renamed target machine wrapper -> target machine box and clarified its semantics with comments

Author: nebulark

compiler/rustc_codegen_llvm/src/back/target_machine_wrapper.rs renamed to compiler/rustc_codegen_llvm/src/back/target_machine_box.rs

@@ -9,13 +9,16 @@ use rustc_data_structures::small_c_str::SmallCStr;
 
 use crate::{errors::LlvmError, llvm};
 
+/// Provides Box like semantics for the foreign llvm::TargetMachine type.
+/// Responsible for safely creating and disposing llvm::TargetMachine via ffi functions.
+/// Not cloneable as there is no clone function for llvm::TargetMachine.
 #[repr(transparent)]
-pub struct TargetMachineWrapper {
+pub struct TargetMachineBox {
     tm_unique: NonNull<llvm::TargetMachine>,
     phantom: PhantomData<llvm::TargetMachine>,
 }
 
-impl TargetMachineWrapper {
+impl TargetMachineBox {
     pub fn new(
         triple: &CStr,
         cpu: &CStr,
@@ -79,7 +82,7 @@ impl TargetMachineWrapper {
     }
 }
 
-impl Deref for TargetMachineWrapper {
+impl Deref for TargetMachineBox {
     type Target = llvm::TargetMachine;
 
     fn deref(&self) -> &Self::Target {
@@ -88,10 +91,10 @@ impl Deref for TargetMachineWrapper {
     }
 }
 
-impl Drop for TargetMachineWrapper {
+impl Drop for TargetMachineBox {
     fn drop(&mut self) {
         // SAFETY: constructing ensures we have a valid pointer created by llvm::LLVMRustCreateTargetMachine
-        // TargetMachineWrapper is not copyable so there is no double free or use after free
+        // TargetMachineBox is not copyable so there is no double free or use after free
         unsafe {
             llvm::LLVMRustDisposeTargetMachine(self.tm_unique.as_mut());
         }

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -2,7 +2,7 @@ use crate::back::lto::ThinBuffer;
 use crate::back::profiling::{
     selfprofile_after_pass_callback, selfprofile_before_pass_callback, LlvmSelfProfiler,
 };
-use crate::back::target_machine_wrapper::TargetMachineWrapper;
+use crate::back::target_machine_box::TargetMachineBox;
 use crate::base;
 use crate::common;
 use crate::errors::{
@@ -99,7 +99,7 @@ pub fn write_output_file<'ll>(
     }
 }
 
-pub fn create_informational_target_machine(sess: &Session) -> TargetMachineWrapper {
+pub fn create_informational_target_machine(sess: &Session) -> TargetMachineBox {
     let config = TargetMachineFactoryConfig { split_dwarf_file: None };
     // Can't use query system here quite yet because this function is invoked before the query
     // system/tcx is set up.
@@ -108,7 +108,7 @@ pub fn create_informational_target_machine(sess: &Session) -> TargetMachineWrapp
         .unwrap_or_else(|err| llvm_err(sess.diagnostic(), err).raise())
 }
 
-pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> TargetMachineWrapper {
+pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> TargetMachineBox {
     let split_dwarf_file = if tcx.sess.target_can_use_split_dwarf() {
         tcx.output_filenames(()).split_dwarf_path(
             tcx.sess.split_debuginfo(),
@@ -260,7 +260,7 @@ pub fn target_machine_factory(
             path_mapping.map_prefix(config.split_dwarf_file.unwrap_or_default()).0;
         let split_dwarf_file = CString::new(split_dwarf_file.to_str().unwrap()).unwrap();
 
-        TargetMachineWrapper::new(
+        TargetMachineBox::new(
             &triple,
             &cpu,
             &features,

compiler/rustc_codegen_llvm/src/lib.rs

@@ -22,7 +22,7 @@ extern crate rustc_macros;
 #[macro_use]
 extern crate tracing;
 
-use back::target_machine_wrapper::TargetMachineWrapper;
+use back::target_machine_box::TargetMachineBox;
 use back::write::{create_informational_target_machine, create_target_machine};
 
 use errors::ParseTargetMachineConfig;
@@ -54,7 +54,7 @@ mod back {
     pub mod archive;
     pub mod lto;
     mod profiling;
-    pub mod target_machine_wrapper;
+    pub mod target_machine_box;
     pub mod write;
 }
 
@@ -164,7 +164,7 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
 impl WriteBackendMethods for LlvmCodegenBackend {
     type Module = ModuleLlvm;
     type ModuleBuffer = back::lto::ModuleBuffer;
-    type TargetMachine = TargetMachineWrapper;
+    type TargetMachine = TargetMachineBox;
     type TargetMachineError = crate::errors::LlvmError<'static>;
     type ThinData = back::lto::ThinData;
     type ThinBuffer = back::lto::ThinBuffer;
@@ -405,7 +405,7 @@ pub struct ModuleLlvm {
     llmod_raw: *const llvm::Module,
 
     // independent from llcx and llmod_raw, resources get disposed by drop impl
-    tm: TargetMachineWrapper,
+    tm: TargetMachineBox,
 }
 
 unsafe impl Send for ModuleLlvm {}