Stabilize the size of incr comp object file names

Author: saethlin

src/context.rs

@@ -6,7 +6,8 @@ use gccjit::{
 use rustc_codegen_ssa::base::wants_msvc_seh;
 use rustc_codegen_ssa::errors as ssa_errors;
 use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeMethods, MiscMethods};
-use rustc_data_structures::base_n;
+use rustc_data_structures::base_n::ToBaseN;
+use rustc_data_structures::base_n::ALPHANUMERIC_ONLY;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_middle::mir::mono::CodegenUnit;
 use rustc_middle::span_bug;
@@ -621,7 +622,7 @@ impl<'b, 'tcx> CodegenCx<'b, 'tcx> {
         let mut name = String::with_capacity(prefix.len() + 6);
         name.push_str(prefix);
         name.push_str(".");
-        base_n::push_str(idx as u128, base_n::ALPHANUMERIC_ONLY, &mut name);
+        name.push_str(&(idx as u64).to_base(ALPHANUMERIC_ONLY));
         name
     }
 }