Fix performance regression in debuginfo file_metadata.

Finding the `SourceFile` associated with a `FileName` called `get_source_file` on
the `SourceMap`, which does a linear search through all files in the `SourceMap`.

This resolves the issue by passing the SourceFile in from the caller (which already
had it available).

Author: arlosi

src/librustc_codegen_llvm/debuginfo/create_scope_map.rs

@@ -76,7 +76,7 @@ fn make_mir_scope(
     }
 
     let loc = cx.lookup_debug_loc(scope_data.span.lo());
-    let file_metadata = file_metadata(cx, &loc.file.name, debug_context.defining_crate);
+    let file_metadata = file_metadata(cx, &loc.file, debug_context.defining_crate);
 
     let scope_metadata = unsafe {
         Some(llvm::LLVMRustDIBuilderCreateLexicalBlock(

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -41,7 +41,7 @@ use rustc_middle::ty::{self, AdtKind, ParamEnv, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::{self, DebugInfo};
 use rustc_span::symbol::{Interner, Symbol};
-use rustc_span::{self, FileName, SourceFileHash, Span};
+use rustc_span::{self, SourceFile, SourceFileHash, Span};
 use rustc_target::abi::{Abi, Align, DiscriminantKind, HasDataLayout, Integer, LayoutOf};
 use rustc_target::abi::{Int, Pointer, F32, F64};
 use rustc_target::abi::{Primitive, Size, VariantIdx, Variants};
@@ -761,14 +761,13 @@ fn hex_encode(data: &[u8]) -> String {
 
 pub fn file_metadata(
     cx: &CodegenCx<'ll, '_>,
-    file_name: &FileName,
+    source_file: &SourceFile,
     defining_crate: CrateNum,
 ) -> &'ll DIFile {
-    debug!("file_metadata: file_name: {}, defining_crate: {}", file_name, defining_crate);
+    debug!("file_metadata: file_name: {}, defining_crate: {}", source_file.name, defining_crate);
 
-    let source_file = cx.sess().source_map().get_source_file(file_name);
-    let hash = source_file.as_ref().map(|f| &f.src_hash);
-    let file_name = Some(file_name.to_string());
+    let hash = Some(&source_file.src_hash);
+    let file_name = Some(source_file.name.to_string());
     let directory = if defining_crate == LOCAL_CRATE {
         Some(cx.sess().working_dir.0.to_string_lossy().to_string())
     } else {
@@ -2331,7 +2330,7 @@ pub fn create_global_var_metadata(cx: &CodegenCx<'ll, '_>, def_id: DefId, global
 
     let (file_metadata, line_number) = if !span.is_dummy() {
         let loc = cx.lookup_debug_loc(span.lo());
-        (file_metadata(cx, &loc.file.name, LOCAL_CRATE), loc.line)
+        (file_metadata(cx, &loc.file, LOCAL_CRATE), loc.line)
     } else {
         (unknown_file_metadata(cx), None)
     };
@@ -2440,6 +2439,6 @@ pub fn extend_scope_to_file(
     file: &rustc_span::SourceFile,
     defining_crate: CrateNum,
 ) -> &'ll DILexicalBlock {
-    let file_metadata = file_metadata(cx, &file.name, defining_crate);
+    let file_metadata = file_metadata(cx, &file, defining_crate);
     unsafe { llvm::LLVMRustDIBuilderCreateLexicalBlockFile(DIB(cx), scope_metadata, file_metadata) }
 }

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -249,7 +249,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         let def_id = instance.def_id();
         let containing_scope = get_containing_scope(self, instance);
         let loc = self.lookup_debug_loc(span.lo());
-        let file_metadata = file_metadata(self, &loc.file.name, def_id.krate);
+        let file_metadata = file_metadata(self, &loc.file, def_id.krate);
 
         let function_type_metadata = unsafe {
             let fn_signature = get_function_signature(self, fn_abi);
@@ -536,7 +536,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         span: Span,
     ) -> &'ll DIVariable {
         let loc = self.lookup_debug_loc(span.lo());
-        let file_metadata = file_metadata(self, &loc.file.name, dbg_context.defining_crate);
+        let file_metadata = file_metadata(self, &loc.file, dbg_context.defining_crate);
 
         let type_metadata = type_metadata(self, variable_type, span);