re PR sanitizer/64906 (-fsanitize=integer-divide-by-zero creates false -Wmaybe-uninitialized warning)

	PR sanitizer/64906
	* c-ubsan.c (ubsan_instrument_division): Also pre-evaluate OP1.

	* c-c++-common/ubsan/pr64906.c: New test.

From-SVN: r228112