@@ -10,7 +10,7 @@ use rustc_middle::query::Providers;
1010use rustc_middle:: ty:: TyCtxt ;
1111use rustc_session:: parse:: feature_err;
1212use rustc_span:: { Span , Symbol , sym} ;
13- use rustc_target:: target_features;
13+ use rustc_target:: target_features:: { self , Stability } ;
1414
1515use crate :: errors;
1616
@@ -87,12 +87,17 @@ pub(crate) fn from_target_feature_attr(
8787 // But ensure the ABI does not forbid enabling this.
8888 // Here we do assume that LLVM doesn't add even more implied features
8989 // we don't know about, at least no features that would have ABI effects!
90- if abi_feature_constraints. incompatible . contains ( & name. as_str ( ) ) {
91- tcx. dcx ( ) . emit_err ( errors:: ForbiddenTargetFeatureAttr {
92- span : item. span ( ) ,
93- feature : name. as_str ( ) ,
94- reason : "this feature is incompatible with the target ABI" ,
95- } ) ;
90+ // We skip this logic in rustdoc, where we want to allow all target features of
91+ // all targets, so we can't check their ABI compatibility and anyway we are not
92+ // generating code so "it's fine".
93+ if !tcx. sess . opts . actually_rustdoc {
94+ if abi_feature_constraints. incompatible . contains ( & name. as_str ( ) ) {
95+ tcx. dcx ( ) . emit_err ( errors:: ForbiddenTargetFeatureAttr {
96+ span : item. span ( ) ,
97+ feature : name. as_str ( ) ,
98+ reason : "this feature is incompatible with the target ABI" ,
99+ } ) ;
100+ }
96101 }
97102 target_features. push ( TargetFeature { name, implied : name != feature_sym } )
98103 }
@@ -142,11 +147,38 @@ pub(crate) fn provide(providers: &mut Providers) {
142147 rust_target_features : |tcx, cnum| {
143148 assert_eq ! ( cnum, LOCAL_CRATE ) ;
144149 if tcx. sess . opts . actually_rustdoc {
145- // rustdoc needs to be able to document functions that use all the features, so
146- // whitelist them all
147- rustc_target:: target_features:: all_rust_features ( )
148- . map ( |( a, b) | ( a. to_string ( ) , b) )
149- . collect ( )
150+ // HACK: rustdoc would like to pretend that we have all the target features, so we
151+ // have to merge all the lists into one. To ensure an unstable target never prevents
152+ // a stable one from working, we merge the stability info of all instances of the
153+ // same target feature name, with the "most stable" taking precedence. And then we
154+ // hope that this doesn't cause issues anywhere else in the compiler...
155+ let mut result: UnordMap < String , Stability > = Default :: default ( ) ;
156+ for ( name, stability) in rustc_target:: target_features:: all_rust_features ( ) {
157+ use std:: collections:: hash_map:: Entry ;
158+ match result. entry ( name. to_owned ( ) ) {
159+ Entry :: Vacant ( vacant_entry) => {
160+ vacant_entry. insert ( stability) ;
161+ }
162+ Entry :: Occupied ( mut occupied_entry) => {
163+ // Merge the two stabilities, "more stable" taking precedence.
164+ match ( occupied_entry. get ( ) , stability) {
165+ ( Stability :: Stable , _)
166+ | (
167+ Stability :: Unstable { .. } ,
168+ Stability :: Unstable { .. } | Stability :: Forbidden { .. } ,
169+ )
170+ | ( Stability :: Forbidden { .. } , Stability :: Forbidden { .. } ) => {
171+ // The stability in the entry is at least as good as the new one, just keep it.
172+ }
173+ _ => {
174+ // Overwrite stabilite.
175+ occupied_entry. insert ( stability) ;
176+ }
177+ }
178+ }
179+ }
180+ }
181+ result
150182 } else {
151183 tcx. sess
152184 . target
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