The relevant peephole2 will never generate alternative (=m,=&a,0,m) because
operand 1 is not dead before the peephole2 pattern.

gcc/ChangeLog:

* config/i386/i386.md (*stack_protect_set_4s_<mode>_di):
Remove alternative 0.

Bootstrapped and regression tested on x86_64-pc-linux-gnu {,-m32}.

Uros.