[Bug target/66750] [4.9/5/6] Aggregate return not generated with -m32 -mregparm=3 or with -miamcu

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66750

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
IA MCU psABI is wrong since the implicit pointer argument isn't passed
on stack.  I will fix it.