Use the same DISubprogram for each instance of the same inlined function within a caller

compiler/rustc_codegen_gcc/src/debuginfo.rs

@@ -55,7 +55,7 @@ impl<'gcc, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         _fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         _llfn: RValue<'gcc>,
         _mir: &mir::Body<'tcx>,
-    ) -> Option<FunctionDebugContext<Self::DIScope, Self::DILocation>> {
+    ) -> Option<FunctionDebugContext<'tcx, Self::DIScope, Self::DILocation>> {
         // TODO(antoyo)
         None
     }

compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs

@@ -20,7 +20,7 @@ pub fn compute_mir_scopes<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     instance: Instance<'tcx>,
     mir: &Body<'tcx>,
-    debug_context: &mut FunctionDebugContext<&'ll DIScope, &'ll DILocation>,
+    debug_context: &mut FunctionDebugContext<'tcx, &'ll DIScope, &'ll DILocation>,
 ) {
     // Find all scopes with variables defined in them.
     let variables = if cx.sess().opts.debuginfo == DebugInfo::Full {
@@ -51,7 +51,7 @@ fn make_mir_scope<'ll, 'tcx>(
     instance: Instance<'tcx>,
     mir: &Body<'tcx>,
     variables: &Option<BitSet<SourceScope>>,
-    debug_context: &mut FunctionDebugContext<&'ll DIScope, &'ll DILocation>,
+    debug_context: &mut FunctionDebugContext<'tcx, &'ll DIScope, &'ll DILocation>,
     instantiated: &mut BitSet<SourceScope>,
     scope: SourceScope,
 ) {
@@ -84,7 +84,6 @@ fn make_mir_scope<'ll, 'tcx>(
     }
 
     let loc = cx.lookup_debug_loc(scope_data.span.lo());
-    let file_metadata = file_metadata(cx, &loc.file);
 
     let dbg_scope = match scope_data.inlined {
         Some((callee, _)) => {
@@ -95,18 +94,26 @@ fn make_mir_scope<'ll, 'tcx>(
                 ty::ParamEnv::reveal_all(),
                 ty::EarlyBinder::bind(callee),
             );
-            let callee_fn_abi = cx.fn_abi_of_instance(callee, ty::List::empty());
-            cx.dbg_scope_fn(callee, callee_fn_abi, None)
+            debug_context.inlined_function_scopes.entry(callee).or_insert_with(|| {
+                let callee_fn_abi = cx.fn_abi_of_instance(callee, ty::List::empty());
+                cx.dbg_scope_fn(callee, callee_fn_abi, None)
+            })
+        }
+        None => {
+            let file_metadata = file_metadata(cx, &loc.file);
+            debug_context
+                .lexical_blocks
+                .entry((parent_scope.dbg_scope, loc.line, loc.col, file_metadata))
+                .or_insert_with(|| unsafe {
+                    llvm::LLVMRustDIBuilderCreateLexicalBlock(
+                        DIB(cx),
+                        parent_scope.dbg_scope,
+                        file_metadata,
+                        loc.line,
+                        loc.col,
+                    )
+                })
         }
-        None => unsafe {
-            llvm::LLVMRustDIBuilderCreateLexicalBlock(
-                DIB(cx),
-                parent_scope.dbg_scope,
-                file_metadata,
-                loc.line,
-                loc.col,
-            )
-        },
     };
 
     let inlined_at = scope_data.inlined.map(|(_, callsite_span)| {

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -5,7 +5,7 @@ use rustc_codegen_ssa::mir::debuginfo::VariableKind::*;
 use self::metadata::{file_metadata, type_di_node};
 use self::metadata::{UNKNOWN_COLUMN_NUMBER, UNKNOWN_LINE_NUMBER};
 use self::namespace::mangled_name_of_instance;
-use self::utils::{create_DIArray, is_node_local_to_unit, DIB};
+use self::utils::{create_DIArray, debug_context, is_node_local_to_unit, DIB};
 
 use crate::abi::FnAbi;
 use crate::builder::Builder;
@@ -67,6 +67,8 @@ pub struct CodegenUnitDebugContext<'ll, 'tcx> {
     type_map: metadata::TypeMap<'ll, 'tcx>,
     namespace_map: RefCell<DefIdMap<&'ll DIScope>>,
     recursion_marker_type: OnceCell<&'ll DIType>,
+    /// Maps a varaible (name, scope, kind (argument or local), span) to its debug information.
+    variables: RefCell<FxHashMap<(Symbol, &'ll DIScope, VariableKind, Span), &'ll DIVariable>>,
 }
 
 impl Drop for CodegenUnitDebugContext<'_, '_> {
@@ -91,6 +93,7 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
             type_map: Default::default(),
             namespace_map: RefCell::new(Default::default()),
             recursion_marker_type: OnceCell::new(),
+            variables: RefCell::new(Default::default()),
         }
     }
 
@@ -292,7 +295,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         llfn: &'ll Value,
         mir: &mir::Body<'tcx>,
-    ) -> Option<FunctionDebugContext<&'ll DIScope, &'ll DILocation>> {
+    ) -> Option<FunctionDebugContext<'tcx, &'ll DIScope, &'ll DILocation>> {
         if self.sess().opts.debuginfo == DebugInfo::None {
             return None;
         }
@@ -304,8 +307,11 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             file_start_pos: BytePos(0),
             file_end_pos: BytePos(0),
         };
-        let mut fn_debug_context =
-            FunctionDebugContext { scopes: IndexVec::from_elem(empty_scope, &mir.source_scopes) };
+        let mut fn_debug_context = FunctionDebugContext {
+            scopes: IndexVec::from_elem(empty_scope, &mir.source_scopes),
+            inlined_function_scopes: Default::default(),
+            lexical_blocks: Default::default(),
+        };
 
         // Fill in all the scopes, with the information from the MIR body.
         compute_mir_scopes(self, instance, mir, &mut fn_debug_context);
@@ -606,33 +612,39 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         variable_kind: VariableKind,
         span: Span,
     ) -> &'ll DIVariable {
-        let loc = self.lookup_debug_loc(span.lo());
-        let file_metadata = file_metadata(self, &loc.file);
-
-        let type_metadata = type_di_node(self, variable_type);
-
-        let (argument_index, dwarf_tag) = match variable_kind {
-            ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
-            LocalVariable => (0, DW_TAG_auto_variable),
-        };
-        let align = self.align_of(variable_type);
-
-        let name = variable_name.as_str();
-        unsafe {
-            llvm::LLVMRustDIBuilderCreateVariable(
-                DIB(self),
-                dwarf_tag,
-                scope_metadata,
-                name.as_ptr().cast(),
-                name.len(),
-                file_metadata,
-                loc.line,
-                type_metadata,
-                true,
-                DIFlags::FlagZero,
-                argument_index,
-                align.bytes() as u32,
-            )
-        }
+        debug_context(self)
+            .variables
+            .borrow_mut()
+            .entry((variable_name, scope_metadata, variable_kind, span))
+            .or_insert_with(|| {
+                let loc = self.lookup_debug_loc(span.lo());
+                let file_metadata = file_metadata(self, &loc.file);
+
+                let type_metadata = type_di_node(self, variable_type);
+
+                let (argument_index, dwarf_tag) = match variable_kind {
+                    ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
+                    LocalVariable => (0, DW_TAG_auto_variable),
+                };
+                let align = self.align_of(variable_type);
+
+                let name = variable_name.as_str();
+                unsafe {
+                    llvm::LLVMRustDIBuilderCreateVariable(
+                        DIB(self),
+                        dwarf_tag,
+                        scope_metadata,
+                        name.as_ptr().cast(),
+                        name.len(),
+                        file_metadata,
+                        loc.line,
+                        type_metadata,
+                        true,
+                        DIFlags::FlagZero,
+                        argument_index,
+                        align.bytes() as u32,
+                    )
+                }
+            })
     }
 }

compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

@@ -1,10 +1,12 @@
 use crate::traits::*;
+use rustc_data_structures::fx::FxHashMap;
 use rustc_index::IndexVec;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
+use rustc_middle::ty::Instance;
 use rustc_middle::ty::Ty;
 use rustc_session::config::DebugInfo;
 use rustc_span::symbol::{kw, Symbol};
@@ -17,11 +19,19 @@ use super::{FunctionCx, LocalRef};
 
 use std::ops::Range;
 
-pub struct FunctionDebugContext<S, L> {
+pub struct FunctionDebugContext<'tcx, S, L> {
+    /// Maps from source code to the corresponding debug info scope.
     pub scopes: IndexVec<mir::SourceScope, DebugScope<S, L>>,
+
+    /// Maps from a given inlined function to its debug info declaration.
+    pub inlined_function_scopes: FxHashMap<Instance<'tcx>, S>,
+
+    /// Maps from a lexical block (parent scope, line, column, file) to its debug info declaration.
+    /// This is particularily useful if the parent scope is an inlined function.
+    pub lexical_blocks: FxHashMap<(S, u32, u32, S), S>,
 }
 
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub enum VariableKind {
     ArgumentVariable(usize /*index*/),
     LocalVariable,

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -45,7 +45,7 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
 
     mir: &'tcx mir::Body<'tcx>,
 
-    debug_context: Option<FunctionDebugContext<Bx::DIScope, Bx::DILocation>>,
+    debug_context: Option<FunctionDebugContext<'tcx, Bx::DIScope, Bx::DILocation>>,
 
     llfn: Bx::Function,
 

compiler/rustc_codegen_ssa/src/traits/debuginfo.rs

@@ -26,7 +26,7 @@ pub trait DebugInfoMethods<'tcx>: BackendTypes {
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         llfn: Self::Function,
         mir: &mir::Body<'tcx>,
-    ) -> Option<FunctionDebugContext<Self::DIScope, Self::DILocation>>;
+    ) -> Option<FunctionDebugContext<'tcx, Self::DIScope, Self::DILocation>>;
 
     // FIXME(eddyb) find a common convention for all of the debuginfo-related
     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).

tests/codegen/debuginfo-inline-callsite-location.rs

@@ -0,0 +1,26 @@
+// compile-flags: -g -O
+
+// Check that each inline call site for the same function uses the same "sub-program" so that LLVM
+// can correctly merge the debug info if it merges the inlined code (e.g., for merging of tail
+// calls to panic.
+
+// CHECK:       tail call void @_ZN4core9panicking5panic17h{{([0-9a-z]{16})}}E
+// CHECK-SAME:  !dbg ![[#first_dbg:]]
+// CHECK:       tail call void @_ZN4core9panicking5panic17h{{([0-9a-z]{16})}}E
+// CHECK-SAME:  !dbg ![[#second_dbg:]]
+
+// CHECK:       ![[#func_dbg:]] = distinct !DISubprogram(name: "unwrap<i32>"
+// CHECK:       ![[#first_dbg]] = !DILocation(line: [[#]]
+// CHECK-SAME:  scope: ![[#func_dbg]], inlinedAt: ![[#]])
+// CHECK:       ![[#second_dbg]] = !DILocation(line: [[#]]
+// CHECK-SAME:  scope: ![[#func_dbg]], inlinedAt: ![[#]])
+
+#![crate_type = "lib"]
+
+#[no_mangle]
+extern "C" fn add_numbers(x: &Option<i32>, y: &Option<i32>) -> i32 {
+    let x1 = x.unwrap();
+    let y1 = y.unwrap();
+
+    x1 + y1
+}