Auto merge of #75278 - cuviper:indexmap, r=Mark-Simulacrum

Upgrade indexmap and use it more

First this upgrades `indexmap` to 1.5.1, which is now based on `hashbrown::raw::RawTable`. This means it shares a lot of the same performance characteristics for insert, lookup, etc., while keeping items in insertion order.

Then across various rustc crates, this replaces a lot of `Vec`+`HashMap` pairs with a single `IndexMap` or `IndexSet`.

Closes #60608.
r? @eddyb

2 files changed, 10 insertions, 16 deletions

diff --git a/src/librustc_codegen_llvm/coverageinfo/mapgen.rs b/src/librustc_codegen_llvm/coverageinfo/mapgen.rs
index 9d2383abeed..b50b3b6d975 100644
--- a/src/librustc_codegen_llvm/coverageinfo/mapgen.rs
+++ b/src/librustc_codegen_llvm/coverageinfo/mapgen.rs
@@ -6,7 +6,7 @@ use llvm::coverageinfo::CounterMappingRegion;
 use log::debug;
 use rustc_codegen_ssa::coverageinfo::map::{Counter, CounterExpression, Region};
 use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods};
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_llvm::RustString;
 
 use std::ffi::CString;
@@ -76,13 +76,12 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
 }
 
 struct CoverageMapGenerator {
-    filenames: Vec<CString>,
-    filename_to_index: FxHashMap<CString, u32>,
+    filenames: FxIndexSet<CString>,
 }
 
 impl CoverageMapGenerator {
     fn new() -> Self {
-        Self { filenames: Vec::new(), filename_to_index: FxHashMap::default() }
+        Self { filenames: FxIndexSet::default() }
     }
 
     /// Using the `expressions` and `counter_regions` collected for the current function, generate
@@ -122,16 +121,8 @@ impl CoverageMapGenerator {
                 let c_filename =
                     CString::new(file_name).expect("null error converting filename to C string");
                 debug!("  file_id: {} = '{:?}'", current_file_id, c_filename);
-                let filenames_index = match self.filename_to_index.get(&c_filename) {
-                    Some(index) => *index,
-                    None => {
-                        let index = self.filenames.len() as u32;
-                        self.filenames.push(c_filename.clone());
-                        self.filename_to_index.insert(c_filename.clone(), index);
-                        index
-                    }
-                };
-                virtual_file_mapping.push(filenames_index);
+                let (filenames_index, _) = self.filenames.insert_full(c_filename);
+                virtual_file_mapping.push(filenames_index as u32);
             }
             mapping_regions.push(CounterMappingRegion::code_region(
                 counter,
diff --git a/src/librustc_codegen_llvm/coverageinfo/mod.rs b/src/librustc_codegen_llvm/coverageinfo/mod.rs
index 7b864e499d1..90831f0bcfb 100644
--- a/src/librustc_codegen_llvm/coverageinfo/mod.rs
+++ b/src/librustc_codegen_llvm/coverageinfo/mod.rs
@@ -97,8 +97,11 @@ impl CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
     }
 }
 
-pub(crate) fn write_filenames_section_to_buffer(filenames: &Vec<CString>, buffer: &RustString) {
-    let c_str_vec = filenames.iter().map(|cstring| cstring.as_ptr()).collect::<Vec<_>>();
+pub(crate) fn write_filenames_section_to_buffer<'a>(
+    filenames: impl IntoIterator<Item = &'a CString>,
+    buffer: &RustString,
+) {
+    let c_str_vec = filenames.into_iter().map(|cstring| cstring.as_ptr()).collect::<Vec<_>>();
     unsafe {
         llvm::LLVMRustCoverageWriteFilenamesSectionToBuffer(
             c_str_vec.as_ptr(),