Fix PR46932: Block auto increment on frame pointer

Fix PR46932: Block auto increment on frame pointer

Block auto increment on frame pointer references.  This is never
beneficial since the SFP expands into SP+C or FP+C during register
allocation.  The generated code for the testcase is now as expected:

	str	x30, [sp, -32]!
	strb	w0, [sp, 31]
	add	x0, sp, 31
	bl	foo3
	ldr	x30, [sp], 32
	ret

    gcc/
	PR middle-end/46932
	* auto-inc-dec.c (parse_add_or_inc): Block autoinc on sfp.

    gcc/testsuite/
	PR middle-end/46932
	* gcc.dg/pr46932.c: New testcase.

From-SVN: r250564