clarified semantics of target machine wrapper

Author: nebulark

compiler/rustc_codegen_llvm/src/back/target_machine_wrapper.rs

@@ -11,8 +11,8 @@ use crate::{errors::LlvmError, llvm};
 
 #[repr(transparent)]
 pub struct TargetMachineWrapper {
-    tm: NonNull<llvm::TargetMachine>,
-    phantom: PhantomData<&'static mut llvm::TargetMachine>,
+    tm_unique: NonNull<llvm::TargetMachine>,
+    phantom: PhantomData<llvm::TargetMachine>,
 }
 
 impl TargetMachineWrapper {
@@ -74,7 +74,7 @@ impl TargetMachineWrapper {
         };
 
         NonNull::new(tm_ptr)
-            .map(|tm| Self { tm, phantom: PhantomData })
+            .map(|tm_unique| Self { tm_unique, phantom: PhantomData })
             .ok_or_else(|| LlvmError::CreateTargetMachine { triple: SmallCStr::from(triple) })
     }
 }
@@ -84,7 +84,7 @@ impl Deref for TargetMachineWrapper {
 
     fn deref(&self) -> &Self::Target {
         // SAFETY: constructing ensures we have a valid pointer created by llvm::LLVMRustCreateTargetMachine
-        unsafe { self.tm.as_ref() }
+        unsafe { self.tm_unique.as_ref() }
     }
 }
 
@@ -93,7 +93,7 @@ impl Drop for TargetMachineWrapper {
         // 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
         unsafe {
-            llvm::LLVMRustDisposeTargetMachine(self.tm.as_mut());
+            llvm::LLVMRustDisposeTargetMachine(self.tm_unique.as_mut());
         }
     }
 }