When the compgotos pass copies the tail of blocks ending in an indirect
jump, there is a micro-optimization to not copy the last one, since the
original block will then just be deleted. This does not work properly
if cleanup_cfg does not merge all pairs of blocks we expect it to.
v2: This also deletes the other use of single_pred_p, which has the same
problem in principle, I just never have triggered it so far.
Tested on powerpc64-linux {-m32,-m64} like before. Is this okay for
trunk?
Segher
2020-08-07 Segher Boessenkool <seg...@kernel.crashing.org>
PR rtl-optimization/96475
* bb-reorder.c (maybe_duplicate_computed_goto): Remove single_pred_p
micro-optimization.
---
gcc/bb-reorder.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/gcc/bb-reorder.c b/gcc/bb-reorder.c
index c635010..76e56b5 100644
--- a/gcc/bb-reorder.c
+++ b/gcc/bb-reorder.c
@@ -2680,9 +2680,6 @@ make_pass_reorder_blocks (gcc::context *ctxt)
static bool
maybe_duplicate_computed_goto (basic_block bb, int max_size)
{
- if (single_pred_p (bb))
- return false;
-
/* Make sure that the block is small enough. */
rtx_insn *insn;
FOR_BB_INSNS (bb, insn)
@@ -2700,10 +2697,9 @@ maybe_duplicate_computed_goto (basic_block bb, int
max_size)
{
basic_block pred = e->src;
- /* Do not duplicate BB into PRED if that is the last predecessor, or if
- we cannot merge a copy of BB with PRED. */
- if (single_pred_p (bb)
- || !single_succ_p (pred)
+ /* Do not duplicate BB into PRED if we cannot merge a copy of BB
+ with PRED. */
+ if (!single_succ_p (pred)
|| e->flags & EDGE_COMPLEX
|| pred->index < NUM_FIXED_BLOCKS
|| (JUMP_P (BB_END (pred)) && !simplejump_p (BB_END (pred)))
--
1.8.3.1
