[PATCH VECT]Support operand swapping for cond_expr in vect_slp

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

Hi,
During analysis, vect_slp checks if statements of a group are isomorphic to each other, specifically, all statements have to be isomorphic to the first one.  Apparently, operands of commutative operators (PLUS_EXPR/MINUS_EXPR etc.) could be swapped when checking isomorphic property.  Though vect_slp has basic support for such commutative operators, the related code is not properly implemented:
  1) vect_build_slp_tree mixes operand swapping in the current slp tree node and operand swapping in its child slp tree nodes.
  2) Operand swapping in the current slp tree is incorrect when vect_get_and_check_slp_defs has already committed to a fixed operand order.
In addition, operand swapping for COND_EXPR is implemented in a wrong way (place) because:
  3) vect_get_and_check_slp_defs swaps operands for COND_EXPR by changing comparison code after vect_build_slp_tree_1 checks the code consistency for the statement group.
  4) vect_build_slp_tree_1 should support operand swapping for COND_EXPR while it doesn't.

This patch addresses above issues.  It supports COND_EXPR by recording swapping information in vect_build_slp_tree_1 and applies the swap in vect_get_check_slp_defs.  It supports two types swapping: swapping and inverting.  The patch also does refactoring so that operand swapping in child slp tree node and the current slp tree node are differentiated.  With this patch, failures (gcc.dg/vect/slp-cond-3.c) revealed by previous COND_EXPR match.pd patches are resolved.
Bootstrap and test on x86_64 and AArch64.  Is it OK?

Thanks,
bin

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

	* tree-vect-slp.c (vect_get_and_check_slp_defs): New parameter SWAP.
	Check slp defs for COND_EXPR by swapping/inverting operands if
	indicated by the new parameter SWAP.
	(vect_build_slp_tree_1): New parameter SWAP.  Check COND_EXPR stmt
	is isomorphic to the first stmt via swapping/inverting.  Store swap
	information in the new parameter SWAP.
	(vect_build_slp_tree): New local array SWAP and pass it to function
	vect_build_slp_tree_1.  Cleanup result handlding code for function
	call to vect_get_and_check_slp_defs.  Skip oeprand swapping if the
	order of operands has been fixed as indicated by SWAP[i].

Attachment: slp-swap-cond_expr-20161024.txt
Description: slp-swap-cond_expr-20161024.txt