[Bug target/52828] New: powerpc -m32 -Os writes register saves below stack

[amodra at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52828

             Bug #: 52828
           Summary: powerpc -m32 -Os writes register saves below stack
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: amodra@gmail.com


An example is gcc.c-torture/compile/20020604-1.c compiled with -m32 -g -Os
-fno-omit-frame-pointer.  (The -fno-omit-frame-pointer is there just to get a
reg saved.  An asm volatile reg clobber gives the same result.)
The relevant part of the prologue code looks like

 lis 0,0xffff
 mr 12,1
 ori 0,0,32736
 stw 31,-4(12)
 stwux 1,1,0
 .cfi_def_cfa_offset 32800
 .cfi_offset 31, 32796

Notice the r31 save before the stack adjust.  Another consequence of the
reordering is wrong debug/eh_frame info for r31.