On Thu, 6 Nov 2014, Jan Hubicka wrote:
> Hi,
> PR63573 is about ICE when expanding thunk call for function taking as a
> parameter structure passed by reference. This structure in fact contains only
> one integer and thus it is promoted to register by argument setup in
> function.c
> (as an optimization). This is an sensible optimization, but when expanding
> the tailcall
> we need memory location to store the value into to pass it again by reference.
> Because we lost the original memory location we ICE because we have
> addressable flag
> set on decl whose DECL_RTL is register.
>
> This patch fixes it up by reverting to original memory location in calls.c.
> This is of course not safe in general because the register value may be
> hcanged, but the path is executed only when THUNK flag of the call statement
> is
> set and that is set only in thunks where the values are not updated. Ugly hack
> but I can not think of better way to fix the ugly hacks already in there to
> make
> thunk expansion happen in tailcall.
>
> This fixed boostrap on ppc64-linux and the set of testsuite failures match
> ones before
> the bug was introduced.
>
> OK?
>
> PR bootstrap/63573
> * calls.c (initialize_argument_information): When emitting thunk call
> use original memory
> placement of the argument.
> Index: calls.c
> ===================================================================
> --- calls.c (revision 216942)
> +++ calls.c (working copy)
> @@ -1210,6 +1211,15 @@ initialize_argument_information (int num
> && TREE_CODE (base) != SSA_NAME
> && (!DECL_P (base) || MEM_P (DECL_RTL (base)))))
> {
> + /* Argument setup code may have copied the value to register. We
> + that optimization now because the tail call code must use
> + the original location. */
The last sentence probably misses some words.
> + if (TREE_CODE (args[i].tree_value) == PARM_DECL
> + && !MEM_P (DECL_RTL (args[i].tree_value))
> + && DECL_INCOMING_RTL (args[i].tree_value)
> + && MEM_P (DECL_INCOMING_RTL (args[i].tree_value)))
> + set_decl_rtl (args[i].tree_value, DECL_INCOMING_RTL
> (args[i].tree_value));
Please fix the long line.
I don't know calls.c so no further comments or approval from me.
Sorry,
Richard.
