On Wed, Mar 09, 2016 at 12:05:51PM +0100, Marek Polacek wrote:
> This PR points out that nested functions returning VM types don't work as
> expected (yeah, go figure). We got an ICE on the testcase because we were
> trying to allocate variable-sized temporary instead of using __builtin_alloca
> or its kin. Jakub suggested to follow what the C++ front end does here. It
> seems to be the case that it creates a TARGET_EXPR if the call doesn't have
> a LHS. That seems to work out well. The run-time testcase sanity-checks that
> we do something reasonable.
>
> Not a regression, but on the other hand the patch doesn't change anything for
> 99.9% programs out there.
Wonder if you still can get an ICE if you add __attribute__((noreturn)) to
such nested function. Quick grep shows that there are some suspicious spots
and others are fine:
cgraphunit.c- /* Build call to the function being thunked. */
cgraphunit.c- if (!VOID_TYPE_P (restype)
cgraphunit.c: && (!alias_is_noreturn || TREE_ADDRESSABLE (restype)))
cgraphunit.c- {
^^^ needs checking
gimplify.c: if (!gimple_call_noreturn_p (call_stmt)
gimplify.c- || TREE_ADDRESSABLE (TREE_TYPE (*to_p)))
gimplify.c- gimple_call_set_lhs (call_stmt, *to_p);
^^^ likewise
tree-cfg.c- if (lhs
tree-cfg.c- && gimple_call_ctrl_altering_p (stmt)
tree-cfg.c: && gimple_call_noreturn_p (stmt)
tree-cfg.c- && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (lhs))) == INTEGER_CST
tree-cfg.c- && !TREE_ADDRESSABLE (TREE_TYPE (lhs)))
tree-cfg.c- {
tree-cfg.c: error ("LHS in noreturn call");
tree-cfg.c- return true;
tree-cfg.c- }
^^^ looks fine
tree-cfgcleanup.c- /* If there is an LHS, remove it, but only if its type has
fixed size.
tree-cfgcleanup.c- The LHS will need to be recreated during RTL expansion
and creating
tree-cfgcleanup.c- temporaries of variable-sized types is not supported.
Also don't
tree-cfgcleanup.c- do this with TREE_ADDRESSABLE types, as assign_temp will
abort. */
tree-cfgcleanup.c- tree lhs = gimple_call_lhs (stmt);
tree-cfgcleanup.c- if (lhs && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (lhs))) ==
INTEGER_CST
tree-cfgcleanup.c- && !TREE_ADDRESSABLE (TREE_TYPE (lhs)))
tree-cfgcleanup.c- {
tree-cfgcleanup.c- gimple_call_set_lhs (stmt, NULL_TREE);
^^^ likewise
Jakub
