[PATCH V3] VECT: Add decrement IV iteration loop control by variable amount support

[juzhe.zhong@rivai.ai]

From: Juzhe-Zhong <juzhe.zhong@rivai.ai>

This patch address all comments from Richard && Bernhard.
Fix all codes following their comments:

1. Remove ifn-specific handling of WHILE_LEN, so there is no change
   in internal-fn.cc in this patch.

2. Add comments for changing interface of "create_iv" function.

3. Reorder the CODE of interface "create_iv", make CODE argument between
   base and step.

4. Fix the misleading and incorrect comments of "vect_set_loop_controls_by_while_len".

5. remove redundant "enum" of "create_iv" interface and function.

Feel free to comment if I meet something.

Thanks.

gcc/ChangeLog:

        * cfgloopmanip.cc (create_empty_loop_on_edge): Adapt create_iv interface change.
        * doc/md.texi: Add WHILE_LEN pattern description.
        * gimple-loop-interchange.cc (tree_loop_interchange::map_inductions_to_loop): Adapt create_iv interface change.
        * internal-fn.def (WHILE_LEN): New ifn.
        * optabs.def (OPTAB_D): New optab pattern.
        * tree-ssa-loop-ivcanon.cc (create_canonical_iv): Adapt create_iv interface change.
        * tree-ssa-loop-ivopts.cc (create_new_iv): Ditto.
        * tree-ssa-loop-manip.cc (create_iv): Ditto.
        (tree_transform_and_unroll_loop): Ditto.
        (canonicalize_loop_ivs): Ditto.
        * tree-ssa-loop-manip.h (create_iv): Add code in the interface.
        * tree-vect-data-refs.cc (vect_create_data_ref_ptr): New function.
        * tree-vect-loop-manip.cc (vect_set_loop_controls_directly): Add decrementing IV loop control support.
        (vect_set_loop_controls_by_while_len): New function.
        (vect_set_loop_condition_partial_vectors): Add decrementing IV loop control support.
        (vect_set_loop_condition_normal): Adapt create_iv interface change.
        * tree-vect-loop.cc (vect_create_epilog_for_reduction): Ditto.
        (vect_get_loop_len): Adapt SLP auto-vectorization for WHILE_LEN.
        * tree-vect-stmts.cc (get_while_len_data_ref_ptr): New function.
        (vectorizable_store): Add WHILE_LEN data reference pointer IV.
        (vectorizable_load): Ditto.
        * tree-vectorizer.h (vect_get_loop_len): Add new arguments to interface.


---
 gcc/cfgloopmanip.cc            |   2 +-
 gcc/doc/md.texi                |  34 ++++
 gcc/gimple-loop-interchange.cc |   2 +-
 gcc/internal-fn.def            |   1 +
 gcc/optabs.def                 |   1 +
 gcc/tree-ssa-loop-ivcanon.cc   |   2 +-
 gcc/tree-ssa-loop-ivopts.cc    |   2 +-
 gcc/tree-ssa-loop-manip.cc     |  18 ++-
 gcc/tree-ssa-loop-manip.h      |   4 +-
 gcc/tree-vect-data-refs.cc     |   8 +-
 gcc/tree-vect-loop-manip.cc    | 280 +++++++++++++++++++++++++++++++--
 gcc/tree-vect-loop.cc          |  29 +++-
 gcc/tree-vect-stmts.cc         |  95 ++++++++++-
 gcc/tree-vectorizer.h          |   4 +-
 14 files changed, 445 insertions(+), 37 deletions(-)

diff --git a/gcc/cfgloopmanip.cc b/gcc/cfgloopmanip.cc
index 0e3ad8ed742..6e09dcbb0b1 100644
--- a/gcc/cfgloopmanip.cc
+++ b/gcc/cfgloopmanip.cc
@@ -826,7 +826,7 @@ create_empty_loop_on_edge (edge entry_edge,
     }
 
   gsi = gsi_last_bb (loop_header);
-  create_iv (initial_value, stride, iv, loop, &gsi, false,
+  create_iv (initial_value, PLUS_EXPR, stride, iv, loop, &gsi, false,
 	     iv_before, iv_after);
 
   /* Insert loop exit condition.  */
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 07bf8bdebff..307d3c407d8 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -4965,6 +4965,40 @@ for (i = 1; i < operand3; i++)
   operand0[i] = operand0[i - 1] && (operand1 + i < operand2);
 @end smallexample
 
+@cindex @code{while_len@var{m}@var{n}} instruction pattern
+@item @code{while_len@var{m}@var{n}}
+Set operand 0 to the number of active elements in vector will be updated value.
+operand 1 is the total elements need to be updated value.
+operand 2 is the vectorization factor.
+The value of operand 0 is target dependent and flexible in each iteration.
+The operation of this pattern can be:
+
+@smallexample
+Case 1:
+operand0 = MIN (operand1, operand2);
+operand2 can be const_poly_int or poly_int related to vector mode size.
+Some target like RISC-V has a standalone instruction to get MIN (n, MODE SIZE) so
+that we can reduce a use of general purpose register.
+
+In this case, only the last iteration of the loop is partial iteration.
+@end smallexample
+
+@smallexample
+Case 2:
+if (operand1 <= operand2)
+  operand0 = operand1;
+else if (operand1 < 2 * operand2)
+  operand0 = IN_RANGE (ceil (operand1 / 2), operand2);
+else
+  operand0 = operand2;
+
+This case will evenly distribute work over the last 2 iterations of a stripmine loop.
+@end smallexample
+
+The output of this pattern is not only used as IV of loop control counter, but also
+is used as the IV of address calculation with multiply/shift operation. This allow
+us dynamic adjust the number of elements is processed in each iteration of the loop.
+
 @cindex @code{check_raw_ptrs@var{m}} instruction pattern
 @item @samp{check_raw_ptrs@var{m}}
 Check whether, given two pointers @var{a} and @var{b} and a length @var{len},
diff --git a/gcc/gimple-loop-interchange.cc b/gcc/gimple-loop-interchange.cc
index 1b77bfd46b2..e5590374e59 100644
--- a/gcc/gimple-loop-interchange.cc
+++ b/gcc/gimple-loop-interchange.cc
@@ -1185,7 +1185,7 @@ tree_loop_interchange::map_inductions_to_loop (loop_cand &src, loop_cand &tgt)
 	  tree var_before, var_after;
 	  tree base = unshare_expr (iv->init_expr);
 	  tree step = unshare_expr (iv->step);
-	  create_iv (base, step, SSA_NAME_VAR (iv->var),
+	  create_iv (base, PLUS_EXPR, step, SSA_NAME_VAR (iv->var),
 		     tgt.m_loop, &incr_pos, false, &var_before, &var_after);
 	  bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_before));
 	  bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_after));
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index 7fe742c2ae7..9f7269f8f60 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -153,6 +153,7 @@ DEF_INTERNAL_OPTAB_FN (VEC_SET, 0, vec_set, vec_set)
 DEF_INTERNAL_OPTAB_FN (LEN_STORE, 0, len_store, len_store)
 
 DEF_INTERNAL_OPTAB_FN (WHILE_ULT, ECF_CONST | ECF_NOTHROW, while_ult, while)
+DEF_INTERNAL_OPTAB_FN (WHILE_LEN, ECF_CONST | ECF_NOTHROW, while_len, binary)
 DEF_INTERNAL_OPTAB_FN (CHECK_RAW_PTRS, ECF_CONST | ECF_NOTHROW,
 		       check_raw_ptrs, check_ptrs)
 DEF_INTERNAL_OPTAB_FN (CHECK_WAR_PTRS, ECF_CONST | ECF_NOTHROW,
diff --git a/gcc/optabs.def b/gcc/optabs.def
index 695f5911b30..f5938bd2c24 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -476,3 +476,4 @@ OPTAB_DC (vec_series_optab, "vec_series$a", VEC_SERIES)
 OPTAB_D (vec_shl_insert_optab, "vec_shl_insert_$a")
 OPTAB_D (len_load_optab, "len_load_$a")
 OPTAB_D (len_store_optab, "len_store_$a")
+OPTAB_D (while_len_optab, "while_len$a")
diff --git a/gcc/tree-ssa-loop-ivcanon.cc b/gcc/tree-ssa-loop-ivcanon.cc
index 9f72d534b7c..6941d0a4d1d 100644
--- a/gcc/tree-ssa-loop-ivcanon.cc
+++ b/gcc/tree-ssa-loop-ivcanon.cc
@@ -113,7 +113,7 @@ create_canonical_iv (class loop *loop, edge exit, tree niter,
 		       niter,
 		       build_int_cst (type, 1));
   incr_at = gsi_last_bb (in->src);
-  create_iv (niter,
+  create_iv (niter, PLUS_EXPR,
 	     build_int_cst (type, -1),
 	     NULL_TREE, loop,
 	     &incr_at, false, var_before, &var);
diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 0dd47910f97..a7377f91f9e 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -7267,7 +7267,7 @@ create_new_iv (struct ivopts_data *data, struct iv_cand *cand)
 
   base = unshare_expr (cand->iv->base);
 
-  create_iv (base, unshare_expr (cand->iv->step),
+  create_iv (base, PLUS_EXPR, unshare_expr (cand->iv->step),
 	     cand->var_before, data->current_loop,
 	     &incr_pos, after, &cand->var_before, &cand->var_after);
 }
diff --git a/gcc/tree-ssa-loop-manip.cc b/gcc/tree-ssa-loop-manip.cc
index a52277abdbf..b0d254b0c89 100644
--- a/gcc/tree-ssa-loop-manip.cc
+++ b/gcc/tree-ssa-loop-manip.cc
@@ -47,7 +47,9 @@ along with GCC; see the file COPYING3.  If not see
    so that we can free them all at once.  */
 static bitmap_obstack loop_renamer_obstack;
 
-/* Creates an induction variable with value BASE + STEP * iteration in LOOP.
+/* Creates an induction variable with value BASE (+/-) STEP * iteration in LOOP.
+   If CODE is PLUS_EXPR, the induction variable is BASE + STEP * iteration.
+   If CODE is MINUS_EXPR, the induction variable is BASE - STEP * iteration.
    It is expected that neither BASE nor STEP are shared with other expressions
    (unless the sharing rules allow this).  Use VAR as a base var_decl for it
    (if NULL, a new temporary will be created).  The increment will occur at
@@ -57,8 +59,8 @@ static bitmap_obstack loop_renamer_obstack;
    VAR_AFTER (unless they are NULL).  */
 
 void
-create_iv (tree base, tree step, tree var, class loop *loop,
-	   gimple_stmt_iterator *incr_pos, bool after,
+create_iv (tree base, tree_code code, tree step, tree var,
+	   class loop *loop, gimple_stmt_iterator *incr_pos, bool after,
 	   tree *var_before, tree *var_after)
 {
   gassign *stmt;
@@ -66,7 +68,9 @@ create_iv (tree base, tree step, tree var, class loop *loop,
   tree initial, step1;
   gimple_seq stmts;
   tree vb, va;
-  enum tree_code incr_op = PLUS_EXPR;
+  /* The code can only be PLUS_EXPR or MINUS_EXPR.  */
+  gcc_assert (code == PLUS_EXPR || code == MINUS_EXPR);
+  tree_code incr_op = code;
   edge pe = loop_preheader_edge (loop);
 
   if (var != NULL_TREE)
@@ -1368,7 +1372,7 @@ tree_transform_and_unroll_loop (class loop *loop, unsigned factor,
       tree ctr_before, ctr_after;
       gimple_stmt_iterator bsi = gsi_last_nondebug_bb (new_exit->src);
       exit_if = as_a <gcond *> (gsi_stmt (bsi));
-      create_iv (exit_base, exit_step, NULL_TREE, loop,
+      create_iv (exit_base, PLUS_EXPR, exit_step, NULL_TREE, loop,
 		 &bsi, false, &ctr_before, &ctr_after);
       gimple_cond_set_code (exit_if, exit_cmp);
       gimple_cond_set_lhs (exit_if, ctr_after);
@@ -1583,8 +1587,8 @@ canonicalize_loop_ivs (class loop *loop, tree *nit, bool bump_in_latch)
     gsi = gsi_last_bb (loop->latch);
   else
     gsi = gsi_last_nondebug_bb (loop->header);
-  create_iv (build_int_cst_type (type, 0), build_int_cst (type, 1), NULL_TREE,
-	     loop, &gsi, bump_in_latch, &var_before, NULL);
+  create_iv (build_int_cst_type (type, 0), PLUS_EXPR, build_int_cst (type, 1),
+	     NULL_TREE, loop, &gsi, bump_in_latch, &var_before, NULL);
 
   rewrite_all_phi_nodes_with_iv (loop, var_before);
 
diff --git a/gcc/tree-ssa-loop-manip.h b/gcc/tree-ssa-loop-manip.h
index d49273a3987..bda09f51d56 100644
--- a/gcc/tree-ssa-loop-manip.h
+++ b/gcc/tree-ssa-loop-manip.h
@@ -22,8 +22,8 @@ along with GCC; see the file COPYING3.  If not see
 
 typedef void (*transform_callback)(class loop *, void *);
 
-extern void create_iv (tree, tree, tree, class loop *, gimple_stmt_iterator *,
-		       bool, tree *, tree *);
+extern void create_iv (tree, tree_code, tree, tree, class loop *,
+		       gimple_stmt_iterator *, bool, tree *, tree *);
 extern void rewrite_into_loop_closed_ssa (bitmap, unsigned);
 extern void verify_loop_closed_ssa (bool, class loop * = NULL);
 
diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
index c03ffb3aaf1..355ede5c0d9 100644
--- a/gcc/tree-vect-data-refs.cc
+++ b/gcc/tree-vect-data-refs.cc
@@ -5101,7 +5101,7 @@ vect_create_data_ref_ptr (vec_info *vinfo, stmt_vec_info stmt_info,
 
       standard_iv_increment_position (loop, &incr_gsi, &insert_after);
 
-      create_iv (aggr_ptr_init,
+      create_iv (aggr_ptr_init, PLUS_EXPR,
 		 fold_convert (aggr_ptr_type, iv_step),
 		 aggr_ptr, loop, &incr_gsi, insert_after,
 		 &indx_before_incr, &indx_after_incr);
@@ -5131,9 +5131,9 @@ vect_create_data_ref_ptr (vec_info *vinfo, stmt_vec_info stmt_info,
     {
       standard_iv_increment_position (containing_loop, &incr_gsi,
 				      &insert_after);
-      create_iv (aptr, fold_convert (aggr_ptr_type, DR_STEP (dr)), aggr_ptr,
-		 containing_loop, &incr_gsi, insert_after, &indx_before_incr,
-		 &indx_after_incr);
+      create_iv (aptr, PLUS_EXPR, fold_convert (aggr_ptr_type, DR_STEP (dr)),
+		 aggr_ptr, containing_loop, &incr_gsi, insert_after,
+		 &indx_before_incr, &indx_after_incr);
       incr = gsi_stmt (incr_gsi);
 
       /* Copy the points-to information if it exists. */
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index f60fa50e8f4..6973314adb5 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -468,8 +468,9 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
   gimple_stmt_iterator incr_gsi;
   bool insert_after;
   standard_iv_increment_position (loop, &incr_gsi, &insert_after);
-  create_iv (build_int_cst (iv_type, 0), nitems_step, NULL_TREE, loop,
-	     &incr_gsi, insert_after, &index_before_incr, &index_after_incr);
+  create_iv (build_int_cst (iv_type, 0), PLUS_EXPR, nitems_step, NULL_TREE,
+	     loop, &incr_gsi, insert_after, &index_before_incr,
+	     &index_after_incr);
 
   tree zero_index = build_int_cst (compare_type, 0);
   tree test_index, test_limit, first_limit;
@@ -682,6 +683,260 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
   return next_ctrl;
 }
 
+/* Helper for vect_set_loop_condition_partial_vectors.  Generate definitions
+   for all the rgroup controls in RGC and return a control that is nonzero
+   when the loop needs to iterate.  Add any new preheader statements to
+   PREHEADER_SEQ.  Use LOOP_COND_GSI to insert code before the exit gcond.
+
+   RGC belongs to loop LOOP.  The loop originally iterated NITERS
+   times and has been vectorized according to LOOP_VINFO.
+
+   Unlike vect_set_loop_controls_directly which is iterating from 0-based IV
+   to TEST_LIMIT - bias.
+
+   In vect_set_loop_controls_by_while_len, we are iterating from start at
+   IV = TEST_LIMIT - bias and keep subtract IV by the length calculated by
+   IFN_WHILE_LEN pattern.
+
+   1. Single rgroup, the Gimple IR should be:
+
+	# vectp_B.6_8 = PHI <vectp_B.6_13(6), &B(5)>
+	# vectp_B.8_16 = PHI <vectp_B.8_17(6), &B(5)>
+	# vectp_A.11_19 = PHI <vectp_A.11_20(6), &A(5)>
+	# vectp_A.13_22 = PHI <vectp_A.13_23(6), &A(5)>
+	# ivtmp_26 = PHI <ivtmp_27(6), _25(5)>
+	_28 = .WHILE_LEN (ivtmp_26, POLY_INT_CST [4, 4]);
+	ivtmp_15 = _28 * 4;
+	vect__1.10_18 = .LEN_LOAD (vectp_B.8_16, 128B, _28, 0);
+	_1 = B[i_10];
+	.LEN_STORE (vectp_A.13_22, 128B, _28, vect__1.10_18, 0);
+	i_7 = i_10 + 1;
+	vectp_B.8_17 = vectp_B.8_16 + ivtmp_15;
+	vectp_A.13_23 = vectp_A.13_22 + ivtmp_15;
+	ivtmp_27 = ivtmp_26 - _28;
+	if (ivtmp_27 != 0)
+	  goto <bb 6>; [83.33%]
+	else
+	  goto <bb 7>; [16.67%]
+
+   Note: We use the outcome of .WHILE_LEN to adjust both loop control IV and
+   data reference pointer IV.
+
+   1). The result of .WHILE_LEN:
+       _28 = .WHILE_LEN (ivtmp_26, POLY_INT_CST [4, 4]);
+       The _28 is not necessary to be VF in any iteration, instead, we allow
+       _28 to be any value as long as it it <= VF. Such flexible WHILE_LEN
+       pattern allows target have various flexible optimizations in vector
+       loop iterations. Target like RISC-V has special application vector
+       length calculation instruction which will distribute even workload
+       in the last 2 iterations.
+
+       Other example is that we can allow even generate _28 <= VF / 2 so
+       that some machine can run vector codes in low power mode.
+
+   2). Loop control IV:
+       ivtmp_27 = ivtmp_26 - _28;
+       if (ivtmp_27 != 0)
+	 goto <bb 6>; [83.33%]
+       else
+	 goto <bb 7>; [16.67%]
+
+       This is the saturating-subtraction towards zero, the outcome of
+       .WHILE_LEN wil make ivtmp_27 never underflow zero.
+
+   3). Data reference pointer IV:
+       ivtmp_15 = _28 * 4;
+       vectp_B.8_17 = vectp_B.8_16 + ivtmp_15;
+       vectp_A.13_23 = vectp_A.13_22 + ivtmp_15;
+
+       The pointer IV is adjusted accurately according to the .WHILE_LEN.
+
+   2. Multiple rgroup, the Gimple IR should be:
+
+	# i_23 = PHI <i_20(6), 0(11)>
+	# vectp_f.8_51 = PHI <vectp_f.8_52(6), f_15(D)(11)>
+	# vectp_d.10_59 = PHI <vectp_d.10_60(6), d_18(D)(11)>
+	# ivtmp_70 = PHI <ivtmp_71(6), _69(11)>
+	# ivtmp_73 = PHI <ivtmp_74(6), _67(11)>
+	_72 = MIN_EXPR <ivtmp_70, 16>;
+	_75 = MIN_EXPR <ivtmp_73, 16>;
+	_1 = i_23 * 2;
+	_2 = (long unsigned int) _1;
+	_3 = _2 * 2;
+	_4 = f_15(D) + _3;
+	_5 = _2 + 1;
+	_6 = _5 * 2;
+	_7 = f_15(D) + _6;
+	.LEN_STORE (vectp_f.8_51, 128B, _75, { 1, 2, 1, 2, 1, 2, 1, 2 }, 0);
+	vectp_f.8_56 = vectp_f.8_51 + 16;
+	.LEN_STORE (vectp_f.8_56, 128B, _72, { 1, 2, 1, 2, 1, 2, 1, 2 }, 0);
+	_8 = (long unsigned int) i_23;
+	_9 = _8 * 4;
+	_10 = d_18(D) + _9;
+	_61 = _75 / 2;
+	.LEN_STORE (vectp_d.10_59, 128B, _61, { 3, 3, 3, 3 }, 0);
+	vectp_d.10_63 = vectp_d.10_59 + 16;
+	_64 = _72 / 2;
+	.LEN_STORE (vectp_d.10_63, 128B, _64, { 3, 3, 3, 3 }, 0);
+	i_20 = i_23 + 1;
+	vectp_f.8_52 = vectp_f.8_56 + 16;
+	vectp_d.10_60 = vectp_d.10_63 + 16;
+	ivtmp_74 = ivtmp_73 - _75;
+	ivtmp_71 = ivtmp_70 - _72;
+	if (ivtmp_74 != 0)
+	  goto <bb 6>; [83.33%]
+	else
+	  goto <bb 13>; [16.67%]
+
+   Note: We DO NOT use .WHILE_LEN in SLP auto-vectorization for multiple
+   rgroups. Instead, we use MIN_EXPR to guarantee we always use VF as the
+   iteration amount for mutiple rgroups.
+
+   The analysis of the flow of multiple rgroups:
+	_72 = MIN_EXPR <ivtmp_70, 16>;
+	_75 = MIN_EXPR <ivtmp_73, 16>;
+	...
+	.LEN_STORE (vectp_f.8_51, 128B, _75, { 1, 2, 1, 2, 1, 2, 1, 2 }, 0);
+	vectp_f.8_56 = vectp_f.8_51 + 16;
+	.LEN_STORE (vectp_f.8_56, 128B, _72, { 1, 2, 1, 2, 1, 2, 1, 2 }, 0);
+	...
+	_61 = _75 / 2;
+	.LEN_STORE (vectp_d.10_59, 128B, _61, { 3, 3, 3, 3 }, 0);
+	vectp_d.10_63 = vectp_d.10_59 + 16;
+	_64 = _72 / 2;
+	.LEN_STORE (vectp_d.10_63, 128B, _64, { 3, 3, 3, 3 }, 0);
+
+  We use _72 = MIN_EXPR <ivtmp_70, 16>; to generate the number of the elements
+  to be processed in each iteration.
+
+  The related STOREs:
+    _72 = MIN_EXPR <ivtmp_70, 16>;
+    .LEN_STORE (vectp_f.8_56, 128B, _72, { 1, 2, 1, 2, 1, 2, 1, 2 }, 0);
+    _64 = _72 / 2;
+    .LEN_STORE (vectp_d.10_63, 128B, _64, { 3, 3, 3, 3 }, 0);
+  Since these 2 STOREs store 2 vectors that the second vector is half elements
+  of the first vector. So the length of second STORE will be _64 = _72 / 2;
+  It's similar to the VIEW_CONVERT of handling masks in SLP.
+*/
+
+static tree
+vect_set_loop_controls_by_while_len (class loop *loop, loop_vec_info loop_vinfo,
+				     gimple_seq *preheader_seq,
+				     gimple_seq *header_seq,
+				     rgroup_controls *rgc, tree niters)
+{
+  tree compare_type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);
+  tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
+  /* We are not allowing masked approach in WHILE_LEN.  */
+  gcc_assert (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
+
+  tree ctrl_type = rgc->type;
+  unsigned int nitems_per_iter = rgc->max_nscalars_per_iter * rgc->factor;
+  poly_uint64 nitems_per_ctrl = TYPE_VECTOR_SUBPARTS (ctrl_type) * rgc->factor;
+  poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
+
+  /* Calculate the maximum number of item values that the rgroup
+     handles in total, the number that it handles for each iteration
+     of the vector loop.  */
+  tree nitems_total = niters;
+  if (nitems_per_iter != 1)
+    {
+      /* We checked before setting LOOP_VINFO_USING_PARTIAL_VECTORS_P that
+	 these multiplications don't overflow.  */
+      tree compare_factor = build_int_cst (compare_type, nitems_per_iter);
+      nitems_total = gimple_build (preheader_seq, MULT_EXPR, compare_type,
+				   nitems_total, compare_factor);
+    }
+
+  /* Convert the comparison value to the IV type (either a no-op or
+     a promotion).  */
+  nitems_total = gimple_convert (preheader_seq, iv_type, nitems_total);
+
+  /* Create an induction variable that counts the number of items
+     processed.  */
+  tree index_before_incr, index_after_incr;
+  gimple_stmt_iterator incr_gsi;
+  bool insert_after;
+  standard_iv_increment_position (loop, &incr_gsi, &insert_after);
+
+  /* Test the decremented IV, which will never underflow 0 since we have
+     IFN_WHILE_LEN to gurantee that.  */
+  tree test_limit = nitems_total;
+
+  /* Provide a definition of each control in the group.  */
+  tree ctrl;
+  unsigned int i;
+  FOR_EACH_VEC_ELT_REVERSE (rgc->controls, i, ctrl)
+    {
+      /* Previous controls will cover BIAS items.  This control covers the
+	 next batch.  */
+      poly_uint64 bias = nitems_per_ctrl * i;
+      tree bias_tree = build_int_cst (iv_type, bias);
+
+      /* Rather than have a new IV that starts at TEST_LIMIT and goes down to
+	 BIAS, prefer to use the same TEST_LIMIT - BIAS based IV for each
+	 control and adjust the bound down by BIAS.  */
+      tree this_test_limit = test_limit;
+      if (i != 0)
+	{
+	  this_test_limit = gimple_build (preheader_seq, MAX_EXPR, iv_type,
+					  this_test_limit, bias_tree);
+	  this_test_limit = gimple_build (preheader_seq, MINUS_EXPR, iv_type,
+					  this_test_limit, bias_tree);
+	}
+
+      /* Create decrement IV.  */
+      create_iv (this_test_limit, MINUS_EXPR, ctrl, NULL_TREE, loop, &incr_gsi,
+		 insert_after, &index_before_incr, &index_after_incr);
+
+      poly_uint64 final_vf = vf * nitems_per_iter;
+      tree vf_step = build_int_cst (iv_type, final_vf);
+      tree res_len;
+      if (nitems_per_iter != 1)
+	{
+	  /* For SLP, we can't allow non-VF number of elements to be processed
+	     in non-final iteration. We force the number of elements to be
+	   processed in each non-final iteration is VF elements. If we allow
+	   non-VF elements processing in non-final iteration will make SLP too
+	   complicated and produce inferior codegen.
+
+	       For example:
+
+		If non-final iteration process VF elements.
+
+		  ...
+		  .LEN_STORE (vectp_f.8_51, 128B, _71, { 1, 2, 1, 2 }, 0);
+		  .LEN_STORE (vectp_f.8_56, 128B, _72, { 1, 2, 1, 2 }, 0);
+		  ...
+
+		If non-final iteration process non-VF elements.
+
+		  ...
+		  .LEN_STORE (vectp_f.8_51, 128B, _71, { 1, 2, 1, 2 }, 0);
+		  if (_71 % 2 == 0)
+		   .LEN_STORE (vectp_f.8_56, 128B, _72, { 1, 2, 1, 2 }, 0);
+		  else
+		   .LEN_STORE (vectp_f.8_56, 128B, _72, { 2, 1, 2, 1 }, 0);
+		  ...
+
+	   This is the simple case of 2-elements interleaved vector SLP. We
+	   consider other interleave vector, the situation will become more
+	   complicated.  */
+	  res_len = gimple_build (header_seq, MIN_EXPR, iv_type,
+				  index_before_incr, vf_step);
+	}
+      else
+	{
+	  res_len = gimple_build (header_seq, IFN_WHILE_LEN, iv_type,
+				  index_before_incr, vf_step);
+	}
+      gassign *assign = gimple_build_assign (ctrl, res_len);
+      gimple_seq_add_stmt (header_seq, assign);
+    }
+
+  return index_after_incr;
+}
+
 /* Set up the iteration condition and rgroup controls for LOOP, given
    that LOOP_VINFO_USING_PARTIAL_VECTORS_P is true for the vectorized
    loop.  LOOP_VINFO describes the vectorization of LOOP.  NITERS is
@@ -703,6 +958,7 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
 
   bool use_masks_p = LOOP_VINFO_FULLY_MASKED_P (loop_vinfo);
   tree compare_type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);
+  tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
   unsigned int compare_precision = TYPE_PRECISION (compare_type);
   tree orig_niters = niters;
 
@@ -757,12 +1013,18 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
 	bool might_wrap_p = vect_rgroup_iv_might_wrap_p (loop_vinfo, rgc);
 
 	/* Set up all controls for this group.  */
-	test_ctrl = vect_set_loop_controls_directly (loop, loop_vinfo,
-						     &preheader_seq,
-						     &header_seq,
-						     loop_cond_gsi, rgc,
-						     niters, niters_skip,
-						     might_wrap_p);
+	if (direct_internal_fn_supported_p (IFN_WHILE_LEN, iv_type,
+					    OPTIMIZE_FOR_SPEED))
+	  test_ctrl
+	    = vect_set_loop_controls_by_while_len (loop, loop_vinfo,
+						   &preheader_seq, &header_seq,
+						   rgc, niters);
+	else
+	  test_ctrl
+	    = vect_set_loop_controls_directly (loop, loop_vinfo, &preheader_seq,
+					       &header_seq, loop_cond_gsi, rgc,
+					       niters, niters_skip,
+					       might_wrap_p);
       }
 
   /* Emit all accumulated statements.  */
@@ -893,7 +1155,7 @@ vect_set_loop_condition_normal (class loop *loop, tree niters, tree step,
     }
 
   standard_iv_increment_position (loop, &incr_gsi, &insert_after);
-  create_iv (init, step, NULL_TREE, loop,
+  create_iv (init, PLUS_EXPR, step, NULL_TREE, loop,
              &incr_gsi, insert_after, &indx_before_incr, &indx_after_incr);
   indx_after_incr = force_gimple_operand_gsi (&loop_cond_gsi, indx_after_incr,
 					      true, NULL_TREE, true,
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 6ea0f21fd13..d6e90ed93cd 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -5567,7 +5567,7 @@ vect_create_epilog_for_reduction (loop_vec_info loop_vinfo,
       gimple_stmt_iterator incr_gsi;
       bool insert_after;
       standard_iv_increment_position (loop, &incr_gsi, &insert_after);
-      create_iv (series_vect, vec_step, NULL_TREE, loop, &incr_gsi,
+      create_iv (series_vect, PLUS_EXPR, vec_step, NULL_TREE, loop, &incr_gsi,
 		 insert_after, &indx_before_incr, &indx_after_incr);
 
       /* Next create a new phi node vector (NEW_PHI_TREE) which starts
@@ -10364,12 +10364,14 @@ vect_record_loop_len (loop_vec_info loop_vinfo, vec_loop_lens *lens,
    rgroup that operates on NVECTORS vectors, where 0 <= INDEX < NVECTORS.  */
 
 tree
-vect_get_loop_len (loop_vec_info loop_vinfo, vec_loop_lens *lens,
-		   unsigned int nvectors, unsigned int index)
+vect_get_loop_len (gimple_stmt_iterator *gsi, loop_vec_info loop_vinfo,
+		   vec_loop_lens *lens, unsigned int nvectors, tree vectype,
+		   unsigned int index)
 {
   rgroup_controls *rgl = &(*lens)[nvectors - 1];
   bool use_bias_adjusted_len =
     LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS (loop_vinfo) != 0;
+  tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
 
   /* Populate the rgroup's len array, if this is the first time we've
      used it.  */
@@ -10400,6 +10402,27 @@ vect_get_loop_len (loop_vec_info loop_vinfo, vec_loop_lens *lens,
 
   if (use_bias_adjusted_len)
     return rgl->bias_adjusted_ctrl;
+  else if (direct_internal_fn_supported_p (IFN_WHILE_LEN, iv_type,
+					   OPTIMIZE_FOR_SPEED))
+    {
+      tree loop_len = rgl->controls[index];
+      poly_int64 nunits1 = TYPE_VECTOR_SUBPARTS (rgl->type);
+      poly_int64 nunits2 = TYPE_VECTOR_SUBPARTS (vectype);
+      if (maybe_ne (nunits1, nunits2))
+	{
+	  /* A loop len for data type X can be reused for data type Y
+	     if X has N times more elements than Y and if Y's elements
+	     are N times bigger than X's.  */
+	  gcc_assert (multiple_p (nunits1, nunits2));
+	  unsigned int factor = exact_div (nunits1, nunits2).to_constant ();
+	  gimple_seq seq = NULL;
+	  loop_len = gimple_build (&seq, RDIV_EXPR, iv_type, loop_len,
+				   build_int_cst (iv_type, factor));
+	  if (seq)
+	    gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
+	}
+      return loop_len;
+    }
   else
     return rgl->controls[index];
 }
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 6b7dbfd4a23..98bef8f4fc9 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -3144,6 +3144,70 @@ vect_get_data_ptr_increment (vec_info *vinfo,
   return iv_step;
 }
 
+/* Prepare the pointer IVs which needs to be updated by a variable amount.
+   Such variable amount is the outcome of .WHILE_LEN. In this case, we can
+   allow each iteration process the flexible number of elements as long as
+   the number <= vf elments.
+
+   Return data reference according to WHILE_LEN.
+   If new statements are needed, insert them before GSI.  */
+
+static tree
+get_while_len_data_ref_ptr (vec_info *vinfo, stmt_vec_info stmt_info,
+			    tree aggr_type, class loop *at_loop, tree offset,
+			    tree *dummy, gimple_stmt_iterator *gsi,
+			    bool simd_lane_access_p, vec_loop_lens *loop_lens,
+			    dr_vec_info *dr_info,
+			    vect_memory_access_type memory_access_type)
+{
+  if (!loop_lens || loop_lens->length () != 1)
+    return NULL_TREE;
+  loop_vec_info loop_vinfo = dyn_cast<loop_vec_info> (vinfo);
+  tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
+  tree step = vect_dr_behavior (vinfo, dr_info)->step;
+  if (!direct_internal_fn_supported_p (IFN_WHILE_LEN, iv_type,
+				       OPTIMIZE_FOR_SPEED))
+    return NULL_TREE;
+
+  if (memory_access_type == VMAT_INVARIANT)
+    return NULL_TREE;
+
+  /* TODO: We don't support gather/scatter or load_lanes/store_lanes for pointer
+     IVs are updated by variable amount but we will support them in the future.
+   */
+  gcc_assert (memory_access_type != VMAT_GATHER_SCATTER
+	      && memory_access_type != VMAT_LOAD_STORE_LANES);
+
+  /* When we support WHILE_LEN pattern, we dynamic adjust
+     the memory address by .WHILE_LEN result.
+
+     The result of .WHILE_LEN is the number of elements to
+     be processed of each iteration. So the memory address
+     adjustment operation should be:
+
+     bytesize = GET_MODE_SIZE (element_mode (aggr_type));
+     addr = addr + .WHILE_LEN (ARG..) * bytesize;
+  */
+  gimple *ptr_incr;
+  tree loop_len
+    = vect_get_loop_len (gsi, loop_vinfo, loop_lens, 1, aggr_type, 0);
+  tree len_type = TREE_TYPE (loop_len);
+  poly_uint64 bytesize = GET_MODE_SIZE (element_mode (aggr_type));
+  /* Since the outcome of .WHILE_LEN is element size, we should adjust
+     it into bytesize so that it can be used in address pointer variable
+     amount IVs adjustment.  */
+  tree tmp = fold_build2 (MULT_EXPR, len_type, loop_len,
+			  build_int_cst (len_type, bytesize));
+  if (tree_int_cst_sgn (step) == -1)
+    tmp = fold_build1 (NEGATE_EXPR, len_type, tmp);
+  tree bump = make_temp_ssa_name (len_type, NULL, "ivtmp");
+  gassign *assign = gimple_build_assign (bump, tmp);
+  gsi_insert_before (gsi, assign, GSI_SAME_STMT);
+  return vect_create_data_ref_ptr (vinfo, stmt_info, aggr_type, at_loop, offset,
+				   dummy, gsi, &ptr_incr, simd_lane_access_p,
+				   bump);
+}
+
 /* Check and perform vectorization of BUILT_IN_BSWAP{16,32,64,128}.  */
 
 static bool
@@ -8195,7 +8259,7 @@ vectorizable_store (vec_info *vinfo,
 
       stride_base = cse_and_gimplify_to_preheader (loop_vinfo, stride_base);
       ivstep = cse_and_gimplify_to_preheader (loop_vinfo, ivstep);
-      create_iv (stride_base, ivstep, NULL,
+      create_iv (stride_base, PLUS_EXPR, ivstep, NULL,
 		 loop, &incr_gsi, insert_after,
 		 &offvar, NULL);
       incr = gsi_stmt (incr_gsi);
@@ -8465,6 +8529,15 @@ vectorizable_store (vec_info *vinfo,
 					  simd_lane_access_p ? loop : NULL,
 					  offset, &dummy, gsi, &ptr_incr,
 					  simd_lane_access_p, bump);
+
+	  tree while_len_data_ref_ptr
+	    = get_while_len_data_ref_ptr (vinfo, stmt_info, aggr_type,
+					  simd_lane_access_p ? loop : NULL,
+					  offset, &dummy, gsi,
+					  simd_lane_access_p, loop_lens,
+					  dr_info, memory_access_type);
+	  if (while_len_data_ref_ptr)
+	    dataref_ptr = while_len_data_ref_ptr;
 	}
       else
 	{
@@ -8652,8 +8725,9 @@ vectorizable_store (vec_info *vinfo,
 	      else if (loop_lens)
 		{
 		  tree final_len
-		    = vect_get_loop_len (loop_vinfo, loop_lens,
-					 vec_num * ncopies, vec_num * j + i);
+		    = vect_get_loop_len (gsi, loop_vinfo, loop_lens,
+					 vec_num * ncopies, vectype,
+					 vec_num * j + i);
 		  tree ptr = build_int_cst (ref_type, align * BITS_PER_UNIT);
 		  machine_mode vmode = TYPE_MODE (vectype);
 		  opt_machine_mode new_ovmode
@@ -9314,7 +9388,7 @@ vectorizable_load (vec_info *vinfo,
 
       stride_base = cse_and_gimplify_to_preheader (loop_vinfo, stride_base);
       ivstep = cse_and_gimplify_to_preheader (loop_vinfo, ivstep);
-      create_iv (stride_base, ivstep, NULL,
+      create_iv (stride_base, PLUS_EXPR, ivstep, NULL,
 		 loop, &incr_gsi, insert_after,
 		 &offvar, NULL);
 
@@ -9798,6 +9872,15 @@ vectorizable_load (vec_info *vinfo,
 					  at_loop,
 					  offset, &dummy, gsi, &ptr_incr,
 					  simd_lane_access_p, bump);
+
+	  tree while_len_data_ref_ptr
+	    = get_while_len_data_ref_ptr (vinfo, stmt_info, aggr_type, at_loop,
+					  offset, &dummy, gsi,
+					  simd_lane_access_p, loop_lens,
+					  dr_info, memory_access_type);
+	  if (while_len_data_ref_ptr)
+	    dataref_ptr = while_len_data_ref_ptr;
+
 	  if (mask)
 	    vec_mask = vec_masks[0];
 	}
@@ -10008,8 +10091,8 @@ vectorizable_load (vec_info *vinfo,
 		    else if (loop_lens && memory_access_type != VMAT_INVARIANT)
 		      {
 			tree final_len
-			  = vect_get_loop_len (loop_vinfo, loop_lens,
-					       vec_num * ncopies,
+			  = vect_get_loop_len (gsi, loop_vinfo, loop_lens,
+					       vec_num * ncopies, vectype,
 					       vec_num * j + i);
 			tree ptr = build_int_cst (ref_type,
 						  align * BITS_PER_UNIT);
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 9cf2fb23fe3..811c17e1d3d 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -2293,8 +2293,8 @@ extern tree vect_get_loop_mask (gimple_stmt_iterator *, vec_loop_masks *,
 				unsigned int, tree, unsigned int);
 extern void vect_record_loop_len (loop_vec_info, vec_loop_lens *, unsigned int,
 				  tree, unsigned int);
-extern tree vect_get_loop_len (loop_vec_info, vec_loop_lens *, unsigned int,
-			       unsigned int);
+extern tree vect_get_loop_len (gimple_stmt_iterator *, loop_vec_info, vec_loop_lens *,
+			       unsigned int, tree, unsigned int);
 extern gimple_seq vect_gen_len (tree, tree, tree, tree);
 extern stmt_vec_info info_for_reduction (vec_info *, stmt_vec_info);
 extern bool reduction_fn_for_scalar_code (code_helper, internal_fn *);
-- 
2.36.1