rs6000: Make deallocation of a large frame work (PR77687)

rs6000: Make deallocation of a large frame work (PR77687)

If we use ABI_V4 and we have a big stack frame, we end the epilogue
with a "mr 1,11" (or similar) instruction.  This instruction however
has no dependencies on the earlier restores from stack (done via r11),
so sched2 can end up reordering the insns, which is bad because we
have no red zone so that you then restore from stack that is already
deallocated.

This fixes it by making that restore depend on the memory accesses.

	PR target/77687
	* config/rs6000/rs6000.c (rs6000_emit_stack_reset): Emit the
	stack_restore_tie insn instead of stack_tie, for the SVR4 and
	SPE ABIs.
	* config/rs6000/rs6000.md (stack_restore_tie): New define_insn.

From-SVN: r242949