PR tree-optimization/85720

	* tree-loop-distribution.c (break_alias_scc_partitions): Don't merge
	SCC if all partitions are builtins.
	(version_loop_by_alias_check): New parameter.  Generate cancelable
	runtime alias check if all partitions are builtins.
	(distribute_loop): Update call to above function.

	gcc/testsuite
	* gcc.dg/tree-ssa/pr85720.c: New test.
	* gcc.target/i386/avx256-unaligned-store-2.c: Disable loop pattern
	distribution.

From-SVN: r260753