From: Segher Boessenkool <segher@kernel.crashing.org>
To: Alan Modra <amodra@gmail.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH 2/8] [RS6000] rs6000_rtx_costs for AND
Date: Tue, 20 Oct 2020 13:55:56 -0500 [thread overview]
Message-ID: <20201020185556.GB2672@gate.crashing.org> (raw)
In-Reply-To: <20201007225800.9536-3-amodra@gmail.com>
On Thu, Oct 08, 2020 at 09:27:54AM +1030, Alan Modra wrote:
> The existing "case AND" in this function is not sufficient for
> optabs.c:avoid_expensive_constant usage, where the AND is passed in
> outer_code. We'd like to cost AND of rs6000_is_valid_and_mask
> or rs6000_is_valid_2insn_and variety there, so that those masks aren't
> seen as expensive (ie. better to load to a reg then AND).
>
> * config/rs6000/rs6000.c (rs6000_rtx_costs): Combine CONST_INT
> AND handling with IOR/XOR. Move costing for AND with
> rs6000_is_valid_and_mask or rs6000_is_valid_2insn_and to
> CONST_INT.
Sorry this took so long to review :-(
On 64-bit BE this leads to *bigger* code, and closer observation shows
that some common sequences degrade on all configs. This seems to mostly
be about "andc" (and its dot form). It wasn't costed properly before,
but after your patch, a single instruction is replaced by three.
Could you look into this?
Segher
next prev parent reply other threads:[~2020-10-20 18:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 22:57 [PATCH 0/8] [RS6000] rs6000_rtx_costs V2 Alan Modra
2020-10-07 22:57 ` [PATCH 1/8] [RS6000] rs6000_rtx_costs comment Alan Modra
2020-10-14 20:08 ` Segher Boessenkool
2020-10-07 22:57 ` [PATCH 2/8] [RS6000] rs6000_rtx_costs for AND Alan Modra
2020-10-20 18:55 ` Segher Boessenkool [this message]
2020-10-21 2:57 ` Alan Modra
2020-10-21 20:29 ` Segher Boessenkool
2020-10-21 22:11 ` Alan Modra
2020-10-22 13:29 ` Segher Boessenkool
2020-10-23 23:18 ` Hans-Peter Nilsson
2020-10-24 1:04 ` Alan Modra
2020-10-07 22:57 ` [PATCH 3/8] [RS6000] rs6000_rtx_costs tidy AND Alan Modra
[not found] ` <20210112033157.GA26219@bubble.grove.modra.org>
2021-01-21 23:09 ` Alan Modra
2021-01-25 22:37 ` Segher Boessenkool
2021-02-01 2:06 ` Alan Modra
2020-10-07 22:57 ` [PATCH 4/8] [RS6000] rs6000_rtx_costs tidy break/return Alan Modra
[not found] ` <20210112033209.GB26219@bubble.grove.modra.org>
2021-01-21 23:09 ` Alan Modra
2021-01-25 22:40 ` Segher Boessenkool
2020-10-07 22:57 ` [PATCH 5/8] [RS6000] rs6000_rtx_costs cost IOR Alan Modra
[not found] ` <20210112033218.GC26219@bubble.grove.modra.org>
2021-01-21 23:10 ` Alan Modra
2021-01-25 22:51 ` Segher Boessenkool
2021-02-01 2:13 ` Alan Modra
2020-10-07 22:57 ` [PATCH 6/8] [RS6000] rs6000_rtx_costs multi-insn constants Alan Modra
2020-10-07 22:57 ` [PATCH 7/8] [RS6000] rs6000_rtx_costs reduce cost for SETs Alan Modra
2020-10-08 18:19 ` will schmidt
[not found] ` <20210112033227.GD26219@bubble.grove.modra.org>
2021-01-21 23:10 ` Alan Modra
2020-10-07 22:58 ` [PATCH 8/8] [RS6000] rs6000_rtx_costs for !speed Alan Modra
[not found] ` <20210112033236.GE26219@bubble.grove.modra.org>
2021-01-21 23:11 ` Alan Modra
2020-12-05 9:12 ` [PATCH 0/8] [RS6000] rs6000_rtx_costs V2 Alan Modra
2021-01-11 21:42 ` Alan Modra
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