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From:   Andreas Schwab <schwab@linux-m68k.org>
To:     Jessica Clarke <jrtc27@jrtc27.com>
Cc:     Changbin Du <changbin.du@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: eliminate unreliable __builtin_frame_address(1)
References: <20220117154433.3124-1-changbin.du@gmail.com>
        <C2470F2D-9E45-49D7-A03B-E6A7BB4B9738@jrtc27.com>
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        <8F8D535F-3637-4BC7-8853-B709EC5D14C9@jrtc27.com>
Date:   Wed, 19 Jan 2022 22:07:39 +0100
In-Reply-To: <8F8D535F-3637-4BC7-8853-B709EC5D14C9@jrtc27.com> (Jessica
        Clarke's message of "Wed, 19 Jan 2022 20:48:48 +0000")
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On Jan 19 2022, Jessica Clarke wrote:

> My point is that the only thing that can possibly read the incoming
> frame pointer of a leaf function is the leaf function itself, and since
> it knows where it’s putting it then there is no ABI issue, it just
> remembers where it put it and loads it from there.

llvm sidesteps that issue by always saving ra when creating a frame,
even in a leaf function, so it can use a constant offset.

-- 
Andreas Schwab, schwab@linux-m68k.org
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"And now for something completely different."