diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm/src/llvm_util.rs')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/llvm_util.rs | 265 |
1 files changed, 174 insertions, 91 deletions
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index 9adb1299b3d..db2b03d9aed 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -1,4 +1,5 @@ -use std::ffi::{CStr, CString, c_char, c_void}; +use std::collections::VecDeque; +use std::ffi::{CStr, CString}; use std::fmt::Write; use std::path::Path; use std::sync::Once; @@ -16,12 +17,12 @@ use rustc_session::Session; use rustc_session::config::{PrintKind, PrintRequest}; use rustc_span::symbol::Symbol; use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport}; -use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES}; +use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES, Stability}; use crate::back::write::create_informational_target_machine; use crate::errors::{ - FixedX18InvalidArch, InvalidTargetFeaturePrefix, PossibleFeature, UnknownCTargetFeature, - UnknownCTargetFeaturePrefix, UnstableCTargetFeature, + FixedX18InvalidArch, ForbiddenCTargetFeature, InvalidTargetFeaturePrefix, PossibleFeature, + UnknownCTargetFeature, UnknownCTargetFeaturePrefix, UnstableCTargetFeature, }; use crate::llvm; @@ -227,6 +228,8 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea "x86" } else if sess.target.arch == "arm64ec" { "aarch64" + } else if sess.target.arch == "sparc64" { + "sparc" } else { &*sess.target.arch }; @@ -276,23 +279,43 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea ("x86", s) if s.starts_with("avx512") => { Some(LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512"))) } + // Support for `wide-arithmetic` will first land in LLVM 20 as part of + // llvm/llvm-project#111598 + ("wasm32" | "wasm64", "wide-arithmetic") if get_version() < (20, 0, 0) => None, + ("sparc", "leoncasa") => Some(LLVMFeature::new("hasleoncasa")), + // In LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available and SPARC-V8+ ABI used". + // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L27-L28 + // Before LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available". + // https://github.com/llvm/llvm-project/blob/llvmorg-18.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L26 + ("sparc", "v8plus") if get_version().0 == 19 => Some(LLVMFeature::new("v9")), + ("sparc", "v8plus") if get_version().0 < 19 => None, (_, s) => Some(LLVMFeature::new(s)), } } -/// Used to generate cfg variables and apply features -/// Must express features in the way Rust understands them +/// Used to generate cfg variables and apply features. +/// Must express features in the way Rust understands them. +/// +/// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen. pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> { - let mut features = vec![]; - - // Add base features for the target + let mut features: FxHashSet<Symbol> = Default::default(); + + // Add base features for the target. + // We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below. + // The reason is that if LLVM considers a feature implied but we do not, we don't want that to + // show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of + // the target CPU, that is still expanded to target features (with all their implied features) by + // LLVM. let target_machine = create_informational_target_machine(sess, true); + // Compute which of the known target features are enabled in the 'base' target machine. + // We only consider "supported" features; "forbidden" features are not reflected in `cfg` as of now. features.extend( sess.target - .supported_target_features() + .rust_target_features() .iter() + .filter(|(_, gate, _)| gate.is_supported()) .filter(|(feature, _, _)| { - // skip checking special features, as LLVM may not understands them + // skip checking special features, as LLVM may not understand them if RUSTC_SPECIAL_FEATURES.contains(feature) { return true; } @@ -321,18 +344,32 @@ pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> { }) { if enabled { + // Also add all transitively implied features. features.extend(sess.target.implied_target_features(std::iter::once(feature))); } else { + // Remove transitively reverse-implied features. + + // We don't care about the order in `features` since the only thing we use it for is the + // `features.contains` below. + #[allow(rustc::potential_query_instability)] features.retain(|f| { - !sess.target.implied_target_features(std::iter::once(*f)).contains(&feature) + if sess.target.implied_target_features(std::iter::once(*f)).contains(&feature) { + // If `f` if implies `feature`, then `!feature` implies `!f`, so we have to + // remove `f`. (This is the standard logical contraposition principle.) + false + } else { + // We can keep `f`. + true + } }); } } // Filter enabled features based on feature gates sess.target - .supported_target_features() + .rust_target_features() .iter() + .filter(|(_, gate, _)| gate.is_supported()) .filter_map(|&(feature, gate, _)| { if sess.is_nightly_build() || allow_unstable || gate.is_stable() { Some(feature) @@ -387,14 +424,76 @@ fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> { ret } -fn print_target_features(out: &mut String, sess: &Session, tm: &llvm::TargetMachine) { +pub(crate) fn print(req: &PrintRequest, out: &mut String, sess: &Session) { + require_inited(); + let tm = create_informational_target_machine(sess, false); + match req.kind { + PrintKind::TargetCPUs => print_target_cpus(sess, &tm, out), + PrintKind::TargetFeatures => print_target_features(sess, &tm, out), + _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req), + } +} + +fn print_target_cpus(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) { + let cpu_names = llvm::build_string(|s| unsafe { + llvm::LLVMRustPrintTargetCPUs(&tm, s); + }) + .unwrap(); + + struct Cpu<'a> { + cpu_name: &'a str, + remark: String, + } + // Compare CPU against current target to label the default. + let target_cpu = handle_native(&sess.target.cpu); + let make_remark = |cpu_name| { + if cpu_name == target_cpu { + // FIXME(#132514): This prints the LLVM target string, which can be + // different from the Rust target string. Is that intended? + let target = &sess.target.llvm_target; + format!( + " - This is the default target CPU for the current build target (currently {target})." + ) + } else { + "".to_owned() + } + }; + let mut cpus = cpu_names + .lines() + .map(|cpu_name| Cpu { cpu_name, remark: make_remark(cpu_name) }) + .collect::<VecDeque<_>>(); + + // Only print the "native" entry when host and target are the same arch, + // since otherwise it could be wrong or misleading. + if sess.host.arch == sess.target.arch { + let host = get_host_cpu_name(); + cpus.push_front(Cpu { + cpu_name: "native", + remark: format!(" - Select the CPU of the current host (currently {host})."), + }); + } + + let max_name_width = cpus.iter().map(|cpu| cpu.cpu_name.len()).max().unwrap_or(0); + writeln!(out, "Available CPUs for this target:").unwrap(); + for Cpu { cpu_name, remark } in cpus { + // Only pad the CPU name if there's a remark to print after it. + let width = if remark.is_empty() { 0 } else { max_name_width }; + writeln!(out, " {cpu_name:<width$}{remark}").unwrap(); + } +} + +fn print_target_features(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) { let mut llvm_target_features = llvm_target_features(tm); let mut known_llvm_target_features = FxHashSet::<&'static str>::default(); let mut rustc_target_features = sess .target - .supported_target_features() + .rust_target_features() .iter() - .filter_map(|(feature, _gate, _implied)| { + .filter_map(|(feature, gate, _implied)| { + if !gate.is_supported() { + // Only list (experimentally) supported features. + return None; + } // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these // strings. let llvm_feature = to_llvm_features(sess, *feature)?.llvm_feature_name; @@ -447,52 +546,31 @@ fn print_target_features(out: &mut String, sess: &Session, tm: &llvm::TargetMach writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n").unwrap(); } -pub(crate) fn print(req: &PrintRequest, mut out: &mut String, sess: &Session) { - require_inited(); - let tm = create_informational_target_machine(sess, false); - match req.kind { - PrintKind::TargetCPUs => { - // SAFETY generate a C compatible string from a byte slice to pass - // the target CPU name into LLVM, the lifetime of the reference is - // at least as long as the C function - let cpu_cstring = CString::new(handle_native(sess.target.cpu.as_ref())) - .unwrap_or_else(|e| bug!("failed to convert to cstring: {}", e)); - unsafe extern "C" fn callback(out: *mut c_void, string: *const c_char, len: usize) { - let out = unsafe { &mut *(out as *mut &mut String) }; - let bytes = unsafe { slice::from_raw_parts(string as *const u8, len) }; - write!(out, "{}", String::from_utf8_lossy(bytes)).unwrap(); - } - unsafe { - llvm::LLVMRustPrintTargetCPUs( - &tm, - cpu_cstring.as_ptr(), - callback, - (&raw mut out) as *mut c_void, - ); - } - } - PrintKind::TargetFeatures => print_target_features(out, sess, &tm), - _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req), - } +/// Returns the host CPU name, according to LLVM. +fn get_host_cpu_name() -> &'static str { + let mut len = 0; + // SAFETY: The underlying C++ global function returns a `StringRef` that + // isn't tied to any particular backing buffer, so it must be 'static. + let slice: &'static [u8] = unsafe { + let ptr = llvm::LLVMRustGetHostCPUName(&mut len); + assert!(!ptr.is_null()); + slice::from_raw_parts(ptr, len) + }; + str::from_utf8(slice).expect("host CPU name should be UTF-8") } -fn handle_native(name: &str) -> &str { - if name != "native" { - return name; - } - - unsafe { - let mut len = 0; - let ptr = llvm::LLVMRustGetHostCPUName(&mut len); - str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap() +/// If the given string is `"native"`, returns the host CPU name according to +/// LLVM. Otherwise, the string is returned as-is. +fn handle_native(cpu_name: &str) -> &str { + match cpu_name { + "native" => get_host_cpu_name(), + _ => cpu_name, } } pub(crate) fn target_cpu(sess: &Session) -> &str { - match sess.opts.cg.target_cpu { - Some(ref name) => handle_native(name), - None => handle_native(sess.target.cpu.as_ref()), - } + let cpu_name = sess.opts.cg.target_cpu.as_deref().unwrap_or_else(|| &sess.target.cpu); + handle_native(cpu_name) } /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`, @@ -558,6 +636,8 @@ pub(crate) fn global_llvm_features( .features .split(',') .filter(|v| !v.is_empty() && backend_feature_name(sess, v).is_some()) + // Drop +v8plus feature introduced in LLVM 20. + .filter(|v| *v != "+v8plus" || get_version() >= (20, 0, 0)) .map(String::from), ); @@ -567,7 +647,7 @@ pub(crate) fn global_llvm_features( // -Ctarget-features if !only_base_features { - let supported_features = sess.target.supported_target_features(); + let known_features = sess.target.rust_target_features(); let mut featsmap = FxHashMap::default(); // insert implied features @@ -601,50 +681,53 @@ pub(crate) fn global_llvm_features( } }; + // Get the backend feature name, if any. + // This excludes rustc-specific features, which do not get passed to LLVM. let feature = backend_feature_name(sess, s)?; // Warn against use of LLVM specific feature names and unstable features on the CLI. if diagnostics { - let feature_state = supported_features.iter().find(|&&(v, _, _)| v == feature); - if feature_state.is_none() { - let rust_feature = - supported_features.iter().find_map(|&(rust_feature, _, _)| { - let llvm_features = to_llvm_features(sess, rust_feature)?; - if llvm_features.contains(feature) - && !llvm_features.contains(rust_feature) - { - Some(rust_feature) - } else { - None + let feature_state = known_features.iter().find(|&&(v, _, _)| v == feature); + match feature_state { + None => { + let rust_feature = + known_features.iter().find_map(|&(rust_feature, _, _)| { + let llvm_features = to_llvm_features(sess, rust_feature)?; + if llvm_features.contains(feature) + && !llvm_features.contains(rust_feature) + { + Some(rust_feature) + } else { + None + } + }); + let unknown_feature = if let Some(rust_feature) = rust_feature { + UnknownCTargetFeature { + feature, + rust_feature: PossibleFeature::Some { rust_feature }, } - }); - let unknown_feature = if let Some(rust_feature) = rust_feature { - UnknownCTargetFeature { - feature, - rust_feature: PossibleFeature::Some { rust_feature }, - } - } else { - UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None } - }; - sess.dcx().emit_warn(unknown_feature); - } else if feature_state - .is_some_and(|(_name, feature_gate, _implied)| !feature_gate.is_stable()) - { - // An unstable feature. Warn about using it. - sess.dcx().emit_warn(UnstableCTargetFeature { feature }); + } else { + UnknownCTargetFeature { + feature, + rust_feature: PossibleFeature::None, + } + }; + sess.dcx().emit_warn(unknown_feature); + } + Some((_, Stability::Stable, _)) => {} + Some((_, Stability::Unstable(_), _)) => { + // An unstable feature. Warn about using it. + sess.dcx().emit_warn(UnstableCTargetFeature { feature }); + } + Some((_, Stability::Forbidden { reason }, _)) => { + sess.dcx().emit_warn(ForbiddenCTargetFeature { feature, reason }); + } } - } - if diagnostics { // FIXME(nagisa): figure out how to not allocate a full hashset here. featsmap.insert(feature, enable_disable == '+'); } - // rustc-specific features do not get passed down to LLVM… - if RUSTC_SPECIFIC_FEATURES.contains(&feature) { - return None; - } - - // ... otherwise though we run through `to_llvm_features` when + // We run through `to_llvm_features` when // passing requests down to LLVM. This means that all in-language // features also work on the command line instead of having two // different names when the LLVM name and the Rust name differ. |