Support debuginfo for custom MIR.

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 +204,52 @@ 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, 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 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,
+                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

@@ -204,7 +204,7 @@ 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]),

library/core/src/intrinsics/mir.rs

@@ -361,6 +361,11 @@ 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.
 ///
@@ -371,6 +376,7 @@ 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)*
@@ -394,26 +400,32 @@ 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
                 $(
-                    ::core::intrinsics::mir::__internal_remove_let!({
-                        {}
-                        { $($block)* }
-                    });
+                    __debuginfo(stringify!($dbg_name), $dbg_data);
                 )*
 
-                RET
+                {
+                    // Finally, the contents of the basic blocks
+                    ::core::intrinsics::mir::__internal_remove_let!({
+                        {}
+                        { $($entry)* }
+                    });
+                    $(
+                        ::core::intrinsics::mir::__internal_remove_let!({
+                            {}
+                            { $($block)* }
+                        });
+                    )*
+
+                    RET
+                }
             }
         }
     }}

tests/mir-opt/building/custom/debuginfo.numbered.built.after.mir

@@ -0,0 +1,11 @@
+// MIR for `numbered` after built
+
+fn numbered(_1: (u32, i32)) -> () {
+    debug first => (_1.0: u32);
+    debug second => (_1.0: u32);
+    let mut _0: ();
+
+    bb0: {
+        return;
+    }
+}

tests/mir-opt/building/custom/debuginfo.pointee.built.after.mir

@@ -0,0 +1,10 @@
+// MIR for `pointee` after built
+
+fn pointee(_1: &mut Option<i32>) -> () {
+    debug foo => (((*_1) as variant#1).0: i32);
+    let mut _0: ();
+
+    bb0: {
+        return;
+    }
+}

tests/mir-opt/building/custom/debuginfo.rs

@@ -0,0 +1,71 @@
+#![feature(custom_mir, core_intrinsics)]
+
+extern crate core;
+use core::intrinsics::mir::*;
+
+// EMIT_MIR debuginfo.pointee.built.after.mir
+#[custom_mir(dialect = "built")]
+fn pointee(opt: &mut Option<i32>) {
+    mir!(
+        debug foo => Field::<i32>(Variant(*opt, 1), 0);
+        {
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR debuginfo.numbered.built.after.mir
+#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
+fn numbered(i: (u32, i32)) {
+    mir!(
+        debug first => i.0;
+        debug second => i.0;
+        {
+            Return()
+        }
+    )
+}
+
+struct S { x: f32 }
+
+// EMIT_MIR debuginfo.structured.built.after.mir
+#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
+fn structured(i: S) {
+    mir!(
+        debug x => i.x;
+        {
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR debuginfo.variant.built.after.mir
+#[custom_mir(dialect = "built")]
+fn variant(opt: Option<i32>) {
+    mir!(
+        debug inner => Field::<i32>(Variant(opt, 1), 0);
+        {
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR debuginfo.variant_deref.built.after.mir
+#[custom_mir(dialect = "built")]
+fn variant_deref(opt: Option<&i32>) {
+    mir!(
+        debug pointer => Field::<&i32>(Variant(opt, 1), 0);
+        debug deref => *Field::<&i32>(Variant(opt, 1), 0);
+        {
+            Return()
+        }
+    )
+}
+
+fn main() {
+    numbered((5, 6));
+    structured(S { x: 5. });
+    variant(Some(5));
+    variant_deref(Some(&5));
+    pointee(&mut Some(5));
+}

tests/mir-opt/building/custom/debuginfo.structured.built.after.mir

@@ -0,0 +1,10 @@
+// MIR for `structured` after built
+
+fn structured(_1: S) -> () {
+    debug x => (_1.0: f32);
+    let mut _0: ();
+
+    bb0: {
+        return;
+    }
+}

tests/mir-opt/building/custom/debuginfo.variant.built.after.mir

@@ -0,0 +1,10 @@
+// MIR for `variant` after built
+
+fn variant(_1: Option<i32>) -> () {
+    debug inner => ((_1 as variant#1).0: i32);
+    let mut _0: ();
+
+    bb0: {
+        return;
+    }
+}

tests/mir-opt/building/custom/debuginfo.variant_deref.built.after.mir

@@ -0,0 +1,11 @@
+// MIR for `variant_deref` after built
+
+fn variant_deref(_1: Option<&i32>) -> () {
+    debug pointer => ((_1 as variant#1).0: &i32);
+    debug deref => (*((_1 as variant#1).0: &i32));
+    let mut _0: ();
+
+    bb0: {
+        return;
+    }
+}