middle-end/101824 - properly handle volatiles in nested fn lowering

middle-end/101824 - properly handle volatiles in nested fn lowering

When we build the COMPONENT_REF of a formerly volatile local off
the FRAME decl we have to make sure to mark the COMPONENT_REF
as TREE_THIS_VOLATILE.  While the GIMPLE operand scanner looks
at the FIELD_DECL this is not how volatile GENERIC refs work.

2021-08-09  Richard Biener  <rguenther@suse.de>

	PR middle-end/101824
	* tree-nested.c (get_frame_field): Mark the COMPONENT_REF as
	volatile in case the variable was.

	* gcc.dg/tree-ssa/pr101824.c: New testcase.