Hi,
This patch fixes PR81832.  Root cause for the ICE is:
  1) Loop has distributed inner loop.
  2) The guarding function call IFN_LOOP_DIST_CALL happens to be in loop's header.
  3) IFN_LOOP_DIST_CALL (int loop's header) is duplicated by pass_ch_vect thus
     not eliminated.

Given pass_ch_vect copies loop header to enable more vectorization, we should
skip loop in this case because distributed inner loop means this loop can not
be vectorized anyway.  One point to mention is name inner_loop_distributed_p
is a little misleading.  The name indicates that each basic block is checked,
but the patch only checks loop's header for simplicity/efficiency's purpose.
Any comment?
Bootstrap and test on x86_64.

Thanks,
bin
2017-08-15  Bin Cheng  <bin.cheng@arm.com>

	PR tree-optimization/81832
	* tree-ssa-loop-ch.c (inner_loop_distributed_p): New function.
	(pass_ch_vect::process_loop_p): Call above function.

gcc/testsuite
2017-08-15  Bin Cheng  <bin.cheng@arm.com>

	PR tree-optimization/81832
	* gcc.dg/tree-ssa/pr81832.c: New test.