Unbox and unwrap the contents of `StatementKind::Coverage`

The payload of coverage statements was historically a structure with several
fields, so it was boxed to avoid bloating `StatementKind`.

Now that the payload is a single relatively-small enum, we can replace
`Box<Coverage>` with just `CoverageKind`.

This patch also adds a size assertion for `StatementKind`, to avoid
accidentally bloating it in the future.

compiler/rustc_codegen_gcc/src/coverageinfo.rs

@@ -1,11 +1,11 @@
 use rustc_codegen_ssa::traits::CoverageInfoBuilderMethods;
-use rustc_middle::mir::Coverage;
+use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::ty::Instance;
 
 use crate::builder::Builder;
 
 impl<'a, 'gcc, 'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
-    fn add_coverage(&mut self, _instance: Instance<'tcx>, _coverage: &Coverage) {
+    fn add_coverage(&mut self, _instance: Instance<'tcx>, _kind: &CoverageKind) {
         // TODO(antoyo)
     }
 }

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -14,7 +14,6 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_llvm::RustString;
 use rustc_middle::bug;
 use rustc_middle::mir::coverage::CoverageKind;
-use rustc_middle::mir::Coverage;
 use rustc_middle::ty::layout::HasTyCtxt;
 use rustc_middle::ty::Instance;
 
@@ -75,7 +74,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
 
 impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
     #[instrument(level = "debug", skip(self))]
-    fn add_coverage(&mut self, instance: Instance<'tcx>, coverage: &Coverage) {
+    fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind) {
         // Our caller should have already taken care of inlining subtleties,
         // so we can assume that counter/expression IDs in this coverage
         // statement are meaningful for the given instance.
@@ -98,7 +97,6 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
             .entry(instance)
             .or_insert_with(|| FunctionCoverageCollector::new(instance, function_coverage_info));
 
-        let Coverage { kind } = coverage;
         match *kind {
             CoverageKind::SpanMarker | CoverageKind::BlockMarker { .. } => unreachable!(
                 "marker statement {kind:?} should have been removed by CleanupPostBorrowck"

compiler/rustc_codegen_ssa/src/mir/coverageinfo.rs

@@ -1,12 +1,12 @@
 use crate::traits::*;
 
-use rustc_middle::mir::Coverage;
+use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::mir::SourceScope;
 
 use super::FunctionCx;
 
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
-    pub fn codegen_coverage(&self, bx: &mut Bx, coverage: &Coverage, scope: SourceScope) {
+    pub fn codegen_coverage(&self, bx: &mut Bx, kind: &CoverageKind, scope: SourceScope) {
         // Determine the instance that coverage data was originally generated for.
         let instance = if let Some(inlined) = scope.inlined_instance(&self.mir.source_scopes) {
             self.monomorphize(inlined)
@@ -15,6 +15,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
 
         // Handle the coverage info in a backend-specific way.
-        bx.add_coverage(instance, coverage);
+        bx.add_coverage(instance, kind);
     }
 }

compiler/rustc_codegen_ssa/src/mir/statement.rs

@@ -64,8 +64,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     cg_indirect_place.storage_dead(bx);
                 }
             }
-            mir::StatementKind::Coverage(box ref coverage) => {
-                self.codegen_coverage(bx, coverage, statement.source_info.scope);
+            mir::StatementKind::Coverage(ref kind) => {
+                self.codegen_coverage(bx, kind, statement.source_info.scope);
             }
             mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(ref op)) => {
                 if !matches!(bx.tcx().sess.opts.optimize, OptLevel::No | OptLevel::Less) {

compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs

@@ -1,5 +1,5 @@
 use super::BackendTypes;
-use rustc_middle::mir::Coverage;
+use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::ty::Instance;
 
 pub trait CoverageInfoBuilderMethods<'tcx>: BackendTypes {
@@ -7,5 +7,5 @@ pub trait CoverageInfoBuilderMethods<'tcx>: BackendTypes {
     ///
     /// This can potentially be a no-op in backends that don't support
     /// coverage instrumentation.
-    fn add_coverage(&mut self, instance: Instance<'tcx>, coverage: &Coverage);
+    fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind);
 }

compiler/rustc_const_eval/src/transform/validate.rs

@@ -346,8 +346,7 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
                     self.fail(location, format!("explicit `{kind:?}` is forbidden"));
                 }
             }
-            StatementKind::Coverage(coverage) => {
-                let kind = &coverage.kind;
+            StatementKind::Coverage(kind) => {
                 if self.mir_phase >= MirPhase::Analysis(AnalysisPhase::PostCleanup)
                     && let CoverageKind::BlockMarker { .. } | CoverageKind::SpanMarker { .. } = kind
                 {

compiler/rustc_middle/src/mir/pretty.rs

@@ -13,7 +13,7 @@ use rustc_middle::mir::interpret::{
     Provenance,
 };
 use rustc_middle::mir::visit::Visitor;
-use rustc_middle::mir::{self, *};
+use rustc_middle::mir::*;
 use rustc_target::abi::Size;
 
 const INDENT: &str = "    ";
@@ -711,7 +711,7 @@ impl Debug for Statement<'_> {
             AscribeUserType(box (ref place, ref c_ty), ref variance) => {
                 write!(fmt, "AscribeUserType({place:?}, {variance:?}, {c_ty:?})")
             }
-            Coverage(box mir::Coverage { ref kind }) => write!(fmt, "Coverage::{kind:?}"),
+            Coverage(ref kind) => write!(fmt, "Coverage::{kind:?}"),
             Intrinsic(box ref intrinsic) => write!(fmt, "{intrinsic}"),
             ConstEvalCounter => write!(fmt, "ConstEvalCounter"),
             Nop => write!(fmt, "nop"),

compiler/rustc_middle/src/mir/syntax.rs

@@ -373,7 +373,7 @@ pub enum StatementKind<'tcx> {
     ///
     /// Interpreters and codegen backends that don't support coverage instrumentation
     /// can usually treat this as a no-op.
-    Coverage(Box<Coverage>),
+    Coverage(CoverageKind),
 
     /// Denotes a call to an intrinsic that does not require an unwind path and always returns.
     /// This avoids adding a new block and a terminator for simple intrinsics.
@@ -517,12 +517,6 @@ pub enum FakeReadCause {
     ForIndex,
 }
 
-#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct Coverage {
-    pub kind: CoverageKind,
-}
-
 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct CopyNonOverlapping<'tcx> {
@@ -1465,5 +1459,6 @@ mod size_asserts {
     static_assert_size!(Place<'_>, 16);
     static_assert_size!(PlaceElem<'_>, 24);
     static_assert_size!(Rvalue<'_>, 40);
+    static_assert_size!(StatementKind<'_>, 16);
     // tidy-alphabetical-end
 }

compiler/rustc_middle/src/mir/visit.rs

@@ -156,10 +156,10 @@ macro_rules! make_mir_visitor {
 
             fn visit_coverage(
                 &mut self,
-                coverage: & $($mutability)? Coverage,
+                kind: & $($mutability)? coverage::CoverageKind,
                 location: Location,
             ) {
-                self.super_coverage(coverage, location);
+                self.super_coverage(kind, location);
             }
 
             fn visit_retag(
@@ -803,7 +803,7 @@ macro_rules! make_mir_visitor {
             }
 
             fn super_coverage(&mut self,
-                              _coverage: & $($mutability)? Coverage,
+                              _kind: & $($mutability)? coverage::CoverageKind,
                               _location: Location) {
             }
 

compiler/rustc_mir_build/src/build/cfg.rs

@@ -107,9 +107,7 @@ impl<'tcx> CFG<'tcx> {
     /// This results in more accurate coverage reports for certain kinds of
     /// syntax (e.g. `continue` or `if !`) that would otherwise not appear in MIR.
     pub(crate) fn push_coverage_span_marker(&mut self, block: BasicBlock, source_info: SourceInfo) {
-        let kind = StatementKind::Coverage(Box::new(Coverage {
-            kind: coverage::CoverageKind::SpanMarker,
-        }));
+        let kind = StatementKind::Coverage(coverage::CoverageKind::SpanMarker);
         let stmt = Statement { source_info, kind };
         self.push(block, stmt);
     }

compiler/rustc_mir_build/src/build/coverageinfo.rs

@@ -127,9 +127,7 @@ impl Builder<'_, '_> {
 
             let marker_statement = mir::Statement {
                 source_info,
-                kind: mir::StatementKind::Coverage(Box::new(mir::Coverage {
-                    kind: CoverageKind::BlockMarker { id },
-                })),
+                kind: mir::StatementKind::Coverage(CoverageKind::BlockMarker { id }),
             };
             self.cfg.push(block, marker_statement);
 

compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs

@@ -18,7 +18,7 @@
 
 use crate::MirPass;
 use rustc_middle::mir::coverage::CoverageKind;
-use rustc_middle::mir::{Body, BorrowKind, Coverage, Rvalue, StatementKind, TerminatorKind};
+use rustc_middle::mir::{Body, BorrowKind, Rvalue, StatementKind, TerminatorKind};
 use rustc_middle::ty::TyCtxt;
 
 pub struct CleanupPostBorrowck;
@@ -30,12 +30,11 @@ impl<'tcx> MirPass<'tcx> for CleanupPostBorrowck {
                 match statement.kind {
                     StatementKind::AscribeUserType(..)
                     | StatementKind::Assign(box (_, Rvalue::Ref(_, BorrowKind::Fake, _)))
-                    | StatementKind::Coverage(box Coverage {
+                    | StatementKind::Coverage(
                         // These kinds of coverage statements are markers inserted during
                         // MIR building, and are not needed after InstrumentCoverage.
-                        kind: CoverageKind::BlockMarker { .. } | CoverageKind::SpanMarker { .. },
-                        ..
-                    })
+                        CoverageKind::BlockMarker { .. } | CoverageKind::SpanMarker { .. },
+                    )
                     | StatementKind::FakeRead(..) => statement.make_nop(),
                     _ => (),
                 }

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -15,7 +15,7 @@ use crate::MirPass;
 
 use rustc_middle::mir::coverage::*;
 use rustc_middle::mir::{
-    self, BasicBlock, BasicBlockData, Coverage, SourceInfo, Statement, StatementKind, Terminator,
+    self, BasicBlock, BasicBlockData, SourceInfo, Statement, StatementKind, Terminator,
     TerminatorKind,
 };
 use rustc_middle::ty::TyCtxt;
@@ -230,10 +230,7 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
     debug!("  injecting statement {counter_kind:?} for {bb:?}");
     let data = &mut mir_body[bb];
     let source_info = data.terminator().source_info;
-    let statement = Statement {
-        source_info,
-        kind: StatementKind::Coverage(Box::new(Coverage { kind: counter_kind })),
-    };
+    let statement = Statement { source_info, kind: StatementKind::Coverage(counter_kind) };
     data.statements.insert(0, statement);
 }
 

compiler/rustc_mir_transform/src/coverage/query.rs

@@ -1,7 +1,7 @@
 use rustc_data_structures::captures::Captures;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::coverage::{CounterId, CoverageKind};
-use rustc_middle::mir::{Body, Coverage, CoverageIdsInfo, Statement, StatementKind};
+use rustc_middle::mir::{Body, CoverageIdsInfo, Statement, StatementKind};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::util::Providers;
@@ -54,7 +54,7 @@ fn coverage_ids_info<'tcx>(
     let mir_body = tcx.instance_mir(instance_def);
 
     let max_counter_id = all_coverage_in_mir_body(mir_body)
-        .filter_map(|coverage| match coverage.kind {
+        .filter_map(|kind| match *kind {
             CoverageKind::CounterIncrement { id } => Some(id),
             _ => None,
         })
@@ -66,12 +66,10 @@ fn coverage_ids_info<'tcx>(
 
 fn all_coverage_in_mir_body<'a, 'tcx>(
     body: &'a Body<'tcx>,
-) -> impl Iterator<Item = &'a Coverage> + Captures<'tcx> {
+) -> impl Iterator<Item = &'a CoverageKind> + Captures<'tcx> {
     body.basic_blocks.iter().flat_map(|bb_data| &bb_data.statements).filter_map(|statement| {
         match statement.kind {
-            StatementKind::Coverage(box ref coverage) if !is_inlined(body, statement) => {
-                Some(coverage)
-            }
+            StatementKind::Coverage(ref kind) if !is_inlined(body, statement) => Some(kind),
             _ => None,
         }
     })

compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs

@@ -187,9 +187,7 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
         // for their parent `BasicBlock`.
         StatementKind::StorageLive(_)
         | StatementKind::StorageDead(_)
-        // Ignore `ConstEvalCounter`s
         | StatementKind::ConstEvalCounter
-        // Ignore `Nop`s
         | StatementKind::Nop => None,
 
         // FIXME(#78546): MIR InstrumentCoverage - Can the source_info.span for `FakeRead`
@@ -211,30 +209,28 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
         StatementKind::FakeRead(box (FakeReadCause::ForGuardBinding, _)) => None,
 
         // Retain spans from most other statements.
-        StatementKind::FakeRead(box (_, _)) // Not including `ForGuardBinding`
+        StatementKind::FakeRead(_)
         | StatementKind::Intrinsic(..)
-        | StatementKind::Coverage(box mir::Coverage {
+        | StatementKind::Coverage(
             // The purpose of `SpanMarker` is to be matched and accepted here.
-            kind: CoverageKind::SpanMarker
-        })
+            CoverageKind::SpanMarker,
+        )
         | StatementKind::Assign(_)
         | StatementKind::SetDiscriminant { .. }
         | StatementKind::Deinit(..)
         | StatementKind::Retag(_, _)
         | StatementKind::PlaceMention(..)
-        | StatementKind::AscribeUserType(_, _) => {
-            Some(statement.source_info.span)
-        }
+        | StatementKind::AscribeUserType(_, _) => Some(statement.source_info.span),
 
-        StatementKind::Coverage(box mir::Coverage {
-            // Block markers are used for branch coverage, so ignore them here.
-            kind: CoverageKind::BlockMarker {..}
-        }) => None,
+        // Block markers are used for branch coverage, so ignore them here.
+        StatementKind::Coverage(CoverageKind::BlockMarker { .. }) => None,
 
-        StatementKind::Coverage(box mir::Coverage {
-            // These coverage statements should not exist prior to coverage instrumentation.
-            kind: CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. }
-        }) => bug!("Unexpected coverage statement found during coverage instrumentation: {statement:?}"),
+        // These coverage statements should not exist prior to coverage instrumentation.
+        StatementKind::Coverage(
+            CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. },
+        ) => bug!(
+            "Unexpected coverage statement found during coverage instrumentation: {statement:?}"
+        ),
     }
 }
 
@@ -382,9 +378,7 @@ pub(super) fn extract_branch_mappings(
     // Fill out the mapping from block marker IDs to their enclosing blocks.
     for (bb, data) in mir_body.basic_blocks.iter_enumerated() {
         for statement in &data.statements {
-            if let StatementKind::Coverage(coverage) = &statement.kind
-                && let CoverageKind::BlockMarker { id } = coverage.kind
-            {
+            if let StatementKind::Coverage(CoverageKind::BlockMarker { id }) = statement.kind {
                 block_markers[id] = Some(bb);
             }
         }