From: Richard Biener <rguenther@suse.de>
To: Robin Dapp <rdapp.gcc@gmail.com>
Cc: "juzhe.zhong@rivai.ai" <juzhe.zhong@rivai.ai>,
gcc-patches <gcc-patches@gcc.gnu.org>,
"richard.sandiford" <richard.sandiford@arm.com>,
krebbel <krebbel@linux.ibm.com>, uweigand <uweigand@de.ibm.com>,
linkw@linux.ibm.com
Subject: Re: [PATCH V2] VECT: Support LEN_MASK_ LOAD/STORE to support flow control for length loop control
Date: Thu, 15 Jun 2023 09:15:38 +0000 (UTC) [thread overview]
Message-ID: <nycvar.YFH.7.77.849.2306150914360.4723@jbgna.fhfr.qr> (raw)
In-Reply-To: <7e31f226-476a-75d1-6a0f-13fa9134e311@gmail.com>
On Thu, 15 Jun 2023, Robin Dapp wrote:
> >>> Can you try using the same wording for length and mask operands
> >>> as for len_load and maskload? Also len_load has the "bias"
> >>> operand which you omit here - IIRC that was added for s390 which
> >>> for unknown reason behaves a little different than power. If
> >>> len support for s390 ever extends to other ops or power or s390
> >>> gain mask support for conditional code we'd likely have to adjust
> >>> each optab you add. Maybe it's better to add the bias operand
> >>> now.
> >
> > I don't know BIAS well and It seems to be a Power target dependent feature.
> > I think len_mask_* in general should only need lenght and mask operand.
> > Actually, the function argument is totally same as vp_load/vp_store in LLVM.
> >
> > Could I just keep current format (without BIAS argument)? And extend it with BIAS if
> > PowerPC want to use LEN_MASK_ * ?
>
> FYI: The only proper user of bias is s390 because the insns cannot handle a
> zero length. Power doesn't actually need it. What we do is just subtract the
> bias (== 1) from the length in case of n_rgroups == 1 and nothing for
> bias == 0 so the actually bias support code needed is small.
Meh, PoP is now behind a paywall, trying to get through ... I wonder
if there's a nice online html documenting the s390 len_load/store
instructions to better understand the need for the bias.
Richard.
next prev parent reply other threads:[~2023-06-15 9:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-12 4:14 juzhe.zhong
2023-06-15 8:06 ` Richard Biener
2023-06-15 8:47 ` juzhe.zhong
2023-06-15 8:58 ` Robin Dapp
2023-06-15 9:01 ` juzhe.zhong
2023-06-15 9:15 ` Richard Biener [this message]
2023-06-15 9:18 ` Robin Dapp
2023-06-15 9:20 ` Robin Dapp
2023-06-15 9:52 ` Richard Biener
2023-06-15 10:08 ` juzhe.zhong
2023-06-15 10:10 ` Robin Dapp
2023-06-15 11:12 ` Richard Biener
[not found] ` <2023061516473052116877@rivai.ai>
2023-06-15 8:56 ` juzhe.zhong
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