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Re: [PATCH,1/2] Extended if-conversion for loops marked with pragma omp simd.


On Thu, Oct 16, 2014 at 5:42 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
> Richard,
>
> Here is reduced patch as you requested. All your remarks have been fixed.
> Could you please look at it ( I have already sent the patch with
> changes in add_to_predicate_list for review).

+             if (dump_file && (dump_flags & TDF_DETAILS))
+               fprintf (dump_file, "More than two phi node args.\n");
+             return false;
+           }
+
+        }

Excess vertical space.


+/* Assumes that BB has more than 2 predecessors.

More than 1 predecessor?

+   Returns false if at least one successor is not on critical edge
+   and true otherwise.  */
+
+static inline bool
+all_edges_are_critical (basic_block bb)
+{

"all_preds_critical_p" would be a better name

+  if (EDGE_COUNT (bb->preds) > 2)
+    {
+      if (!flag_force_vectorize)
+       return false;
+    }

as I said in the last review I don't think we should restrict edge
predicates to flag_force_vectorize.  At least I can't see how
if-conversion is magically more expensive for that case?

So please rework the patch so critical edges are always handled
correctly.

Ok with that and the above suggested changes.

Thanks,
Richard.


> Thanks.
> Yuri.
> ChangeLog
> 2014-10-16  Yuri Rumyantsev  <ysrumyan@gmail.com>
>
> (flag_force_vectorize): New variable.
> (edge_predicate): New function.
> (set_edge_predicate): New function.
> (add_to_dst_predicate_list): Conditionally invoke add_to_predicate_list
> if destination block of edge is not always executed. Set-up predicate
> for critical edge.
> (if_convertible_phi_p): Accept phi nodes with more than two args
> if FLAG_FORCE_VECTORIZE was set-up.
> (ifcvt_can_use_mask_load_store): Use FLAG_FORCE_VECTORIZE.
> (if_convertible_stmt_p): Fix up pre-function comments.
> (all_edges_are_critical): New function.
> (if_convertible_bb_p): Allow bb has more than two predecessors if
> FLAG_FORCE_VECTORIZE was set-up. Use call of all_edges_are_critical
> to reject block if-conversion with incoming critical edges only if
> FLAG_FORCE_VECTORIZE was not set-up.
> (predicate_bbs): Skip loop exit block also.Invoke build2_loc
> to compute predicate instead of fold_build2_loc.
> Add zeroing of edge 'aux' field.
> (find_phi_replacement_condition): Extend function interface:
> it returns NULL if given phi node must be handled by means of
> extended phi node predication. If number of predecessors of phi-block
> is equal 2 and atleast one incoming edge is not critical original
> algorithm is used.
> (tree_if_conversion): Temporary set-up FLAG_FORCE_VECTORIZE to false.
> Nullify 'aux' field of edges for blocks with two successors.
>
>
>
> 2014-10-15 13:50 GMT+04:00 Richard Biener <richard.guenther@gmail.com>:
>> On Mon, Oct 13, 2014 at 11:38 AM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>> Richard,
>>>
>>> Here is updated patch (part1) for extended if conversion.
>>>
>>> Second part of patch will be sent later.
>>
>> Ok, I'm starting to look at this.  I'd still like you to split things up
>> more.
>>
>>  static inline void
>>  add_to_predicate_list (struct loop *loop, basic_block bb, tree nc)
>>  {
>> ...
>>
>> +      /* We use notion of cd equivalence to get simplier predicate for
>> +        join block, e.g. if join block has 2 predecessors with predicates
>> +        p1 & p2 and p1 & !p2, we'd like to get p1 for it instead of
>> +        p1 & p2 | p1 & !p2.  */
>> +      if (dom_bb != loop->header
>> +         && get_immediate_dominator (CDI_POST_DOMINATORS, dom_bb) == bb)
>> +       {
>> +         gcc_assert (flow_bb_inside_loop_p (loop, dom_bb));
>> +         bc = bb_predicate (dom_bb);
>> +         gcc_assert (!is_true_predicate (bc));
>>
>> these changes look worthwhile even for !flag_force_vectorize.  So please
>> split the change to add_to_predicate_list out and compute post-dominators
>> unconditionally.  Note that you should call free_dominance_info
>> (CDI_POST_DOMINATORS) at the end of if-conversion.
>>
>> +  if (!dominated_by_p (CDI_DOMINATORS, loop->latch, e->dest))
>> +    add_to_predicate_list (loop, e->dest, cond);
>> +
>> +  /* If edge E is critical save predicate on it.  */
>> +  if (EDGE_COUNT (e->dest->preds) >= 2)
>> +    set_edge_predicate (e, cond);
>>
>> how do we know the edge is critical by this simple check?  Why not
>> simply always save edge predicates (well, you kind of do but omit
>> the case where e->src dominates e->dest).
>>
>> Btw, you can rely on edge->aux being NULL at the start of the
>> pass but need to clear it at the end (best use clear_aux_for_edges ()
>> for that).  So stuff like
>>
>> +         extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
>> +         if (flag_force_vectorize)
>> +           true_edge->aux = false_edge->aux = NULL;
>>
>> shouldn't be necessary.
>>
>> I think the edge predicate handling should also be unconditionally
>> and not depend on flag_force_vectorize.
>>
>> +      /* The loop latch and loop exit block are always executed and
>> +        have no extra conditions to be processed: skip them.  */
>> +      if (bb == loop->latch
>> +         || bb_with_exit_edge_p (loop, bb))
>>
>> I don't think the edge stuff is true - given you still only reset the
>> loop->latch bb predicate the change looks broken.
>>
>> +         /* Fold_build2 can produce bool conversion which is not
>> +             supported by vectorizer, so re-build it without folding.
>> +            For example, such conversion is generated for sequence:
>> +               _Bool _7, _8, _9;
>> +               _7 = _6 != 13; _8 = _6 != 0; _9 = _8 & _9;
>> +               if (_9 != 0)  --> (bool)_9.  */
>> +
>> +         if (CONVERT_EXPR_P (c)
>> +             && TREE_CODE_CLASS (code) == tcc_comparison)
>>
>> I think you should simply use canonicalize_cond_expr_cond on the
>> folding result.  Or rather _not_ fold at all - we are taking the
>> operands from the GIMPLE condition unmodified after all.
>>
>> -         add_to_dst_predicate_list (loop, false_edge,
>> -                                    unshare_expr (cond), c2);
>> +         add_to_dst_predicate_list (loop, false_edge, unshare_expr (cond),
>> +                                    unshare_expr (c2));
>>
>> why is it necessary to unshare c2?
>>
>> Please split out the PHI-with-multi-arg handling  (I have not looked at
>> that in detail).
>>
>> Thanks,
>> Richard.
>>
>>
>>> Changelog.
>>>
>>> 2014-10-13  Yuri Rumyantsev  <ysrumyan@gmail.com>
>>>
>>> * tree-if-conv.c (cgraph.h): Add include file to detect function clone.
>>> (flag_force_vectorize): New variable.
>>> (edge_predicate): New function.
>>> (set_edge_predicate): New function.
>>> (add_to_predicate_list): Check unconditionally that bb is always
>>> executed to early exit. Use predicate of cd-equivalent block
>>> for join blocks if it exists.
>>> (add_to_dst_predicate_list): Invoke add_to_predicate_list if
>>> destination block of edge is not always executed. Set-up predicate
>>> for critical edge.
>>> (if_convertible_phi_p): Accept phi nodes with more than two args
>>> if FLAG_FORCE_VECTORIZE was set-up.
>>> (ifcvt_can_use_mask_load_store): Use FLAG_FORCE_VECTORIZE.
>>> (if_convertible_stmt_p): Fix up pre-function comments.
>>> (all_edges_are_critical): New function.
>>> (if_convertible_bb_p): Allow bb has more than two predecessors if
>>> FLAG_FORCE_VECTORIZE was set-up. Use call of all_edges_are_critical
>>> to reject block if-conversion with incoming critical edges only if
>>> FLAG_FORCE_VECTORIZE was not set-up.
>>> (predicate_bbs): Skip loop exit block also. Add check that if
>>> fold_build2 produces bool conversion, recompute predicate using
>>> build2_loc. Add zeroing of edge 'aux' field under FLAG_FORCE_VECTORIZE.
>>> (if_convertible_loop_p_1): Recompute POST_DOMINATOR tree if
>>> FLAG_FORCE_VECTORIZE was set-up to calculate cd equivalent bb's.
>>> (find_phi_replacement_condition): Extend function interface:
>>> it returns NULL if given phi node must be handled by means of
>>> extended phi node predication. If number of predecessors of phi-block
>>> is equal 2 and atleast one incoming edge is not critical original
>>> algorithm is used.
>>> (get_predicate_for_edge): New function.
>>> (find_insertion_point): New function.
>>> (predicate_arbitrary_scalar_phi): New function.
>>> (predicate_all_scalar_phis): Introduce new variable BEFORE.
>>> Invoke find_insertion_point to initialize gsi and
>>> predicate_arbitrary_scalar_phi if TRUE_BB is NULL - it signals
>>> that extended predication must be applied).
>>> (insert_gimplified_predicates): Add test for non-predicated basic
>>> blocks that there are no gimplified statements to insert. Insert
>>> predicates at the block begining for extended if-conversion.
>>> (tree_if_conversion): Initialize flag_force_vectorize from current
>>> loop or outer loop (to support pragma omp declare).Do loop versioning
>>> for innermost loop marked with pragma omp simd and
>>> FLAG_TREE_LOOP_IF_CONVERT was not sett-up. Nullify 'aux' field of edges
>>> for blocks with two successors.
>>>
>>>
>>>
>>>
>>> 2014-09-22 12:28 GMT+04:00 Yuri Rumyantsev <ysrumyan@gmail.com>:
>>>> Richard,
>>>>
>>>> here is reduced patch (part.1) which was reduced almost twice.
>>>> Let's me also answer on your comments.
>>>>
>>>> 1. I really use edge field 'aux' to keep predicate for critical edges.
>>>> My previous code was not correct and now it looks like:
>>>>
>>>>   if (EDGE_COUNT (b->succs) == 1 || EDGE_COUNT (e->dest->preds) == 1)
>>>>     /* Edge E is not critical,  use predicate of edge source bb. */
>>>>     c = bb_predicate (b);
>>>>   else
>>>>     /* Edge E is critical and its aux field contains predicate.  */
>>>>     c = edge_predicate (e);
>>>>
>>>> 2. I completely delete all code related to creation of conditional
>>>> expressions and completely rely on bool pattern recognition in
>>>> vectorizer. But we need to delete all dead predicate computations
>>>> which are not used since they prevent vectorization. I will add this
>>>> local-dce function in next patch.
>>>> 3. I also did not include in this patch recognition of general
>>>> phi-nodes with two arguments only for which conversion of conditional
>>>> scalar reduction can be applied also.
>>>> Note that all these changes are applied for loop marked with pragma
>>>> omp simd only.
>>>>
>>>> 2014-09-22  Yuri Rumyantsev  <ysrumyan@gmail.com>
>>>>
>>>> * tree-if-conv.c (cgraph.h): Add include file to detect function clone.
>>>> (flag_force_vectorize): New variable.
>>>> (edge_predicate): New function.
>>>> (set_edge_predicate): New function.
>>>> (convert_name_to_cmp): New function.
>>>> (add_to_predicate_list): Check unconditionally that bb is always
>>>> executed to early exit. Use predicate of cd-equivalent block
>>>> for join blocks if it exists.
>>>> (add_to_dst_predicate_list): Invoke add_to_predicate_list if
>>>> destination block of edge is not always executed. Set-up predicate
>>>> for critical edge.
>>>> (if_convertible_phi_p): Accept phi nodes with more than two args
>>>> if FLAG_FORCE_VECTORIZE was set-up.
>>>> (ifcvt_can_use_mask_load_store): Use FLAG_FORCE_VECTORIZE.
>>>> (if_convertible_stmt_p): Fix up pre-function comments.
>>>> (all_edges_are_critical): New function.
>>>> (if_convertible_bb_p): Allow bb has more than two predecessors if
>>>> FLAG_FORCE_VECTORIZE was set-up. Use call of all_edges_are_critical
>>>> to reject block if-conversion with incoming critical edges only if
>>>> FLAG_FORCE_VECTORIZE was not set-up.
>>>> (predicate_bbs): Skip loop exit block also. Add check that if
>>>> fold_build2 produces bool conversion, recompute predicate using
>>>> build2_loc. Add zeroing of edge 'aux' field under FLAG_FORCE_VECTORIZE.
>>>> (if_convertible_loop_p_1): Recompute POST_DOMINATOR tree if
>>>> FLAG_FORCE_VECTORIZE was set-up to calculate cd equivalent bb's.
>>>> (find_phi_replacement_condition): Extend function interface:
>>>> it returns NULL if given phi node must be handled by means of
>>>> extended phi node predication. If number of predecessors of phi-block
>>>> is equal 2 and atleast one incoming edge is not critical original
>>>> algorithm is used.
>>>> (get_predicate_for_edge): New function.
>>>> (find_insertion_point): New function.
>>>> (predicate_arbitrary_scalar_phi): New function.
>>>> (predicate_all_scalar_phis): Introduce new variable BEFORE.
>>>> Invoke find_insertion_point to initialize gsi and
>>>> predicate_arbitrary_scalar_phi if TRUE_BB is NULL - it signals
>>>> that extended predication must be applied).
>>>> (insert_gimplified_predicates): Add test for non-predicated basic
>>>> blocks that there are no gimplified statements to insert. Insert
>>>> predicates at the block begining for extended if-conversion.
>>>> (tree_if_conversion): Initialize flag_force_vectorize from current
>>>> loop or outer loop (to support pragma omp declare).Do loop versioning
>>>> for innermost loop marked with pragma omp simd and
>>>> FLAG_TREE_LOOP_IF_CONVERT was not sett-up. Nullify 'aux' field of edges
>>>> for blocks with two successors.
>>>>
>>>>
>>>>
>>>>
>>>> 2014-09-08 17:10 GMT+04:00 Richard Biener <richard.guenther@gmail.com>:
>>>>> On Fri, Aug 15, 2014 at 2:02 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>> Richard!
>>>>>> Here is updated patch with the following changes:
>>>>>>
>>>>>> 1. Any restrictions on phi-function were eliminated for extended conversion.
>>>>>> 2.  Put predicate for critical edges to 'aux' field of edge, i.e.
>>>>>> negate_predicate was deleted.
>>>>>> 3. Deleted splitting of critical edges, i.e. both outgoing edges can
>>>>>> be critical.
>>>>>> 4. Use notion of cd-equivalence to set-up predicate for join basic
>>>>>> blocks to simplify it.
>>>>>> 5. I decided to not design pre-pass since it will lead generating
>>>>>> chain of cond expressions for phi-node if conversion, whereas for phi
>>>>>> of kind
>>>>>>   x = PHI <1(2), 1(3), 2(4)>
>>>>>> only one cond expression is required and this is considered as simple
>>>>>> optimization for arbitrary phi-function. More precise,
>>>>>> if phi-function have only two different arguments and one of them has
>>>>>> single occurrence, if- conversion is performed as if phi have only 2
>>>>>> arguments.
>>>>>> For arbitrary phi function a chain of cond expressions is produced.
>>>>>>
>>>>>> Updated patch is attached.
>>>>>>
>>>>>> Any comments will be appreciated.
>>>>>
>>>>> The patch is still very big and does multiple things at once which makes
>>>>> it hard to review.
>>>>>
>>>>> In addition to that it changes function singatures without updating
>>>>> the function comments.  For example what is the convert_bool
>>>>> argument doing to add_to_dst_predicate_list?  Why do we need
>>>>> all this added logic.
>>>>>
>>>>> You duplicate operand_equal_for_phi_arg_p.
>>>>>
>>>>> I think the code handling PHIs with more than two operands but
>>>>> only two unequal operands is useful generally, so that's an obvious
>>>>> candidate for splitting out into a separate patch.
>>>>>
>>>>> +   CONVERT_BOOL argument was added to convert bool predicate computations
>>>>> +   which is not supported by vectorizer to int type through creating of
>>>>> +   conditional expressions.  */
>>>>>
>>>>> Example?  The vectorizer has patterns for bool predicate computations.
>>>>> This seems to be another feature that needs splitting out.
>>>>>
>>>>> The way you get around the critical edge parts looks awkward to me.
>>>>> Please either do _all_ predicates as edge predicates or simply
>>>>> split critical edges (of the respective loop body).
>>>>>
>>>>> I still think that an utility doing same PHI arg merging by introducing
>>>>> forwarder blocks would be nicer to have.
>>>>>
>>>>> I'd restructure the main tree_if_conversion function to apply these
>>>>> CFG pre-transforms when we are going to version the loop
>>>>> for if conversion (eventually transitioning to always doing that).
>>>>>
>>>>> So - please split up the patch.  It's way too big.
>>>>>
>>>>> Thanks,
>>>>> Richard.
>>>>>
>>>>>> 2014-08-15  Yuri Rumyantsev  <ysrumyan@gmail.com>
>>>>>>
>>>>>> * tree-if-conv.c (cgraph.h): Add include file to detect function clone.
>>>>>> (flag_force_vectorize): New variable.
>>>>>> (edge_predicate): New function.
>>>>>> (set_edge_predicate): New function.
>>>>>> (add_stmt_to_bb_predicate_gimplified_stmts): New function.
>>>>>> (init_bb_predicate): Add initialization of negate_predicate field.
>>>>>> (reset_bb_predicate): Reset negate_predicate to NULL_TREE.
>>>>>> (convert_name_to_cmp): New function.
>>>>>> (get_type_for_cond): New function.
>>>>>> (convert_bool_predicate): New function.
>>>>>> (predicate_disjunction): New function.
>>>>>> (predicate_conjunction): New function.
>>>>>> (add_to_predicate_list): Add convert_bool argument.
>>>>>> Use predicate of cd-equivalent block if convert_bool is true and
>>>>>> such bb exists; save it in static variable for further possible use.
>>>>>> Add call of predicate_disjunction if convert_bool argument is true.
>>>>>> (add_to_dst_predicate_list): Add convert_bool argument.
>>>>>> Add early function exit if edge target block is always executed.
>>>>>> Add call of predicate_conjunction if convert_bool argument is true.
>>>>>> Pass convert_bool argument for add_to_predicate_list.
>>>>>> Set-up predicate for crritical edge if convert_bool is true.
>>>>>> (equal_phi_args): New function.
>>>>>> (phi_has_two_different_args): New function.
>>>>>> (if_convertible_phi_p): Accept phi nodes with more than two args
>>>>>> if flag_force_vectorize wa set-up.
>>>>>> (ifcvt_can_use_mask_load_store): Add test on flag_force_vectorize.
>>>>>> (if_convertible_stmt_p): Allow calls of function clones if
>>>>>> flag_force_vectorize was set-up.
>>>>>> (all_edges_are_critical): New function.
>>>>>> (if_convertible_bb_p): Allow bb has more than two predecessors if
>>>>>> flag_force_vectorize was set-up. Use call of all_edges_are_critical
>>>>>> to reject block if-conversion with imcoming critical edges only if
>>>>>> flag_force_vectorize was not set-up.
>>>>>> (walk_cond_tree): New function.
>>>>>> (vect_bool_pattern_is_applicable): New function.
>>>>>> (predicate_bbs): Add convert_bool argument which is used to transform
>>>>>> comparison expressions of boolean type into conditional expressions
>>>>>> with integral operands. If convert_bool argument was set-up and
>>>>>> vect bool pattern can be appied perform the following transformation:
>>>>>> (bool) x != 0  --> y = (int) x; x != 0;
>>>>>> Add check that if fold_build2 produces bool conversion if convert_bool
>>>>>> was set-up, recompute predicate using build2_loc. Additional argument
>>>>>> 'convert_bool" is passed to add_to_dst_predicate_list and
>>>>>> add_to_predicate_list.
>>>>>> (if_convertible_loop_p_1): Recompute POST_DOMINATOR tree if
>>>>>> flag_force_vectorize was set-up to calculate cd equivalent bb's.
>>>>>> Call predicate_bbs with additional argument equal to false.
>>>>>> (find_phi_replacement_condition): Extend function interface:
>>>>>> it returns NULL if given phi node must be handled by means of
>>>>>> extended phi node predication. If number of predecessors of phi-block
>>>>>> is equal 2 and atleast one incoming edge is not critical original
>>>>>> algorithm is used.
>>>>>> (is_cond_scalar_reduction): Add 'extended' argument which signals that
>>>>>> phi arguments must be evaluated through phi_has_two_different_args.
>>>>>> (predicate_scalar_phi): Add invoÑation of convert_name_to_cmp if cond
>>>>>> is SSA_NAME. Add 'false' argument to call of is_cond_scalar_reduction.
>>>>>> (get_predicate_for_edge): New function.
>>>>>> (find_insertion_point): New function.
>>>>>> (predicate_arbitrary_phi): New function.
>>>>>> (predicate_extended_scalar_phi): New function.
>>>>>> (predicate_all_scalar_phis): Add code to set-up gimple statement
>>>>>> iterator for predication of extended scalar phi's for insertion.
>>>>>> (insert_gimplified_predicates): Add test for non-predicated basic
>>>>>> blocks that there are no gimplified statements to insert. Insert
>>>>>> predicates at the block begining for extended if-conversion.
>>>>>> (predicate_mem_writes): Invoke convert_name_to_cmp for extended
>>>>>> predication to build mask.
>>>>>> (combine_blocks): Pass flag_force_vectorize to predicate_bbs.
>>>>>> (tree_if_conversion): Initialize flag_force_vectorize from current
>>>>>> loop or outer loop (to support pragma omp declare).Do loop versioning
>>>>>> for innermost loop marked with pragma omp simd.
>>>>>>
>>>>>> 2014-08-01 13:40 GMT+04:00 Richard Biener <richard.guenther@gmail.com>:
>>>>>>> On Wed, Jun 25, 2014 at 4:06 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>>>> Hi All,
>>>>>>>>
>>>>>>>> We implemented additional support for pragma omp simd in part of
>>>>>>>> extended if-conversion loops with such pragma. These extensions
>>>>>>>> include:
>>>>>>>>
>>>>>>>> 1. All extensions are performed only if considered loop or its outer
>>>>>>>>    loop was marked with pragma omp simd (force_vectorize); For ordinary
>>>>>>>>    loops behavior was not changed.
>>>>>>>> 2. Took off cfg restriction on basic block which can have more than 2
>>>>>>>>    predecessors.
>>>>>>>> 3. Put additional restriction on phi nodes which was missed in current design:
>>>>>>>>    all phi nodes must be in non-predicated basic block to conform
>>>>>>>>    semantic of COND_EXPR which is used for transformation.
>>>>>>>
>>>>>>> How is that so?  If the PHI is predicated then its result will be used
>>>>>>> in a PHI node again and thus we'd create a sequence of COND_EXPRs.
>>>>>>>
>>>>>>> No?
>>>>>>>
>>>>>>>> 4. Extend predication of phi nodes: phi may have more than 2 arguments
>>>>>>>> with some limitations:
>>>>>>>>    - for phi nodes which have more than 2 arguments, but only two
>>>>>>>>    arguments are different and one of them has the only occurence,
>>>>>>>> transformation to  single COND_EXPR can be done.
>>>>>>>>    - if phi node has more different arguments and all edge predicates
>>>>>>>>    correspondent to phi-arguments are disjoint, a chain of COND_EXPR
>>>>>>>>    will be generated for it. In current design very simple check is used:
>>>>>>>>    check starting from end that two edges correspondent to neighbor
>>>>>>>> arguments have common predecessor which is used for further check
>>>>>>>> with next edge.
>>>>>>>>  These guarantee that phi predication will produce the correct result.
>>>>>>>
>>>>>>> Btw, you can think of these extensions as unfactoring a PHI node by
>>>>>>> inserting forwarder blocks.  Thus
>>>>>>>
>>>>>>>    x = PHI <1(2), 1(3), 2(4)>
>>>>>>>
>>>>>>> becomes
>>>>>>>
>>>>>>>   bb 5: <forwarder-from(2)-and(3)>
>>>>>>>
>>>>>>>   x = PHI <1(5), 2(4)>
>>>>>>>
>>>>>>> and
>>>>>>>
>>>>>>>   x = PHI <1(2), 2(3), 3(4)>
>>>>>>>
>>>>>>> becomes
>>>>>>>
>>>>>>>   bb 5:
>>>>>>>   x' = PHI <1(2), 2(3)>
>>>>>>>
>>>>>>>   b = PHI<x'(5), 3(4)>
>>>>>>>
>>>>>>> which means that 3) has to work.  Note that we want this kind of
>>>>>>> PHI transforms for out-of-SSA as well to reduce the number of
>>>>>>> copies we need to insert on edges.
>>>>>>>
>>>>>>> Thus it would be nice if you implemented 4) in terms of a pre-pass
>>>>>>> over the force_vect loops PHI nodes, applying that CFG transform.
>>>>>>> And make 3) work properly if it doesn't already.
>>>>>>>
>>>>>>> It looks like you introduce a "negate predicate" to work around the
>>>>>>> critical edge limitation?  Please instead change if-conversion to
>>>>>>> work with edge predicates (as opposed to BB predicates).
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Richard.
>>>>>>>
>>>>>>>>
>>>>>>>> Here is example of such extended predication (compile with -march=core-avx2):
>>>>>>>> #pragma omp simd safelen(8)
>>>>>>>>   for (i=0; i<512; i++)
>>>>>>>>   {
>>>>>>>>     float t = a[i];
>>>>>>>>     if (t > 0 & t < 1.0e+17f)
>>>>>>>>       if (c[i] != 0)
>>>>>>>> res += 1;
>>>>>>>>   }
>>>>>>>>   <bb 4>:
>>>>>>>>   # res_15 = PHI <res_1(5), 0(3)>
>>>>>>>>   # i_16 = PHI <i_11(5), 0(3)>
>>>>>>>>   # ivtmp_17 = PHI <ivtmp_14(5), 512(3)>
>>>>>>>>   t_5 = a[i_16];
>>>>>>>>   _6 = t_5 > 0.0;
>>>>>>>>   _7 = t_5 < 9.9999998430674944e+16;
>>>>>>>>   _8 = _7 & _6;
>>>>>>>>   _ifc__28 = (unsigned int) _8;
>>>>>>>>   _10 = &c[i_16];
>>>>>>>>   _ifc__36 = _ifc__28 != 0 ? 4294967295 : 0;
>>>>>>>>   _9 = MASK_LOAD (_10, 0B, _ifc__36);
>>>>>>>>   _ifc__29 = _ifc__28 != 0 ? 1 : 0;
>>>>>>>>   _ifc__30 = (int) _ifc__29;
>>>>>>>>   _ifc__31 = _9 != 0 ? _ifc__30 : 0;
>>>>>>>>   _ifc__32 = _ifc__28 != 0 ? 1 : 0;
>>>>>>>>   _ifc__33 = (int) _ifc__32;
>>>>>>>>   _ifc__34 = _9 == 0 ? _ifc__33 : 0;
>>>>>>>>   _ifc__35 = _ifc__31 != 0 ? 1 : 0;
>>>>>>>>   res_1 = res_15 + _ifc__35;
>>>>>>>>   i_11 = i_16 + 1;
>>>>>>>>   ivtmp_14 = ivtmp_17 - 1;
>>>>>>>>   if (ivtmp_14 != 0)
>>>>>>>>     goto <bb 4>;
>>>>>>>>
>>>>>>>> Bootstrap and regression testing did not show any new failures.
>>>>>>>>
>>>>>>>> gcc/ChageLog
>>>>>>>>
>>>>>>>> 2014-06-25  Yuri Rumyantsev  <ysrumyan@gmail.com>
>>>>>>>>
>>>>>>>> * tree-if-conv.c (flag_force_vectorize): New variable.
>>>>>>>> (struct bb_predicate_s): Add negate_predicate field.
>>>>>>>> (bb_negate_predicate): New function.
>>>>>>>> (set_bb_negate_predicate): New function.
>>>>>>>> (bb_copy_predicate): New function.
>>>>>>>> (add_stmt_to_bb_predicate_gimplified_stmts): New function.
>>>>>>>> (init_bb_predicate): Add initialization of negate_predicate field.
>>>>>>>> (reset_bb_predicate): Reset negate_predicate to NULL_TREE.
>>>>>>>> (convert_name_to_cmp): New function.
>>>>>>>> (get_type_for_cond): New function.
>>>>>>>> (convert_bool_predicate): New function.
>>>>>>>> (predicate_disjunction): New function.
>>>>>>>> (predicate_conjunction): New function.
>>>>>>>> (add_to_predicate_list): Add convert_bool argument.
>>>>>>>> Add call of predicate_disjunction if convert_bool argument is true.
>>>>>>>> (add_to_dst_predicate_list): Add convert_bool argument.
>>>>>>>> Add early function exit if edge target block is always executed.
>>>>>>>> Add call of predicate_conjunction if convert_bool argument is true.
>>>>>>>> Pass convert_bool argument for add_to_predicate_list.
>>>>>>>> (equal_phi_args): New function.
>>>>>>>> (phi_has_two_different_args): New function.
>>>>>>>> (phi_args_disjoint): New function.
>>>>>>>> (if_convertible_phi_p): Accept phi nodes with more than two args
>>>>>>>> for loops marked with pragma omp simd. Add check that phi nodes are
>>>>>>>> in non-predicated basic blocks.
>>>>>>>> (ifcvt_can_use_mask_load_store): Use flag_force_vectorize.
>>>>>>>> (all_edges_are_critical): New function.
>>>>>>>> (if_convertible_bb_p): Allow bb has more than two predecessors if
>>>>>>>> flag_force_vectorize was setup. Use call of all_edges_are_critical
>>>>>>>> to reject block if-conversion with imcoming critical edges only if
>>>>>>>> flag_force_vectorize was not setup.
>>>>>>>> (walk_cond_tree): New function.
>>>>>>>> (vect_bool_pattern_is_applicable): New function.
>>>>>>>> (predicate_bbs): Add convert_bool argument that is used to transform
>>>>>>>> comparison expressions of boolean type into conditional expressions
>>>>>>>> with integral operands. If bool_conv argument is false or both
>>>>>>>> outgoing edges are not critical old algorithm of predicate assignments
>>>>>>>> is used, otherwise the following code was added: check on applicable
>>>>>>>> of vect-bool-pattern recognition and trnasformation of
>>>>>>>> (bool) x != 0  --> y = (int) x; x != 0;
>>>>>>>> compute predicates for both outgoing edges one of which is critical
>>>>>>>> one using 'normal' edge, i.e. compute true and false predicates using
>>>>>>>> normal outgoing edge only; evaluated predicates are stored in
>>>>>>>> predicate and negate_predicate fields of struct bb_predicate_s and
>>>>>>>> negate_predicate of normal edge conatins predicate of critical edge,
>>>>>>>> but generated gimplified statements are stored in their destination
>>>>>>>> block fields. Additional argument 'convert_bool" is passed to
>>>>>>>> add_to_dst_predicate_list and add_to_predicate_list.
>>>>>>>> (if_convertible_loop_p_1): Call predicate_bbs with additional argument
>>>>>>>> equal to false.
>>>>>>>> (find_phi_replacement_condition): Extend function interface:
>>>>>>>> it returns NULL if given phi node must be handled by means of
>>>>>>>> extended phi node predication. If number of predecessors of phi-block
>>>>>>>> is equal 2 and atleast one incoming edge is not critical original
>>>>>>>> algorithm is used.
>>>>>>>> (is_cond_scalar_reduction): Add 'extended' argument which signals that
>>>>>>>> both phi arguments must be evaluated through phi_has_two_different_args.
>>>>>>>> (predicate_scalar_phi): Add invoÑation of convert_name_to_cmp if cond
>>>>>>>> is SSA_NAME. Add 'false' argument to call of is_cond_scalar_reduction.
>>>>>>>> (get_predicate_for_edge): New function.
>>>>>>>> (find_insertion_point): New function.
>>>>>>>> (predicate_phi_disjoint_args): New function.
>>>>>>>> (predicate_extended_scalar_phi): New function.
>>>>>>>> (predicate_all_scalar_phis): Add code to set-up gimple statement
>>>>>>>> iterator for predication of extended scalar phi's for insertion.
>>>>>>>> (insert_gimplified_predicates): Add test for non-predicated basic
>>>>>>>> blocks that there are no gimplified statements to insert. Insert
>>>>>>>> predicates at the block begining for extended if-conversion.
>>>>>>>> (predicate_mem_writes): Invoke convert_name_to_cmp for extended
>>>>>>>> predication to build mask.
>>>>>>>> (combine_blocks): Pass flag_force_vectorize to predicate_bbs.
>>>>>>>> (split_crit_edge): New function.
>>>>>>>> (tree_if_conversion): Initialize flag_force_vectorize from current
>>>>>>>> loop or outer loop (to support pragma omp declare). Invoke
>>>>>>>> split_crit_edge for extended predication. Do loop versioning for
>>>>>>>> innermost loop marked with pragma omp simd.


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