[Bug tree-optimization/82697] [6/7/8 Regression] Wrong optimization with aliasing and "if"

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82697

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |4.2.4
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2017-10-24
     Ever confirmed|0                           |1
            Summary|Wrong optimization with     |[6/7/8 Regression] Wrong
                   |aliasing and "if"           |optimization with aliasing
                   |                            |and "if"
   Target Milestone|---                         |6.5
      Known to fail|                            |4.3.5, 4.8.5, 7.2.1, 8.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
This is a bug in conditional store elimination happening with -O1+ and
-fstrict-aliasing:



test (int * pi, long int * pl, int f)
{
  long int cstore_10;

  <bb 2> [100.00%]:
  *pi_5(D) = 1;
  if (f_7(D) != 0)
    goto <bb 4>; [54.00%]
  else
    goto <bb 3>; [46.00%]

  <bb 3> [46.00%]:

  <bb 4> [100.00%]:
  # cstore_10 = PHI <0(3), 2(2)>
  *pl_3(D) = cstore_10;

so it sank a store across another store.