Hi, Richi.
>> check here the target supports VEC_EXTRACT
>> else set LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P to false with a
>> diagnostic.
I am wondering target has VEC_EXTRACT but no EXTRACT_LAST, and such target is
using MASK as the loop control.
It seems that it will cause ICE for such target ? (Not sure whether we
currently have such target so far).
Thanks.
juzhe.zh...@rivai.ai
From: Richard Biener
Date: 2023-08-11 19:10
To: juzhe.zh...@rivai.ai
CC: gcc-patches; richard.sandiford; linkw; krebbel
Subject: Re: Re: [PATCH V3] VECT: Support loop len control on EXTRACT_LAST
vectorization
On Fri, 11 Aug 2023, juzhe.zh...@rivai.ai wrote:
> Hi, Richi.
>
> > 1. Target is using loop MASK as the partial vector loop control.
> >> I don't think it checks for this?
>
> I am not sure whether I understand EXTRACT_LAST correctly.
> But if target doesn't use loop MASK for partial vector loop control, how does
> target use EXTRACT_LAST?
> Since EXTRACT_LAST is always extracting the last element of the vector
> according to MASK operand.
>
> > But we don't really know this at this point? The only thing we know
> > is that nothing set LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P to false.
>
> Yes. So I am try to use 'get_len_load_store' to check whether target support
> LEN loop control.
>
> Well, I admit it's not a good idea.
>
>
> > I think it should work to change the direct_internal_fn_supported_p
> > check for IFN_EXTRACT_LAST to a "poitive" one guarding
>
> > gcc_assert (ncopies == 1 && !slp_node);
> > vect_record_loop_mask (loop_vinfo,
> > &LOOP_VINFO_MASKS (loop_vinfo),
> > 1, vectype, NULL);
>
> > and in the else branch check for VEC_EXTRACT support and if present
> > record a loop len. Just in this case this particular order would
> > be important.
>
> Do you mean change the codes as follows :?
>
> - if (!direct_internal_fn_supported_p (IFN_EXTRACT_LAST, vectype,
> - OPTIMIZE_FOR_SPEED))
> - {
> - if (dump_enabled_p ())
> - dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> - "can't operate on partial vectors "
> - "because the target doesn't support extract "
> - "last reduction.\n");
> - LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
> - }
> - else if (slp_node)
> if (slp_node)
> {
> if (dump_enabled_p ())
> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> "can't operate on partial vectors "
> "because an SLP statement is live after "
> "the loop.\n");
> LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
> }
> else if (ncopies > 1)
> {
> if (dump_enabled_p ())
> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> "can't operate on partial vectors "
> "because ncopies is greater than 1.\n");
> LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
> }
> else
> {
> gcc_assert (ncopies == 1 && !slp_node);
> if (direct_internal_fn_supported_p (IFN_EXTRACT_LAST, vectype,
> OPTIMIZE_FOR_SPEED))
> vect_record_loop_mask (loop_vinfo,
> &LOOP_VINFO_MASKS (loop_vinfo),
> 1, vectype, NULL);
> else
check here the target supports VEC_EXTRACT
> vect_record_loop_len (loop_vinfo,
> &LOOP_VINFO_LENS (loop_vinfo),
> 1, vectype, 1);
else set LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P to false with a
diagnostic.
> }
>
>
> Thanks.
>
>
> juzhe.zh...@rivai.ai
>
> From: Richard Biener
> Date: 2023-08-11 18:21
> To: juzhe.zh...@rivai.ai
> CC: gcc-patches; richard.sandiford; linkw; krebbel
> Subject: Re: Re: [PATCH V3] VECT: Support loop len control on EXTRACT_LAST
> vectorization
> On Fri, 11 Aug 2023, juzhe.zh...@rivai.ai wrote:
>
> > 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.
>
> I don't think it checks for this?
>
> > 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).
>
> But we don't really know this at this point? The only thing we know
> is that nothing set LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P to false.
>
> > 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.
>
> I think it should work to change the direct_internal_fn_supported_p
> check for IFN_EXTRACT_LAST to a "poitive" one guarding
>
> gcc_assert (ncopies == 1 && !slp_node);
> vect_record_loop_mask (loop_vinfo,
> &LOOP_VINFO_MASKS (loop_vinfo),
> 1, vectype, NULL);
>
> and in the else branch check for VEC_EXTRACT support and if present
> record a loop len. Just in this case this particular order would
> be important.
>
> > >> 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.
>
> Yeah, just to double-check the bias stuff works correctly.
>
> Richard.
>
> > 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:
> > >
> >
> >
>
>
--
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)
