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move cfg(target_feature) computation into shared place

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This commit is contained in:
Ralf Jung 2025-05-10 22:53:38 +02:00
parent 044514eb26
commit d70ec32ea7
3 changed files with 126 additions and 119 deletions
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59
compiler/rustc_codegen_gcc/src/lib.rs
View file

@ -103,7 +103,9 @@ use rustc_codegen_ssa::back::write::{
};
use rustc_codegen_ssa::base::codegen_crate;
use rustc_codegen_ssa::traits::{CodegenBackend, ExtraBackendMethods, WriteBackendMethods};
use rustc_codegen_ssa::{CodegenResults, CompiledModule, ModuleCodegen, TargetConfig};
use rustc_codegen_ssa::{
CodegenResults, CompiledModule, ModuleCodegen, TargetConfig, target_features,
};
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::sync::IntoDynSyncSend;
use rustc_errors::DiagCtxtHandle;
@ -476,42 +478,25 @@ fn to_gcc_opt_level(optlevel: Option<OptLevel>) -> OptimizationLevel {
/// Returns the features that should be set in `cfg(target_feature)`.
fn target_config(sess: &Session, target_info: &LockedTargetInfo) -> TargetConfig {
// TODO(antoyo): use global_gcc_features.
let f = |allow_unstable| {
sess.target
.rust_target_features()
.iter()
.filter_map(|&(feature, gate, _)| {
if allow_unstable
|| (gate.in_cfg()
&& (sess.is_nightly_build() || gate.requires_nightly().is_none()))
{
Some(feature)
} else {
None
}
})
.filter(|feature| {
// TODO: we disable Neon for now since we don't support the LLVM intrinsics for it.
if *feature == "neon" {
return false;
}
target_info.cpu_supports(feature)
// cSpell:disable
/*
adx, aes, avx, avx2, avx512bf16, avx512bitalg, avx512bw, avx512cd, avx512dq, avx512er, avx512f, avx512fp16, avx512ifma,
avx512pf, avx512vbmi, avx512vbmi2, avx512vl, avx512vnni, avx512vp2intersect, avx512vpopcntdq,
bmi1, bmi2, cmpxchg16b, ermsb, f16c, fma, fxsr, gfni, lzcnt, movbe, pclmulqdq, popcnt, rdrand, rdseed, rtm,
sha, sse, sse2, sse3, sse4.1, sse4.2, sse4a, ssse3, tbm, vaes, vpclmulqdq, xsave, xsavec, xsaveopt, xsaves
*/
// cSpell:enable
})
.map(Symbol::intern)
.collect()
};
let target_features = f(false);
let unstable_target_features = f(true);
let (unstable_target_features, target_features) = target_features::cfg_target_feature(
sess,
/* FIXME: we ignore `-Ctarget-feature` */ "",
|feature| {
// TODO: we disable Neon for now since we don't support the LLVM intrinsics for it.
if feature == "neon" {
return false;
}
target_info.cpu_supports(feature)
// cSpell:disable
/*
adx, aes, avx, avx2, avx512bf16, avx512bitalg, avx512bw, avx512cd, avx512dq, avx512er, avx512f, avx512fp16, avx512ifma,
avx512pf, avx512vbmi, avx512vbmi2, avx512vl, avx512vnni, avx512vp2intersect, avx512vpopcntdq,
bmi1, bmi2, cmpxchg16b, ermsb, f16c, fma, fxsr, gfni, lzcnt, movbe, pclmulqdq, popcnt, rdrand, rdseed, rtm,
sha, sse, sse2, sse3, sse4.1, sse4.2, sse4a, ssse3, tbm, vaes, vpclmulqdq, xsave, xsavec, xsaveopt, xsaves
*/
// cSpell:enable
},
);
let has_reliable_f16 = target_info.supports_target_dependent_type(CType::Float16);
let has_reliable_f128 = target_info.supports_target_dependent_type(CType::Float128);

87
compiler/rustc_codegen_llvm/src/llvm_util.rs
View file

@ -6,9 +6,9 @@ use std::sync::Once;
use std::{ptr, slice, str};
use libc::c_int;
use rustc_codegen_ssa::TargetConfig;
use rustc_codegen_ssa::base::wants_wasm_eh;
use rustc_codegen_ssa::codegen_attrs::check_tied_features;
use rustc_codegen_ssa::{TargetConfig, target_features};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::small_c_str::SmallCStr;
use rustc_data_structures::unord::UnordSet;
@ -17,9 +17,8 @@ use rustc_middle::bug;
use rustc_session::Session;
use rustc_session::config::{PrintKind, PrintRequest};
use rustc_session::features::{StabilityExt, retpoline_features_by_flags};
use rustc_span::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_SPECIFIC_FEATURES;
use smallvec::{SmallVec, smallvec};
use crate::back::write::create_informational_target_machine;
@ -343,18 +342,11 @@ pub(crate) fn target_config(sess: &Session) -> TargetConfig {
// 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.
let mut features: FxHashSet<Symbol> = sess
.target
.rust_target_features()
.iter()
.filter(|(feature, _, _)| {
// skip checking special features, as LLVM may not understand them
if RUSTC_SPECIAL_FEATURES.contains(feature) {
return true;
}
let (unstable_target_features, target_features) =
target_features::cfg_target_feature(sess, &sess.opts.cg.target_feature, |feature| {
if let Some(feat) = to_llvm_features(sess, feature) {
// All the LLVM features this expands to must be enabled.
for llvm_feature in feat {
let cstr = SmallCStr::new(llvm_feature);
// `LLVMRustHasFeature` is moderately expensive. On targets with many
@ -368,73 +360,8 @@ pub(crate) fn target_config(sess: &Session) -> TargetConfig {
} else {
false
}
})
.map(|(feature, _, _)| Symbol::intern(feature))
.collect();
});
// Add enabled and remove disabled features.
for (enabled, feature) in
sess.opts.cg.target_feature.split(',').filter_map(|s| match s.chars().next() {
Some('+') => Some((true, Symbol::intern(&s[1..]))),
Some('-') => Some((false, Symbol::intern(&s[1..]))),
_ => None,
})
{
if enabled {
// Also add all transitively 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.extend(
sess.target
.implied_target_features(feature.as_str())
.iter()
.map(|s| Symbol::intern(s)),
);
} 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| {
if sess.target.implied_target_features(f.as_str()).contains(&feature.as_str()) {
// 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.
let f = |allow_unstable| {
sess.target
.rust_target_features()
.iter()
.filter_map(|(feature, gate, _)| {
// The `allow_unstable` set is used by rustc internally to determined which target
// features are truly available, so we want to return even perma-unstable
// "forbidden" features.
if allow_unstable
|| (gate.in_cfg()
&& (sess.is_nightly_build() || gate.requires_nightly().is_none()))
{
Some(Symbol::intern(feature))
} else {
None
}
})
.filter(|feature| features.contains(&feature))
.collect()
};
let target_features = f(false);
let unstable_target_features = f(true);
let mut cfg = TargetConfig {
target_features,
unstable_target_features,

99
compiler/rustc_codegen_ssa/src/target_features.rs
View file

@ -1,5 +1,5 @@
use rustc_attr_data_structures::InstructionSetAttr;
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_data_structures::unord::{UnordMap, UnordSet};
use rustc_errors::Applicability;
use rustc_hir as hir;
@ -8,11 +8,12 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
use rustc_middle::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_session::Session;
use rustc_session::features::StabilityExt;
use rustc_session::lint::builtin::AARCH64_SOFTFLOAT_NEON;
use rustc_session::parse::feature_err;
use rustc_span::{Span, Symbol, sym};
use rustc_target::target_features::{self, Stability};
use rustc_target::target_features::{self, RUSTC_SPECIAL_FEATURES, Stability};
use crate::errors;
@ -156,6 +157,100 @@ pub(crate) fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId,
}
}
/// Utility function for a codegen backend to compute `cfg(target_feature)`, or more specifically,
/// to populate `sess.unstable_target_features` and `sess.target_features` (these are the first and
/// 2nd component of the return value, respectively).
///
/// `target_feature_flag` is the value of `-Ctarget-feature` (giving the caller a chance to override it).
/// `target_base_has_feature` should check whether the given feature (a Rust feature name!) is enabled
/// in the "base" target machine, i.e., without applying `-Ctarget-feature`.
///
/// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled elsewhere.
pub fn cfg_target_feature(
sess: &Session,
target_feature_flag: &str,
mut is_feature_enabled: impl FnMut(&str) -> bool,
) -> (Vec<Symbol>, Vec<Symbol>) {
// 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.
let mut features: FxHashSet<Symbol> = sess
.target
.rust_target_features()
.iter()
.filter(|(feature, _, _)| {
// Skip checking special features, those are not known to the backend.
if RUSTC_SPECIAL_FEATURES.contains(feature) {
return true;
}
is_feature_enabled(feature)
})
.map(|(feature, _, _)| Symbol::intern(feature))
.collect();
// Add enabled and remove disabled features.
for (enabled, feature) in
target_feature_flag.split(',').filter_map(|s| match s.chars().next() {
Some('+') => Some((true, Symbol::intern(&s[1..]))),
Some('-') => Some((false, Symbol::intern(&s[1..]))),
_ => None,
})
{
if enabled {
// Also add all transitively 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.extend(
sess.target
.implied_target_features(feature.as_str())
.iter()
.map(|s| Symbol::intern(s)),
);
} 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| {
if sess.target.implied_target_features(f.as_str()).contains(&feature.as_str()) {
// 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.
let f = |allow_unstable| {
sess.target
.rust_target_features()
.iter()
.filter_map(|(feature, gate, _)| {
// The `allow_unstable` set is used by rustc internally to determine which target
// features are truly available, so we want to return even perma-unstable
// "forbidden" features.
if allow_unstable
|| (gate.in_cfg()
&& (sess.is_nightly_build() || gate.requires_nightly().is_none()))
{
Some(Symbol::intern(feature))
} else {
None
}
})
.filter(|feature| features.contains(&feature))
.collect()
};
(f(true), f(false))
}
pub(crate) fn provide(providers: &mut Providers) {
*providers = Providers {
rust_target_features: |tcx, cnum| {