On Thu, 10 Aug 2023, juzhe.zh...@rivai.ai wrote:
> >> I guess as a temporary thing your approach is OK but we shouldn't
> >> add these as part of new code - it's supposed to handle legacy
> >> cases that we didn't fixup yet.
>
> Do you mean we need to fix LC SSA PHI flow so that we don't need to
> set vinfo->any_known_not_updated_vssa = true ?
>
> After it's fixed then this patch with removing
> 'vinfo->any_known_not_updated_vssa = true' is ok for trunk, am I right?
I want to know why we don't need this for SVE fully masked loops. What
inserts the required LC SSA PHI in that case?
> Thanks.
>
>
> juzhe.zh...@rivai.ai
>
> From: Richard Biener
> Date: 2023-08-10 15:58
> To: Ju-Zhe Zhong
> CC: gcc-patches; richard.sandiford
> Subject: Re: [PATCH V2] VECT: Support loop len control on EXTRACT_LAST
> vectorization
> On Thu, 10 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 - 1 - bias, 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 - 1 - BIAS).
> >
> > NOTE: This patch set 'vinfo->any_known_not_updated_vssa = true;' since the
> > original STMT is a simple
> > assignment wheras VEC_EXTRACT is neither pure nor const function
> > according to internal-fn.def:
> >
> > DEF_INTERNAL_OPTAB_FN (VEC_EXTRACT, 0, vec_extract, vec_extract)
> >
> > If we don't set 'vinfo->any_known_not_updated_vssa' as true, it will
> > cause ICE in:
> >
> > if (need_ssa_update_p (cfun))
> > {
> > gcc_assert (loop_vinfo->any_known_not_updated_vssa); ---->
> > Report assertion fail here.
> > fun->gimple_df->ssa_renaming_needed = false;
> > todo |= TODO_update_ssa_only_virtuals;
> > }
> >
> > I saw there are 2 places set 'vinfo->any_known_not_updated_vssa' as
> > true:
> >
> > - The one is in 'vectorizable_simd_clone_call':
> >
> > /* When the original call is pure or const but the SIMD ABI dictates
> > an aggregate return we will have to use a virtual definition and
> > in a loop eventually even need to add a virtual PHI. That's
> > not straight-forward so allow to fix this up via renaming. */
> > if (gimple_call_lhs (stmt)
> > && !gimple_vdef (stmt)
> > && TREE_CODE (TREE_TYPE (TREE_TYPE (bestn->decl))) == ARRAY_TYPE)
> > vinfo->any_known_not_updated_vssa = true;
> >
> > - The other is in 'vectorizable_load':
> >
> > if (memory_access_type == VMAT_LOAD_STORE_LANES)
> > vinfo->any_known_not_updated_vssa = true;
> >
> > It seems that they are the same reason as me doing in
> > 'vectorizable_live_operation'.
> > Feel free to correct me if I am wrong.
>
> You should always manually update things. Did you verify the mask
> case is handled by this?
>
> There's the odd
>
> if (stmts)
> {
> gimple_stmt_iterator exit_gsi = gsi_after_labels (exit_bb);
> gsi_insert_seq_before (&exit_gsi, stmts, GSI_SAME_STMT);
>
> /* Remove existing phi from lhs and create one copy from
> new_tree. */
> tree lhs_phi = NULL_TREE;
> gimple_stmt_iterator gsi;
> for (gsi = gsi_start_phis (exit_bb);
> !gsi_end_p (gsi); gsi_next (&gsi))
> {
> gimple *phi = gsi_stmt (gsi);
> if ((gimple_phi_arg_def (phi, 0) == lhs))
> {
> remove_phi_node (&gsi, false);
> lhs_phi = gimple_phi_result (phi);
> gimple *copy = gimple_build_assign (lhs_phi, new_tree);
> gsi_insert_before (&exit_gsi, copy, GSI_SAME_STMT);
> break;
> }
> }
>
> code but I don't think it will create new LC PHIs for the mask, instead
> it will break LC SSA as well by removing a PHI?
>
> I guess as a temporary thing your approach is OK but we shouldn't
> add these as part of new code - it's supposed to handle legacy
> cases that we didn't fixup yet.
>
> Richard.
>
>
>
> > Bootstrap and Regression on X86 passed.
> >
> > 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 | 74 +++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 68 insertions(+), 6 deletions(-)
> >
> > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> > index 00058c3c13e..208918f53fb 100644
> > --- a/gcc/tree-vect-loop.cc
> > +++ b/gcc/tree-vect-loop.cc
> > @@ -8964,6 +8964,24 @@ 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;
> > + if (!get_len_load_store_mode (TYPE_MODE (vectype), true).exists (&vmode)
> > + || !get_len_load_store_mode (TYPE_MODE (vectype), false).exists
> > (&vmode))
> > + return false;
> > +
> > + /* Target need to support VEC_EXTRACT to extract the last active
> > element. */
> > + return convert_optab_handler (vec_extract_optab,
> > + TYPE_MODE (vectype),
> > + 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,
> > @@ -10282,7 +10300,8 @@ vectorizable_live_operation (vec_info *vinfo,
> > 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,
> > @@ -10311,9 +10330,14 @@ vectorizable_live_operation (vec_info *vinfo,
> > 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);
> > + else
> > + vect_record_loop_mask (loop_vinfo,
> > + &LOOP_VINFO_MASKS (loop_vinfo),
> > + 1, vectype, NULL);
> > }
> > }
> > /* ??? Enable for loop costing as well. */
> > @@ -10339,7 +10363,9 @@ vectorizable_live_operation (vec_info *vinfo,
> > 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];
> > @@ -10383,7 +10409,43 @@ vectorizable_live_operation (vec_info *vinfo,
> >
> > 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);
> > + tree scalar_type = TREE_TYPE (STMT_VINFO_VECTYPE (stmt_info));
> > + 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_one
> > + = size_binop (PLUS_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, MINUS_EXPR, TREE_TYPE (len), len, bias_one);
> > +
> > + tree scalar_res = gimple_build (&stmts, CFN_VEC_EXTRACT, scalar_type,
> > + vec_lhs_phi, last_index);
> > +
> > + /* Convert the extracted vector element to the scalar type. */
> > + new_tree = gimple_convert (&stmts, lhs_type, scalar_res);
> > + /* When the original stmt is an assignment but VEC_EXTRACT is not pure
> > + or const since it may return a memory result. We will have to use
> > + a virtual definition and in a loop eventually even need to add a
> > + virtual PHI. That's not straight-forward so allow to fix this up
> > + via renaming. */
> > + vinfo->any_known_not_updated_vssa = true;
> > + }
> > + else if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo))
> > {
> > /* Emit:
> >
> >
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
