Introduce FunctionDebugContext

This will make it easier to move TyCtxt requiring operations before clif
ir compilation.

src/base.rs

@@ -214,10 +214,10 @@ fn compile_fn<'tcx>(
     let unwind_context = &mut cx.unwind_context;
     cx.profiler.verbose_generic_activity("generate debug info").run(|| {
         if let Some(debug_context) = debug_context {
-            debug_context.define_function(
+            debug_context.define_function(codegened_func.symbol_name.name).finalize(
+                debug_context,
                 tcx,
                 codegened_func.func_id,
-                codegened_func.symbol_name.name,
                 context,
                 codegened_func.function_span,
                 &codegened_func.source_info_set,

src/debuginfo/mod.rs

@@ -10,7 +10,9 @@
 use cranelift_codegen::ir::Endianness;
 use cranelift_codegen::isa::TargetIsa;
 
-use gimli::write::{Address, AttributeValue, DwarfUnit, LineProgram, LineString, Range, RangeList};
+use gimli::write::{
+    Address, AttributeValue, DwarfUnit, LineProgram, LineString, Range, RangeList, UnitEntryId,
+};
 use gimli::{Encoding, Format, LineEncoding, RunTimeEndian};
 
 pub(crate) use emit::{DebugReloc, DebugRelocName};
@@ -23,6 +25,10 @@ pub(crate) struct DebugContext {
     unit_range_list: RangeList,
 }
 
+pub(crate) struct FunctionDebugContext {
+    entry_id: UnitEntryId,
+}
+
 impl DebugContext {
     pub(crate) fn new(tcx: TyCtxt<'_>, isa: &dyn TargetIsa) -> Self {
         let encoding = Encoding {
@@ -93,17 +99,7 @@ pub(crate) fn new(tcx: TyCtxt<'_>, isa: &dyn TargetIsa) -> Self {
         DebugContext { endian, dwarf, unit_range_list: RangeList(Vec::new()) }
     }
 
-    pub(crate) fn define_function(
-        &mut self,
-        tcx: TyCtxt<'_>,
-        func_id: FuncId,
-        name: &str,
-        context: &Context,
-        function_span: Span,
-        source_info_set: &indexmap::IndexSet<SourceInfo>,
-    ) {
-        let symbol = func_id.as_u32() as usize;
-
+    pub(crate) fn define_function(&mut self, name: &str) -> FunctionDebugContext {
         // FIXME: add to appropriate scope instead of root
         let scope = self.dwarf.unit.root();
 
@@ -114,15 +110,37 @@ pub(crate) fn define_function(
         entry.set(gimli::DW_AT_name, AttributeValue::StringRef(name_id));
         entry.set(gimli::DW_AT_linkage_name, AttributeValue::StringRef(name_id));
 
-        let end =
-            self.create_debug_lines(tcx, symbol, entry_id, context, function_span, source_info_set);
+        FunctionDebugContext { entry_id }
+    }
+}
 
-        self.unit_range_list.0.push(Range::StartLength {
+impl FunctionDebugContext {
+    pub(crate) fn finalize(
+        self,
+        debug_context: &mut DebugContext,
+        tcx: TyCtxt<'_>,
+        func_id: FuncId,
+        context: &Context,
+        function_span: Span,
+        source_info_set: &indexmap::IndexSet<SourceInfo>,
+    ) {
+        let symbol = func_id.as_u32() as usize;
+
+        let end = debug_context.create_debug_lines(
+            tcx,
+            symbol,
+            self.entry_id,
+            context,
+            function_span,
+            source_info_set,
+        );
+
+        debug_context.unit_range_list.0.push(Range::StartLength {
             begin: Address::Symbol { symbol, addend: 0 },
             length: u64::from(end),
         });
 
-        let func_entry = self.dwarf.unit.get_mut(entry_id);
+        let func_entry = debug_context.dwarf.unit.get_mut(self.entry_id);
         // Gdb requires both DW_AT_low_pc and DW_AT_high_pc. Otherwise the DW_TAG_subprogram is skipped.
         func_entry.set(
             gimli::DW_AT_low_pc,