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
vect_record_loop_len (loop_vinfo,
&LOOP_VINFO_LENS (loop_vinfo),
1, vectype, 1);
}
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)
