Auto merge of #114904 - cjgillot:no-ref-debuginfo, r=wesleywiser

Remove references in VarDebugInfo

The codegen implementation is broken, and attempted to read uninitialized memory.

Fixes #114488

Author: bors

compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

@@ -42,9 +42,6 @@ pub struct PerLocalVarDebugInfo<'tcx, D> {
 
     /// `.place.projection` from `mir::VarDebugInfo`.
     pub projection: &'tcx ty::List<mir::PlaceElem<'tcx>>,
-
-    /// `references` from `mir::VarDebugInfo`.
-    pub references: u8,
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -323,7 +320,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     dbg_var,
                     fragment: None,
                     projection: ty::List::empty(),
-                    references: 0,
                 })
             }
         } else {
@@ -399,15 +395,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         &self,
         bx: &mut Bx,
         local: mir::Local,
-        mut base: PlaceRef<'tcx, Bx::Value>,
+        base: PlaceRef<'tcx, Bx::Value>,
         var: PerLocalVarDebugInfo<'tcx, Bx::DIVariable>,
     ) {
         let Some(dbg_var) = var.dbg_var else { return };
         let Some(dbg_loc) = self.dbg_loc(var.source_info) else { return };
 
-        let DebugInfoOffset { mut direct_offset, indirect_offsets, result: _ } =
+        let DebugInfoOffset { direct_offset, indirect_offsets, result: _ } =
             calculate_debuginfo_offset(bx, local, &var, base.layout);
-        let mut indirect_offsets = &indirect_offsets[..];
 
         // When targeting MSVC, create extra allocas for arguments instead of pointing multiple
         // dbg_var_addr() calls into the same alloca with offsets. MSVC uses CodeView records
@@ -421,45 +416,29 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             // LLVM can handle simple things but anything more complex than just a direct
             // offset or one indirect offset of 0 is too complex for it to generate CV records
             // correctly.
-            && (direct_offset != Size::ZERO || !matches!(indirect_offsets, [Size::ZERO] | []));
+            && (direct_offset != Size::ZERO || !matches!(&indirect_offsets[..], [Size::ZERO] | []));
+
+        if should_create_individual_allocas {
+            let DebugInfoOffset { direct_offset: _, indirect_offsets: _, result: place } =
+                calculate_debuginfo_offset(bx, local, &var, base);
 
-        let create_alloca = |bx: &mut Bx, place: PlaceRef<'tcx, Bx::Value>, refcount| {
             // Create a variable which will be a pointer to the actual value
             let ptr_ty = Ty::new_ptr(
                 bx.tcx(),
                 ty::TypeAndMut { mutbl: mir::Mutability::Mut, ty: place.layout.ty },
             );
             let ptr_layout = bx.layout_of(ptr_ty);
             let alloca = PlaceRef::alloca(bx, ptr_layout);
-            bx.set_var_name(alloca.llval, &format!("{}.ref{}.dbg.spill", var.name, refcount));
+            bx.set_var_name(alloca.llval, &(var.name.to_string() + ".dbg.spill"));
 
             // Write the pointer to the variable
             bx.store(place.llval, alloca.llval, alloca.align);
 
             // Point the debug info to `*alloca` for the current variable
-            alloca
-        };
-
-        if var.references > 0 {
-            base = calculate_debuginfo_offset(bx, local, &var, base).result;
-
-            // Point the debug info to `&...&base == alloca` for the current variable
-            for refcount in 0..var.references {
-                base = create_alloca(bx, base, refcount);
-            }
-
-            direct_offset = Size::ZERO;
-            indirect_offsets = &[];
-        } else if should_create_individual_allocas {
-            let place = calculate_debuginfo_offset(bx, local, &var, base).result;
-
-            // Point the debug info to `*alloca` for the current variable
-            base = create_alloca(bx, place, 0);
-            direct_offset = Size::ZERO;
-            indirect_offsets = &[Size::ZERO];
+            bx.dbg_var_addr(dbg_var, dbg_loc, alloca.llval, Size::ZERO, &[Size::ZERO], None);
+        } else {
+            bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, direct_offset, &indirect_offsets, None);
         }
-
-        bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, direct_offset, indirect_offsets, None);
     }
 
     pub fn debug_introduce_locals(&self, bx: &mut Bx) {
@@ -492,7 +471,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             };
 
             let dbg_var = dbg_scope_and_span.map(|(dbg_scope, _, span)| {
-                let (mut var_ty, var_kind) = match var.value {
+                let (var_ty, var_kind) = match var.value {
                     mir::VarDebugInfoContents::Place(place) => {
                         let var_ty = self.monomorphized_place_ty(place.as_ref());
                         let var_kind = if let Some(arg_index) = var.argument_index
@@ -529,13 +508,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                 };
 
-                for _ in 0..var.references {
-                    var_ty = Ty::new_ptr(
-                        bx.tcx(),
-                        ty::TypeAndMut { mutbl: mir::Mutability::Mut, ty: var_ty },
-                    );
-                }
-
                 self.cx.create_dbg_var(var.name, var_ty, dbg_scope, var_kind, span)
             });
 
@@ -547,7 +519,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         dbg_var,
                         fragment: None,
                         projection: place.projection,
-                        references: var.references,
                     });
                 }
                 mir::VarDebugInfoContents::Const(c) => {
@@ -601,7 +572,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 Some(fragment_start..fragment_start + fragment_layout.size)
                             },
                             projection: place.projection,
-                            references: var.references,
                         });
                     }
                 }

compiler/rustc_const_eval/src/transform/validate.rs

@@ -701,12 +701,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             VarDebugInfoContents::Const(_) => {}
             VarDebugInfoContents::Place(place) => {
                 check_place(self, place);
-                if debuginfo.references != 0 && place.projection.last() == Some(&PlaceElem::Deref) {
-                    self.fail(
-                        START_BLOCK.start_location(),
-                        format!("debuginfo {debuginfo:?}, has both ref and deref"),
-                    );
-                }
             }
             VarDebugInfoContents::Composite { ty, ref fragments } => {
                 for f in fragments {

compiler/rustc_middle/src/mir/mod.rs

@@ -1109,10 +1109,6 @@ pub struct VarDebugInfo<'tcx> {
     /// originated from (starting from 1). Note, if MIR inlining is enabled, then this is the
     /// argument number in the original function before it was inlined.
     pub argument_index: Option<u16>,
-
-    /// The data represents `name` dereferenced `references` times,
-    /// and not the direct value.
-    pub references: u8,
 }
 
 ///////////////////////////////////////////////////////////////////////////

compiler/rustc_middle/src/mir/pretty.rs

@@ -555,13 +555,8 @@ fn write_scope_tree(
         }
 
         let indented_debug_info = format!(
-            "{0:1$}debug {2} => {3:&<4$}{5:?};",
-            INDENT,
-            indent,
-            var_debug_info.name,
-            "",
-            var_debug_info.references as usize,
-            var_debug_info.value,
+            "{0:1$}debug {2} => {3:?};",
+            INDENT, indent, var_debug_info.name, var_debug_info.value,
         );
 
         if tcx.sess.opts.unstable_opts.mir_include_spans {

compiler/rustc_middle/src/mir/visit.rs

@@ -840,7 +840,6 @@ macro_rules! make_mir_visitor {
                     source_info,
                     value,
                     argument_index: _,
-                    references: _,
                 } = var_debug_info;
 
                 self.visit_source_info(source_info);

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -438,7 +438,6 @@ CloneLiftImpls! {
     (),
     bool,
     usize,
-    u8,
     u16,
     u32,
     u64,

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -2242,7 +2242,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         self.var_debug_info.push(VarDebugInfo {
             name,
             source_info: debug_source_info,
-            references: 0,
             value: VarDebugInfoContents::Place(for_arm_body.into()),
             argument_index: None,
         });
@@ -2262,7 +2261,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             self.var_debug_info.push(VarDebugInfo {
                 name,
                 source_info: debug_source_info,
-                references: 0,
                 value: VarDebugInfoContents::Place(ref_for_guard.into()),
                 argument_index: None,
             });

compiler/rustc_mir_build/src/build/mod.rs

@@ -820,7 +820,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 };
                 self.var_debug_info.push(VarDebugInfo {
                     name,
-                    references: 0,
                     source_info: SourceInfo::outermost(captured_place.var_ident.span),
                     value: VarDebugInfoContents::Place(use_place),
                     argument_index: None,
@@ -851,7 +850,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 self.var_debug_info.push(VarDebugInfo {
                     name,
                     source_info,
-                    references: 0,
                     value: VarDebugInfoContents::Place(arg_local.into()),
                     argument_index: Some(argument_index as u16 + 1),
                 });

compiler/rustc_mir_transform/src/ref_prop.rs

@@ -265,7 +265,6 @@ fn compute_replacement<'tcx>(
         targets,
         storage_to_remove,
         allowed_replacements,
-        fully_replacable_locals,
         any_replacement: false,
     };
 
@@ -346,7 +345,6 @@ struct Replacer<'tcx> {
     storage_to_remove: BitSet<Local>,
     allowed_replacements: FxHashSet<(Local, Location)>,
     any_replacement: bool,
-    fully_replacable_locals: BitSet<Local>,
 }
 
 impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
@@ -366,12 +364,6 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
             if let Some((&PlaceElem::Deref, rest)) = target.projection.split_last() {
                 *place = Place::from(target.local).project_deeper(rest, self.tcx);
                 self.any_replacement = true;
-            } else if self.fully_replacable_locals.contains(place.local)
-                && let Some(references) = debuginfo.references.checked_add(1)
-            {
-                debuginfo.references = references;
-                *place = target;
-                self.any_replacement = true;
             } else {
                 break
             }

compiler/rustc_type_ir/src/structural_impls.rs

@@ -23,7 +23,6 @@ TrivialTypeTraversalImpls! {
     (),
     bool,
     usize,
-    u8,
     u16,
     u32,
     u64,