re PR rtl-optimization/7130 (miscompiled code for gcc-3.1 on powerpc-unknown-linux-gnu with -funroll-all-loops)

	PR optimization/7130
	* loop.h (struct loop_info): Add "preconditioned".
	* unroll.c (unroll_loop): Set it.
	* doloop.c (doloop_modify_runtime): Correct count for unrolled loops.

From-SVN: r55598