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[66.111.4.227]) by smtp.gmail.com with ESMTPSA id jo19-20020a170906f6d300b00992d70f8078sm151634ejb.106.2023.06.29.12.46.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jun 2023 12:46:41 -0700 (PDT) Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailauth.nyi.internal (Postfix) with ESMTP id B3C9227C0054; Thu, 29 Jun 2023 15:46:39 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute5.internal (MEProxy); Thu, 29 Jun 2023 15:46:39 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedviedrtdeggddugedvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvfevuffkfhggtggujgesthdtredttddtvdenucfhrhhomhepuehoqhhu nhcuhfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrihhlrdgtohhmqeenucggtffrrg htthgvrhhnpeeghedvgedttdfhtefhueelgfetfffgvdfhjeduffeitdduhffgieegueej fedtveenucffohhmrghinhepghhithhhuhgsrdgtohhmpdhgihhthhhusghushgvrhgtoh hnthgvnhhtrdgtohhmpdgrrghrtghhieeguhhnkhhnohifnhhnohhnvgdrrhhsnecuvehl uhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepsghoqhhunhdomh gvshhmthhprghuthhhphgvrhhsohhnrghlihhthidqieelvdeghedtieegqddujeejkeeh heehvddqsghoqhhunhdrfhgvnhhgpeepghhmrghilhdrtghomhesfhhigihmvgdrnhgrmh gv X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Thu, 29 Jun 2023 15:46:38 -0400 (EDT) Date: Thu, 29 Jun 2023 12:46:13 -0700 From: Boqun Feng To: Jamie Cunliffe Cc: catalin.marinas@arm.com, lina@asahilina.net, linux-arm-kernel@lists.infradead.org, ojeda@kernel.org, rust-for-linux@vger.kernel.org, steve.capper@arm.com, will@kernel.org Subject: Re: [PATCH v2 1/3] arm64: rust: Enable Rust support for AArch64 Message-ID: References: <20230612152639.1446766-1-Jamie.Cunliffe@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230612152639.1446766-1-Jamie.Cunliffe@arm.com> Precedence: bulk List-ID: X-Mailing-List: rust-for-linux@vger.kernel.org On Mon, Jun 12, 2023 at 04:26:39PM +0100, Jamie Cunliffe wrote: > > I don't think you need "-fp-armv8" here, because "aarch64-unknown-none" > > target doesn't have the target-feature "fp-arm64": > > > > rustc +1.68.2 --print cfg --target aarch64-unknown-none | grep target_feature > > > > target_feature="neon" > > > > , and having the "-fp-armv8" gave me a warning at compile time: > > > > RUSTC L rust/core.o warning: unknown feature specified for `-Ctarget-feature`: `fp-armv8` > > | > > = note: it is still passed through to the codegen backend > > = help: consider filing a feature request > > Rust removed the fp feature for arm64 and tied it with Neon. However > this initially had a bug that meant it couldn't be disabled. This has > now been fixed in https://github.com/rust-lang/rust/pull/107294 so > once we can update rustc we can fix that warning by removing the > `-fp-armv8`. Until we do that we still need the `-fp-armv8` otherwise > we will get some floating point usage. This can be seen by doing an > objdump of core.o if you build after removing the `-fp-armv8`. > Thanks for the information (and the fix)! That's good to know. Looks like the fix will be in 1.71, then agree, we should keep `-fp-armv8` until we update to 1.71 or later. Regards, Boqun > > You can also see that fp-armv8 is enabled in the aarch64-unknown-none target > here: https://raw.githubusercontent.com/rust-lang/rust/master/compiler/rustc_target/src/spec/aarch64_unknown_none.rs > > > Thanks, > Jamie.