gcov: Use unshare_expr() in gen_counter_update()

gcov: Use unshare_expr() in gen_counter_update()

This fixes issues like this:

  gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c: In function 'main':
  gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c:19:1: error: incorrect sharing of tree nodes
  __gcov0.main[0]
  # .MEM_12 = VDEF <.MEM_9>
  __gcov0.main[0] = PROF_edge_counter_4;
  during IPA pass: profile
  gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c:19:1: internal compiler error: verify_gimple failed

Unshare the counter expression in the second gimple_build_assign() in
gen_counter_update().  This is similar to the original
gimple_gen_edge_profiler() for "ref":

void
gimple_gen_edge_profiler (int edgeno, edge e)
{
  tree one;

  one = build_int_cst (gcov_type_node, 1);

  if (flag_profile_update == PROFILE_UPDATE_ATOMIC)
[...]
  else
    {
      tree ref = tree_coverage_counter_ref (GCOV_COUNTER_ARCS, edgeno);
      tree gcov_type_tmp_var = make_temp_ssa_name (gcov_type_node,
						   NULL, "PROF_edge_counter");
      gassign *stmt1 = gimple_build_assign (gcov_type_tmp_var, ref);
      gcov_type_tmp_var = make_temp_ssa_name (gcov_type_node,
					      NULL, "PROF_edge_counter");
      gassign *stmt2 = gimple_build_assign (gcov_type_tmp_var, PLUS_EXPR,
					    gimple_assign_lhs (stmt1), one);
      gassign *stmt3 = gimple_build_assign (unshare_expr (ref),
					    gimple_assign_lhs (stmt2));
      gsi_insert_on_edge (e, stmt1);
      gsi_insert_on_edge (e, stmt2);
      gsi_insert_on_edge (e, stmt3);
    }
}

However, the orignal gimple_gen_time_profiler() did not use unshare_expr() for
the counter expression (tree_time_profiler_counter):

void
gimple_gen_time_profiler (unsigned tag)
{
[...]

  /* Emit: counters[0] = ++__gcov_time_profiler_counter.  */
  if (flag_profile_update == PROFILE_UPDATE_ATOMIC)
[...]
  else
    {
      tree tmp = make_temp_ssa_name (type, NULL, "PROF_time_profile");
      gassign *assign = gimple_build_assign (tmp, tree_time_profiler_counter);
      gsi_insert_before (&gsi, assign, GSI_NEW_STMT);

      tmp = make_temp_ssa_name (type, NULL, "PROF_time_profile");
      assign = gimple_build_assign (tmp, PLUS_EXPR, gimple_assign_lhs (assign),
				    one);
      gsi_insert_after (&gsi, assign, GSI_NEW_STMT);
      assign = gimple_build_assign (original_ref, tmp);
      gsi_insert_after (&gsi, assign, GSI_NEW_STMT);
      assign = gimple_build_assign (tree_time_profiler_counter, tmp);
      gsi_insert_after (&gsi, assign, GSI_NEW_STMT);
    }
}

gcc/ChangeLog:

	* tree-profile.cc (gen_counter_update): Use unshare_expr() for the
	counter expression in the second gimple_build_assign().