target/8515: incomming altivec vectors on the stack unaligned to 16

[pinskia at physics dot uc dot edu]

>Number:         8515
>Category:       target
>Synopsis:       incomming altivec vectors on the stack unaligned to 16
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Nov 09 22:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Andrew Pinski
>Release:        gcc version 3.3 20021108 (experimental)
>Organization:
>Environment:
powerpc-apple-darwin6.1
>Description:
gcc stores incomming altivec vector arguments on the stack unaligned to 16 but to an 8 byte alignment which is wrong because stvx and lvx do not care about the lower 8 bits of the address so it could corrupted the stack.
>How-To-Repeat:
Run the following program and see that three out of the four addresses are not 16 byte aligned.
Compiled with -maltivec -include altivec.h -Wa,-force_cpusubtype_ALL.

void PrintShortVector (vector signed short v );
void PrintShortVector1 (vector signed short v );

void main()
{
        PrintShortVector((vector signed short){1,2,3,4,5,6,7,8});
        PrintShortVector1((vector signed short){1,2,3,4,5,6,7,8});
}


  void PrintShortVector (vector signed short v )
  {
      signed short *vec = (signed short*)&v;
      printf ("(%p) (%p) %hd %hd %hd %hd %hd %hd %hd %hd ",
             vec, &v, vec[0], vec[1], vec[2], vec[3], vec[4], vec[5], vec[6], vec[7]);
  }


  typedef union {
      vector signed short v ;
      signed short vs[8] ;
  } vv ;

  void PrintShortVector1 (vector signed short v)
  {
      vv vv;

      vv.v = v;
      printf ("(%p) (%p) %hd %hd %hd %hd %hd %hd %hd %hd ",  &vv, &v, vv.vs[0], vv.vs[1], vv.vs[2], vv.vs[3], vv.vs[4], vv.vs[5], vv.vs[6], vv.vs[7]);
  }


According to hartwood@crosslink.net, it happens also on a VxWorks cross-compiler.
>Fix:
do not know
>Release-Note:
>Audit-Trail:
>Unformatted: