Rollup merge of #147015 - Zalathar:dispose-tm, r=lqd

Use `LLVMDisposeTargetMachine`

After bumping the minimum LLVM version to 20 (#145071), we no longer need to run any custom code when disposing of a TargetMachine, so we can just use the upstream LLVM-C function.

Author: Zalathar

compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs

@@ -95,8 +95,6 @@ impl Drop for OwnedTargetMachine {
         // SAFETY: constructing ensures we have a valid pointer created by
         // llvm::LLVMRustCreateTargetMachine OwnedTargetMachine is not copyable so there is no
         // double free or use after free.
-        unsafe {
-            llvm::LLVMRustDisposeTargetMachine(self.tm_unique.as_ptr());
-        }
+        unsafe { llvm::LLVMDisposeTargetMachine(self.tm_unique) };
     }
 }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1053,6 +1053,8 @@ unsafe extern "C" {
         SLen: c_uint,
     ) -> MetadataKindId;
 
+    pub(crate) fn LLVMDisposeTargetMachine(T: ptr::NonNull<TargetMachine>);
+
     // Create modules.
     pub(crate) fn LLVMModuleCreateWithNameInContext(
         ModuleID: *const c_char,
@@ -2499,7 +2501,6 @@ unsafe extern "C" {
         UseWasmEH: bool,
     ) -> *mut TargetMachine;
 
-    pub(crate) fn LLVMRustDisposeTargetMachine(T: *mut TargetMachine);
     pub(crate) fn LLVMRustAddLibraryInfo<'a>(
         PM: &PassManager<'a>,
         M: &'a Module,

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -359,10 +359,6 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   return wrap(TM);
 }
 
-extern "C" void LLVMRustDisposeTargetMachine(LLVMTargetMachineRef TM) {
-  delete unwrap(TM);
-}
-
 // Unfortunately, the LLVM C API doesn't provide a way to create the
 // TargetLibraryInfo pass, so we use this method to do so.
 extern "C" void LLVMRustAddLibraryInfo(LLVMPassManagerRef PMR, LLVMModuleRef M,