Deduplicate inlined function debug info, but create a new lexical scope to child subsequent scopes and variables from colliding

Author: dpaoliello

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,
 ) {
@@ -86,7 +86,7 @@ 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 {
+    let parent_dbg_scope = match scope_data.inlined {
         Some((callee, _)) => {
             // FIXME(eddyb) this would be `self.monomorphize(&callee)`
             // if this is moved to `rustc_codegen_ssa::mir::debuginfo`.
@@ -95,18 +95,22 @@ 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 => unsafe {
-            llvm::LLVMRustDIBuilderCreateLexicalBlock(
-                DIB(cx),
-                parent_scope.dbg_scope,
-                file_metadata,
-                loc.line,
-                loc.col,
-            )
-        },
+        None => parent_scope.dbg_scope,
+    };
+
+    let dbg_scope = unsafe {
+        llvm::LLVMRustDIBuilderCreateLexicalBlock(
+            DIB(cx),
+            parent_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

@@ -292,7 +292,7 @@ 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 +304,10 @@ 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(),
+        };
 
         // Fill in all the scopes, with the information from the MIR body.
         compute_mir_scopes(self, instance, mir, &mut fn_debug_context);

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};
@@ -17,10 +19,13 @@ 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 an inlined function to its debug info declaration.
+    pub inlined_function_scopes: FxHashMap<Instance<'tcx>, S>,
+}
 #[derive(Copy, Clone)]
 pub enum VariableKind {
     ArgumentVariable(usize /*index*/),

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -46,7 +46,7 @@ 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 +1,28 @@
+// 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-DAG:   ![[#func_dbg:]] = distinct !DISubprogram(name: "unwrap<i32>"
+// CHECK-DAG:   ![[#first_scope:]] = distinct !DILexicalBlock(scope: ![[#func_dbg]],
+// CHECK:       ![[#second_scope:]] = distinct !DILexicalBlock(scope: ![[#func_dbg]],
+// CHECK:       ![[#first_dbg]] = !DILocation(line: [[#]]
+// CHECK-SAME:  scope: ![[#first_scope]], inlinedAt: ![[#]])
+// CHECK:       ![[#second_dbg]] = !DILocation(line: [[#]]
+// CHECK-SAME:  scope: ![[#second_scope]], 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
+}