re PR c++/70295 (bogus -Wnonnull-compare for "dynamic_cast<const FuSelection *>(this...

re PR c++/70295 (bogus -Wnonnull-compare for "dynamic_cast<const FuSelection *>(this) != nullptr")

	PR c++/70295
	* gimplify.c (gimplify_modify_expr): Call gimple_set_no_warning
	on assign if (*from_p) is a comparison, set it to
	TREE_NO_WARNING (*from_p).

	* c-c++-common/nonnull-1.c (func): Remove parens around cp4 != 0.
	(func2): New function for cond with parens, xfail warning for c++.
	* g++.dg/warn/Wnonnull-compare-8.C: New test.

From-SVN: r234392