[PATCH] Fix path splitting to handle empty else block
Richard Biener
rguenther@suse.de
Tue Jul 5 13:23:00 GMT 2016
The following patch fixes a FAIL of gcc.dg/tree-ssa/split-path-5.c
with hoisting enabled which leaves both cases of the testcase as
if (pred)
tmp = tmp + 4;
and thus with empty else (by hoisting a conversion). While this
eventually is if-convertible it shouldn't prevent path splitting
as the case is an IV related increment.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2016-07-05 Richard Biener <rguenther@suse.de>
* gimple-ssa-split-paths.c (find_block_to_duplicate_for_splitting_pa):
Handle empty else block.
(is_feasible_trace): Likewise.
(split_paths): Likewise.
Index: gcc/gimple-ssa-split-paths.c
===================================================================
--- gcc/gimple-ssa-split-paths.c (revision 237955)
+++ gcc/gimple-ssa-split-paths.c (working copy)
@@ -76,14 +76,19 @@ find_block_to_duplicate_for_splitting_pa
return NULL;
/* And that BB's immediate dominator's successors are the
- predecessors of BB. */
- if (!find_edge (bb_idom, EDGE_PRED (bb, 0)->src)
- || !find_edge (bb_idom, EDGE_PRED (bb, 1)->src))
+ predecessors of BB or BB itself. */
+ if (!(EDGE_PRED (bb, 0)->src == bb_idom
+ || find_edge (bb_idom, EDGE_PRED (bb, 0)->src))
+ || !(EDGE_PRED (bb, 1)->src == bb_idom
+ || find_edge (bb_idom, EDGE_PRED (bb, 1)->src)))
return NULL;
- /* And that the predecessors of BB each have a single successor. */
- if (!single_succ_p (EDGE_PRED (bb, 0)->src)
- || !single_succ_p (EDGE_PRED (bb, 1)->src))
+ /* And that the predecessors of BB each have a single successor
+ or are BB's immediate domiator itself. */
+ if (!(EDGE_PRED (bb, 0)->src == bb_idom
+ || single_succ_p (EDGE_PRED (bb, 0)->src))
+ || !(EDGE_PRED (bb, 1)->src == bb_idom
+ || single_succ_p (EDGE_PRED (bb, 1)->src)))
return NULL;
/* So at this point we have a simple diamond for an IF-THEN-ELSE
@@ -148,8 +153,10 @@ is_feasible_trace (basic_block bb)
basic_block pred1 = EDGE_PRED (bb, 0)->src;
basic_block pred2 = EDGE_PRED (bb, 1)->src;
int num_stmts_in_join = count_stmts_in_block (bb);
- int num_stmts_in_pred1 = count_stmts_in_block (pred1);
- int num_stmts_in_pred2 = count_stmts_in_block (pred2);
+ int num_stmts_in_pred1
+ = EDGE_COUNT (pred1->succs) == 1 ? count_stmts_in_block (pred1) : 0;
+ int num_stmts_in_pred2
+ = EDGE_COUNT (pred2->succs) == 1 ? count_stmts_in_block (pred2) : 0;
/* This is meant to catch cases that are likely opportunities for
if-conversion. Essentially we look for the case where
@@ -292,6 +299,8 @@ split_paths ()
"Duplicating join block %d into predecessor paths\n",
bb->index);
basic_block pred0 = EDGE_PRED (bb, 0)->src;
+ if (EDGE_COUNT (pred0->succs) != 1)
+ pred0 = EDGE_PRED (bb, 1)->src;
transform_duplicate (pred0, bb);
changed = true;
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