From 1fac8a0eab870f25fa4c8ab21f0e14e54cdda4a4 Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Tue, 22 Aug 2023 20:30:19 +1000
Subject: [PATCH] Treat `StatementKind::Coverage` as completely opaque for SMIR
 purposes

Coverage statements in MIR are heavily tied to internal details of the coverage
implementation that are likely to change, and are unlikely to be useful to
third-party tools for the foreseeable future.
---
 compiler/rustc_smir/src/rustc_smir/mod.rs     | 56 +------------------
 .../rustc_smir/src/stable_mir/mir/body.rs     | 43 ++------------
 2 files changed, 5 insertions(+), 94 deletions(-)

diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index 7e8ac9a141a70..69909fcea0a86 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -14,7 +14,6 @@ use crate::stable_mir::ty::{
 };
 use crate::stable_mir::{self, Context};
 use rustc_hir as hir;
-use rustc_middle::mir::coverage::CodeRegion;
 use rustc_middle::mir::interpret::alloc_range;
 use rustc_middle::mir::{self, ConstantKind};
 use rustc_middle::ty::{self, Ty, TyCtxt, Variance};
@@ -168,10 +167,7 @@ impl<'tcx> Stable<'tcx> for mir::Statement<'tcx> {
                     variance: variance.stable(tables),
                 }
             }
-            Coverage(coverage) => stable_mir::mir::Statement::Coverage(stable_mir::mir::Coverage {
-                kind: coverage.kind.stable(tables),
-                code_region: coverage.code_region.as_ref().map(|reg| reg.stable(tables)),
-            }),
+            Coverage(coverage) => stable_mir::mir::Statement::Coverage(opaque(coverage)),
             Intrinsic(intrinstic) => {
                 stable_mir::mir::Statement::Intrinsic(intrinstic.stable(tables))
             }
@@ -472,30 +468,6 @@ impl<'tcx> Stable<'tcx> for mir::Place<'tcx> {
     }
 }
 
-impl<'tcx> Stable<'tcx> for mir::coverage::CoverageKind {
-    type T = stable_mir::mir::CoverageKind;
-    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
-        use rustc_middle::mir::coverage::CoverageKind;
-        match self {
-            CoverageKind::Counter { function_source_hash, id } => {
-                stable_mir::mir::CoverageKind::Counter {
-                    function_source_hash: *function_source_hash as usize,
-                    id: opaque(id),
-                }
-            }
-            CoverageKind::Expression { id, lhs, op, rhs } => {
-                stable_mir::mir::CoverageKind::Expression {
-                    id: opaque(id),
-                    lhs: opaque(lhs),
-                    op: op.stable(tables),
-                    rhs: opaque(rhs),
-                }
-            }
-            CoverageKind::Unreachable => stable_mir::mir::CoverageKind::Unreachable,
-        }
-    }
-}
-
 impl<'tcx> Stable<'tcx> for mir::UserTypeProjection {
     type T = stable_mir::mir::UserTypeProjection;
 
@@ -504,18 +476,6 @@ impl<'tcx> Stable<'tcx> for mir::UserTypeProjection {
     }
 }
 
-impl<'tcx> Stable<'tcx> for mir::coverage::Op {
-    type T = stable_mir::mir::Op;
-
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
-        use rustc_middle::mir::coverage::Op::*;
-        match self {
-            Subtract => stable_mir::mir::Op::Subtract,
-            Add => stable_mir::mir::Op::Add,
-        }
-    }
-}
-
 impl<'tcx> Stable<'tcx> for mir::Local {
     type T = stable_mir::mir::Local;
     fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
@@ -562,20 +522,6 @@ impl<'tcx> Stable<'tcx> for ty::UserTypeAnnotationIndex {
     }
 }
 
-impl<'tcx> Stable<'tcx> for CodeRegion {
-    type T = stable_mir::mir::CodeRegion;
-
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
-        stable_mir::mir::CodeRegion {
-            file_name: self.file_name.as_str().to_string(),
-            start_line: self.start_line as usize,
-            start_col: self.start_col as usize,
-            end_line: self.end_line as usize,
-            end_col: self.end_col as usize,
-        }
-    }
-}
-
 impl<'tcx> Stable<'tcx> for mir::UnwindAction {
     type T = stable_mir::mir::UnwindAction;
     fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
diff --git a/compiler/rustc_smir/src/stable_mir/mir/body.rs b/compiler/rustc_smir/src/stable_mir/mir/body.rs
index c16bd6cbd70e2..a2ab51ff8467c 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/body.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/body.rs
@@ -135,9 +135,10 @@ pub enum AsyncGeneratorKind {
 }
 
 pub(crate) type LocalDefId = Opaque;
-pub(crate) type CounterValueReference = Opaque;
-pub(crate) type InjectedExpressionId = Opaque;
-pub(crate) type ExpressionOperandId = Opaque;
+/// [`rustc_middle::mir::Coverage`] is heavily tied to internal details of the
+/// coverage implementation that are likely to change, and are unlikely to be
+/// useful to third-party tools for the foreseeable future.
+pub(crate) type Coverage = Opaque;
 
 /// The FakeReadCause describes the type of pattern why a FakeRead statement exists.
 #[derive(Clone, Debug)]
@@ -166,42 +167,6 @@ pub enum Variance {
     Bivariant,
 }
 
-#[derive(Clone, Debug)]
-pub enum Op {
-    Subtract,
-    Add,
-}
-
-#[derive(Clone, Debug)]
-pub enum CoverageKind {
-    Counter {
-        function_source_hash: usize,
-        id: CounterValueReference,
-    },
-    Expression {
-        id: InjectedExpressionId,
-        lhs: ExpressionOperandId,
-        op: Op,
-        rhs: ExpressionOperandId,
-    },
-    Unreachable,
-}
-
-#[derive(Clone, Debug)]
-pub struct CodeRegion {
-    pub file_name: String,
-    pub start_line: usize,
-    pub start_col: usize,
-    pub end_line: usize,
-    pub end_col: usize,
-}
-
-#[derive(Clone, Debug)]
-pub struct Coverage {
-    pub kind: CoverageKind,
-    pub code_region: Option<CodeRegion>,
-}
-
 #[derive(Clone, Debug)]
 pub struct CopyNonOverlapping {
     pub src: Operand,