Rollup merge of rust-lang#56278 - eddyb:mir-debuginfo-proof, r=nikomatsakis

Future-proof MIR for dedicated debuginfo.

This is rust-lang#56231 without the last commit (the one that actually moves to `VarDebuginfo`).
Nothing should be broken, but it should no longer depend on debuginfo for anything else.

r? @nikomatsakis

Author: Centril

src/librustc/mir/mod.rs

@@ -4,7 +4,7 @@
 
 use crate::hir::def::{CtorKind, Namespace};
 use crate::hir::def_id::DefId;
-use crate::hir::{self, HirId, InlineAsm as HirInlineAsm};
+use crate::hir::{self, InlineAsm as HirInlineAsm};
 use crate::mir::interpret::{ConstValue, InterpError, Scalar};
 use crate::mir::visit::MirVisitable;
 use rustc_apfloat::ieee::{Double, Single};
@@ -138,16 +138,20 @@ pub struct Mir<'tcx> {
     /// If this MIR was built for a constant, this will be 0.
     pub arg_count: usize,
 
-    /// Names and capture modes of all the closure upvars, assuming
-    /// the first argument is either the closure or a reference to it.
-    pub upvar_decls: Vec<UpvarDecl>,
-
     /// Mark an argument local (which must be a tuple) as getting passed as
     /// its individual components at the LLVM level.
     ///
     /// This is used for the "rust-call" ABI.
     pub spread_arg: Option<Local>,
 
+    /// Names and capture modes of all the closure upvars, assuming
+    /// the first argument is either the closure or a reference to it.
+    // NOTE(eddyb) This is *strictly* a temporary hack for codegen
+    // debuginfo generation, and will be removed at some point.
+    // Do **NOT** use it for anything else, upvar information should not be
+    // in the MIR, please rely on local crate HIR or other side-channels.
+    pub __upvar_debuginfo_codegen_only_do_not_use: Vec<UpvarDebuginfo>,
+
     /// Mark this MIR of a const context other than const functions as having converted a `&&` or
     /// `||` expression into `&` or `|` respectively. This is problematic because if we ever stop
     /// this conversion from happening and use short circuiting, we will cause the following code
@@ -173,7 +177,7 @@ impl<'tcx> Mir<'tcx> {
         local_decls: LocalDecls<'tcx>,
         user_type_annotations: CanonicalUserTypeAnnotations<'tcx>,
         arg_count: usize,
-        upvar_decls: Vec<UpvarDecl>,
+        __upvar_debuginfo_codegen_only_do_not_use: Vec<UpvarDebuginfo>,
         span: Span,
         control_flow_destroyed: Vec<(Span, String)>,
     ) -> Self {
@@ -197,7 +201,7 @@ impl<'tcx> Mir<'tcx> {
             local_decls,
             user_type_annotations,
             arg_count,
-            upvar_decls,
+            __upvar_debuginfo_codegen_only_do_not_use,
             spread_arg: None,
             span,
             cache: cache::Cache::new(),
@@ -431,7 +435,7 @@ impl_stable_hash_for!(struct Mir<'tcx> {
     local_decls,
     user_type_annotations,
     arg_count,
-    upvar_decls,
+    __upvar_debuginfo_codegen_only_do_not_use,
     spread_arg,
     control_flow_destroyed,
     span,
@@ -983,16 +987,11 @@ impl<'tcx> LocalDecl<'tcx> {
 
 /// A closure capture, with its name and mode.
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
-pub struct UpvarDecl {
+pub struct UpvarDebuginfo {
     pub debug_name: Name,
 
-    /// `HirId` of the captured variable
-    pub var_hir_id: ClearCrossCrate<HirId>,
-
     /// If true, the capture is behind a reference.
     pub by_ref: bool,
-
-    pub mutability: Mutability,
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -3156,7 +3155,7 @@ CloneTypeFoldableAndLiftImpls! {
     MirPhase,
     Mutability,
     SourceInfo,
-    UpvarDecl,
+    UpvarDebuginfo,
     FakeReadCause,
     RetagKind,
     SourceScope,
@@ -3178,7 +3177,7 @@ BraceStructTypeFoldableImpl! {
         local_decls,
         user_type_annotations,
         arg_count,
-        upvar_decls,
+        __upvar_debuginfo_codegen_only_do_not_use,
         spread_arg,
         control_flow_destroyed,
         span,

src/librustc/mir/tcx.rs

@@ -133,41 +133,6 @@ impl<'tcx> Place<'tcx> {
                 proj.base.ty(local_decls, tcx).projection_ty(tcx, &proj.elem),
         }
     }
-
-    /// If this is a field projection, and the field is being projected from a closure type,
-    /// then returns the index of the field being projected. Note that this closure will always
-    /// be `self` in the current MIR, because that is the only time we directly access the fields
-    /// of a closure type.
-    pub fn is_upvar_field_projection<'cx, 'gcx>(&self, mir: &'cx Mir<'tcx>,
-                                                tcx: &TyCtxt<'cx, 'gcx, 'tcx>) -> Option<Field> {
-        let (place, by_ref) = if let Place::Projection(ref proj) = self {
-            if let ProjectionElem::Deref = proj.elem {
-                (&proj.base, true)
-            } else {
-                (self, false)
-            }
-        } else {
-            (self, false)
-        };
-
-        match place {
-            Place::Projection(ref proj) => match proj.elem {
-                ProjectionElem::Field(field, _ty) => {
-                    let base_ty = proj.base.ty(mir, *tcx).ty;
-
-                    if (base_ty.is_closure() || base_ty.is_generator()) &&
-                        (!by_ref || mir.upvar_decls[field.index()].by_ref)
-                    {
-                        Some(field)
-                    } else {
-                        None
-                    }
-                },
-                _ => None,
-            }
-            _ => None,
-        }
-    }
 }
 
 pub enum RvalueInitializationState {

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -542,7 +542,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         finalize(self)
     }
 
-    fn debuginfo_upvar_decls_ops_sequence(&self, byte_offset_of_var_in_env: u64) -> [i64; 4] {
+    fn debuginfo_upvar_ops_sequence(&self, byte_offset_of_var_in_env: u64) -> [i64; 4] {
         unsafe {
             [llvm::LLVMRustDIBuilderCreateOpDeref(),
              llvm::LLVMRustDIBuilderCreateOpPlusUconst(),

src/librustc_codegen_ssa/mir/mod.rs

@@ -598,9 +598,10 @@ fn arg_local_refs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
                 tmp
             }
         };
+        let upvar_debuginfo = &mir.__upvar_debuginfo_codegen_only_do_not_use;
         arg_scope.map(|scope| {
             // Is this a regular argument?
-            if arg_index > 0 || mir.upvar_decls.is_empty() {
+            if arg_index > 0 || upvar_debuginfo.is_empty() {
                 // The Rust ABI passes indirect variables using a pointer and a manual copy, so we
                 // need to insert a deref here, but the C ABI uses a pointer and a copy using the
                 // byval attribute, for which LLVM always does the deref itself,
@@ -638,16 +639,16 @@ fn arg_local_refs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
             let (def_id, upvar_substs) = match closure_layout.ty.sty {
                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs)),
                 ty::Generator(def_id, substs, _) => (def_id, UpvarSubsts::Generator(substs)),
-                _ => bug!("upvar_decls with non-closure arg0 type `{}`", closure_layout.ty)
+                _ => bug!("upvar debuginfo with non-closure arg0 type `{}`", closure_layout.ty)
             };
             let upvar_tys = upvar_substs.upvar_tys(def_id, tcx);
 
             let extra_locals = {
-                let upvars = mir.upvar_decls
+                let upvars = upvar_debuginfo
                     .iter()
                     .zip(upvar_tys)
                     .enumerate()
-                    .map(|(i, (decl, ty))| (i, decl.debug_name, decl.by_ref, ty));
+                    .map(|(i, (upvar, ty))| (i, upvar.debug_name, upvar.by_ref, ty));
 
                 let generator_fields = mir.generator_layout.as_ref().map(|generator_layout| {
                     let (def_id, gen_substs) = match closure_layout.ty.sty {
@@ -656,7 +657,7 @@ fn arg_local_refs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
                     };
                     let state_tys = gen_substs.state_tys(def_id, tcx);
 
-                    let upvar_count = mir.upvar_decls.len();
+                    let upvar_count = upvar_debuginfo.len();
                     generator_layout.fields
                         .iter()
                         .zip(state_tys)
@@ -673,7 +674,7 @@ fn arg_local_refs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
             for (field, name, by_ref, ty) in extra_locals {
                 let byte_offset_of_var_in_env = closure_layout.fields.offset(field).bytes();
 
-                let ops = bx.debuginfo_upvar_decls_ops_sequence(byte_offset_of_var_in_env);
+                let ops = bx.debuginfo_upvar_ops_sequence(byte_offset_of_var_in_env);
 
                 // The environment and the capture can each be indirect.
                 let mut ops = if env_ref { &ops[..] } else { &ops[1..] };

src/librustc_codegen_ssa/traits/debuginfo.rs

@@ -37,7 +37,7 @@ pub trait DebugInfoMethods<'tcx>: BackendTypes {
         defining_crate: CrateNum,
     ) -> Self::DIScope;
     fn debuginfo_finalize(&self);
-    fn debuginfo_upvar_decls_ops_sequence(&self, byte_offset_of_var_in_env: u64) -> [i64; 4];
+    fn debuginfo_upvar_ops_sequence(&self, byte_offset_of_var_in_env: u64) -> [i64; 4];
 }
 
 pub trait DebugInfoBuilderMethods<'tcx>: BackendTypes {

src/librustc_mir/borrow_check/error_reporting.rs

@@ -1088,7 +1088,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                         | LocalKind::Temp => bug!("temporary or return pointer with a name"),
                         LocalKind::Var => "local variable ",
                         LocalKind::Arg
-                        if !self.mir.upvar_decls.is_empty()
+                        if !self.upvars.is_empty()
                             && local == Local::new(1) => {
                             "variable captured by `move` "
                         }
@@ -1632,11 +1632,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                 match proj.elem {
                     ProjectionElem::Deref => {
                         let upvar_field_projection =
-                            place.is_upvar_field_projection(self.mir, &self.infcx.tcx);
+                            self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
                             let var_index = field.index();
-                            let name = self.mir.upvar_decls[var_index].debug_name.to_string();
-                            if self.mir.upvar_decls[var_index].by_ref {
+                            let name = self.upvars[var_index].name.to_string();
+                            if self.upvars[var_index].by_ref {
                                 buf.push_str(&name);
                             } else {
                                 buf.push_str(&format!("*{}", &name));
@@ -1694,10 +1694,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                         autoderef = true;
 
                         let upvar_field_projection =
-                            place.is_upvar_field_projection(self.mir, &self.infcx.tcx);
+                            self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
                             let var_index = field.index();
-                            let name = self.mir.upvar_decls[var_index].debug_name.to_string();
+                            let name = self.upvars[var_index].name.to_string();
                             buf.push_str(&name);
                         } else {
                             let field_name = self.describe_field(&proj.base, field);