Make dependency_formats an FxIndexMap rather than a list of tuples

It is treated as a map already. This is using FxIndexMap rather than
UnordMap because the latter doesn't provide an api to pick a single
value iff all values are equal, which each_linked_rlib depends on.

compiler/rustc_codegen_cranelift/src/driver/jit.rs

@@ -287,12 +287,7 @@ fn dep_symbol_lookup_fn(
 
     let mut dylib_paths = Vec::new();
 
-    let data = &crate_info
-        .dependency_formats
-        .iter()
-        .find(|(crate_type, _data)| *crate_type == rustc_session::config::CrateType::Executable)
-        .unwrap()
-        .1;
+    let data = &crate_info.dependency_formats[&rustc_session::config::CrateType::Executable].1;
     // `used_crates` is in reverse postorder in terms of dependencies. Reverse the order here to
     // get a postorder which ensures that all dependencies of a dylib are loaded before the dylib
     // itself. This helps the dynamic linker to find dylibs not in the regular dynamic library

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -236,7 +236,13 @@ pub fn each_linked_rlib(
 ) -> Result<(), errors::LinkRlibError> {
     let crates = info.used_crates.iter();
 
-    let fmts = if crate_type.is_none() {
+    let fmts = if let Some(crate_type) = crate_type {
+        let Some(fmts) = info.dependency_formats.get(&crate_type) else {
+            return Err(errors::LinkRlibError::MissingFormat);
+        };
+
+        fmts
+    } else {
         for combination in info.dependency_formats.iter().combinations(2) {
             let (ty1, list1) = &combination[0];
             let (ty2, list2) = &combination[1];
@@ -252,18 +258,7 @@ pub fn each_linked_rlib(
         if info.dependency_formats.is_empty() {
             return Err(errors::LinkRlibError::MissingFormat);
         }
-        &info.dependency_formats[0].1
-    } else {
-        let fmts = info
-            .dependency_formats
-            .iter()
-            .find_map(|&(ty, ref list)| if Some(ty) == crate_type { Some(list) } else { None });
-
-        let Some(fmts) = fmts else {
-            return Err(errors::LinkRlibError::MissingFormat);
-        };
-
-        fmts
+        info.dependency_formats.first().unwrap().1
     };
 
     for &cnum in crates {
@@ -624,8 +619,7 @@ fn link_staticlib(
     let fmts = codegen_results
         .crate_info
         .dependency_formats
-        .iter()
-        .find_map(|&(ty, ref list)| if ty == CrateType::Staticlib { Some(list) } else { None })
+        .get(&CrateType::Staticlib)
         .expect("no dependency formats for staticlib");
 
     let mut all_rust_dylibs = vec![];
@@ -2355,11 +2349,10 @@ fn linker_with_args(
     // they are used within inlined functions or instantiated generic functions. We do this *after*
     // handling the raw-dylib symbols in the current crate to make sure that those are chosen first
     // by the linker.
-    let (_, dependency_linkage) = codegen_results
+    let dependency_linkage = codegen_results
         .crate_info
         .dependency_formats
-        .iter()
-        .find(|(ty, _)| *ty == crate_type)
+        .get(&crate_type)
         .expect("failed to find crate type in dependency format list");
 
     // We sort the libraries below
@@ -2738,11 +2731,10 @@ fn add_upstream_rust_crates(
     // Linking to a rlib involves just passing it to the linker (the linker
     // will slurp up the object files inside), and linking to a dynamic library
     // involves just passing the right -l flag.
-    let (_, data) = codegen_results
+    let data = codegen_results
         .crate_info
         .dependency_formats
-        .iter()
-        .find(|(ty, _)| *ty == crate_type)
+        .get(&crate_type)
         .expect("failed to find crate type in dependency format list");
 
     if sess.target.is_like_aix {

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1749,7 +1749,7 @@ fn for_each_exported_symbols_include_dep<'tcx>(
     }
 
     let formats = tcx.dependency_formats(());
-    let deps = formats.iter().find_map(|(t, list)| (*t == crate_type).then_some(list)).unwrap();
+    let deps = &formats[&crate_type];
 
     for (index, dep_format) in deps.iter().enumerate() {
         let cnum = CrateNum::new(index + 1);

compiler/rustc_metadata/src/dependency_format.rs

@@ -77,7 +77,7 @@ pub(crate) fn calculate(tcx: TyCtxt<'_>) -> Dependencies {
             verify_ok(tcx, &linkage);
             (ty, linkage)
         })
-        .collect::<Vec<_>>()
+        .collect()
 }
 
 fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2164,10 +2164,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     fn encode_dylib_dependency_formats(&mut self) -> LazyArray<Option<LinkagePreference>> {
         empty_proc_macro!(self);
         let formats = self.tcx.dependency_formats(());
-        for (ty, arr) in formats.iter() {
-            if *ty != CrateType::Dylib {
-                continue;
-            }
+        if let Some(arr) = formats.get(&CrateType::Dylib) {
             return self.lazy_array(arr.iter().map(|slot| match *slot {
                 Linkage::NotLinked | Linkage::IncludedFromDylib => None,
 

compiler/rustc_middle/src/middle/dependency_format.rs

@@ -7,6 +7,7 @@
 // FIXME: move this file to rustc_metadata::dependency_format, but
 // this will introduce circular dependency between rustc_metadata and rustc_middle
 
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_macros::{Decodable, Encodable, HashStable};
 use rustc_session::config::CrateType;
 
@@ -18,7 +19,7 @@ pub type DependencyList = Vec<Linkage>;
 /// A mapping of all required dependencies for a particular flavor of output.
 ///
 /// This is local to the tcx, and is generally relevant to one session.
-pub type Dependencies = Vec<(CrateType, DependencyList)>;
+pub type Dependencies = FxIndexMap<CrateType, DependencyList>;
 
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Encodable, Decodable)]
 pub enum Linkage {