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Sun, 06 Oct 2024 01:06:40 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240925150059.3955569-30-ardb+git@google.com> <20240925150059.3955569-55-ardb+git@google.com> <99446363-152f-43a8-8b74-26f0d883a364@zytor.com> <5c7490bb-aa74-427b-849e-c28c343b7409@zytor.com> <3bbb85ae-8ba5-4777-999f-d20705c386e7@zytor.com> In-Reply-To: From: Uros Bizjak Date: Sun, 6 Oct 2024 10:06:33 +0200 Message-ID: Subject: Re: [RFC PATCH 25/28] x86: Use PIE codegen for the core kernel To: Linus Torvalds Cc: "H. Peter Anvin" , Ard Biesheuvel , Ard Biesheuvel , linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-doc@vger.kernel.org, linux-pm@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-perf-users@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, Oct 6, 2024 at 2:00=E2=80=AFAM Linus Torvalds wrote: > > On Sat, 5 Oct 2024 at 16:37, H. Peter Anvin wrote: > > > > Sadly, that is not correct; neither gcc nor clang uses lea: > > Looking around, this may be intentional. At least according to Agner, > several cores do better at "mov immediate" compared to "lea". > > Eg a RIP-relative LEA on Zen 2 gets a throughput of two per cycle, but > a "MOV r,i" gets four. That got fixed in Zen 3 and later, but > apparently Intel had similar issues (Ivy Bridge: 1 LEA per cycle, vs 3 > "mov i,r". Haswell is 1:4). Yes, this is the case. I just missed your reply when replying to Peter's mail with a not so precise answer. Uros.