From: "Kewen.Lin" <linkw@linux.ibm.com>
To: "juzhe.zhong@rivai.ai" <juzhe.zhong@rivai.ai>,
"richard.sandiford" <richard.sandiford@arm.com>,
rguenther <rguenther@suse.de>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>,
jeffreyalaw <jeffreyalaw@gmail.com>, rdapp <rdapp@linux.ibm.com>
Subject: Re: [PATCH] VECT: Add WHILE_LEN pattern for decrement IV support for auto-vectorization
Date: Wed, 12 Apr 2023 20:56:58 +0800 [thread overview]
Message-ID: <d431841e-8f8e-3c11-e348-87f3014f5d8e@linux.ibm.com> (raw)
In-Reply-To: <E8B085826C635D01+2023041219371911535174@rivai.ai>
Hi!
on 2023/4/12 19:37, juzhe.zhong@rivai.ai wrote:
> Thank you. Richard. >> I think that already works for them (could be misremembering). >> However, IIUC, they have no special instruction to calculate the >> length (unlike for RVV), and so it's open-coded using vect_get_len.
>
> Thank you. Richard.
>
>
>>> I think that already works for them (could be misremembering).
>>> However, IIUC, they have no special instruction to calculate the
>>> length (unlike for RVV), and so it's open-coded using vect_get_len.
>
Yeah, Richard is right, we don't have some special hardware instruction
for efficient length calculation.
> Yeah, the current flow using min, sub, and then min in vect_get_len
> is working for IBM. But I wonder whether switching the current flow of
> length-loop-control into the WHILE_LEN pattern that this patch can improve
> their performance.
Based on some cons for the vector load/store with length in bytes on Power
(like we need one extra GPR holding the length, the length needs to be the
most significant 8 bits requiring an extra shifting etc.), we use normal
vector load/store in main loop and only use vector load/store with length
for the epilogue. For the epilogue, the remaining length is known less
than the whole vector length, so the related sequence can be optimized.
I just had a check on s390 code, which also enables it only for the
epilogue. From this perspective, this WHILE_LEN proposal may not give us
more. But for the case of vect-partial-vector-usage=2 (fully adopting
vector with length on the main loop), I think the proposed sequence looks
better to me.
BR,
Kewen
next prev parent reply other threads:[~2023-04-12 12:57 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-07 1:47 juzhe.zhong
2023-04-07 3:23 ` Li, Pan2
2023-04-11 12:12 ` juzhe.zhong
2023-04-11 12:44 ` Richard Sandiford
2023-04-12 7:00 ` Richard Biener
2023-04-12 8:00 ` juzhe.zhong
2023-04-12 8:42 ` Richard Biener
2023-04-12 9:15 ` juzhe.zhong
2023-04-12 9:29 ` Richard Biener
2023-04-12 9:42 ` Robin Dapp
2023-04-12 11:17 ` Richard Sandiford
2023-04-12 11:37 ` juzhe.zhong
2023-04-12 12:24 ` Richard Sandiford
2023-04-12 14:18 ` 钟居哲
2023-04-13 6:47 ` Richard Biener
2023-04-13 9:54 ` juzhe.zhong
2023-04-18 9:32 ` Richard Sandiford
2023-04-12 12:56 ` Kewen.Lin [this message]
2023-04-12 13:22 ` 钟居哲
2023-04-13 7:29 ` Kewen.Lin
2023-04-13 13:44 ` 钟居哲
2023-04-14 2:54 ` Kewen.Lin
2023-04-14 3:09 ` juzhe.zhong
2023-04-14 5:40 ` Kewen.Lin
2023-04-14 3:39 ` juzhe.zhong
2023-04-14 6:31 ` Kewen.Lin
2023-04-14 6:39 ` juzhe.zhong
2023-04-14 7:41 ` Kewen.Lin
2023-04-14 6:52 ` Richard Biener
2023-04-12 11:42 ` Richard Biener
[not found] ` <2023041217154958074655@rivai.ai>
2023-04-12 9:20 ` juzhe.zhong
2023-04-19 21:53 ` 钟居哲
2023-04-20 8:52 ` Richard Sandiford
2023-04-20 8:57 ` juzhe.zhong
2023-04-20 9:11 ` Richard Sandiford
2023-04-20 9:19 ` juzhe.zhong
2023-04-20 9:22 ` Richard Sandiford
2023-04-20 9:50 ` Richard Biener
2023-04-20 9:54 ` Richard Sandiford
2023-04-20 10:38 ` juzhe.zhong
2023-04-20 12:05 ` Richard Biener
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