re PR c/80097 (internal compiler error in c_fully_fold_internal with std=c89 and -fsanitize=float-divide-by-zero)

	PR c/80097
	* c-typeck.c (build_binary_op): Add EXCESS_PRECISION_EXPR only around
	optional COMPOUND_EXPR with ubsan instrumentation.

	* gcc.dg/ubsan/pr80097.c: New test.

From-SVN: r246302