Use -Zdisable-incr-comp-backend-caching instead of an env var

Author: bjorn3

build_system/build_sysroot.rs

@@ -231,6 +231,8 @@ fn build_clif_sysroot_for_triple(
     // inlining.
     rustflags.push("-Zinline-mir".to_owned());
 
+    rustflags.push("-Zdisable-incr-comp-backend-caching".to_owned());
+
     if let Some(prefix) = env::var_os("CG_CLIF_STDLIB_REMAP_PATH_PREFIX") {
         rustflags.push("--remap-path-prefix".to_owned());
         rustflags.push(format!("library/={}/library", prefix.to_str().unwrap()));

build_system/main.rs

@@ -59,7 +59,6 @@ fn main() {
     if env::var_os("RUST_BACKTRACE").is_none() {
         env::set_var("RUST_BACKTRACE", "1");
     }
-    env::set_var("CG_CLIF_DISABLE_INCR_CACHE", "1");
 
     let mut args = env::args().skip(1);
     let command = match args.next().as_deref() {

src/driver/aot.rs

@@ -1,7 +1,6 @@
 //! The AOT driver uses [`cranelift_object`] to write object files suitable for linking into a
 //! standalone executable.
 
-use std::env;
 use std::fs::File;
 use std::io::BufWriter;
 use std::path::PathBuf;
@@ -30,10 +29,6 @@ use crate::global_asm::{GlobalAsmConfig, GlobalAsmContext};
 use crate::prelude::*;
 use crate::unwind_module::UnwindModule;
 
-fn disable_incr_cache() -> bool {
-    env::var("CG_CLIF_DISABLE_INCR_CACHE").as_deref() == Ok("1")
-}
-
 struct ModuleCodegenResult {
     module: CompiledModule,
     existing_work_product: Option<(WorkProductId, WorkProduct)>,
@@ -64,8 +59,6 @@ impl OngoingCodegen {
     ) -> (CompiledModules, FxIndexMap<WorkProductId, WorkProduct>) {
         let mut work_products = FxIndexMap::default();
         let mut modules = vec![];
-        let disable_incr_cache = disable_incr_cache();
-
         for module_codegen in self.modules {
             let module_codegen_result = match module_codegen {
                 OngoingModuleCodegen::Sync(module_codegen_result) => module_codegen_result,
@@ -84,7 +77,7 @@ impl OngoingCodegen {
             if let Some((work_product_id, work_product)) = existing_work_product {
                 work_products.insert(work_product_id, work_product);
             } else {
-                let work_product = if disable_incr_cache {
+                let work_product = if sess.opts.unstable_opts.disable_incr_comp_backend_caching {
                     None
                 } else if let Some(global_asm_object) = &module.global_asm_object {
                     rustc_incremental::copy_cgu_workproduct_to_incr_comp_cache_dir(
@@ -458,10 +451,9 @@ pub(crate) fn run_aot(tcx: TyCtxt<'_>) -> Box<OngoingCodegen> {
 
     let global_asm_config = Arc::new(crate::global_asm::GlobalAsmConfig::new(tcx));
 
-    let disable_incr_cache = disable_incr_cache();
     let (todo_cgus, done_cgus) =
         cgus.iter().enumerate().partition::<Vec<_>, _>(|&(i, _)| match cgu_reuse[i] {
-            _ if disable_incr_cache => true,
+            _ if tcx.sess.opts.unstable_opts.disable_incr_comp_backend_caching => true,
             CguReuse::No => true,
             CguReuse::PreLto | CguReuse::PostLto => false,
         });