On Wed, 7 Jun 2023, juzhe.zh...@rivai.ai wrote: > Hi, Richi. Since SELECT_VL only apply on single-rgroup (ncopies == 1 && > vec_num == 1) > Should I make SELECT_VL stuff out side the loop? > > for (i = 0; i < vec_num; i++) > for (j = 0; j < ncopies; j++) > ....
No, but please put assertions into the iteration so it's obvious the SELECT_VL doesn't reach there. > Thanks. > > > juzhe.zh...@rivai.ai > > From: Richard Biener > Date: 2023-06-07 15:41 > To: Ju-Zhe Zhong > CC: gcc-patches; richard.sandiford > Subject: Re: [PATCH V3] VECT: Add SELECT_VL support > On Mon, 5 Jun 2023, juzhe.zh...@rivai.ai wrote: > > > From: Ju-Zhe Zhong <juzhe.zh...@rivai.ai> > > > > Co-authored-by: Richard Sandiford<richard.sandif...@arm.com> > > > > This patch address comments from Richard and rebase to trunk. > > > > This patch is adding SELECT_VL middle-end support > > allow target have target dependent optimization in case of > > length calculation. > > > > This patch is inspired by RVV ISA and LLVM: > > https://reviews.llvm.org/D99750 > > > > The SELECT_VL is same behavior as LLVM "get_vector_length" with > > these following properties: > > > > 1. Only apply on single-rgroup. > > 2. non SLP. > > 3. adjust loop control IV. > > 4. adjust data reference IV. > > 5. allow non-vf elements processing in non-final iteration > > > > Code: > > # void vvaddint32(size_t n, const int*x, const int*y, int*z) > > # { for (size_t i=0; i<n; i++) { z[i]=x[i]+y[i]; } } > > > > Take RVV codegen for example: > > > > Before this patch: > > vvaddint32: > > ble a0,zero,.L6 > > csrr a4,vlenb > > srli a6,a4,2 > > .L4: > > mv a5,a0 > > bleu a0,a6,.L3 > > mv a5,a6 > > .L3: > > vsetvli zero,a5,e32,m1,ta,ma > > vle32.v v2,0(a1) > > vle32.v v1,0(a2) > > vsetvli a7,zero,e32,m1,ta,ma > > sub a0,a0,a5 > > vadd.vv v1,v1,v2 > > vsetvli zero,a5,e32,m1,ta,ma > > vse32.v v1,0(a3) > > add a2,a2,a4 > > add a3,a3,a4 > > add a1,a1,a4 > > bne a0,zero,.L4 > > .L6: > > ret > > > > After this patch: > > > > vvaddint32: > > vsetvli t0, a0, e32, ta, ma # Set vector length based on 32-bit vectors > > vle32.v v0, (a1) # Get first vector > > sub a0, a0, t0 # Decrement number done > > slli t0, t0, 2 # Multiply number done by 4 bytes > > add a1, a1, t0 # Bump pointer > > vle32.v v1, (a2) # Get second vector > > add a2, a2, t0 # Bump pointer > > vadd.vv v2, v0, v1 # Sum vectors > > vse32.v v2, (a3) # Store result > > add a3, a3, t0 # Bump pointer > > bnez a0, vvaddint32 # Loop back > > ret # Finished > > > > gcc/ChangeLog: > > > > * doc/md.texi: Add SELECT_VL support. > > * internal-fn.def (SELECT_VL): Ditto. > > * optabs.def (OPTAB_D): Ditto. > > * tree-vect-loop-manip.cc (vect_set_loop_controls_directly): Ditto. > > * tree-vect-loop.cc (_loop_vec_info::_loop_vec_info): Ditto. > > * tree-vect-stmts.cc (get_select_vl_data_ref_ptr): Ditto. > > (vectorizable_store): Ditto. > > (vectorizable_load): Ditto. > > * tree-vectorizer.h (LOOP_VINFO_USING_SELECT_VL_P): Ditto. > > > > Co-authored-by: Richard Sandiford<richard.sandif...@arm.com> > > > > --- > > gcc/doc/md.texi | 22 ++++++++++++ > > gcc/internal-fn.def | 1 + > > gcc/optabs.def | 1 + > > gcc/tree-vect-loop-manip.cc | 32 ++++++++++++----- > > gcc/tree-vect-loop.cc | 72 +++++++++++++++++++++++++++++++++++++ > > gcc/tree-vect-stmts.cc | 66 ++++++++++++++++++++++++++++++++++ > > gcc/tree-vectorizer.h | 6 ++++ > > 7 files changed, 191 insertions(+), 9 deletions(-) > > > > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi > > index 6a435eb4461..95f7fe1f802 100644 > > --- a/gcc/doc/md.texi > > +++ b/gcc/doc/md.texi > > @@ -4974,6 +4974,28 @@ for (i = 1; i < operand3; i++) > > operand0[i] = operand0[i - 1] && (operand1 + i < operand2); > > @end smallexample > > > > +@cindex @code{select_vl@var{m}} instruction pattern > > +@item @code{select_vl@var{m}} > > +Set operand 0 to the number of scalar iterations that should be handled > > +by one iteration of a vector loop. Operand 1 is the total number of > > +scalar iterations that the loop needs to process and operand 2 is a > > +maximum bound on the result (also known as the maximum ``vectorization > > +factor''). > > + > > +The maximum value of operand 0 is given by: > > +@smallexample > > +operand0 = MIN (operand1, operand2) > > +@end smallexample > > +However, targets might choose a lower value than this, based on > > +target-specific criteria. Each iteration of the vector loop might > > +therefore process a different number of scalar iterations, which in turn > > +means that induction variables will have a variable step. Because of > > +this, it is generally not useful to define this instruction if it will > > +always calculate the maximum value. > > + > > +This optab is only useful on targets that implement @samp{len_load_@var{m}} > > +and/or @samp{len_store_@var{m}}. > > + > > @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/internal-fn.def b/gcc/internal-fn.def > > index 7fe742c2ae7..6f6fa7d37f9 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 (SELECT_VL, ECF_CONST | ECF_NOTHROW, select_vl, > > 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..b637471b76e 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 (select_vl_optab, "select_vl$a") > > diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc > > index 3f735945e67..1c8100c1a1c 100644 > > --- a/gcc/tree-vect-loop-manip.cc > > +++ b/gcc/tree-vect-loop-manip.cc > > @@ -534,7 +534,7 @@ vect_set_loop_controls_directly (class loop *loop, > > loop_vec_info loop_vinfo, > > _10 = (unsigned long) count_12(D); > > ... > > # ivtmp_9 = PHI <ivtmp_35(6), _10(5)> > > - _36 = MIN_EXPR <ivtmp_9, POLY_INT_CST [4, 4]>; > > + _36 = (MIN_EXPR | SELECT_VL) <ivtmp_9, POLY_INT_CST [4, 4]>; > > ... > > vect__4.8_28 = .LEN_LOAD (_17, 32B, _36, 0); > > ... > > @@ -549,15 +549,28 @@ vect_set_loop_controls_directly (class loop *loop, > > loop_vec_info loop_vinfo, > > tree step = rgc->controls.length () == 1 ? rgc->controls[0] > > : make_ssa_name (iv_type); > > /* Create decrement IV. */ > > - create_iv (nitems_total, MINUS_EXPR, nitems_step, NULL_TREE, loop, > > - &incr_gsi, insert_after, &index_before_incr, > > - &index_after_incr); > > - gimple_seq_add_stmt (header_seq, gimple_build_assign (step, MIN_EXPR, > > - index_before_incr, > > - nitems_step)); > > + if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo)) > > + { > > + create_iv (nitems_total, MINUS_EXPR, step, NULL_TREE, loop, &incr_gsi, > > + insert_after, &index_before_incr, &index_after_incr); > > + tree len = gimple_build (header_seq, IFN_SELECT_VL, iv_type, > > + index_before_incr, nitems_step); > > + gimple_seq_add_stmt (header_seq, gimple_build_assign (step, len)); > > + } > > + else > > + { > > + create_iv (nitems_total, MINUS_EXPR, nitems_step, NULL_TREE, loop, > > + &incr_gsi, insert_after, &index_before_incr, > > + &index_after_incr); > > + gimple_seq_add_stmt (header_seq, > > + gimple_build_assign (step, MIN_EXPR, > > + index_before_incr, > > + nitems_step)); > > + } > > *iv_step = step; > > *compare_step = nitems_step; > > - return index_before_incr; > > + return LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) ? index_after_incr > > + : index_before_incr; > > } > > > > /* Create increment IV. */ > > @@ -888,7 +901,8 @@ vect_set_loop_condition_partial_vectors (class loop > > *loop, > > /* Get a boolean result that tells us whether to iterate. */ > > edge exit_edge = single_exit (loop); > > gcond *cond_stmt; > > - if (LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo)) > > + if (LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo) > > + && !LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo)) > > { > > gcc_assert (compare_step); > > tree_code code = (exit_edge->flags & EDGE_TRUE_VALUE) ? LE_EXPR : > > GT_EXPR; > > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc > > index 5b7a0da0034..ace9e759f5b 100644 > > --- a/gcc/tree-vect-loop.cc > > +++ b/gcc/tree-vect-loop.cc > > @@ -974,6 +974,7 @@ _loop_vec_info::_loop_vec_info (class loop *loop_in, > > vec_info_shared *shared) > > can_use_partial_vectors_p (param_vect_partial_vector_usage != 0), > > using_partial_vectors_p (false), > > using_decrementing_iv_p (false), > > + using_select_vl_p (false), > > epil_using_partial_vectors_p (false), > > partial_load_store_bias (0), > > peeling_for_gaps (false), > > @@ -2737,6 +2738,77 @@ start_over: > > LOOP_VINFO_VECT_FACTOR (loop_vinfo)))) > > LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo) = true; > > > > + /* If a loop uses length controls and has a decrementing loop control IV, > > + we will normally pass that IV through a MIN_EXPR to calcaluate the > > + basis for the length controls. E.g. in a loop that processes one > > + element per scalar iteration, the number of elements would be > > + MIN_EXPR <N, VF>, where N is the number of scalar iterations left. > > + > > + This MIN_EXPR approach allows us to use pointer IVs with an invariant > > + step, since only the final iteration of the vector loop can have > > + inactive lanes. > > + > > + However, some targets have a dedicated instruction for calculating the > > + preferred length, given the total number of elements that still need > > to > > + be processed. This is encapsulated in the SELECT_VL internal > > function. > > + > > + If the target supports SELECT_VL, we can use it instead of MIN_EXPR > > + to determine the basis for the length controls. However, unlike the > > + MIN_EXPR calculation, the SELECT_VL calculation can decide to make > > + lanes inactive in any iteration of the vector loop, not just the last > > + iteration. This SELECT_VL approach therefore requires us to use > > pointer > > + IVs with variable steps. > > + > > + Once we've decided how many elements should be processed by one > > + iteration of the vector loop, we need to populate the rgroup controls. > > + If a loop has multiple rgroups, we need to make sure that those > > rgroups > > + "line up" (that is, they must be consistent about which elements are > > + active and which aren't). This is done by > > vect_adjust_loop_lens_control. > > + > > + In principle, it would be possible to use > > vect_adjust_loop_lens_control > > + on either the result of a MIN_EXPR or the result of a SELECT_VL. > > + However: > > + > > + (1) In practice, it only makes sense to use SELECT_VL when a vector > > + operation will be controlled directly by the result. It is not > > + worth using SELECT_VL if it would only be the input to other > > + calculations. > > + > > + (2) If we use SELECT_VL for an rgroup that has N controls, each > > associated > > + pointer IV will need N updates by a variable amount (N-1 updates > > + within the iteration and 1 update to move to the next iteration). > > + > > + Because of this, we prefer to use the MIN_EXPR approach whenever there > > + is more than one length control. > > + > > + In addition, SELECT_VL always operates to a granularity of 1 unit. > > + If we wanted to use it to control an SLP operation on N consecutive > > + elements, we would need to make the SELECT_VL inputs measure scalar > > + iterations (rather than elements) and then multiply the SELECT_VL > > + result by N. But using SELECT_VL this way is inefficient because > > + of (1) above. > > + > > + 2. We don't apply SELECT_VL on single-rgroup when both (1) and (2) are > > + satisfied: > > + > > + (1). LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo) is true. > > + (2). LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant () is true. > > + > > + Since SELECT_VL (variable step) will make SCEV analysis failed and > > then > > + we will fail to gain benefits of following unroll optimizations. We > > prefer > > + using the MIN_EXPR approach in this situation. */ > > + if (LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo)) > > + { > > + tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo); > > + if (direct_internal_fn_supported_p (IFN_SELECT_VL, iv_type, > > + OPTIMIZE_FOR_SPEED) > > + && LOOP_VINFO_LENS (loop_vinfo).length () == 1 > > + && LOOP_VINFO_LENS (loop_vinfo)[0].factor == 1 && !slp > > + && (!LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo) > > + || !LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ())) > > + LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) = true; > > + } > > + > > /* If we're vectorizing an epilogue loop, the vectorized loop either > > needs > > to be able to handle fewer than VF scalars, or needs to have a lower > > VF > > than the main loop. */ > > diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc > > index e37c401b688..b28226b6e7e 100644 > > --- a/gcc/tree-vect-stmts.cc > > +++ b/gcc/tree-vect-stmts.cc > > @@ -3148,6 +3148,57 @@ 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 .SELECT_VL. 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 SELECT_VL. > > + If new statements are needed, insert them before GSI. */ > > + > > +static tree > > +get_select_vl_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) > > +{ > > + loop_vec_info loop_vinfo = dyn_cast<loop_vec_info> (vinfo); > > + tree step = vect_dr_behavior (vinfo, dr_info)->step; > > + > > + /* 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); > > At least for VMAT_GATHER_SCATTER you wouldn't execute this function > but get into > > else if (STMT_VINFO_GATHER_SCATTER_P (stmt_info)) > { > vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info, > slp_node, &gs_info, > &dataref_ptr, > &vec_offsets); > > no? > > This function belongs to tree-vect-data-refs.cc alongside the > other vect_create_data_ref_* functions. > > > + /* When we support SELECT_VL pattern, we dynamic adjust > > + the memory address by .SELECT_VL result. > > + > > + The result of .SELECT_VL is the number of elements to > > + be processed of each iteration. So the memory address > > + adjustment operation should be: > > + > > + addr = addr + .SELECT_VL (ARG..) * step; > > + */ > > + gimple *ptr_incr; > > + tree loop_len > > + = vect_get_loop_len (loop_vinfo, gsi, loop_lens, 1, aggr_type, 0, 0); > > + tree len_type = TREE_TYPE (loop_len); > > + /* Since the outcome of .SELECT_VL 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, > > + wide_int_to_tree (len_type, wi::to_widest (step))); > > + 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); > > so with this it seems you compute just 'bump', but ... > > > +} > > + > > /* Check and perform vectorization of BUILT_IN_BSWAP{16,32,64,128}. */ > > > > static bool > > @@ -8631,6 +8682,14 @@ vectorizable_store (vec_info *vinfo, > > vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info, > > slp_node, &gs_info, &dataref_ptr, > > &vec_offsets); > > + else if (loop_lens && LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) > > + && memory_access_type != VMAT_INVARIANT) > > + dataref_ptr > > + = get_select_vl_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); > > ... before the loop we compute 'bump' and that you do not touch? That > means you do not support ncopies != 1? Can you place an assert > in the else branch of the if (j == 0) that LOOP_VINFO_USING_SELECT_VL_P > is false? > > It would be better to put this before the existing > vect_create_data_ref_ptr, like > > else if (STMT_VINFO_GATHER_SCATTER_P (stmt_info)) > vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info, > slp_node, &gs_info, &dataref_ptr, > &vec_offsets); > else > { > if (LOOP_VINFO_USING_SELECT_VL_P) > bump = vect_get_loop_variant_data_ptr_increment (....); > > dataref_ptr > = vect_create_data_ref_ptr (vinfo, first_stmt_info, > aggr_type, > simd_lane_access_p ? loop : > NULL, > offset, &dummy, gsi, &ptr_incr, > simd_lane_access_p, bump); > } > > because indeed you have to place the computation inside of the loop. > And also in the place we compute 'bump' add the case > LOOP_VINFO_USING_SELECT_VL_P initializing bump to NULL_TREE and > a comment indicating the variable bump is computed inside the loop. > > For the case of ncopies != 1 how are you dealing with that? I suppose > for j != ncopies - 1 the bump is actually exactly VF? > > Thanks, > Richard, > > > else > > dataref_ptr > > = vect_create_data_ref_ptr (vinfo, first_stmt_info, aggr_type, > > @@ -10022,6 +10081,13 @@ vectorizable_load (vec_info *vinfo, > > slp_node, &gs_info, &dataref_ptr, > > &vec_offsets); > > } > > + else if (loop_lens && LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) > > + && memory_access_type != VMAT_INVARIANT) > > + dataref_ptr > > + = get_select_vl_data_ref_ptr (vinfo, stmt_info, aggr_type, > > + at_loop, offset, &dummy, gsi, > > + simd_lane_access_p, loop_lens, > > + dr_info, memory_access_type); > > else > > dataref_ptr > > = vect_create_data_ref_ptr (vinfo, first_stmt_info, aggr_type, > > diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h > > index 34552f6bf9e..c6e0140a0b5 100644 > > --- a/gcc/tree-vectorizer.h > > +++ b/gcc/tree-vectorizer.h > > @@ -825,6 +825,11 @@ public: > > (b) can iterate more than once. */ > > bool using_decrementing_iv_p; > > > > + /* True if we've decided to use output of select_vl to adjust IV of > > + both loop control and data reference pointer. This is only true > > + for single-rgroup control. */ > > + bool using_select_vl_p; > > + > > /* True if we've decided to use partially-populated vectors for the > > epilogue of loop. */ > > bool epil_using_partial_vectors_p; > > @@ -898,6 +903,7 @@ public: > > #define LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P(L) > > (L)->can_use_partial_vectors_p > > #define LOOP_VINFO_USING_PARTIAL_VECTORS_P(L) (L)->using_partial_vectors_p > > #define LOOP_VINFO_USING_DECREMENTING_IV_P(L) (L)->using_decrementing_iv_p > > +#define LOOP_VINFO_USING_SELECT_VL_P(L) (L)->using_select_vl_p > > #define LOOP_VINFO_EPIL_USING_PARTIAL_VECTORS_P(L) > > \ > > (L)->epil_using_partial_vectors_p > > #define LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS(L) (L)->partial_load_store_bias > > > > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)
