Avoid a branch on key being local for queries that use the same local and extern providers

compiler/rustc_macros/src/query.rs

@@ -55,6 +55,9 @@ enum QueryModifier {
 
     /// Always evaluate the query, ignoring its dependencies
     EvalAlways(Ident),
+
+    /// Use a separate query provider for local and extern crates
+    SeparateProvideExtern(Ident),
 }
 
 impl Parse for QueryModifier {
@@ -118,6 +121,8 @@ impl Parse for QueryModifier {
             Ok(QueryModifier::Anon(modifier))
         } else if modifier == "eval_always" {
             Ok(QueryModifier::EvalAlways(modifier))
+        } else if modifier == "separate_provide_extern" {
+            Ok(QueryModifier::SeparateProvideExtern(modifier))
         } else {
             Err(Error::new(modifier.span(), "unknown query modifier"))
         }
@@ -214,6 +219,9 @@ struct QueryModifiers {
 
     // Always evaluate the query, ignoring its dependencies
     eval_always: Option<Ident>,
+
+    /// Use a separate query provider for local and extern crates
+    separate_provide_extern: Option<Ident>,
 }
 
 /// Process query modifiers into a struct, erroring on duplicates
@@ -227,6 +235,7 @@ fn process_modifiers(query: &mut Query) -> QueryModifiers {
     let mut no_hash = None;
     let mut anon = None;
     let mut eval_always = None;
+    let mut separate_provide_extern = None;
     for modifier in query.modifiers.0.drain(..) {
         match modifier {
             QueryModifier::LoadCached(tcx, id, block) => {
@@ -317,6 +326,15 @@ fn process_modifiers(query: &mut Query) -> QueryModifiers {
                 }
                 eval_always = Some(ident);
             }
+            QueryModifier::SeparateProvideExtern(ident) => {
+                if separate_provide_extern.is_some() {
+                    panic!(
+                        "duplicate modifier `separate_provide_extern` for query `{}`",
+                        query.name
+                    );
+                }
+                separate_provide_extern = Some(ident);
+            }
         }
     }
     let desc = desc.unwrap_or_else(|| {
@@ -332,6 +350,7 @@ fn process_modifiers(query: &mut Query) -> QueryModifiers {
         no_hash,
         anon,
         eval_always,
+        separate_provide_extern,
     }
 }
 
@@ -462,6 +481,10 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
         if let Some(eval_always) = &modifiers.eval_always {
             attributes.push(quote! { (#eval_always) });
         };
+        // Pass on the separate_provide_extern modifier
+        if let Some(separate_provide_extern) = &modifiers.separate_provide_extern {
+            attributes.push(quote! { (#separate_provide_extern) });
+        }
 
         // This uses the span of the query definition for the commas,
         // which can be important if we later encounter any ambiguity