On Fri, Nov 3, 2017 at 4:49 AM, Jeff Law <l...@redhat.com> wrote:
>
>
>
> Several passes which perform dominator walks want to identify when block has
> a single incoming edge, ignoring loop backedges.
>
> I'm aware of 4 implementations of this code. 3 of the 4 are identical in
> function. The 4th (tree-ssa-dom.c) has an additional twist that it also
> ignores edges that are not marked as executable.
>
> So I've taken the more general implementation from tree-ssa-dom.c and
> conditionalized the handling of unexecutable edges on a flag and moved the
> implementation into cfganal.c where it more naturally belongs.
>
> Bootstrapped and regression tested on x86_64. OK for the trunk?
Minor nits (sorry...)
> Jeff
>
> * cfganal.c (single_incoming_edge_ignoring_loop_edges): New function
> extracted from tree-ssa-dom.c.
> * cfganal.h (single_incoming_edge_ignoring_loop_edges): Prototype.
> * tree-ssa-dom.c (single_incoming_edge_ignoring_loop_edges): Remove.
> (record_equivalences_from_incoming_edge): Add additional argument
> to single_incoming_edge_ignoring_loop_edges call.
> * tree-ssa-uncprop.c (single_incoming_edge_ignoring_loop_edges):
> Remove.
> (uncprop_dom_walker::before_dom_children): Add additional argument
> to single_incoming_edge_ignoring_loop_edges call.
> * tree-ssa-sccvn.c (sccvn_dom_walker::before_dom_children): Use
> single_incoming_edge_ignoring_loop_edges rather than open coding.
> * tree-vrp.c (evrp_dom_walker::before_dom_children): Similarly.
>
>
>
>
>
> diff --git a/gcc/cfganal.c b/gcc/cfganal.c
> index c506067..14d94b2 100644
> --- a/gcc/cfganal.c
> +++ b/gcc/cfganal.c
> @@ -1554,3 +1554,38 @@ single_pred_before_succ_order (void)
> #undef MARK_VISITED
> #undef VISITED_P
> }
> +
> +/* Ignoring loop backedges, if BB has precisely one incoming edge then
> + return that edge. Otherwise return NULL. */
> +edge
> +single_incoming_edge_ignoring_loop_edges (basic_block bb,
> + bool ignore_unreachable)
single_pred_edge_ignoring_loop_edges and ignore_not_executable
to better match existing CFG functions and actual edge flag use.
Ok with that change.
Thanks,
Richard.
> +{
> + edge retval = NULL;
> + edge e;
> + edge_iterator ei;
> +
> + FOR_EACH_EDGE (e, ei, bb->preds)
> + {
> + /* A loop back edge can be identified by the destination of
> + the edge dominating the source of the edge. */
> + if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
> + continue;
> +
> + /* We can safely ignore edges that are not executable. */
> + if (ignore_unreachable
> + && (e->flags & EDGE_EXECUTABLE) == 0)
> + continue;
> +
> + /* If we have already seen a non-loop edge, then we must have
> + multiple incoming non-loop edges and thus we return NULL. */
> + if (retval)
> + return NULL;
> +
> + /* This is the first non-loop incoming edge we have found. Record
> + it. */
> + retval = e;
> + }
> +
> + return retval;
> +}
> diff --git a/gcc/cfganal.h b/gcc/cfganal.h
> index 39bb5e5..74975e5 100644
> --- a/gcc/cfganal.h
> +++ b/gcc/cfganal.h
> @@ -77,5 +77,6 @@ extern void bitmap_intersection_of_preds (sbitmap, sbitmap
> *, basic_block);
> extern void bitmap_union_of_succs (sbitmap, sbitmap *, basic_block);
> extern void bitmap_union_of_preds (sbitmap, sbitmap *, basic_block);
> extern basic_block * single_pred_before_succ_order (void);
> +extern edge single_incoming_edge_ignoring_loop_edges (basic_block, bool);
>
> #endif /* GCC_CFGANAL_H */
> diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
> index 06be69a..31f88b4 100644
> --- a/gcc/tree-ssa-dom.c
> +++ b/gcc/tree-ssa-dom.c
> @@ -113,7 +113,6 @@ static void eliminate_redundant_computations
> (gimple_stmt_iterator *,
> class avail_exprs_stack *);
> static void record_equivalences_from_stmt (gimple *, int,
> class avail_exprs_stack *);
> -static edge single_incoming_edge_ignoring_loop_edges (basic_block);
> static void dump_dominator_optimization_stats (FILE *file,
> hash_table<expr_elt_hasher>
> *);
>
> @@ -1057,39 +1056,6 @@ record_equivalences_from_phis (basic_block bb)
> }
> }
>
> -/* Ignoring loop backedges, if BB has precisely one incoming edge then
> - return that edge. Otherwise return NULL. */
> -static edge
> -single_incoming_edge_ignoring_loop_edges (basic_block bb)
> -{
> - edge retval = NULL;
> - edge e;
> - edge_iterator ei;
> -
> - FOR_EACH_EDGE (e, ei, bb->preds)
> - {
> - /* A loop back edge can be identified by the destination of
> - the edge dominating the source of the edge. */
> - if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
> - continue;
> -
> - /* We can safely ignore edges that are not executable. */
> - if ((e->flags & EDGE_EXECUTABLE) == 0)
> - continue;
> -
> - /* If we have already seen a non-loop edge, then we must have
> - multiple incoming non-loop edges and thus we return NULL. */
> - if (retval)
> - return NULL;
> -
> - /* This is the first non-loop incoming edge we have found. Record
> - it. */
> - retval = e;
> - }
> -
> - return retval;
> -}
> -
> /* Record any equivalences created by the incoming edge to BB into
> CONST_AND_COPIES and AVAIL_EXPRS_STACK. If BB has more than one
> incoming edge, then no equivalence is created. */
> @@ -1107,7 +1073,7 @@ record_equivalences_from_incoming_edge (basic_block
> bb,
> the parent was followed. */
> parent = get_immediate_dominator (CDI_DOMINATORS, bb);
>
> - e = single_incoming_edge_ignoring_loop_edges (bb);
> + e = single_incoming_edge_ignoring_loop_edges (bb, true);
>
> /* If we had a single incoming edge from our parent block, then enter
> any data associated with the edge into our tables. */
> diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
> index 306080b..1c99d3b 100644
> --- a/gcc/tree-ssa-sccvn.c
> +++ b/gcc/tree-ssa-sccvn.c
> @@ -4847,34 +4847,18 @@ sccvn_dom_walker::after_dom_children (basic_block
> bb)
> edge
> sccvn_dom_walker::before_dom_children (basic_block bb)
> {
> - edge e;
> - edge_iterator ei;
> -
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file, "Visiting BB %d\n", bb->index);
>
> /* If we have a single predecessor record the equivalence from a
> possible condition on the predecessor edge. */
> - edge pred_e = NULL;
> - FOR_EACH_EDGE (e, ei, bb->preds)
> - {
> - /* Ignore simple backedges from this to allow recording conditions
> - in loop headers. */
> - if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
> - continue;
> - if (! pred_e)
> - pred_e = e;
> - else
> - {
> - pred_e = NULL;
> - break;
> - }
> - }
> + edge pred_e = single_incoming_edge_ignoring_loop_edges (bb, false);
> if (pred_e)
> {
> /* Check if there are multiple executable successor edges in
> the source block. Otherwise there is no additional info
> to be recorded. */
> + edge_iterator ei;
> edge e2;
> FOR_EACH_EDGE (e2, ei, pred_e->src->succs)
> if (e2 != pred_e
> diff --git a/gcc/tree-ssa-uncprop.c b/gcc/tree-ssa-uncprop.c
> index 200ec70..4cc7714 100644
> --- a/gcc/tree-ssa-uncprop.c
> +++ b/gcc/tree-ssa-uncprop.c
> @@ -408,40 +408,10 @@ uncprop_into_successor_phis (basic_block bb)
> }
> }
>
> -/* Ignoring loop backedges, if BB has precisely one incoming edge then
> - return that edge. Otherwise return NULL. */
> -static edge
> -single_incoming_edge_ignoring_loop_edges (basic_block bb)
> -{
> - edge retval = NULL;
> - edge e;
> - edge_iterator ei;
> -
> - FOR_EACH_EDGE (e, ei, bb->preds)
> - {
> - /* A loop back edge can be identified by the destination of
> - the edge dominating the source of the edge. */
> - if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
> - continue;
> -
> - /* If we have already seen a non-loop edge, then we must have
> - multiple incoming non-loop edges and thus we return NULL. */
> - if (retval)
> - return NULL;
> -
> - /* This is the first non-loop incoming edge we have found. Record
> - it. */
> - retval = e;
> - }
> -
> - return retval;
> -}
> -
> edge
> uncprop_dom_walker::before_dom_children (basic_block bb)
> {
> basic_block parent;
> - edge e;
> bool recorded = false;
>
> /* If this block is dominated by a single incoming edge and that edge
> @@ -450,7 +420,7 @@ uncprop_dom_walker::before_dom_children (basic_block bb)
> parent = get_immediate_dominator (CDI_DOMINATORS, bb);
> if (parent)
> {
> - e = single_incoming_edge_ignoring_loop_edges (bb);
> + edge e = single_incoming_edge_ignoring_loop_edges (bb, false);
>
> if (e && e->src == parent && e->aux)
> {
> diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
> index 63ee156..39e9156 100644
> --- a/gcc/tree-vrp.c
> +++ b/gcc/tree-vrp.c
> @@ -10970,33 +10970,17 @@ evrp_dom_walker::try_find_new_range (tree name,
> edge
> evrp_dom_walker::before_dom_children (basic_block bb)
> {
> - tree op0 = NULL_TREE;
> - edge_iterator ei;
> - edge e;
> -
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file, "Visiting BB%d\n", bb->index);
>
> stack.safe_push (std::make_pair (NULL_TREE, (value_range *)NULL));
>
> - edge pred_e = NULL;
> - FOR_EACH_EDGE (e, ei, bb->preds)
> - {
> - /* Ignore simple backedges from this to allow recording conditions
> - in loop headers. */
> - if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
> - continue;
> - if (! pred_e)
> - pred_e = e;
> - else
> - {
> - pred_e = NULL;
> - break;
> - }
> - }
> + edge pred_e = single_incoming_edge_ignoring_loop_edges (bb, false);
> if (pred_e)
> {
> gimple *stmt = last_stmt (pred_e->src);
> + tree op0 = NULL_TREE;
> +
> if (stmt
> && gimple_code (stmt) == GIMPLE_COND
> && (op0 = gimple_cond_lhs (stmt))
> @@ -11040,6 +11024,8 @@ evrp_dom_walker::before_dom_children (basic_block
> bb)
>
> /* Visit PHI stmts and discover any new VRs possible. */
> bool has_unvisited_preds = false;
> + edge_iterator ei;
> + edge e;
> FOR_EACH_EDGE (e, ei, bb->preds)
> if (e->flags & EDGE_EXECUTABLE
> && !(e->src->flags & BB_VISITED))
>
