backport: re PR rtl-optimization/7130 (miscompiled code for gcc-3.1 on powerpc-unknow...

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

	Merge from mainline.
	2002-07-20  Alan Modra  <amodra@bigpond.net.au>
	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.

	2002-06-24  Alan Modra  <amodra@bigpond.net.au>
	PR optimization/6984
	* doloop.c (doloop_valid_p): Correct comment.
	(doloop_modify_runtime <abs_inc != 1>): Simplify.
	(doloop_modify_runtime <do-while>): Don't emit code when NE.

From-SVN: r57225