Fix ia64 gdb miscompilation reported by Kevin Buettner.

	* combine.c (force_to_mode, case LSHIFTRT): Check that shift shift
	plus mask size is smaller or equal to the mode size.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@33157 138bc75d-0d04-0410-961f-82ee72b054a4