Comment # 17 on bug 1048861 from Michael Matz

(In reply to Richard Biener from comment #16)
> As was my guess, this is unaligned stack.  Not sure why __strspn_sse42 needs
> to spill, but ...

strspn is implemented as C code, so the compiler spills.  Jon, if you want to
dig further, you can help us in determining which routines has (invalidly)
misaligned the stack pointer.  So the __strspn_sse42 has an %esp which doesn't
have zero as last digit (i.e. it's not 16-byte aligned).  Go upward the call
stack and for each frame upwards print $esp in hex.  So repeat the following
commands and give us the output here:

(gdb) p/x $esp
(gdb) up

(until you reach a frame where 'up' doesn't go further up)