Hi, Richi. Thanks for comments. >>this is in a if (j == 0) branch, please put the assert into the >>else {} block of it instead. You still run the 'bump' computation >>before the loop, so if you intend to never handle j != 0 you could >>put it there, too. But at least avoid calling >>vect_get_data_ptr_increment in that code when you re-do it here. Ok >> btw, I wonder how vect_create_data_ref_ptr and >>vect_get_data_ptr_increment handle LEN when not using .SELECT_VL? >>Are they always using the constant VF here? Yes, when we are not using SELECT_VL, we always use VF. >>Can't this be done in vect_get_data_ptr_increment by instead >>of using VF for LOOP_VINFO_USING_SELECT_VL_P use >>vect_get_loop_len () and so only change one place? oK, I will try that in V6 patch. Thanks. juzhe.zhong@rivai.ai From: Richard Biener Date: 2023-06-09 16:13 To: Ju-Zhe Zhong CC: gcc-patches; richard.sandiford Subject: Re: [PATCH V5] VECT: Add SELECT_VL support On Thu, 8 Jun 2023, juzhe.zhong@rivai.ai wrote: > From: Ju-Zhe Zhong > > Co-authored-by: Richard Sandiford > Co-authored-by: Richard Biener > > This patch address comments from Richard && Richi 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 > 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 > Co-authored-by: Richard Biener > > --- > 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 | 86 ++++++++++++++++++++++++++++++++----- > gcc/tree-vectorizer.h | 6 +++ > 7 files changed, 201 insertions(+), 19 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 3ac9d82aace..5d638de6d06 100644 > --- a/gcc/internal-fn.def > +++ b/gcc/internal-fn.def > @@ -177,6 +177,7 @@ 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 6c064ff4993..f31b69c5d85 100644 > --- a/gcc/optabs.def > +++ b/gcc/optabs.def > @@ -488,3 +488,4 @@ 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 > - _36 = MIN_EXPR ; > + _36 = (MIN_EXPR | SELECT_VL) ; > ... > 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 , 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 c7e4e71d3c5..34e4ad3c922 100644 > --- a/gcc/tree-vect-stmts.cc > +++ b/gcc/tree-vect-stmts.cc > @@ -3148,6 +3148,52 @@ 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 > +vect_get_loop_variant_data_ptr_increment ( > + vec_info *vinfo, tree aggr_type, gimple_stmt_iterator *gsi, > + vec_loop_lens *loop_lens, dr_vec_info *dr_info, > + vect_memory_access_type memory_access_type) > +{ > + loop_vec_info loop_vinfo = dyn_cast (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); > + > + /* 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; > + */ > + 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 bump; > +} > + > /* Check and perform vectorization of BUILT_IN_BSWAP{16,32,64,128}. */ > > static bool > @@ -8655,11 +8701,21 @@ vectorizable_store (vec_info *vinfo, > slp_node, &gs_info, &dataref_ptr, > &vec_offsets); > else > - 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); > + { > + if (loop_lens && LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) > + && memory_access_type != VMAT_INVARIANT) > + bump = vect_get_loop_variant_data_ptr_increment ( > + vinfo, aggr_type, gsi, loop_lens, dr_info, > + memory_access_type); > + > + if (j != 0) > + gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo)); this is in a if (j == 0) branch, please put the assert into the else {} block of it instead. You still run the 'bump' computation before the loop, so if you intend to never handle j != 0 you could put it there, too. But at least avoid calling vect_get_data_ptr_increment in that code when you re-do it here. Btw, > + 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); > + } > } > else > { > @@ -10046,11 +10102,21 @@ vectorizable_load (vec_info *vinfo, > &vec_offsets); > } > else > - dataref_ptr > - = vect_create_data_ref_ptr (vinfo, first_stmt_info, aggr_type, > - at_loop, > - offset, &dummy, gsi, &ptr_incr, > - simd_lane_access_p, bump); > + { > + if (loop_lens && LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) > + && memory_access_type != VMAT_INVARIANT) > + bump = vect_get_loop_variant_data_ptr_increment ( > + vinfo, aggr_type, gsi, loop_lens, dr_info, > + memory_access_type); > + > + if (j != 0) > + gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo)); same here > + dataref_ptr > + = vect_create_data_ref_ptr (vinfo, first_stmt_info, aggr_type, > + at_loop, offset, &dummy, gsi, > + &ptr_incr, simd_lane_access_p, > + bump); btw, I wonder how vect_create_data_ref_ptr and vect_get_data_ptr_increment handle LEN when not using .SELECT_VL? Are they always using the constant VF here? Can't this be done in vect_get_data_ptr_increment by instead of using VF for LOOP_VINFO_USING_SELECT_VL_P use vect_get_loop_len () and so only change one place? > + } > if (mask) > vec_mask = vec_masks[0]; > } > diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h > index 1e44f8542d7..af25d20bd7e 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 SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)