path oracle: Do not look at root oracle for killed defs.

path oracle: Do not look at root oracle for killed defs.

The problem here is that we are incorrectly threading 41->20->21 here:

  <bb 35> [local count: 56063504182]:
  _134 = M.10_120 + 1;
  if (_71 <= _134)
    goto <bb 19>; [11.00%]
  else
    goto <bb 41>; [89.00%]
...
...
...
  <bb 41> [local count: 49896518755]:

  <bb 20> [local count: 56063503181]:
  # lb_75 = PHI <_134(41), 1(18)>
  _117 = mstep_49 + lb_75;
  _118 = _117 + -1;
  _119 = mstep_49 + _118;
  M.10_120 = MIN_EXPR <_119, _71>;
  if (lb_75 > M.10_120)
    goto <bb 21>; [11.00%]
  else
    goto <bb 22>; [89.00%]

First, lb_17 == _134 because of the PHI.
Second, _134 > M.10_120 because of _134 = M.10_120 + 1.

We then assume that lb_75 > M.10_120, but this is incorrect because
M.10_120 was killed along the path.

This incorrect thread causes the miscompilation in 527.cam4_r.

Tested on x86-64 and ppc64le Linux.

gcc/ChangeLog:

	PR tree-optimization/103061
	* value-relation.cc (path_oracle::path_oracle): Initialize
	m_killed_defs.
	(path_oracle::killing_def): Set m_killed_defs.
	(path_oracle::query_relation): Do not look at the root oracle for
	killed defs.
	* value-relation.h (class path_oracle): Add m_killed_defs.