From: Jamie Cunliffe <Jamie.Cunliffe@arm.com>
To: boqun.feng@gmail.com
Cc: Jamie.Cunliffe@arm.com, 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
Date: Mon, 12 Jun 2023 16:26:39 +0100 [thread overview]
Message-ID: <20230612152639.1446766-1-Jamie.Cunliffe@arm.com> (raw)
In-Reply-To: <ZINlqb3XHmz+dyLr@boqun-archlinux>
> 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`.
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.
next prev parent reply other threads:[~2023-06-12 15:27 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-06 14:56 [PATCH v2 0/3] Rust enablement for AArch64 Jamie Cunliffe
2023-06-06 14:56 ` [PATCH v2 1/3] arm64: rust: Enable Rust support " Jamie Cunliffe
2023-06-09 17:47 ` Boqun Feng
2023-06-12 15:26 ` Jamie Cunliffe [this message]
2023-06-29 19:46 ` Boqun Feng
2023-08-15 18:00 ` Boqun Feng
2023-06-06 14:56 ` [PATCH v2 2/3] arm64: rust: Enable PAC support for Rust Jamie Cunliffe
2023-06-06 14:56 ` [PATCH v2 3/3] arm64: Restrict Rust support to little endian only Jamie Cunliffe
2023-06-06 15:25 ` [PATCH v2 0/3] Rust enablement for AArch64 Miguel Ojeda
2023-06-09 18:34 ` Boqun Feng
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