Auto merge of #68965 - eddyb:mir-inline-scope, r=<try>

 rustc_mir: track inlined callees in SourceScopeData.

This would be a prerequisite for generating the correct debuginfo in codegen, which would look similar to what LLVM inlining generates (we should be able to "fake it" as well).

Also, `#[track_caller]` is now correct in the face of MIR inlining (cc @anp).

However, the debuginfo side isn't implemented yet. I might take a stab at it soon, not sure.

r? @rust-lang/wg-mir-opt

src/librustc/mir/mod.rs

@@ -112,7 +112,7 @@ pub struct Body<'tcx> {
 
     /// A list of source scopes; these are referenced by statements
     /// and used for debuginfo. Indexed by a `SourceScope`.
-    pub source_scopes: IndexVec<SourceScope, SourceScopeData>,
+    pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
 
     /// The yield type of the function, if it is a generator.
     pub yield_ty: Option<Ty<'tcx>>,
@@ -179,7 +179,7 @@ pub struct Body<'tcx> {
 impl<'tcx> Body<'tcx> {
     pub fn new(
         basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
-        source_scopes: IndexVec<SourceScope, SourceScopeData>,
+        source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
         local_decls: LocalDecls<'tcx>,
         user_type_annotations: CanonicalUserTypeAnnotations<'tcx>,
         arg_count: usize,
@@ -1916,11 +1916,16 @@ rustc_index::newtype_index! {
     }
 }
 
-#[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
-pub struct SourceScopeData {
+#[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)]
+pub struct SourceScopeData<'tcx> {
     pub span: Span,
     pub parent_scope: Option<SourceScope>,
 
+    /// Whether this scope is the root of a scope tree of another body,
+    /// inlined into this body by the MIR inliner.
+    /// `ty::Instance` is the callee, and the `Span` is the call site.
+    pub inlined: Option<(ty::Instance<'tcx>, Span)>,
+
     /// Crate-local information for this source scope, that can't (and
     /// needn't) be tracked across crates.
     pub local_data: ClearCrossCrate<SourceScopeLocalData>,
@@ -2621,7 +2626,6 @@ CloneTypeFoldableAndLiftImpls! {
     FakeReadCause,
     RetagKind,
     SourceScope,
-    SourceScopeData,
     SourceScopeLocalData,
     UserTypeAnnotationIndex,
 }

src/librustc/mir/visit.rs

@@ -94,7 +94,7 @@ macro_rules! make_mir_visitor {
             }
 
             fn visit_source_scope_data(&mut self,
-                                           scope_data: & $($mutability)? SourceScopeData) {
+                                           scope_data: & $($mutability)? SourceScopeData<'tcx>) {
                 self.super_source_scope_data(scope_data);
             }
 
@@ -329,17 +329,45 @@ macro_rules! make_mir_visitor {
                 }
             }
 
-            fn super_source_scope_data(&mut self, scope_data: & $($mutability)? SourceScopeData) {
+            fn super_source_scope_data(
+                &mut self,
+                scope_data: & $($mutability)? SourceScopeData<'tcx>,
+            ) {
                 let SourceScopeData {
                     span,
                     parent_scope,
+                    inlined,
                     local_data: _,
                 } = scope_data;
 
                 self.visit_span(span);
                 if let Some(parent_scope) = parent_scope {
                     self.visit_source_scope(parent_scope);
                 }
+                if let Some((callee, callsite_span)) = inlined {
+                    let location = START_BLOCK.start_location();
+
+                    self.visit_span(callsite_span);
+
+                    let ty::Instance { def: callee_def, substs: callee_substs } = callee;
+                    match callee_def {
+                        ty::InstanceDef::Item(_def_id) |
+                        ty::InstanceDef::Intrinsic(_def_id) |
+                        ty::InstanceDef::VtableShim(_def_id) |
+                        ty::InstanceDef::ReifyShim(_def_id) |
+                        ty::InstanceDef::Virtual(_def_id, _) |
+                        ty::InstanceDef::ClosureOnceShim { call_once: _def_id } |
+                        ty::InstanceDef::DropGlue(_def_id, None) => {}
+
+                        ty::InstanceDef::FnPtrShim(_def_id, ty) |
+                        ty::InstanceDef::DropGlue(_def_id, Some(ty)) |
+                        ty::InstanceDef::CloneShim(_def_id, ty) => {
+                            // FIXME(eddyb) use a better `TyContext` here.
+                            self.visit_ty(ty, TyContext::Location(location));
+                        }
+                    }
+                    self.visit_substs(callee_substs, location);
+                }
             }
 
             fn super_statement(&mut self,

src/librustc/ty/instance.rs

@@ -6,6 +6,7 @@ use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_macros::HashStable;
+use rustc_span::sym;
 use rustc_target::spec::abi::Abi;
 
 use std::fmt;
@@ -40,6 +41,11 @@ pub enum InstanceDef<'tcx> {
 
     /// `<fn() as FnTrait>::call_*`
     /// `DefId` is `FnTrait::call_*`.
+    ///
+    /// NB: the (`fn` pointer) type must be monomorphic for MIR shims to work.
+    // FIXME(eddyb) support generating shims for a "shallow type",
+    // e.g. `fn(_, _) -> _` instead of requiring a fully monomorphic
+    // `fn(Foo, Bar) -> Baz` etc.
     FnPtrShim(DefId, Ty<'tcx>),
 
     /// `<dyn Trait as Trait>::fn`, "direct calls" of which are implicitly
@@ -55,9 +61,19 @@ pub enum InstanceDef<'tcx> {
     },
 
     /// `drop_in_place::<T>; None` for empty drop glue.
+    ///
+    /// NB: the type must be monomorphic for MIR shims to work.
+    // FIXME(eddyb) support generating shims for a "shallow type",
+    // e.g. `Foo<_>` or `[_]` instead of requiring a fully monomorphic
+    // `Foo<Bar>` or `[String]` etc.
     DropGlue(DefId, Option<Ty<'tcx>>),
 
     ///`<T as Clone>::clone` shim.
+    ///
+    /// NB: the type must be monomorphic for MIR shims to work.
+    // FIXME(eddyb) support generating shims for a "shallow type",
+    // e.g. `Foo<_>` or `[_]` instead of requiring a fully monomorphic
+    // `Foo<Bar>` or `[String]` etc.
     CloneShim(DefId, Ty<'tcx>),
 }
 
@@ -282,21 +298,28 @@ impl<'tcx> Instance<'tcx> {
                     debug!(" => intrinsic");
                     ty::InstanceDef::Intrinsic(def_id)
                 }
-                _ => {
-                    if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
-                        let ty = substs.type_at(0);
-                        if ty.needs_drop(tcx, ty::ParamEnv::reveal_all()) {
-                            debug!(" => nontrivial drop glue");
-                            ty::InstanceDef::DropGlue(def_id, Some(ty))
-                        } else {
-                            debug!(" => trivial drop glue");
-                            ty::InstanceDef::DropGlue(def_id, None)
+                ty::FnDef(def_id, substs)
+                    if Some(def_id) == tcx.lang_items().drop_in_place_fn() =>
+                {
+                    let ty = substs.type_at(0);
+
+                    if ty.needs_drop(tcx, param_env) {
+                        // `DropGlue` requires a monomorphic aka concrete type.
+                        if ty.needs_subst() {
+                            return None;
                         }
+
+                        debug!(" => nontrivial drop glue");
+                        ty::InstanceDef::DropGlue(def_id, Some(ty))
                     } else {
-                        debug!(" => free item");
-                        ty::InstanceDef::Item(def_id)
+                        debug!(" => trivial drop glue");
+                        ty::InstanceDef::DropGlue(def_id, None)
                     }
                 }
+                _ => {
+                    debug!(" => free item");
+                    ty::InstanceDef::Item(def_id)
+                }
             };
             Some(Instance { def: def, substs: substs })
         };
@@ -457,20 +480,44 @@ fn resolve_associated_item<'tcx>(
                 trait_closure_kind,
             ))
         }
-        traits::VtableFnPointer(ref data) => Some(Instance {
-            def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
-            substs: rcvr_substs,
-        }),
+        traits::VtableFnPointer(ref data) => {
+            // `FnPtrShim` requires a monomorphic aka concrete type.
+            if data.fn_ty.needs_subst() {
+                return None;
+            }
+
+            Some(Instance {
+                def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
+                substs: rcvr_substs,
+            })
+        }
         traits::VtableObject(ref data) => {
             let index = traits::get_vtable_index_of_object_method(tcx, data, def_id);
             Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs })
         }
         traits::VtableBuiltin(..) => {
-            if tcx.lang_items().clone_trait().is_some() {
-                Some(Instance {
-                    def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
-                    substs: rcvr_substs,
-                })
+            if Some(trait_ref.def_id) == tcx.lang_items().clone_trait() {
+                // FIXME(eddyb) use lang items for methods instead of names.
+                let name = tcx.item_name(def_id);
+                if name == sym::clone {
+                    let self_ty = trait_ref.self_ty();
+
+                    // `CloneShim` requires a monomorphic aka concrete type.
+                    if self_ty.needs_subst() {
+                        return None;
+                    }
+
+                    Some(Instance {
+                        def: ty::InstanceDef::CloneShim(def_id, self_ty),
+                        substs: rcvr_substs,
+                    })
+                } else {
+                    assert_eq!(name, sym::clone_from);
+
+                    // Use the default `fn clone_from` from `trait Clone`.
+                    let substs = tcx.erase_regions(&rcvr_substs);
+                    Some(ty::Instance::new(def_id, substs))
+                }
             } else {
                 None
             }

src/librustc_codegen_ssa/mir/block.rs

@@ -15,7 +15,7 @@ use rustc::mir::interpret::PanicInfo;
 use rustc::ty::layout::{self, FnAbiExt, HasTyCtxt, LayoutOf};
 use rustc::ty::{self, Instance, Ty, TypeFoldable};
 use rustc_index::vec::Idx;
-use rustc_span::{source_map::Span, symbol::Symbol};
+use rustc_span::{Span, Symbol};
 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
 use rustc_target::spec::abi::Abi;
 
@@ -408,7 +408,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.set_debug_loc(&mut bx, terminator.source_info);
 
         // Get the location information.
-        let location = self.get_caller_location(&mut bx, span).immediate();
+        let location = self.get_caller_location(&mut bx, terminator.source_info).immediate();
 
         // Put together the arguments to the panic entry point.
         let (lang_item, args) = match msg {
@@ -444,7 +444,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
         cleanup: Option<mir::BasicBlock>,
     ) {
-        let span = terminator.source_info.span;
+        let source_info = terminator.source_info;
+        let span = source_info.span;
+
         // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
         let callee = self.codegen_operand(&mut bx, func);
 
@@ -530,7 +532,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             if layout.abi.is_uninhabited() {
                 let msg_str = format!("Attempted to instantiate uninhabited type {}", ty);
                 let msg = bx.const_str(Symbol::intern(&msg_str));
-                let location = self.get_caller_location(&mut bx, span).immediate();
+                let location = self.get_caller_location(&mut bx, source_info).immediate();
 
                 // Obtain the panic entry point.
                 let def_id =
@@ -575,7 +577,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         if intrinsic == Some("caller_location") {
             if let Some((_, target)) = destination.as_ref() {
-                let location = self.get_caller_location(&mut bx, span);
+                let location = self.get_caller_location(&mut bx, source_info);
 
                 if let ReturnDest::IndirectOperand(tmp, _) = ret_dest {
                     location.val.store(&mut bx, tmp);
@@ -627,13 +629,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 })
                 .collect();
 
-            bx.codegen_intrinsic_call(
-                *instance.as_ref().unwrap(),
-                &fn_abi,
-                &args,
-                dest,
-                terminator.source_info.span,
-            );
+            bx.codegen_intrinsic_call(*instance.as_ref().unwrap(), &fn_abi, &args, dest, span);
 
             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
                 self.store_return(&mut bx, ret_dest, &fn_abi.ret, dst.llval);
@@ -739,7 +735,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 args.len() + 1,
                 "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR",
             );
-            let location = self.get_caller_location(&mut bx, span);
+            let location = self.get_caller_location(&mut bx, source_info);
             let last_arg = fn_abi.args.last().unwrap();
             self.codegen_argument(&mut bx, location, &mut llargs, last_arg);
         }
@@ -982,17 +978,46 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
     }
 
-    fn get_caller_location(&mut self, bx: &mut Bx, span: Span) -> OperandRef<'tcx, Bx::Value> {
-        self.caller_location.unwrap_or_else(|| {
+    fn get_caller_location(
+        &mut self,
+        bx: &mut Bx,
+        source_info: mir::SourceInfo,
+    ) -> OperandRef<'tcx, Bx::Value> {
+        let tcx = bx.tcx();
+
+        let mut span_to_caller_location = |span: Span| {
             let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
-            let caller = bx.tcx().sess.source_map().lookup_char_pos(topmost.lo());
-            let const_loc = bx.tcx().const_caller_location((
+            let caller = tcx.sess.source_map().lookup_char_pos(topmost.lo());
+            let const_loc = tcx.const_caller_location((
                 Symbol::intern(&caller.file.name.to_string()),
                 caller.line as u32,
                 caller.col_display as u32 + 1,
             ));
             OperandRef::from_const(bx, const_loc)
-        })
+        };
+
+        // Walk up the `SourceScope`s, in case some of them are from MIR inlining.
+        let mut caller_span = source_info.span;
+        let mut scope = source_info.scope;
+        loop {
+            let scope_data = &self.mir.source_scopes[scope];
+
+            if let Some((callee, callsite_span)) = scope_data.inlined {
+                // Stop before ("inside") the callsite of a non-`#[track_caller]` function.
+                if !callee.def.requires_caller_location(tcx) {
+                    return span_to_caller_location(caller_span);
+                }
+                caller_span = callsite_span;
+            }
+
+            match scope_data.parent_scope {
+                Some(parent) => scope = parent,
+                None => break,
+            }
+        }
+
+        // No inlined `SourceScope`s, or all of them were `#[track_caller]`.
+        self.caller_location.unwrap_or_else(|| span_to_caller_location(caller_span))
     }
 
     fn get_personality_slot(&mut self, bx: &mut Bx) -> PlaceRef<'tcx, Bx::Value> {

src/librustc_mir/interpret/intrinsics/caller_location.rs

@@ -14,11 +14,33 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// `None` is returned and the callsite of the function invocation itself should be used.
     crate fn find_closest_untracked_caller_location(&self) -> Option<Span> {
         let mut caller_span = None;
-        for next_caller in self.stack.iter().rev() {
-            if !next_caller.instance.def.requires_caller_location(*self.tcx) {
+        for frame in self.stack.iter().rev() {
+            if let Some(source_info) = frame.current_source_info() {
+                // Walk up the `SourceScope`s, in case some of them are from MIR inlining.
+                let mut scope = source_info.scope;
+                loop {
+                    let scope_data = &frame.body.source_scopes[scope];
+
+                    if let Some((callee, callsite_span)) = scope_data.inlined {
+                        // Stop before ("inside") the callsite of a non-`#[track_caller]` function.
+                        if !callee.def.requires_caller_location(*self.tcx) {
+                            return caller_span;
+                        }
+                        caller_span = Some(callsite_span);
+                    }
+
+                    match scope_data.parent_scope {
+                        Some(parent) => scope = parent,
+                        None => break,
+                    }
+                }
+            }
+
+            // Stop before ("inside") the callsite of a non-`#[track_caller]` function.
+            if !frame.instance.def.requires_caller_location(*self.tcx) {
                 return caller_span;
             }
-            caller_span = Some(next_caller.span);
+            caller_span = Some(frame.span);
         }
 
         caller_span