some seemingly redundant register uses in nios gcc compiled assembly code

[Ian Lance Taylor]

Liu Haibin <liu.haibin@gmail.com> writes:

> Does the following rtl implicitly indicate that r5 is used?
> 
> (expr_list (use (reg:DF 6 r6))
>         (expr_list (use (reg:DF 4 r4))

If DFmode requires two registers on your machine--which does appear to
be the case based on the assembly code which you showed--then (use
(reg:DF 4 r4)) does indeed indicate a case of r5.  It indicates a use
of all registers from 4 up to but not including register number
    4 + HARD_REGNO_NREGS (4, DFmode)

Ian