tree-optimization/88240 - stopgap for floating point code-hoisting issues

tree-optimization/88240 - stopgap for floating point code-hoisting issues

This adds a stopgap measure to avoid performing code-hoisting
on mixed type loads when the load we'd insert in the hoisting
position would be a floating point one.  This is because certain
targets (hello x87) cannot perform floating point loads without
possibly altering the bit representation and thus cannot be used
in place of integral loads.

2020-08-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/88240
	* tree-ssa-sccvn.h (vn_reference_s::punned): New flag.
	* tree-ssa-sccvn.c (vn_reference_insert): Initialize punned.
	(vn_reference_insert_pieces): Likewise.
	(visit_reference_op_call): Likewise.
	(visit_reference_op_load): Track whether a ref was punned.
	* tree-ssa-pre.c (do_hoist_insertion): Refuse to perform hoist
	insertion on punned floating point loads.

	* gcc.target/i386/pr88240.c: New testcase.

(cherry picked from commit 1af5cdd77985daf76130f527deac425c43df9f49)