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bb-reorder: Remove a misfiring micro-optimization (PR96475) 

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.  It
also does not work if that last block can be merged into multiple
predecessors.

2020-09-09  Segher Boessenkool  <segher@kernel.crashing.org>

	PR rtl-optimization/96475
	* bb-reorder.c (maybe_duplicate_computed_goto): Remove single_pred_p
	micro-optimization.
This commit is contained in:
Segher Boessenkool 2020-08-07 01:31:38 +00:00
parent ad2a37157d
commit 69ca5f3a98
1 changed files with 3 additions and 7 deletions
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10
gcc/bb-reorder.c
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@ -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)))