middle-end/100786 - constant folding from incompatible alias

middle-end/100786 - constant folding from incompatible alias

The following avoids us ICEing doing constant folding from variables
with aliases of different types.  The issue appears both in
folding and CCP and FRE can do more fancy stuff to still constant
fold cases where the load is smaller than the initializer so
defer it to there.

2022-01-20  Richard Biener  <rguenther@suse.de>

	PR middle-end/100786
	* gimple-fold.c (get_symbol_constant_value): Only return
	values of compatible type to the symbol.

	* gcc.dg/torture/pr100786.c: New testcase.

(cherry picked from commit 5c12507f5d0bc080e4f346af99824e039236e61c)