https://bugs.freedesktop.org/show_bug.cgi?id=93936
--- Comment #5 from Gert Wollny gw.fossdev@gmail.com --- Some new register allocation in TGSI landed in v17.3 and was later further improved. Could you recheck with version 17.3+ or, if that doesn't work, with the current git?
On AMD 5450 and 6870 it works (the register limit is the same).