linux-kernel - Re: [PATCH v2] x86: Alias memset to __builtin

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Message-ID: <7a87a9b971caefa847c412608c98c0a2e1835904.camel@perches.com>
Date:   Tue, 24 Mar 2020 08:08:04 -0700
From:   Joe Perches <joe@...ches.com>
To:     Clement Courbet <courbet@...gle.com>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH v2]     x86: Alias memset to __builtin_memset.

On Tue, 2020-03-24 at 15:07 +0100, Clement Courbet wrote:
>     Recent compilers know the meaning of builtins (`memset`,
>     `memcpy`, ...) and can replace calls by inline code when
>     deemed better. For example, `memset(p, 0, 4)` will be lowered
>     to a four-byte zero store.
> 
>     When using -ffreestanding (this is the case e.g. building on
>     clang), these optimizations are disabled. This means that **all**
>     memsets, including those with small, constant sizes, will result
>     in an actual call to memset.
[]
>     In terms of code size, this grows the clang-built kernel a
>     bit (+0.022%):
>     440285512 vmlinux.clang.after
>     440383608 vmlinux.clang.before

This shows the kernel getting smaller not larger.
Is this still reversed or is this correct?