[Bug 1661051] Re: vec_xl and vec_xst intrinsics are broken in GCC 6 for ppc64 and ppc64el

[LocutusOfBorg]

** Package changed: gcc-4.9 (Ubuntu) => gcc-6 (Ubuntu)

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Title:
  vec_xl and vec_xst intrinsics are broken in GCC 6 for ppc64 and
  ppc64el

Status in gcc-6 package in Ubuntu:
  New

Bug description:
  ---Problem Description---
  Please apply the patch from revision 245075 of the FSF gcc-6-branch as a bug fix for upstream bug PR79268, wherever GCC 6 is available.  Without the fix, wrong code will be generated in some cases for the vec_xl and vec_xst intrinsic functions, which provide access to unaligned vector load and store instructions on POWER8 and later.  The bug also shows up as a compile-time error when using a pointer-to-vector-pixel type as an argument to vec_xl or vec_xst.  This latter failure mode has been seen in the field.  A workaround for all failure modes is to replace vec_xl by vec_vsx_ld, and replace vex_xst by vec_vsx_st, but of course this is an invasive solution, and a fix to the compiler is preferred.  Thank you!

  ---Steps to Reproduce---
   #include <altivec.h>
  extern vector pixel vp, *vpp;
  ...
  vp = vec_xl (0, vpp);
   
  Bill Schmidt (wschmidt at us.ibm.com), Peter Bergner (bergner at us.ibm.com)

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