When -stack-clash-protection option is specified and APX push2pop2 is
enabled, there will be two calls to emitSPUpdate function which emits
two STACKALLOC_W_PROBING pseudo instructions. The pseudo instruction for
push2 padding is silently ignored which leads to the stack misaligned to
16 bytes and GP exception in runtime. Fixed by directly emitting "push
%rax" instruction for push2 padding, instead of calling emitSPUpdate.
There was a similar issue on https://reviews.llvm.org/D150033.
b1dcf78378