Rollup merge of #111382 - Zalathar:ffi, r=cuviper

Isolate coverage FFI type layouts from their underlying LLVM C++ types

I noticed that several of the types used to send coverage information through FFI are not properly isolated from the layout of their corresponding C++ types in the LLVM API.

This PR adds more explicitly-defined FFI struct/enum types in `CoverageMappingWrapper.cpp`, so that Rust source files in `rustc_codegen_ssa` and `rustc_codegen_llvm` aren't directly exposed to LLVM C++ types.

1 files changed, 11 insertions, 7 deletions

diff --git a/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs b/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
index e288760a02b..1791ce4b315 100644
--- a/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
+++ b/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
@@ -1,6 +1,6 @@
 use rustc_middle::mir::coverage::{CounterValueReference, MappedExpressionIndex};
 
-/// Aligns with [llvm::coverage::Counter::CounterKind](https://github.com/rust-lang/llvm-project/blob/rustc/13.0-2021-09-30/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L95)
+/// Must match the layout of `LLVMRustCounterKind`.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub enum CounterKind {
@@ -17,8 +17,10 @@ pub enum CounterKind {
 ///     `instrprof.increment()`)
 ///   * For `CounterKind::Expression`, `id` is the index into the coverage map's array of
 ///     counter expressions.
-/// Aligns with [llvm::coverage::Counter](https://github.com/rust-lang/llvm-project/blob/rustc/13.0-2021-09-30/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L102-L103)
-/// Important: The Rust struct layout (order and types of fields) must match its C++ counterpart.
+///
+/// Corresponds to struct `llvm::coverage::Counter`.
+///
+/// Must match the layout of `LLVMRustCounter`.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub struct Counter {
@@ -59,7 +61,9 @@ impl Counter {
     }
 }
 
-/// Aligns with [llvm::coverage::CounterExpression::ExprKind](https://github.com/rust-lang/llvm-project/blob/rustc/13.0-2021-09-30/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L150)
+/// Corresponds to enum `llvm::coverage::CounterExpression::ExprKind`.
+///
+/// Must match the layout of `LLVMRustCounterExprKind`.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub enum ExprKind {
@@ -67,9 +71,9 @@ pub enum ExprKind {
     Add = 1,
 }
 
-/// Aligns with [llvm::coverage::CounterExpression](https://github.com/rust-lang/llvm-project/blob/rustc/13.0-2021-09-30/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L151-L152)
-/// Important: The Rust struct layout (order and types of fields) must match its C++
-/// counterpart.
+/// Corresponds to struct `llvm::coverage::CounterExpression`.
+///
+/// Must match the layout of `LLVMRustCounterExpression`.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub struct CounterExpression {