[PATCH VECT]Swap operands for cond_reduction when necessary

[Bin Cheng <Bin dot Cheng at arm dot com>]

Hi,
For stmt defining reduction, GCC vectorizer assumes that the reduction variable is always the last (second) operand.  Another fact is that vectorizer doesn't swap operands for cond_reduction during analysis stage.  The problem is GCC middle-end may canonicalize cond_expr into a form that reduction variable is not the last one.  At the moment, such case cannot be vectorized.
The patch fixes this issue by swapping operands in cond_reduction when it's necessary.  The patch also swaps it back if vectorization fails.  The patch resolves failures introduced by previous match.pd patches.  In addition, couple cases are XPASSed on AArch64 now, which means more loops are vectorized.  I will send following patch addressing those XPASS tests.
Bootstrap and test on x86_64 and AArch64 ongoing, is it OK?

Thanks,
bin

2016-10-25  Bin Cheng  <bin.cheng@arm.com>

	* tree-vect-loop.c (destroy_loop_vec_info): Handle cond_expr.
	(vect_is_simple_reduction): Swap cond_reduction by inversion.

Attachment: vect-swap-cond_reduction-20161024.txt
Description: vect-swap-cond_reduction-20161024.txt