codegen_ssa: consolidate tied feature checking

`rustc_codegen_llvm` and `rustc_codegen_gcc` duplicated logic for
checking if tied target features were partially enabled. This commit
consolidates these checks into `rustc_codegen_ssa` in the
`codegen_fn_attrs` query, which also is run pre-monomorphisation for
each function, which ensures that this check is run for unused functions,
as would be expected.

Author: davidtwco

compiler/rustc_codegen_gcc/messages.ftl

@@ -8,9 +8,6 @@ codegen_gcc_invalid_minimum_alignment =
 codegen_gcc_lto_not_supported =
     LTO is not supported. You may get a linker error.
 
-codegen_gcc_tied_target_features = the target features {$features} must all be either enabled or disabled together
-    .help = add the missing features in a `target_feature` attribute
-
 codegen_gcc_unwinding_inline_asm =
     GCC backend does not support unwinding from inline asm
 

compiler/rustc_codegen_gcc/src/attributes.rs

@@ -7,11 +7,9 @@ use rustc_attr::InstructionSetAttr;
 #[cfg(feature = "master")]
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty;
-use rustc_span::symbol::sym;
 
 use crate::context::CodegenCx;
-use crate::errors::TiedTargetFeatures;
-use crate::gcc_util::{check_tied_features, to_gcc_features};
+use crate::gcc_util::to_gcc_features;
 
 /// Get GCC attribute for the provided inline heuristic.
 #[cfg(feature = "master")]
@@ -72,26 +70,10 @@ pub fn from_fn_attrs<'gcc, 'tcx>(
         }
     }
 
-    let function_features = codegen_fn_attrs
+    let mut function_features = codegen_fn_attrs
         .target_features
         .iter()
         .map(|features| features.name.as_str())
-        .collect::<Vec<&str>>();
-
-    if let Some(features) = check_tied_features(
-        cx.tcx.sess,
-        &function_features.iter().map(|features| (*features, true)).collect(),
-    ) {
-        let span = cx
-            .tcx
-            .get_attr(instance.def_id(), sym::target_feature)
-            .map_or_else(|| cx.tcx.def_span(instance.def_id()), |a| a.span);
-        cx.tcx.dcx().create_err(TiedTargetFeatures { features: features.join(", "), span }).emit();
-        return;
-    }
-
-    let mut function_features = function_features
-        .iter()
         .flat_map(|feat| to_gcc_features(cx.tcx.sess, feat).into_iter())
         .chain(codegen_fn_attrs.instruction_set.iter().map(|x| match *x {
             InstructionSetAttr::ArmA32 => "-thumb-mode", // TODO(antoyo): support removing feature.

compiler/rustc_codegen_gcc/src/errors.rs

@@ -1,9 +1,6 @@
-use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
-use crate::fluent_generated as fluent;
-
 #[derive(Diagnostic)]
 #[diag(codegen_gcc_unknown_ctarget_feature_prefix)]
 #[note]
@@ -45,15 +42,6 @@ pub(crate) struct InvalidMinimumAlignment {
     pub err: String,
 }
 
-#[derive(Diagnostic)]
-#[diag(codegen_gcc_tied_target_features)]
-#[help]
-pub(crate) struct TiedTargetFeatures {
-    #[primary_span]
-    pub span: Span,
-    pub features: String,
-}
-
 #[derive(Diagnostic)]
 #[diag(codegen_gcc_copy_bitcode)]
 pub(crate) struct CopyBitcode {
@@ -78,27 +66,3 @@ pub(crate) struct LtoDylib;
 pub(crate) struct LtoBitcodeFromRlib {
     pub gcc_err: String,
 }
-
-pub(crate) struct TargetFeatureDisableOrEnable<'a> {
-    pub features: &'a [&'a str],
-    pub span: Option<Span>,
-    pub missing_features: Option<MissingFeatures>,
-}
-
-#[derive(Subdiagnostic)]
-#[help(codegen_gcc_missing_features)]
-pub(crate) struct MissingFeatures;
-
-impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
-        let mut diag = Diag::new(dcx, level, fluent::codegen_gcc_target_feature_disable_or_enable);
-        if let Some(span) = self.span {
-            diag.span(span);
-        };
-        if let Some(missing_features) = self.missing_features {
-            diag.subdiagnostic(missing_features);
-        }
-        diag.arg("features", self.features.join(", "));
-        diag
-    }
-}

compiler/rustc_codegen_gcc/src/gcc_util.rs

@@ -1,15 +1,14 @@
 #[cfg(feature = "master")]
 use gccjit::Context;
+use rustc_codegen_ssa::codegen_attrs::check_tied_features;
+use rustc_codegen_ssa::errors::TargetFeatureDisableOrEnable;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::bug;
 use rustc_session::Session;
 use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES;
 use smallvec::{smallvec, SmallVec};
 
-use crate::errors::{
-    PossibleFeature, TargetFeatureDisableOrEnable, UnknownCTargetFeature,
-    UnknownCTargetFeaturePrefix,
-};
+use crate::errors::{PossibleFeature, UnknownCTargetFeature, UnknownCTargetFeaturePrefix};
 
 /// The list of GCC features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
 /// `--target` and similar).
@@ -185,23 +184,6 @@ pub fn to_gcc_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]>
     }
 }
 
-// Given a map from target_features to whether they are enabled or disabled,
-// ensure only valid combinations are allowed.
-pub fn check_tied_features(
-    sess: &Session,
-    features: &FxHashMap<&str, bool>,
-) -> Option<&'static [&'static str]> {
-    for tied in sess.target.tied_target_features() {
-        // Tied features must be set to the same value, or not set at all
-        let mut tied_iter = tied.iter();
-        let enabled = features.get(tied_iter.next().unwrap());
-        if tied_iter.any(|feature| enabled != features.get(feature)) {
-            return Some(tied);
-        }
-    }
-    None
-}
-
 fn arch_to_gcc(name: &str) -> &str {
     match name {
         "M68020" => "68020",

compiler/rustc_codegen_llvm/messages.ftl

@@ -33,9 +33,6 @@ codegen_llvm_lto_proc_macro = lto cannot be used for `proc-macro` crate type wit
 codegen_llvm_mismatch_data_layout =
     data-layout for target `{$rustc_target}`, `{$rustc_layout}`, differs from LLVM target's `{$llvm_target}` default layout, `{$llvm_layout}`
 
-codegen_llvm_missing_features =
-    add the missing features in a `target_feature` attribute
-
 codegen_llvm_multiple_source_dicompileunit = multiple source DICompileUnits found
 codegen_llvm_multiple_source_dicompileunit_with_llvm_err = multiple source DICompileUnits found: {$llvm_err}
 
@@ -63,9 +60,6 @@ codegen_llvm_serialize_module_with_llvm_err = failed to serialize module {$name}
 codegen_llvm_symbol_already_defined =
     symbol `{$symbol_name}` is already defined
 
-codegen_llvm_target_feature_disable_or_enable =
-    the target features {$features} must all be either enabled or disabled together
-
 codegen_llvm_target_machine = could not create LLVM TargetMachine for triple: {$triple}
 codegen_llvm_target_machine_with_llvm_err = could not create LLVM TargetMachine for triple: {$triple}: {$llvm_err}
 

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -6,12 +6,11 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::{BranchProtection, FunctionReturn, OptLevel, PAuthKey, PacRet};
-use rustc_span::symbol::sym;
 use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
 use smallvec::SmallVec;
 
 use crate::context::CodegenCx;
-use crate::errors::{MissingFeatures, SanitizerMemtagRequiresMte, TargetFeatureDisableOrEnable};
+use crate::errors::SanitizerMemtagRequiresMte;
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::{self, AllocKindFlags, Attribute, AttributeKind, AttributePlace, MemoryEffects};
 use crate::value::Value;
@@ -503,26 +502,6 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     let function_features =
         codegen_fn_attrs.target_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
 
-    if let Some(f) = llvm_util::check_tied_features(
-        cx.tcx.sess,
-        &function_features.iter().map(|f| (*f, true)).collect(),
-    ) {
-        let span = cx
-            .tcx
-            .get_attrs(instance.def_id(), sym::target_feature)
-            .next()
-            .map_or_else(|| cx.tcx.def_span(instance.def_id()), |a| a.span);
-        cx.tcx
-            .dcx()
-            .create_err(TargetFeatureDisableOrEnable {
-                features: f,
-                span: Some(span),
-                missing_features: Some(MissingFeatures),
-            })
-            .emit();
-        return;
-    }
-
     let function_features = function_features
         .iter()
         // Convert to LLVMFeatures and filter out unavailable ones

compiler/rustc_codegen_llvm/src/errors.rs

@@ -80,30 +80,6 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
     }
 }
 
-pub(crate) struct TargetFeatureDisableOrEnable<'a> {
-    pub features: &'a [&'a str],
-    pub span: Option<Span>,
-    pub missing_features: Option<MissingFeatures>,
-}
-
-#[derive(Subdiagnostic)]
-#[help(codegen_llvm_missing_features)]
-pub(crate) struct MissingFeatures;
-
-impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
-        let mut diag = Diag::new(dcx, level, fluent::codegen_llvm_target_feature_disable_or_enable);
-        if let Some(span) = self.span {
-            diag.span(span);
-        };
-        if let Some(missing_features) = self.missing_features {
-            diag.subdiagnostic(missing_features);
-        }
-        diag.arg("features", self.features.join(", "));
-        diag
-    }
-}
-
 #[derive(Diagnostic)]
 #[diag(codegen_llvm_lto_disallowed)]
 pub(crate) struct LtoDisallowed;

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -6,6 +6,7 @@ use std::{ptr, slice, str};
 
 use libc::c_int;
 use rustc_codegen_ssa::base::wants_wasm_eh;
+use rustc_codegen_ssa::codegen_attrs::check_tied_features;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_data_structures::unord::UnordSet;
@@ -19,8 +20,8 @@ use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATU
 
 use crate::back::write::create_informational_target_machine;
 use crate::errors::{
-    FixedX18InvalidArch, InvalidTargetFeaturePrefix, PossibleFeature, TargetFeatureDisableOrEnable,
-    UnknownCTargetFeature, UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
+    FixedX18InvalidArch, InvalidTargetFeaturePrefix, PossibleFeature, UnknownCTargetFeature,
+    UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
 };
 use crate::llvm;
 
@@ -286,25 +287,6 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
     }
 }
 
-/// Given a map from target_features to whether they are enabled or disabled,
-/// ensure only valid combinations are allowed.
-pub(crate) fn check_tied_features(
-    sess: &Session,
-    features: &FxHashMap<&str, bool>,
-) -> Option<&'static [&'static str]> {
-    if !features.is_empty() {
-        for tied in sess.target.tied_target_features() {
-            // Tied features must be set to the same value, or not set at all
-            let mut tied_iter = tied.iter();
-            let enabled = features.get(tied_iter.next().unwrap());
-            if tied_iter.any(|f| enabled != features.get(f)) {
-                return Some(tied);
-            }
-        }
-    }
-    None
-}
-
 /// Used to generate cfg variables and apply features
 /// Must express features in the way Rust understands them
 pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
@@ -696,7 +678,7 @@ pub(crate) fn global_llvm_features(
         features.extend(feats);
 
         if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
-            sess.dcx().emit_err(TargetFeatureDisableOrEnable {
+            sess.dcx().emit_err(rustc_codegen_ssa::errors::TargetFeatureDisableOrEnable {
                 features: f,
                 span: None,
                 missing_features: None,

compiler/rustc_codegen_ssa/messages.ftl

@@ -183,6 +183,8 @@ codegen_ssa_metadata_object_file_write = error writing metadata object file: {$e
 
 codegen_ssa_missing_cpp_build_tool_component = or a necessary component may be missing from the "C++ build tools" workload
 
+codegen_ssa_missing_features = add the missing features in a `target_feature` attribute
+
 codegen_ssa_missing_memory_ordering = Atomic intrinsic missing memory ordering
 
 codegen_ssa_missing_query_depgraph =
@@ -238,6 +240,9 @@ codegen_ssa_stripping_debug_info_failed = stripping debug info with `{$util}` fa
 
 codegen_ssa_symbol_file_write_failure = failed to write symbols file: {$error}
 
+codegen_ssa_target_feature_disable_or_enable =
+    the target features {$features} must all be either enabled or disabled together
+
 codegen_ssa_target_feature_safe_trait = `#[target_feature(..)]` cannot be applied to safe trait method
     .label = cannot be applied to safe trait method
     .label_def = not an `unsafe` function

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -1,5 +1,6 @@
 use rustc_ast::{ast, attr, MetaItemKind, NestedMetaItem};
 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
 use rustc_errors::{struct_span_code_err, DiagMessage, SubdiagMessage};
 use rustc_hir as hir;
@@ -13,13 +14,13 @@ use rustc_middle::middle::codegen_fn_attrs::{
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self as ty, TyCtxt};
-use rustc_session::lint;
 use rustc_session::parse::feature_err;
+use rustc_session::{lint, Session};
 use rustc_span::symbol::Ident;
 use rustc_span::{sym, Span};
 use rustc_target::spec::{abi, SanitizerSet};
 
-use crate::errors;
+use crate::errors::{self, MissingFeatures, TargetFeatureDisableOrEnable};
 use crate::target_features::{check_target_feature_trait_unsafe, from_target_feature};
 
 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
@@ -680,9 +681,47 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         }
     }
 
+    if let Some(features) = check_tied_features(
+        tcx.sess,
+        &codegen_fn_attrs
+            .target_features
+            .iter()
+            .map(|features| (features.name.as_str(), true))
+            .collect(),
+    ) {
+        let span =
+            tcx.get_attr(did, sym::target_feature).map_or_else(|| tcx.def_span(did), |a| a.span);
+        tcx.dcx()
+            .create_err(TargetFeatureDisableOrEnable {
+                features,
+                span: Some(span),
+                missing_features: Some(MissingFeatures),
+            })
+            .emit();
+    }
+
     codegen_fn_attrs
 }
 
+/// Given a map from target_features to whether they are enabled or disabled, ensure only valid
+/// combinations are allowed.
+pub fn check_tied_features(
+    sess: &Session,
+    features: &FxHashMap<&str, bool>,
+) -> Option<&'static [&'static str]> {
+    if !features.is_empty() {
+        for tied in sess.target.tied_target_features() {
+            // Tied features must be set to the same value, or not set at all
+            let mut tied_iter = tied.iter();
+            let enabled = features.get(tied_iter.next().unwrap());
+            if tied_iter.any(|f| enabled != features.get(f)) {
+                return Some(tied);
+            }
+        }
+    }
+    None
+}
+
 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
 /// applied to the method prototype.
 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {