Re: Re: [PATCH V2] VECT: Support CALL vectorization for COND_LEN_*

[钟居哲 <juzhe.zhong@rivai.ai>]

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Yeah. I have tried this case too.

But this case doesn't need to be vectorized as COND_FMA, am I right?

The thing I wonder is that whether this condtion:

if  (mask_opno >= 0 && reduc_idx >= 0)

or similar as len
if  (len_opno >= 0 && reduc_idx >= 0)

Whether they are redundant in vectorizable_call ?


juzhe.zhong@rivai.ai
 
From: Richard Biener
Date: 2023-07-31 21:33
To: juzhe.zhong@rivai.ai
CC: richard.sandiford; gcc-patches
Subject: Re: Re: [PATCH V2] VECT: Support CALL vectorization for COND_LEN_*
On Mon, 31 Jul 2023, juzhe.zhong@rivai.ai wrote:
 
> Hi, Richi.
> 
> >> I think you need to use fma from math.h together with -ffast-math
> >>to get fma.
> 
> As you said, this is one of the case I tried:
> https://godbolt.org/z/xMzrrv5dT 
> GCC failed to vectorize.
> 
> Could you help me with this?
 
double foo (double *a, double *b, double *c)
{
  double result = 0.0;
  for (int i = 0; i < 1024; ++i)
    result += __builtin_fma (a[i], b[i], c[i]);
  return result;
}
 
with -mavx2 -mfma -Ofast this is vectorized on x86_64 to
 
...
  vect__9.13_27 = MEM <vector(4) double> [(double *)vectp_a.11_29];
  _9 = *_8;
  vect__10.14_26 = .FMA (vect__7.10_30, vect__9.13_27, vect__4.7_33);
  vect_result_17.15_25 = vect__10.14_26 + vect_result_20.4_36;
...
 
but ifcvt still shows
 
  _9 = *_8;
  _10 = __builtin_fma (_7, _9, _4);
  result_17 = _10 + result_20;
 
still vectorizable_call has IFN_FMA with
 
  /* First try using an internal function.  */
  code_helper convert_code = MAX_TREE_CODES;
  if (cfn != CFN_LAST
      && (modifier == NONE
          || (modifier == NARROW
              && simple_integer_narrowing (vectype_out, vectype_in,
                                           &convert_code))))
    ifn = vectorizable_internal_function (cfn, callee, vectype_out,
                                          vectype_in);
 
from CFN_BUILT_IN_FMA
 
 
 
> Thanks.
> 
> 
> juzhe.zhong@rivai.ai
>  
> From: Richard Biener
> Date: 2023-07-31 20:00
> To: juzhe.zhong@rivai.ai
> CC: richard.sandiford; gcc-patches
> Subject: Re: Re: [PATCH V2] VECT: Support CALL vectorization for COND_LEN_*
> On Mon, 31 Jul 2023, juzhe.zhong@rivai.ai wrote:
>  
> > Ok . Thanks Richard.
> > 
> > Could you give me a case that SVE can vectorize a reduction with FMA?
> > Meaning it will go into vectorize_call and vectorize FMA into COND_FMA ?
> > 
> > I tried many times to reproduce such cases but I failed.
>  
> I think you need to use fma from math.h together with -ffast-math
> to get fma.
>  
> Richard.
>  
> > Thanks.
> > 
> > 
> > juzhe.zhong@rivai.ai
> >  
> > From: Richard Sandiford
> > Date: 2023-07-31 18:19
> > To: Juzhe-Zhong
> > CC: gcc-patches; rguenther
> > Subject: Re: [PATCH V2] VECT: Support CALL vectorization for COND_LEN_*
> > Juzhe-Zhong <juzhe.zhong@rivai.ai> writes:
> > > Hi, Richard and Richi.
> > >
> > > Base on the suggestions from Richard:
> > > https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625396.html
> > >
> > > This patch choose (1) approach that Richard provided, meaning:
> > >
> > > RVV implements cond_* optabs as expanders.  RVV therefore supports
> > > both IFN_COND_ADD and IFN_COND_LEN_ADD.  No dummy length arguments
> > > are needed at the gimple level.
> > >
> > > Such approach can make codes much cleaner and reasonable.
> > >
> > > Consider this following case:
> > > void foo (float * __restrict a, float * __restrict b, int * __restrict cond, int n)
> > > {
> > >   for (int i = 0; i < n; i++)
> > >     if (cond[i])
> > >       a[i] = b[i] + a[i];
> > > }
> > >
> > >
> > > Output of RISC-V (32-bits) gcc (trunk) (Compiler #3)
> > > <source>:5:21: missed: couldn't vectorize loop
> > > <source>:5:21: missed: not vectorized: control flow in loop.
> > >
> > > ARM SVE:
> > >
> > > ...
> > > mask__27.10_51 = vect__4.9_49 != { 0, ... };
> > > ...
> > > vec_mask_and_55 = loop_mask_49 & mask__27.10_51;
> > > ...
> > > vect__9.17_62 = .COND_ADD (vec_mask_and_55, vect__6.13_56, vect__8.16_60, vect__6.13_56);
> > >
> > > For RVV, we want IR as follows:
> > >
> > > ...
> > > _68 = .SELECT_VL (ivtmp_66, POLY_INT_CST [4, 4]);
> > > ...
> > > mask__27.10_51 = vect__4.9_49 != { 0, ... };
> > > ...
> > > vect__9.17_60 = .COND_LEN_ADD (mask__27.10_51, vect__6.13_55, vect__8.16_59, vect__6.13_55, _68, 0);
> > > ...
> > >
> > > Both len and mask of COND_LEN_ADD are real not dummy.
> > >
> > > This patch has been fully tested in RISC-V port with supporting both COND_* and COND_LEN_*.
> > >
> > > And also, Bootstrap and Regression on X86 passed.
> > >
> > > OK for trunk?
> > >
> > > gcc/ChangeLog:
> > >
> > >         * internal-fn.cc (FOR_EACH_LEN_FN_PAIR): New macro.
> > >         (get_len_internal_fn): New function.
> > >         (CASE): Ditto.
> > >         * internal-fn.h (get_len_internal_fn): Ditto.
> > >         * tree-vect-stmts.cc (vectorizable_call): Support CALL vectorization with COND_LEN_*.
> > >
> > > ---
> > >  gcc/internal-fn.cc     | 46 ++++++++++++++++++++++
> > >  gcc/internal-fn.h      |  1 +
> > >  gcc/tree-vect-stmts.cc | 87 +++++++++++++++++++++++++++++++++++++-----
> > >  3 files changed, 125 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
> > > index 8e294286388..379220bebc7 100644
> > > --- a/gcc/internal-fn.cc
> > > +++ b/gcc/internal-fn.cc
> > > @@ -4443,6 +4443,52 @@ get_conditional_internal_fn (internal_fn fn)
> > >      }
> > >  }
> > >  
> > > +/* Invoke T(IFN) for each internal function IFN that also has an
> > > +   IFN_COND_LEN_* or IFN_MASK_LEN_* form.  */
> > > +#define FOR_EACH_LEN_FN_PAIR(T)                                                \
> > > +  T (MASK_LOAD, MASK_LEN_LOAD)                                                 \
> > > +  T (MASK_STORE, MASK_LEN_STORE)                                               \
> > > +  T (MASK_GATHER_LOAD, MASK_LEN_GATHER_LOAD)                                   \
> > > +  T (MASK_SCATTER_STORE, MASK_LEN_SCATTER_STORE)                               \
> > > +  T (COND_ADD, COND_LEN_ADD)                                                   \
> > > +  T (COND_SUB, COND_LEN_SUB)                                                   \
> > > +  T (COND_MUL, COND_LEN_MUL)                                                   \
> > > +  T (COND_DIV, COND_LEN_DIV)                                                   \
> > > +  T (COND_MOD, COND_LEN_MOD)                                                   \
> > > +  T (COND_RDIV, COND_LEN_RDIV)                                                 \
> > > +  T (COND_FMIN, COND_LEN_FMIN)                                                 \
> > > +  T (COND_FMAX, COND_LEN_FMAX)                                                 \
> > > +  T (COND_MIN, COND_LEN_MIN)                                                   \
> > > +  T (COND_MAX, COND_LEN_MAX)                                                   \
> > > +  T (COND_AND, COND_LEN_AND)                                                   \
> > > +  T (COND_IOR, COND_LEN_IOR)                                                   \
> > > +  T (COND_XOR, COND_LEN_XOR)                                                   \
> > > +  T (COND_SHL, COND_LEN_SHL)                                                   \
> > > +  T (COND_SHR, COND_LEN_SHR)                                                   \
> > > +  T (COND_NEG, COND_LEN_NEG)                                                   \
> > > +  T (COND_FMA, COND_LEN_FMA)                                                   \
> > > +  T (COND_FMS, COND_LEN_FMS)                                                   \
> > > +  T (COND_FNMA, COND_LEN_FNMA)                                                 \
> > > +  T (COND_FNMS, COND_LEN_FNMS)
> >  
> > With the earlier patch to add DEF_INTERNAL_COND_FN and
> > DEF_INTERNAL_SIGNED_COND_FN, I think we should use those to handle
> > the COND_* cases, rather than putting them in this macro.
> >  
> > Thanks,
> > Richard
> >  
> > 
>  
> 
 
-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)