[Bug tree-optimization/83843] [8 Regression] wrong code at -O2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83843

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-01-15
                 CC|                            |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
-fno-store-merging fixes it.

test (unsigned char * buf, unsigned char * tab)
{
...
  _6 = _2 ^ _5;
  bswapsrc_18 = (short unsigned int) _6;
  _19 = bswapsrc_18 r>> 8;
  MEM[(unsigned char *)buf_15(D)] = _19;

looks suspicious.