From b807d5970bd5b20d2dd22d76a05a4f65dbea03a5 Mon Sep 17 00:00:00 2001 From: Jubilee Young Date: Fri, 3 Dec 2021 17:56:59 -0800 Subject: Fold aarch64 feature +fp into +neon Arm's FEAT_FP and Feat_AdvSIMD describe the same thing on AArch64: The Neon unit, which handles both floating point and SIMD instructions. Moreover, a configuration for AArch64 must include both or neither. Arm says "entirely proprietary" toolchains may omit floating point: https://developer.arm.com/documentation/102374/0101/Data-processing---floating-point In the Programmer's Guide for Armv8-A, Arm says AArch64 can have both FP and Neon or neither in custom implementations: https://developer.arm.com/documentation/den0024/a/AArch64-Floating-point-and-NEON In "Bare metal boot code for Armv8-A", enabling Neon and FP is just disabling the same trap flag: https://developer.arm.com/documentation/dai0527/a In an unlikely future where "Neon and FP" become unrelated, we can add "[+-]fp" as its own feature flag. Until then, we can simplify programming with Rust on AArch64 by folding both into "[+-]neon", which is valid as it supersets both. "[+-]neon" is retained for niche uses such as firmware, kernels, "I just hate floats", and so on. --- compiler/rustc_codegen_llvm/src/llvm_util.rs | 1 - 1 file changed, 1 deletion(-) (limited to 'compiler/rustc_codegen_llvm/src') diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index 3ce594b945a..e70866a3b70 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -187,7 +187,6 @@ pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2] ("x86", "avx512vaes") => smallvec!["vaes"], ("x86", "avx512gfni") => smallvec!["gfni"], ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"], - ("aarch64", "fp") => smallvec!["fp-armv8"], ("aarch64", "rcpc2") => smallvec!["rcpc-immo"], ("aarch64", "dpb") => smallvec!["ccpp"], ("aarch64", "dpb2") => smallvec!["ccdp"], -- cgit 1.4.1-3-g733a5 From 990c297ffb86af3d6d80172effcee8fb8b83e304 Mon Sep 17 00:00:00 2001 From: Jubilee Young Date: Sat, 19 Mar 2022 19:36:42 -0700 Subject: Filter for all features instead of any Adds regression tests for feature logic Co-authored-by: bjorn3 Co-authored-by: Simonas Kazlauskas --- compiler/rustc_codegen_llvm/src/llvm_util.rs | 9 ++-- src/test/ui/target-feature/no-llvm-leaks.rs | 64 ++++++++++++++++++++++++++++ 2 files changed, 70 insertions(+), 3 deletions(-) create mode 100644 src/test/ui/target-feature/no-llvm-leaks.rs (limited to 'compiler/rustc_codegen_llvm/src') diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index e70866a3b70..abcdb81c0e2 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -229,6 +229,8 @@ pub fn check_tied_features( None } +// Used to generate cfg variables and apply features +// Must express features in the way Rust understands them pub fn target_features(sess: &Session) -> Vec { let target_machine = create_informational_target_machine(sess); let mut features: Vec = @@ -238,13 +240,14 @@ pub fn target_features(sess: &Session) -> Vec { if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None } }) .filter(|feature| { + // check that all features in a given smallvec are enabled for llvm_feature in to_llvm_features(sess, feature) { let cstr = SmallCStr::new(llvm_feature); - if unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } { - return true; + if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } { + return false; } } - false + true }) .map(|feature| Symbol::intern(feature)) .collect(); diff --git a/src/test/ui/target-feature/no-llvm-leaks.rs b/src/test/ui/target-feature/no-llvm-leaks.rs new file mode 100644 index 00000000000..5a71b2166c3 --- /dev/null +++ b/src/test/ui/target-feature/no-llvm-leaks.rs @@ -0,0 +1,64 @@ +// revisions: aarch64 x86-64 +// [aarch64] compile-flags: -Ctarget-feature=+neon,+fp16,+fhm --target=aarch64-unknown-linux-gnu +// [aarch64] needs-llvm-components: aarch64 +// [x86-64] compile-flags: -Ctarget-feature=+sse4.2,+rdrand --target=x86_64-unknown-linux-gnu +// [x86-64] needs-llvm-components: x86 +// build-pass +#![no_core] +#![crate_type = "rlib"] +#![feature(intrinsics, rustc_attrs, no_core, lang_items, staged_api)] +#![stable(feature = "test", since = "1.0.0")] + +// Supporting minimal rust core code +#[lang = "sized"] +trait Sized {} +#[lang = "copy"] +trait Copy {} +impl Copy for bool {} + +extern "rust-intrinsic" { + #[rustc_const_stable(feature = "test", since = "1.0.0")] + fn unreachable() -> !; +} + +#[rustc_builtin_macro] +macro_rules! cfg { + ($($cfg:tt)*) => {}; +} + +// Test code +const fn do_or_die(cond: bool) { + if cond { + } else { + unsafe { unreachable() } + } +} + +macro_rules! assert { + ($x:expr $(,)?) => { + const _: () = do_or_die($x); + }; +} + + +#[cfg(target_arch = "aarch64")] +fn check_aarch64() { + // This checks that the rustc feature name is used, not the LLVM feature. + assert!(cfg!(target_feature = "neon")); + assert!(cfg!(not(target_feature = "fp-armv8"))); + assert!(cfg!(target_feature = "fhm")); + assert!(cfg!(not(target_feature = "fp16fml"))); + assert!(cfg!(target_feature = "fp16")); + assert!(cfg!(not(target_feature = "fullfp16"))); +} + +#[cfg(target_arch = "x86_64")] +fn check_x86_64() { + // This checks that the rustc feature name is used, not the LLVM feature. + assert!(cfg!(target_feature = "rdrand")); + assert!(cfg!(not(target_feature = "rdrnd"))); + + // Likewise: We enable LLVM's crc32 feature with SSE4.2, but Rust says it's just SSE4.2 + assert!(cfg!(target_feature = "sse4.2")); + assert!(cfg!(not(target_feature = "crc32"))); +} -- cgit 1.4.1-3-g733a5