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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?
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