[Bug rtl-optimization/58029] New: base_alias_check says pretend-args saves and varargs accesses don't alias

[amylaar at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58029

            Bug ID: 58029
           Summary: base_alias_check says pretend-args saves and varargs
                    accesses don't alias
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amylaar at gcc dot gnu.org

When the frame is set up by the prologue, some pretend args saves have to
be done using the stack pointer, as the frame pointer can't be saved until
later.
For va_arg, OTOH, it is natural to use the hard frame pointer, if no frame
pointer elimination takes place.

gcc.dg/torture/stackalign/vararg-1.c fails at -Os / -O2 or higher for
epiphany-elf because base_alias_check says the store of the pretend args
and the va_arg loads don't alias, and the stores get scheduled after the
load.