Hi, Richi. >> So how can we resolve the issue when a non-VL operation like >> .VEC_EXTRACT is used for _len support?
Do you mean non-VL extract last operation (I am sorry that not sure whether I understand your question correctly)? If yes, the answer is for RVV, we are reusing the same flow as ARM SVE (BIT_FILED_REF approach), see the example below: https://godbolt.org/z/cqrWrY8q4 #define EXTRACT_LAST(TYPE) \ TYPE __attribute__ ((noinline, noclone)) \ test_##TYPE (TYPE *x, int n, TYPE value) \ { \ TYPE last; \ for (int j = 0; j < 64; ++j) \ { \ last = x[j]; \ x[j] = last * value; \ } \ return last; \ } #define TEST_ALL(T) \ T (uint8_t) \ TEST_ALL (EXTRACT_LAST) vect_cst__22 = {value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D), value_12(D)}; vect_last_11.6_3 = MEM <vector(64) unsigned char> [(uint8_t *)x_10(D)]; vect__4.7_23 = vect_last_11.6_3 * vect_cst__22; MEM <vector(64) unsigned char> [(uint8_t *)x_10(D)] = vect__4.7_23; _21 = BIT_FIELD_REF <vect_last_11.6_3, 8, 504>; This approach works perfectly for both RVV and ARM SVE for non-VL and non-MASK EXTRACT_LAST operation. >> So, why do we test for get_len_load_store_mode and not just for >> VEC_EXTRACT? Before answer this question, let me first elaborate how ARM SVE is doing with MASK EXTRACT_LAST. Here is the example: https://godbolt.org/z/8cTv1jqMb ARM SVE IR: <bb 4> [local count: 955630224]: # ivtmp_31 = PHI <ivtmp_32(4), 0(3)> # loop_mask_22 = PHI <next_mask_35(4), max_mask_34(3)> -----> For RVV, we want this to be loop_len = SELECT_VL; _7 = &MEM <vector([16,16]) unsigned char> [(uint8_t *)x_11(D) + ivtmp_31 * 1]; vect_last_12.8_23 = .MASK_LOAD (_7, 8B, loop_mask_22); vect__4.9_27 = vect_last_12.8_23 * vect_cst__26; .MASK_STORE (_7, 8B, loop_mask_22, vect__4.9_27); ivtmp_32 = ivtmp_31 + POLY_INT_CST [16, 16]; _1 = (unsigned int) ivtmp_32; next_mask_35 = .WHILE_ULT (_1, bnd.5_6, { 0, ... }); if (next_mask_35 != { 0, ... }) goto <bb 4>; [89.00%] else goto <bb 5>; [11.00%] <bb 5> [local count: 105119324]: _25 = .EXTRACT_LAST (loop_mask_22, vect_last_12.8_23); [tail call] ----> Use the last mask generated in BB 4, so for RVV, we are using the loop_len. So this patch is trying to optimize the codegen with simulating same flow as ARM SVE but with replacing 'loop_mask_22' (This is generated in BB4) into 'loop_len'. For ARM SVE, they only check whether target support EXTRACT_LAST pattern, this pattern is supported means: 1. Target is using loop MASK as the partial vector loop control. 2. extract_last optab is enabled in the backend. So for RVV, we are also checking same conditions: 1. Target is using loop LEN as the partial vector loop control (I use get_len_load_store_mode to check whether target is using loop LEN as the partial vector loop control). 2. vec_extract optab is enabled in the backend. An alternative approach is that we can adding EXTRACT_LAST_LEN internal FN, then we can only check this like ARM SVE only check EXTRACT_LAST. >> can we double-check this on powerpc and s390? Sure, I hope it can be beneficial to powerpc and s390. And, I think Richard's comments are also very important so I am gonna wait for it. Thanks. juzhe.zh...@rivai.ai From: Richard Biener Date: 2023-08-11 15:01 To: Ju-Zhe Zhong CC: gcc-patches; richard.sandiford; linkw; krebbel Subject: Re: [PATCH V3] VECT: Support loop len control on EXTRACT_LAST vectorization On Fri, 11 Aug 2023, juzhe.zh...@rivai.ai wrote: > From: Ju-Zhe Zhong <juzhe.zh...@rivai.ai> > > Hi, Richard and Richi. > > This patch add support live vectorization by VEC_EXTRACT for LEN loop control. > > Consider this following case: > > #include <stdint.h> > > #define EXTRACT_LAST(TYPE) \ > TYPE __attribute__ ((noinline, noclone)) \ > test_##TYPE (TYPE *x, int n, TYPE value) \ > { \ > TYPE last; \ > for (int j = 0; j < n; ++j) \ > { \ > last = x[j]; \ > x[j] = last * value; \ > } \ > return last; \ > } > > #define TEST_ALL(T) \ > T (uint8_t) \ > > TEST_ALL (EXTRACT_LAST) > > ARM SVE IR: > > Preheader: > max_mask_34 = .WHILE_ULT (0, bnd.5_6, { 0, ... }); > > Loop: > ... > # loop_mask_22 = PHI <next_mask_35(4), max_mask_34(3)> > ... > vect_last_12.8_23 = .MASK_LOAD (_7, 8B, loop_mask_22); > vect__4.9_27 = vect_last_12.8_23 * vect_cst__26; > .MASK_STORE (_7, 8B, loop_mask_22, vect__4.9_27); > ... > next_mask_35 = .WHILE_ULT (_1, bnd.5_6, { 0, ... }); > ... > > Epilogue: > _25 = .EXTRACT_LAST (loop_mask_22, vect_last_12.8_23); > > For RVV since we prefer len in loop control, after this patch for RVV: > > Loop: > ... > loop_len_22 = SELECT_VL; > vect_last_12.8_23 = .MASK_LOAD (_7, 8B, loop_len_22); > vect__4.9_27 = vect_last_12.8_23 * vect_cst__26; > .MASK_STORE (_7, 8B, loop_len_22, vect__4.9_27); > ... > > Epilogue: > _25 = .VEC_EXTRACT (loop_len_22 + bias - 1, vect_last_12.8_23); > > Details of this approach: > > 1. Step 1 - Add 'vect_can_vectorize_extract_last_with_len_p' to enable live > vectorization > for LEN loop control. > > This function we check whether target support: > - Use LEN as the loop control. > - Support VEC_EXTRACT optab. > > 2. Step 2 - Record LEN for loop control if > 'vect_can_vectorize_extract_last_with_len_p' is true. > > 3. Step 3 - Gerenate VEC_EXTRACT (v, LEN + BIAS - 1). > > The only difference between mask and len is that len is using length > generated by SELECT_VL and > use VEC_EXTRACT pattern. The rest of the live vectorization is totally the > same ARM SVE. > > Bootstrap and Regression on X86 passed. > > Tested on ARM QEMU. > > Ok for trunk? > > gcc/ChangeLog: > > * tree-vect-loop.cc (vect_can_vectorize_extract_last_with_len_p): New > function. > (vectorizable_live_operation): Add loop len control. > > --- > gcc/tree-vect-loop.cc | 76 +++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 70 insertions(+), 6 deletions(-) > > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc > index bf8d677b584..809b73b966c 100644 > --- a/gcc/tree-vect-loop.cc > +++ b/gcc/tree-vect-loop.cc > @@ -8963,6 +8963,27 @@ vect_can_vectorize_without_simd_p (code_helper code) > && vect_can_vectorize_without_simd_p (tree_code (code))); > } > > +/* Return true if target supports extract last vectorization with LEN. */ > + > +static bool > +vect_can_vectorize_extract_last_with_len_p (tree vectype) > +{ > + /* Return false if target doesn't support LEN in loop control. */ > + machine_mode vmode; > + machine_mode vec_mode = TYPE_MODE (vectype); > + if (!VECTOR_MODE_P (vec_mode)) > + return false; > + if (!get_len_load_store_mode (vec_mode, true).exists (&vmode) > + || !get_len_load_store_mode (vec_mode, false).exists (&vmode)) > + return false; So this "hidden" bit in the end decides whether to ... > + /* Target need to support VEC_EXTRACT to extract the last active element. > */ > + return convert_optab_handler (vec_extract_optab, > + vec_mode, > + TYPE_MODE (TREE_TYPE (vectype))) > + != CODE_FOR_nothing; > +} > + > /* Create vector init for vectorized iv. */ > static tree > vect_create_nonlinear_iv_init (gimple_seq* stmts, tree init_expr, > @@ -10279,7 +10300,8 @@ vectorizable_live_operation (vec_info *vinfo, > stmt_vec_info stmt_info, > if (loop_vinfo && LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)) > { > if (!direct_internal_fn_supported_p (IFN_EXTRACT_LAST, vectype, > - OPTIMIZE_FOR_SPEED)) > + OPTIMIZE_FOR_SPEED) > + && !vect_can_vectorize_extract_last_with_len_p (vectype)) > { > if (dump_enabled_p ()) > dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, > @@ -10308,9 +10330,14 @@ vectorizable_live_operation (vec_info *vinfo, > stmt_vec_info stmt_info, > else > { > gcc_assert (ncopies == 1 && !slp_node); > - vect_record_loop_mask (loop_vinfo, > - &LOOP_VINFO_MASKS (loop_vinfo), > - 1, vectype, NULL); > + if (vect_can_vectorize_extract_last_with_len_p (vectype)) > + vect_record_loop_len (loop_vinfo, > + &LOOP_VINFO_LENS (loop_vinfo), > + 1, vectype, 1); .. record a loop_len here. I think powerpc at least has .VEC_EXTRACT as well but of course .VEC_EXTRACT support itself doesn't have anything to do with 'len' support. x86 has .VEC_SET but not yet .VEC_EXTRACT, if it gets .VEC_EXTRACT its partial vector support still wants masks, not lens (and once we record both we fail). So how can we resolve the issue when a non-VL operation like .VEC_EXTRACT is used for _len support? Note x86 doens't yet support IFN_EXTRACT_LAST either. So, why do we test for get_len_load_store_mode and not just for VEC_EXTRACT? > + else > + vect_record_loop_mask (loop_vinfo, > + &LOOP_VINFO_MASKS (loop_vinfo), > + 1, vectype, NULL); > } > } > /* ??? Enable for loop costing as well. */ > @@ -10336,7 +10363,9 @@ vectorizable_live_operation (vec_info *vinfo, > stmt_vec_info stmt_info, > gimple *vec_stmt; > if (slp_node) > { > - gcc_assert (!loop_vinfo || !LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)); > + gcc_assert (!loop_vinfo > + || (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo) > + && !LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo))); > > /* Get the correct slp vectorized stmt. */ > vec_lhs = SLP_TREE_VEC_DEFS (slp_node)[vec_entry]; > @@ -10380,7 +10409,42 @@ vectorizable_live_operation (vec_info *vinfo, > stmt_vec_info stmt_info, > > gimple_seq stmts = NULL; > tree new_tree; > - if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)) > + if (LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo)) > + { > + /* Emit: > + > + SCALAR_RES = VEC_EXTRACT <VEC_LHS, LEN + BIAS - 1> > + > + where VEC_LHS is the vectorized live-out result and MASK is > + the loop mask for the final iteration. */ > + gcc_assert (ncopies == 1 && !slp_node); > + gimple_seq tem = NULL; > + gimple_stmt_iterator gsi = gsi_last (tem); > + tree len > + = vect_get_loop_len (loop_vinfo, &gsi, > + &LOOP_VINFO_LENS (loop_vinfo), > + 1, vectype, 0, 0); > + > + /* BIAS - 1. */ > + signed char biasval = LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS (loop_vinfo); > + tree bias_minus_one > + = int_const_binop (MINUS_EXPR, > + build_int_cst (TREE_TYPE (len), biasval), > + build_one_cst (TREE_TYPE (len))); > + > + /* LAST_INDEX = LEN + (BIAS - 1). */ > + tree last_index = gimple_build (&stmts, PLUS_EXPR, TREE_TYPE (len), > + len, bias_minus_one); > + > + /* SCALAR_RES = VEC_EXTRACT <VEC_LHS, LEN + BIAS - 1>. */ > + tree scalar_res > + = gimple_build (&stmts, CFN_VEC_EXTRACT, TREE_TYPE (vectype), > + vec_lhs_phi, last_index); > + can we double-check this on powerpc and s390? Thanks, Richard. > + /* Convert the extracted vector element to the scalar type. */ > + new_tree = gimple_convert (&stmts, lhs_type, scalar_res); > + } > + else if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)) > { > /* Emit: >
