re PR rtl-optimization/70174 (ICE at -O1 and above on x86_64-linux-gnu in gen_lowpart_general, at rtlhooks.c:63)

	PR rtl-optimization/70174
	* expmed.c (store_bit_field_using_insv): Use gen_lowpart_if_possible
	followed by gen_lowpart on force_reg instead of just gen_lowpart.

	* gcc.dg/pr70174.c: New test.

From-SVN: r234137