Do not unnecessarily eval consts in codegen

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -125,7 +125,9 @@ fn build_fixed_size_array_di_node<'ll, 'tcx>(
 
     let (size, align) = cx.size_and_align_of(array_type);
 
-    let upper_bound = len.eval_target_usize(cx.tcx, ty::ParamEnv::reveal_all()) as c_longlong;
+    let upper_bound = len
+        .try_to_target_usize(cx.tcx)
+        .expect("expected monomorphic const in codegen") as c_longlong;
 
     let subrange =
         unsafe { Some(llvm::LLVMRustDIBuilderGetOrCreateSubrange(DIB(cx), 0, upper_bound)) };