[Bug tree-optimization/71915] New: A missed opportunity for SLSR

["marxin at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71915

            Bug ID: 71915
           Summary: A missed opportunity for SLSR
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

Hello.

This is a follow-up of PR71490, where we started to FAIL slsr-8.c test-case.
Problem is that starting from r237185, we sink into both branches:

Sinking x3_18 = c_13(D) + _9;
 from bb 2 to bb 3
Sinking _9 = -_8;
 from bb 2 to bb 3
Sinking _8 = _7 * 4;
 from bb 2 to bb 3
Sinking _7 = (long unsigned int) a3_17;
 from bb 2 to bb 3
Sinking a3_17 = s_11(D) * 6;
 from bb 2 to bb 3
Sinking x2_16 = c_13(D) + _6;
 from bb 2 to bb 5
Sinking _6 = -_5;
 from bb 2 to bb 5
Sinking _5 = _4 * 4;
 from bb 2 to bb 5
Sinking _4 = (long unsigned int) a2_15;
 from bb 2 to bb 5
Sinking a2_15 = s_11(D) * 4;
 from bb 2 to bb 5
f (int s, int * c)
{
  int * x3;
  int * x2;
  int * x1;
  int a3;
  int a2;
  int a1;
  long unsigned int _1;
  long unsigned int _2;
  sizetype _3;
  long unsigned int _4;
  long unsigned int _5;
  sizetype _6;
  long unsigned int _7;
  long unsigned int _8;
  sizetype _9;
  int * iftmp.0_10;

  <bb 2>:
  a1_12 = s_11(D) * 2;
  _1 = (long unsigned int) a1_12;
  _2 = _1 * 4;
  _3 = -_2;
  x1_14 = c_13(D) + _3;
  if (x1_14 != 0B)
    goto <bb 5>;
  else
    goto <bb 3>;

  <bb 5>:
  a2_15 = s_11(D) * 4;
  _4 = (long unsigned int) a2_15;
  _5 = _4 * 4;
  _6 = -_5;
  x2_16 = c_13(D) + _6;
  goto <bb 4>;

  <bb 3>:
  a3_17 = s_11(D) * 6;
  _7 = (long unsigned int) a3_17;
  _8 = _7 * 4;
  _9 = -_8;
  x3_18 = c_13(D) + _9;

  <bb 4>:
  # iftmp.0_10 = PHI <x2_16(5), x3_18(3)>
  return iftmp.0_10;

}

While in time when the test-case was introduced, we sank just to one branch:
Sinking x3_18 = c_7(D) + _17;
 from bb 2 to bb 3
Sinking _17 = -_16;
 from bb 2 to bb 3
Sinking _16 = _15 * 4;
 from bb 2 to bb 3
Sinking _15 = (long unsigned int) a3_14;
 from bb 2 to bb 3
Sinking a3_14 = s_2(D) * 6;
 from bb 2 to bb 3
f (int s, int * c)
{
  int * x3;
  int * x2;
  int * x1;
  int a3;
  int a2;
  int a1;
  int * iftmp.0;
  long unsigned int _4;
  long unsigned int _5;
  sizetype _6;
  long unsigned int _10;
  long unsigned int _11;
  sizetype _12;
  long unsigned int _15;
  long unsigned int _16;
  sizetype _17;

  <bb 2>:
  a1_3 = s_2(D) * 2;
  _4 = (long unsigned int) a1_3;
  _5 = _4 * 4;
  _6 = -_5;
  x1_8 = c_7(D) + _6;
  a2_9 = s_2(D) * 4;
  _10 = (long unsigned int) a2_9;
  _11 = _10 * 4;
  _12 = -_11;
  x2_13 = c_7(D) + _12;
  if (x1_8 != 0B)
    goto <bb 5>;
  else
    goto <bb 3>;

  <bb 5>:
  goto <bb 4>;

  <bb 3>:
  a3_14 = s_2(D) * 6;
  _15 = (long unsigned int) a3_14;
  _16 = _15 * 4;
  _17 = -_16;
  x3_18 = c_7(D) + _17;

  <bb 4>:
  # iftmp.0_1 = PHI <x2_13(5), x3_18(3)>
  return iftmp.0_1;

}

Because of that, slsr does not cover one opportunity.

Martin