[Bug target/63234] arm used label is removed

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

--- Comment #7 from Mikael Pettersson <mikpelinux at gmail dot com> ---
The wrong-code started in the 4.7 dev cycle with r183328, a fix for a similar
bug (PR50313) in 4.6.  That fix was backported to 4.6 but doesn't trigger this
PR there (I just re-checked with 4.6.4).

The bug is masked on trunk by r211885, a generic missed-optimization tweak, and
even earlier for Cortex-A9 by a costing tweak in r203828, but I doubt either of
those actually fixes the underlying problem.