This fixes the case where we try to fold a read from an
array initalizer and happen to cross the boundary of
multiple CTORs which isn't really supported.  For the
interesting cases like the testcase we actually handle
the folding by encoding the whole initializer.

2020-07-10  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/96133
	* gimple-fold.c (fold_array_ctor_reference): Do not
	recurse to folding a CTOR that does not fully cover the
	asked for object.

	* gcc.dg/torture/pr96133.c: New testcase.

(cherry picked from commit 6e41c27bf549d957eb399d39d7d0c213f8733351)