Hi All, Here is the second patch related to extended predication. Few comments which explain a main goal of design.
1. I don't want to insert any critical edge splitting since it may
lead to less efficient binaries.
2. One special case of extended PHI node predication was introduced
when #arguments is more than 2 but only two arguments are different
and one argument has the only occurrence. For such PHI conditional
scalar reduction is applied.
This is correspondent to the following statement:
if (q1 && q2 && q3) var++
New function phi_has_two_different_args was introduced to detect such phi.
3. Original algorithm for PHI predication used assumption that at
least one incoming edge for blocks containing PHI is not critical - it
guarantees that all computations related to predicate of normal edge
are already inserted above this block and
code related to PHI predication can be inserted at the beginning of
block. But this is not true for critical edges for which predicate
computations are in the block where code for phi predication must be
inserted. So new function find_insertion_point is introduced which is
simply found out the last statement in block defining predicates
correspondent to all incoming edges and insert phi predication code
after it (with some minor exceptions).
ChangeLog:
2014-10-24 Yuri Rumyantsev <ysrum...@gmail.com>
* tree-if-conv.c (ifcvt_can_use_mask_load_store): Use
FLAG_FORCE_VECTORIZE instead of loop flag.
(if_convertible_bb_p): Allow bb has more than 2 predecessors if
FLAG_FORCE_VECTORIZE is true.
(if_convertible_bb_p): Delete check that bb has at least one
non-critical incoming edge.
(phi_has_two_different_args): New function.
(is_cond_scalar_reduction): Add argument EXTENDED to choose access
to phi arguments. Invoke phi_has_two_different_args to get phi
arguments if EXTENDED is true. Change check that block
containing reduction statement candidate is predecessor
of phi-block since phi may have more than two arguments.
(convert_scalar_cond_reduction): Add argument BEFORE to insert
statement before/after gsi point.
(predicate_scalar_phi): Add argument false (which means non-extended
predication) to call of is_cond_scalar_reduction. Add argument
true (which correspondent to argument BEFORE) to call of
convert_scalar_cond_reduction.
(get_predicate_for_edge): New function.
(predicate_arbitrary_scalar_phi): New function.
(predicate_extended_scalar_phi): New function.
(find_insertion_point): New function.
(predicate_all_scalar_phis): Add two boolean variables EXTENDED and
BEFORE. Initialize EXTENDED to true if BB containing phi has more
than 2 predecessors or both incoming edges are critical. Invoke
find_phi_replacement_condition and predicate_scalar_phi or
find_insertion_point and predicate_extended_scalar_phi depending on
EXTENDED value.
(insert_gimplified_predicates): Add check that non-predicated block
may have statements to insert. Insert predicate of BB just after label
if FLAG_FORCE_VECTORIZE is true.
(tree_if_conversion): Add initialization of FLAG_FORCE_VECTORIZE which
is copy of inner or outer loop field force_vectorize.
if-conv.patch2
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