basic_block_head[]/basic_block_tail[] questions

[Toshiyasu Morita]

> 
> 
>   In message < 199808151124.EAA24081@netcom8.netcom.com >you write:
>   > I'm seeing some strange problems with reload and I think it may have 
>   > something to do with basic_block_head[] and basic_block_tail[]...
>   > 
>   > Specifically, the current implementation of basic_block_head[] and 
>   > basic_block_tail[] seem to point at actual insns. This seems bad
>   > because reload calls emit_insn_before() and emit_insn_after(), and these 
>   > functions seem unaware of the existence of the basic_block_head/tail arrays.
>   > 
>   > Consider: if reload generates a spill for the first insn of a 
>   > basic block, it seems to insert the insns into the basic block outside 
>   > the one intended, or even outside the outermost basic block, like this:
> It's a problem, but not a serious one.  Nothing bad should happen as
> far as I know.

Actually, I found this anomoly while investigating PR 16819, in which a 
C++ constructor fails to return 'this', and I suspect this anomoly is the
root reason for this bug.

Toshi