Stop find_split_point from clobbering constant pool entries

[Richard Henderson]

On Sat, Nov 01, 2003 at 11:33:16AM +0000, Richard Sandiford wrote:
>       /* A MEM is allowed to be shared if its address is constant.
> 
> 	 We used to allow sharing of MEMs which referenced
> 	 virtual_stack_vars_rtx or virtual_incoming_args_rtx, but
> 	 that can lose.  instantiate_virtual_regs will not unshare
> 	 the MEMs, and combine may change the structure of the address
> 	 because it looks safe and profitable in one context, but
> 	 in some other context it creates unrecognizable RTL.  */
>       if (CONSTANT_ADDRESS_P (XEXP (x, 0)))

Personally I think this is bogus.  IIRC this can cause problems in
rare cases for amd64 where 

	(set (reg) (mem (64-bit-constant))

is valid for reg=%rax, but for a different destination register we
have to reload the constant.  Which causes reload to run into shared
rtl problems.

IMO we should just remove this special case.


r~