Rollup merge of #62422 - lzutao:remove-some-mem-uinit, r=alexcrichton

Remove some uses of mem::uninitialized

cc #62397
r? @RalfJung

src/librustc_codegen_llvm/common.rs

@@ -170,8 +170,7 @@ impl CodegenCx<'ll, 'tcx> {
     pub fn const_get_real(&self, v: &'ll Value) -> Option<(f64, bool)> {
         unsafe {
             if self.is_const_real(v) {
-                #[allow(deprecated)]
-                let mut loses_info: llvm::Bool = ::std::mem::uninitialized();
+                let mut loses_info: llvm::Bool = 0;
                 let r = llvm::LLVMConstRealGetDouble(v, &mut loses_info);
                 let loses_info = if loses_info == 1 { true } else { false };
                 Some((r, loses_info))