Hi,
I removed unsafe loop optimization on TREE level last year, so GCC doesn't do unsafe
loop optimizations on TREE now.  All "unsafe loop optimizations" warnings reported by
TREE optimizers are simply missed optimizations.  This patch turns such warning into
missed optimization messages.  I didn't change when this will be dumped, for now it is
when called from ivopts.
Bootstrap and test on x86_64 and AArch64.  Is it OK?

Thanks,
bin
2017-07-13  Bin Cheng  <bin.cheng@arm.com>

	PR target/81408
	* tree-ssa-loop-niter.c (number_of_iterations_exit): Dump missed
	optimization for loop niter analysis.

gcc/testsuite/ChangeLog
2017-07-13  Bin Cheng  <bin.cheng@arm.com>

	PR target/81408
	* g++.dg/tree-ssa/pr81408.C: New.
	* gcc.dg/tree-ssa/pr19210-1.c: Check dump message rather than warning.