Some aliasing questions

Richard Biener rguenther@suse.de
Tue Apr 12 15:50:00 GMT 2016


On April 12, 2016 5:11:45 PM GMT+02:00, Richard Henderson <rth@redhat.com> wrote:
>On 04/11/2016 05:30 PM, Alan Modra wrote:
>> Either way, when we split to
>> 	set (reg tmp) (high (const (minus ((symbol_ref) (reg 2)))))
>> 	.. mem (lo_sum (reg tmp) (const (minus ((symbol_ref) (reg 2)))))
>> both high and lo_sum reference r2 and the linker could happily
>replace
>> rtmp in the lo_sum insn with r2 when the high address is known to be
>> zero.
>
>It would be interesting to see if the r2 reference in fact gets picked
>up 
>inside the const.  My first reaction is that I could imagine tracking
>skipping 
>over it completely, since we've been promised that the expression is
>constant.
>
>Alternately, perhaps alias.c should reuse the existing
>delegitimize_address 
>hook, allowing it to look through your current unspecs.

Wouldn't that be quite expensive (building RTL)?

Richard.
>
>r~




More information about the Gcc mailing list