From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/bug: Remove specific powerpc BUG_ON()
Date: Thu, 11 Feb 2021 06:22:11 -0600 [thread overview]
Message-ID: <20210211122211.GC28121@gate.crashing.org> (raw)
In-Reply-To: <1613036567.zvyupcz926.astroid@bobo.none>
On Thu, Feb 11, 2021 at 08:04:55PM +1000, Nicholas Piggin wrote:
> Excerpts from Christophe Leroy's message of February 11, 2021 5:41 pm:
> > As modern powerpc implement branch folding, that's even more efficient.
Ah, it seems you mean what Arm calls branch folding. Sure, power4
already did that, and this has not changed.
> I think POWER will speculate conditional traps as non faulting always
> so it should be just as good if not better than the branch.
Right, these are not branch instructions, so are not branch predicted;
all trap instructions are assumed to fall through, like all other
non-branch instructions.
Segher
WARNING: multiple messages have this Message-ID (diff)
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/bug: Remove specific powerpc BUG_ON()
Date: Thu, 11 Feb 2021 06:22:11 -0600 [thread overview]
Message-ID: <20210211122211.GC28121@gate.crashing.org> (raw)
In-Reply-To: <1613036567.zvyupcz926.astroid@bobo.none>
On Thu, Feb 11, 2021 at 08:04:55PM +1000, Nicholas Piggin wrote:
> Excerpts from Christophe Leroy's message of February 11, 2021 5:41 pm:
> > As modern powerpc implement branch folding, that's even more efficient.
Ah, it seems you mean what Arm calls branch folding. Sure, power4
already did that, and this has not changed.
> I think POWER will speculate conditional traps as non faulting always
> so it should be just as good if not better than the branch.
Right, these are not branch instructions, so are not branch predicted;
all trap instructions are assumed to fall through, like all other
non-branch instructions.
Segher
next prev parent reply other threads:[~2021-02-11 12:31 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 7:41 [PATCH] powerpc/bug: Remove specific powerpc BUG_ON() Christophe Leroy
2021-02-11 7:41 ` Christophe Leroy
2021-02-11 10:04 ` Nicholas Piggin
2021-02-11 10:04 ` Nicholas Piggin
2021-02-11 11:50 ` Segher Boessenkool
2021-02-11 11:50 ` Segher Boessenkool
2021-02-11 22:47 ` Nicholas Piggin
2021-02-11 22:47 ` Nicholas Piggin
2021-02-11 12:22 ` Segher Boessenkool [this message]
2021-02-11 12:22 ` Segher Boessenkool
2021-02-11 11:49 ` Segher Boessenkool
2021-02-11 11:49 ` Segher Boessenkool
2021-02-11 12:26 ` Christophe Leroy
2021-02-11 12:26 ` Christophe Leroy
2021-02-11 12:39 ` Segher Boessenkool
2021-02-11 12:39 ` Segher Boessenkool
2021-02-11 14:09 ` Christophe Leroy
2021-02-11 14:09 ` Christophe Leroy
2021-02-11 14:30 ` Segher Boessenkool
2021-02-11 14:30 ` Segher Boessenkool
2021-02-11 15:30 ` Christophe Leroy
2021-02-11 15:30 ` Christophe Leroy
2021-02-27 10:31 ` Christophe Leroy
2021-02-27 10:31 ` Christophe Leroy
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