RE: RE: [PATCH 9/21]middle-end: implement vectorizable_early_exit for codegen of exit code

[Tamar Christina <Tamar.Christina@arm.com>]

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Hi Juzhe,

I meant that “lens” is undefined, from looking around I guess that needs to be

  vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);

for `bias` I meant

    cond = gimple_build (&cond_gsi, IFN_VCOND_MASK_LEN, truth_type,
                         all true mask, cond, all false mask, len, bias);

that variable `bias` isn’t defined. And I can’t find any other usage of IFN_VCOND_MASK_LEN creation to figure out what it’s supposed to be 😊

is it just an SImode 0?

Thanks,
Tamar


From: juzhe.zhong@rivai.ai <juzhe.zhong@rivai.ai>
Sent: Thursday, November 30, 2023 11:49 AM
To: Tamar Christina <Tamar.Christina@arm.com>; gcc-patches <gcc-patches@gcc.gnu.org>
Cc: Richard Biener <richard.guenther@gmail.com>
Subject: Re: RE: [PATCH 9/21]middle-end: implement vectorizable_early_exit for codegen of exit code

Thanks Tamar.

I am not sure whether I am not on the same page with you.

IMHO, ARM SVE will use the final mask = loop mask (generate by WHILE_ULT) & conditional mask.
Use that final mask to do the cbranch. Am I right ?

If yes, I leverage that for length and avoid too much codes change in your patch.

So, for RVV, the length is pretty same as loop mask in ARM SVE.
For example, suppose n = 4, in ARM SVE, WHILE_ULT (whilelo) generate mask = 0b11110000000....
Then use that mask to control the operations.

For RVV, is the same, length will be 4, then we will only process the elements with index < 4.

For bias, I think that won't be the issue. Currently, BIAS is not used by RVV and only used on len_load/len_store for IBM targets.
So, the bias value by default is 0 in all other situations except len_load/len_store specifically for IBM.

________________________________
juzhe.zhong@rivai.ai<mailto:juzhe.zhong@rivai.ai>

From: Tamar Christina<mailto:Tamar.Christina@arm.com>
Date: 2023-11-30 18:39
To: juzhe.zhong@rivai.ai<mailto:juzhe.zhong@rivai.ai>; gcc-patches<mailto:gcc-patches@gcc.gnu.org>
CC: Richard Biener<mailto:richard.guenther@gmail.com>
Subject: RE: [PATCH 9/21]middle-end: implement vectorizable_early_exit for codegen of exit code
Hi Juzhe,

I’m happy to take the hunks, just that I can’t test it and don’t know the specifics of how it lens work.
I still need to read up on it.

I tried adding that chunk in, but for the first bit `lens` seems undefined, and the second bit it seems `bias` is undefined.

I’ll also need what to do for vectorizable_live_operations how to get the first element rather than the last.

Thanks,
Tamar

From: juzhe.zhong@rivai.ai<mailto:juzhe.zhong@rivai.ai> <juzhe.zhong@rivai.ai<mailto:juzhe.zhong@rivai.ai>>
Sent: Thursday, November 30, 2023 4:48 AM
To: gcc-patches <gcc-patches@gcc.gnu.org<mailto:gcc-patches@gcc.gnu.org>>
Cc: Richard Biener <richard.guenther@gmail.com<mailto:richard.guenther@gmail.com>>; Tamar Christina <Tamar.Christina@arm.com<mailto:Tamar.Christina@arm.com>>
Subject: [PATCH 9/21]middle-end: implement vectorizable_early_exit for codegen of exit code

Hi, Richard and Tamar.

I am sorry for bothering you.
Hope you don't mind I give some comments:

Can we support partial vector for length ?

IMHO, we can do that as follows:

bool length_loop_p = LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo);

if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
  {
    if (direct_internal_fn_supported_p (IFN_VCOND_MASK_LEN, vectype,
                                        OPTIMIZE_FOR_SPEED))
      vect_record_loop_len (loop_vinfo, lens, ncopies, vectype, 1);
    else
      vect_record_loop_mask (loop_vinfo, masks, ncopies, truth_type, NULL);
  }

if (length_loop_p)
  {
    tree len = vect_get_loop_len (loop_vinfo, gsi, loop_lens, 1, vectype, 0, 0);
    /* Use VCOND_MASK_LEN (all true, cond, all false, len, bias) to generate
       final mask = i < len + bias ? cond[i] : false.  */
    cond = gimple_build (&cond_gsi, IFN_VCOND_MASK_LEN, truth_type,
                         all true mask, cond, all false mask, len, bias);
  }
else if (masked_loop_p)
  {
    tree mask
      = vect_get_loop_mask (loop_vinfo, gsi, masks, ncopies, truth_type, 0);
    cond
      = prepare_vec_mask (loop_vinfo, TREE_TYPE (mask), mask, cond, &cond_gsi);
  }

This is a prototype. Is this idea reasonable to Richi ?

Thanks.

________________________________
juzhe.zhong@rivai.ai<mailto:juzhe.zhong@rivai.ai>