linux-kernel - Re: [PATCH V13 - RESEND 02/10] arm64/perf: Add BRBE registers and fields

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Message-ID: <20230815203527.GB971582@hirez.programming.kicks-ass.net>
Date:   Tue, 15 Aug 2023 22:35:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     James Clark <james.clark@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, Mark Brown <broonie@...nel.org>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Suzuki Poulose <suzuki.poulose@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH V13 - RESEND 02/10] arm64/perf: Add BRBE registers and
 fields

On Tue, Aug 15, 2023 at 02:05:36PM +0100, Mark Rutland wrote:

> From a quick dig, it's supposed to be like that: the GNU assembler uses a
> different operator precedence to C, and clang's assembler does the same for
> compatibility. What a great.

GNU assembler doesn't even have a consistent true value for boolean
expressions. The comparisons use -1/~0 as true value while the logical
ops use 1.

It's as if they purposefully want to mess you up :-(

  https://sourceware.org/binutils/docs-2.38/as.html#Infix-Ops