[PATCH] readelf: Remove show_op_index variable

[Mark Wielaard]

Hi Timm,

On Tue, 2021-02-02 at 11:23 +0100, Timm Bäder via Elfutils-devel wrote:
> advance_pc() uses show_op_index to save whether the current op_index
> is
> > 0 OR the new op_index is > 0.
> 
> The new op index is calculated via
> 
> new_op_index = (op_index + op_advance) % max_ops_per_instr;
> 
> since all of the variables involved are unsigned,
> new_op_index >= op_index is always true.
> 
> So...
> 
> if op_index > 0, then new_op_index > 0
> if op_index == 0, then new_op_index >= 0
> 
> and if the new_op_index is > 0, then the old one was as well.
> 
> In any case, we only need to check the new_op_index, since show_op_index
> used to OR the two comparisons.
> 
> In other words:
> 
>  op_index > 0  |  new_op_index > 0  || show_op_index
>  ------------------------------------------------
>       true           true                true
>      false           true                true
>       true          false                true     xx
>      false          false                false
> 
> ... but since the third line (marked with xx) is not possible,
> the table becomes:
> 
>  op_index > 0  |  new_op_index > 0  || show_op_index
>  ------------------------------------------------
>       true           true                true
>      false           true                true
>      false          false                false
> 
> ... and show_op_index is equal to (new_op_index > 0).
> So, remove the show_op_index variable and simply replace it by comparing
> the new op_index > 0.

Very nice simplification. Thanks for the extensive commit message.

In most cases max_ops_per_instr is actually 1. In which case op_index
will always be zero.

Pushed to trunk.

Thanks,

Mark