of the transforms properly preserve ptype semantics but most don't
