static void
emit_mfence_after_loop (struct loop *loop)
{
VEC (edge, heap) *exits = get_loop_exit_edges (loop);
edge exit;
gimple call;
gimple_stmt_iterator bsi;
unsigned i;
for (i = 0; VEC_iterate (edge, exits, i, exit); i++)
{
call = gimple_build_call (FENCE_FOLLOWING_MOVNT, 0);
if (!single_pred_p (exit->dest)
/* If possible, we prefer not to insert the fence on other paths
in cfg. */
&& !(exit->flags & EDGE_ABNORMAL))
split_loop_exit_edge (exit);
bsi = gsi_after_labels (exit->dest);
gsi_insert_before (&bsi, call, GSI_NEW_STMT);
mark_virtual_ops_for_renaming (call);
}
VEC_free (edge, heap, exits);
update_ssa (TODO_update_ssa_only_virtuals);
}
static bool
may_use_storent_in_loop_p (struct loop *loop)
{
bool ret = true;
if (loop->inner != NULL)
return false;
/* If we must issue a mfence insn after using storent, check that there
is a suitable place for it at each of the loop exits. */
if (FENCE_FOLLOWING_MOVNT != NULL_TREE)
{
VEC (edge, heap) *exits = get_loop_exit_edges (loop);
unsigned i;
edge exit;
for (i = 0; VEC_iterate (edge, exits, i, exit); i++)
if ((exit->flags & EDGE_ABNORMAL)
&& exit->dest == EXIT_BLOCK_PTR)
ret = false;
VEC_free (edge, heap, exits);
}
return ret;
}
static edge
loop_edge_to_cancel (struct loop *loop)
{
vec<edge> exits;
unsigned i;
edge edge_to_cancel;
gimple_stmt_iterator gsi;
/* We want only one predecestor of the loop. */
if (EDGE_COUNT (loop->latch->preds) > 1)
return NULL;
exits = get_loop_exit_edges (loop);
FOR_EACH_VEC_ELT (exits, i, edge_to_cancel)
{
/* Find the other edge than the loop exit
leaving the conditoinal. */
if (EDGE_COUNT (edge_to_cancel->src->succs) != 2)
continue;
if (EDGE_SUCC (edge_to_cancel->src, 0) == edge_to_cancel)
edge_to_cancel = EDGE_SUCC (edge_to_cancel->src, 1);
else
edge_to_cancel = EDGE_SUCC (edge_to_cancel->src, 0);
/* We only can handle conditionals. */
if (!(edge_to_cancel->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
continue;
/* We should never have conditionals in the loop latch. */
gcc_assert (edge_to_cancel->dest != loop->header);
/* Check that it leads to loop latch. */
if (edge_to_cancel->dest != loop->latch)
continue;
exits.release ();
/* Verify that the code in loop latch does nothing that may end program
execution without really reaching the exit. This may include
non-pure/const function calls, EH statements, volatile ASMs etc. */
for (gsi = gsi_start_bb (loop->latch); !gsi_end_p (gsi); gsi_next (&gsi))
if (gimple_has_side_effects (gsi_stmt (gsi)))
return NULL;
return edge_to_cancel;
}
exits.release ();
return NULL;
}