Use safe FFI for various functions in codegen_llvm

Author: oli-obk

compiler/rustc_codegen_llvm/src/builder.rs

@@ -100,9 +100,7 @@ impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
     }
 
     fn ret_void(&mut self) {
-        unsafe {
-            llvm::LLVMBuildRetVoid(self.llbuilder);
-        }
+        llvm::LLVMBuildRetVoid(self.llbuilder);
     }
 
     fn ret(&mut self, v: &'ll Value) {
@@ -293,9 +291,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn ret_void(&mut self) {
-        unsafe {
-            llvm::LLVMBuildRetVoid(self.llbuilder);
-        }
+        llvm::LLVMBuildRetVoid(self.llbuilder);
     }
 
     fn ret(&mut self, v: &'ll Value) {

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1204,7 +1204,7 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetCurrentDebugLocation2<'a>(Builder: &Builder<'a>) -> Option<&'a Metadata>;
 
     // Terminators
-    pub(crate) fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
+    pub(crate) safe fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
     pub(crate) fn LLVMBuildRet<'a>(B: &Builder<'a>, V: &'a Value) -> &'a Value;
     pub(crate) fn LLVMBuildBr<'a>(B: &Builder<'a>, Dest: &'a BasicBlock) -> &'a Value;
     pub(crate) fn LLVMBuildCondBr<'a>(