From: 钟居哲 <juzhe.zhong@rivai.ai>
To: rdapp.gcc <rdapp.gcc@gmail.com>, gcc-patches <gcc-patches@gcc.gnu.org>
Cc: rdapp.gcc <rdapp.gcc@gmail.com>,
kito.cheng <kito.cheng@gmail.com>,
kito.cheng <kito.cheng@sifive.com>,
"Jeff Law" <jeffreyalaw@gmail.com>
Subject: Re: Re: [PATCH] RISC-V: Teach liveness computation loop invariant shift amount[Dynamic LMUL]
Date: Sat, 6 Jan 2024 10:13:50 +0800 [thread overview]
Message-ID: <E21AA9BD0749CFAB+2024010610135034383124@rivai.ai> (raw)
In-Reply-To: <733f0455-b8ed-43aa-9084-46d84fb2fef8@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1670 bytes --]
Thanks Robin.
is_gimple_constant makes more senes. Committed with addressing your comments.
juzhe.zhong@rivai.ai
From: Robin Dapp
Date: 2024-01-05 17:54
To: Juzhe-Zhong; gcc-patches
CC: rdapp.gcc; kito.cheng; kito.cheng; jeffreyalaw
Subject: Re: [PATCH] RISC-V: Teach liveness computation loop invariant shift amount[Dynamic LMUL]
> 1). We not only have vashl_optab,vashr_optab,vlshr_optab which vectorize shift with vector shift amount,
> that is, vectorization of 'a[i] >> x[i]', the shift amount is loop variant.
> 2). But also, we have ashl_optab, ashr_optab, lshr_optab which can vectorize shift with scalar shift amount,
> that is, vectorization of 'a[i] >> x', the shift amount is loop invariant.
>
> +static bool
> +loop_invariant_op_p (class loop *loop,
> + tree op)
> +{
> + if (is_gimple_min_invariant (op))
> + return true;
> + if (SSA_NAME_IS_DEFAULT_DEF (op)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (SSA_NAME_DEF_STMT (op))))
> + return true;
> + return gimple_uid (SSA_NAME_DEF_STMT (op)) & 1;
> +}
> +
Looks like this is straight from tree-ssa-loop-ch. Do we need
is_gimple_min_invariant (is_gimple_constant could be sufficient?)
and DEFAULT_DEF for our case? The rhs of a shift should never contain
a default def?
I'm not entirely happy about the "loop invariant" heuristic/proxy
of the shift amount being vectorizable. That seems like something
that could bite us in the future in case we do slp-like vectorization
on loop-invariant (but varying) data.
As it helps for now and is not a correctness issue I'd still tend to
go forward with it.
Regards
Robin
next prev parent reply other threads:[~2024-01-06 2:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-05 1:53 Juzhe-Zhong
2024-01-05 9:54 ` Robin Dapp
2024-01-06 2:13 ` 钟居哲 [this message]
2024-01-08 16:45 ` Robin Dapp
2024-01-09 1:25 ` juzhe.zhong
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