From: Andrew Cooper <Andrew.Cooper3@citrix.com>
To: Mark Rutland <mark.rutland@arm.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"will@kernel.org" <will@kernel.org>,
"marcan@marcan.st" <marcan@marcan.st>,
"maz@kernel.org" <maz@kernel.org>,
"szabolcs.nagy@arm.com" <szabolcs.nagy@arm.com>,
"f.fainelli@gmail.com" <f.fainelli@gmail.com>,
"opendmb@gmail.com" <opendmb@gmail.com>,
"Andrew Pinski" <pinskia@gmail.com>,
Ard Biesheuvel <ardb@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>,
Jeremy Linton <jeremy.linton@arm.com>
Subject: Re: GCC 12 miscompilation of volatile asm (was: Re: [PATCH] arm64/io: Remind compiler that there is a memory side effect)
Date: Tue, 5 Apr 2022 13:20:50 +0000 [thread overview]
Message-ID: <7988e82a-8494-a954-0a79-7f86d34a96ad@citrix.com> (raw)
In-Reply-To: <Ykw+bVS9WY/JfoYO@FVFF77S0Q05N>
On 05/04/2022 14:04, Mark Rutland wrote:
> On Tue, Apr 05, 2022 at 01:51:30PM +0100, Mark Rutland wrote:
> My x86_64 test case is:
>
> Per compiler explorer (https://godbolt.org/z/cveff9hq5) GCC trunk currently
> compiles this as:
>
> | msr_rmw_set_bits:
> | mov rcx, rdi
> | rdmsr
> | sal rdx, 32
> | mov eax, eax
> | or rax, rsi
> | or rax, rdx
> | mov rdx, rax
> | shr rdx, 32
> | wrmsr
> | ret
> | func_with_msr_side_effects:
> | ret
>
Yeah... that code gen is very broken for func_with_msr_side_effects().
~Andrew
next prev parent reply other threads:[~2022-04-05 13:20 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-01 16:44 [PATCH] arm64/io: Remind compiler that there is a memory side effect Jeremy Linton
2022-04-01 17:22 ` Mark Rutland
2022-04-03 7:36 ` Andrew Pinski
2022-04-03 7:47 ` Ard Biesheuvel
2022-04-03 7:47 ` Ard Biesheuvel
2022-04-04 9:14 ` Will Deacon
2022-04-03 17:40 ` Doug Berger
2022-04-05 12:51 ` GCC 12 miscompilation of volatile asm (was: Re: [PATCH] arm64/io: Remind compiler that there is a memory side effect) Mark Rutland
2022-04-05 13:04 ` Mark Rutland
2022-04-05 13:20 ` Andrew Cooper [this message]
2022-04-05 14:05 ` Peter Zijlstra
2022-04-11 10:22 ` Mark Rutland
2022-04-11 10:31 ` Mark Rutland
2022-04-11 19:02 ` Jeremy Linton
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