Possible bug in xlaqz0

[thijssteel]

Description

Line 681 in dlaqz0 https://github.com/Reference-LAPACK/lapack/blob/master/SRC/dlaqz0.f#L681

calculates the position of the shifts as SHIFTPOS = ISTOP-N_DEFLATED-N_UNDEFLATED+1
However, ISTOP has already been updated on line 665.

I will investigate further when I have some spare time.

Checklist

• I've included a minimal example to reproduce the issue
• [x ] I'd be willing to make a PR to solve this issue