[Bug debug/83391] [8 Regression] error: definition in block 9 does not dominate use in block 8

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83391

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #6)
> The bb is split in:
> #0  gsi_split_seq_before (i=0x7fffffffd940, pnew_seq=0x7fffffffd918) at
> ../../gcc/gimple-iterator.c:415
> #1  0x00000000011fc89d in gimple_split_block (bb=<basic_block 0x7fffefacb888
> (9)>, stmt=0x0) at ../../gcc/tree-cfg.c:6130
> #2  0x0000000000bf2f15 in split_block_1 (bb=<basic_block 0x7fffefacb888
> (9)>, i=0x0) at ../../gcc/cfghooks.c:520
> #3  0x0000000000bf30d4 in split_block_after_labels (bb=<basic_block
> 0x7fffefacb888 (9)>) at ../../gcc/cfghooks.c:572
> #4  0x0000000000bf3aa7 in make_forwarder_block (bb=<basic_block
> 0x7fffefacb888 (9)>, redirect_edge_p=0xc0438c <mfb_keep_just(edge_def*)>, 
>     new_bb_cbk=0x0) at ../../gcc/cfghooks.c:875
> #5  0x0000000000c0462b in create_preheader (loop=0x7fffefc20330, flags=1) at
> ../../gcc/cfgloopmanip.c:1501
> #6  0x0000000000c04788 in create_preheaders (flags=1) at
> ../../gcc/cfgloopmanip.c:1552
> #7  0x0000000000f6dab6 in apply_loop_flags (flags=3) at
> ../../gcc/loop-init.c:64
> #8  0x0000000000f6dbf4 in loop_optimizer_init (flags=3) at
> ../../gcc/loop-init.c:123
> 
> Do we really need to allow debug stmts before labels?

Pleeeease not.

> If yes, I have a fix for gimple_make_forwarder_block.