Reimplement references VarDebugInfo

compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

@@ -508,7 +508,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                 };
 
-                self.cx.create_dbg_var(var.name, var_ty, dbg_scope, var_kind, span)
+                let name = if var.references > 0 {
+                    Symbol::intern(&format!("{0:*<1$}{2}", "", var.references as usize, var.name))
+                } else {
+                    var.name
+                };
+
+                self.cx.create_dbg_var(name, var_ty, dbg_scope, var_kind, span)
             });
 
             match var.value {

compiler/rustc_const_eval/src/transform/validate.rs

@@ -701,6 +701,12 @@ 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

@@ -1109,6 +1109,10 @@ 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

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

compiler/rustc_middle/src/mir/visit.rs

@@ -840,6 +840,7 @@ 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

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

compiler/rustc_mir_build/src/build/custom/parse.rs

@@ -1,5 +1,6 @@
 use rustc_index::IndexSlice;
-use rustc_middle::{mir::*, thir::*, ty::Ty};
+use rustc_middle::ty::{self, Ty};
+use rustc_middle::{mir::*, thir::*};
 use rustc_span::Span;
 
 use super::{PResult, ParseCtxt, ParseError};
@@ -159,6 +160,14 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         );
         self.parse_local_decls(local_decls.iter().copied())?;
 
+        let (debuginfo, rest) = parse_by_kind!(self, rest, _, "body with debuginfo",
+            ExprKind::Block { block } => {
+                let block = &self.thir[*block];
+                (&block.stmts, block.expr.unwrap())
+            },
+        );
+        self.parse_debuginfo(debuginfo.iter().copied())?;
+
         let block_defs = parse_by_kind!(self, rest, _, "body with block defs",
             ExprKind::Block { block } => &self.thir[*block].stmts,
         );
@@ -195,6 +204,63 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         Ok(())
     }
 
+    fn parse_debuginfo(&mut self, stmts: impl Iterator<Item = StmtId>) -> PResult<()> {
+        for stmt in stmts {
+            let stmt = &self.thir[stmt];
+            let expr = match stmt.kind {
+                StmtKind::Let { span, .. } => {
+                    return Err(ParseError {
+                        span,
+                        item_description: format!("{:?}", stmt),
+                        expected: "debuginfo".to_string(),
+                    });
+                }
+                StmtKind::Expr { expr, .. } => expr,
+            };
+            let span = self.thir[expr].span;
+            let (name, mut operand) = parse_by_kind!(self, expr, _, "debuginfo",
+                @call("mir_debuginfo", args) => {
+                    (args[0], args[1])
+                },
+            );
+            let name = parse_by_kind!(self, name, _, "debuginfo",
+                ExprKind::Literal { lit, neg: false } => lit,
+            );
+            let Some(name) = name.node.str() else {
+                return Err(ParseError {
+                    span,
+                    item_description: format!("{:?}", name),
+                    expected: "string".to_string(),
+                });
+            };
+            let mut references = 0;
+            loop {
+                parse_by_kind!(self, operand, _, "debuginfo",
+                    ExprKind::Borrow { arg, .. } => {
+                        references += 1;
+                        operand = *arg;
+                    },
+                    _ => break,
+                );
+            }
+            let operand = self.parse_operand(operand)?;
+            let value = match operand {
+                Operand::Constant(c) => VarDebugInfoContents::Const(*c),
+                Operand::Copy(p) | Operand::Move(p) => VarDebugInfoContents::Place(p),
+            };
+            let dbginfo = VarDebugInfo {
+                name,
+                source_info: SourceInfo { span, scope: self.source_scope },
+                argument_index: None,
+                references,
+                value,
+            };
+            self.body.var_debug_info.push(dbginfo);
+        }
+
+        Ok(())
+    }
+
     fn parse_let_statement(&mut self, stmt_id: StmtId) -> PResult<(LocalVarId, Ty<'tcx>, Span)> {
         let pattern = match &self.thir[stmt_id].kind {
             StmtKind::Let { pattern, .. } => pattern,

compiler/rustc_mir_build/src/build/custom/parse/instruction.rs

@@ -205,7 +205,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         )
     }
 
-    fn parse_operand(&self, expr_id: ExprId) -> PResult<Operand<'tcx>> {
+    pub fn parse_operand(&self, expr_id: ExprId) -> PResult<Operand<'tcx>> {
         parse_by_kind!(self, expr_id, expr, "operand",
             @call("mir_move", args) => self.parse_place(args[0]).map(Operand::Move),
             @call("mir_static", args) => self.parse_static(args[0]),

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

@@ -2242,6 +2242,7 @@ 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,
         });
@@ -2261,6 +2262,7 @@ 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

@@ -820,6 +820,7 @@ 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,
@@ -850,6 +851,7 @@ 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

@@ -265,6 +265,7 @@ fn compute_replacement<'tcx>(
         targets,
         storage_to_remove,
         allowed_replacements,
+        fully_replacable_locals,
         any_replacement: false,
     };
 
@@ -345,6 +346,7 @@ 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> {
@@ -364,6 +366,12 @@ 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

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

library/core/src/intrinsics/mir.rs

@@ -12,7 +12,8 @@
 //!
 //! Typical usage will look like this:
 //!
-//! ```rust
+#![cfg_attr(bootstrap, doc = "```rust,ignore")]
+#![cfg_attr(not(bootstrap), doc = "```rust")]
 //! #![feature(core_intrinsics, custom_mir)]
 #![cfg_attr(not(bootstrap), doc = "#![allow(internal_features)]")]
 //!
@@ -62,7 +63,8 @@
 //!
 //! # Examples
 //!
-//! ```rust
+#![cfg_attr(bootstrap, doc = "```rust,ignore")]
+#![cfg_attr(not(bootstrap), doc = "```rust")]
 //! #![feature(core_intrinsics, custom_mir)]
 #![cfg_attr(not(bootstrap), doc = "#![allow(internal_features)]")]
 //!
@@ -316,9 +318,10 @@ define!(
     ///
     /// # Examples
     ///
-    /// ```rust
-    #[cfg_attr(not(bootstrap), doc = "#![allow(internal_features)]")]
+    #[cfg_attr(bootstrap, doc = "```rust,ignore")]
+    #[cfg_attr(not(bootstrap), doc = "```rust")]
     /// #![feature(custom_mir, core_intrinsics)]
+    #[cfg_attr(not(bootstrap), doc = "#![allow(internal_features)]")]
     ///
     /// use core::intrinsics::mir::*;
     ///
@@ -360,6 +363,11 @@ define!(
     #[doc(hidden)]
     fn __internal_make_place<T>(place: T) -> *mut T
 );
+define!(
+    "mir_debuginfo",
+    #[doc(hidden)]
+    fn __debuginfo<T>(name: &'static str, s: T)
+);
 
 /// Macro for generating custom MIR.
 ///
@@ -370,6 +378,7 @@ pub macro mir {
     (
         $(type RET = $ret_ty:ty ;)?
         $(let $local_decl:ident $(: $local_decl_ty:ty)? ;)*
+        $(debug $dbg_name:ident => $dbg_data:expr ;)*
 
         {
             $($entry:tt)*
@@ -393,26 +402,32 @@ pub macro mir {
             $(
                 let $local_decl $(: $local_decl_ty)? ;
             )*
-
             ::core::intrinsics::mir::__internal_extract_let!($($entry)*);
             $(
                 ::core::intrinsics::mir::__internal_extract_let!($($block)*);
             )*
 
             {
-                // Finally, the contents of the basic blocks
-                ::core::intrinsics::mir::__internal_remove_let!({
-                    {}
-                    { $($entry)* }
-                });
+                // Now debuginfo
                 $(
+                    __debuginfo(stringify!($dbg_name), $dbg_data);
+                )*
+
+                {
+                    // Finally, the contents of the basic blocks
                     ::core::intrinsics::mir::__internal_remove_let!({
                         {}
-                        { $($block)* }
+                        { $($entry)* }
                     });
-                )*
+                    $(
+                        ::core::intrinsics::mir::__internal_remove_let!({
+                            {}
+                            { $($block)* }
+                        });
+                    )*
 
-                RET
+                    RET
+                }
             }
         }
     }}

tests/codegen/slice-ref-equality.rs

@@ -44,48 +44,48 @@ pub fn is_zero_array(data: &[u8; 4]) -> bool {
 // equality for non-byte types also just emit a `bcmp`, not a loop.
 
 // CHECK-LABEL: @eq_slice_of_nested_u8(
-// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %1
-// CHECK-SAME: [[USIZE]] noundef %3
+// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %x.1
+// CHECK-SAME: [[USIZE]] noundef %y.1
 #[no_mangle]
 fn eq_slice_of_nested_u8(x: &[[u8; 3]], y: &[[u8; 3]]) -> bool {
-    // CHECK: icmp eq [[USIZE]] %1, %3
-    // CHECK: %[[BYTES:.+]] = mul nsw [[USIZE]] %1, 3
+    // CHECK: icmp eq [[USIZE]] %x.1, %y.1
+    // CHECK: %[[BYTES:.+]] = mul nsw [[USIZE]] %x.1, 3
     // CHECK: tail call{{( noundef)?}} i32 @{{bcmp|memcmp}}(ptr
     // CHECK-SAME: , [[USIZE]]{{( noundef)?}} %[[BYTES]])
     x == y
 }
 
 // CHECK-LABEL: @eq_slice_of_i32(
-// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %1
-// CHECK-SAME: [[USIZE]] noundef %3
+// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %x.1
+// CHECK-SAME: [[USIZE]] noundef %y.1
 #[no_mangle]
 fn eq_slice_of_i32(x: &[i32], y: &[i32]) -> bool {
-    // CHECK: icmp eq [[USIZE]] %1, %3
-    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %1, 2
+    // CHECK: icmp eq [[USIZE]] %x.1, %y.1
+    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %x.1, 2
     // CHECK: tail call{{( noundef)?}} i32 @{{bcmp|memcmp}}(ptr
     // CHECK-SAME: , [[USIZE]]{{( noundef)?}} %[[BYTES]])
     x == y
 }
 
 // CHECK-LABEL: @eq_slice_of_nonzero(
-// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %1
-// CHECK-SAME: [[USIZE]] noundef %3
+// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %x.1
+// CHECK-SAME: [[USIZE]] noundef %y.1
 #[no_mangle]
 fn eq_slice_of_nonzero(x: &[NonZeroU32], y: &[NonZeroU32]) -> bool {
-    // CHECK: icmp eq [[USIZE]] %1, %3
-    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %1, 2
+    // CHECK: icmp eq [[USIZE]] %x.1, %y.1
+    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %x.1, 2
     // CHECK: tail call{{( noundef)?}} i32 @{{bcmp|memcmp}}(ptr
     // CHECK-SAME: , [[USIZE]]{{( noundef)?}} %[[BYTES]])
     x == y
 }
 
 // CHECK-LABEL: @eq_slice_of_option_of_nonzero(
-// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %1
-// CHECK-SAME: [[USIZE]] noundef %3
+// CHECK-SAME: [[USIZE:i16|i32|i64]] noundef %x.1
+// CHECK-SAME: [[USIZE]] noundef %y.1
 #[no_mangle]
 fn eq_slice_of_option_of_nonzero(x: &[Option<NonZeroI16>], y: &[Option<NonZeroI16>]) -> bool {
-    // CHECK: icmp eq [[USIZE]] %1, %3
-    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %1, 1
+    // CHECK: icmp eq [[USIZE]] %x.1, %y.1
+    // CHECK: %[[BYTES:.+]] = shl nsw [[USIZE]] %x.1, 1
     // CHECK: tail call{{( noundef)?}} i32 @{{bcmp|memcmp}}(ptr
     // CHECK-SAME: , [[USIZE]]{{( noundef)?}} %[[BYTES]])
     x == y