rust-lang · antoyo · May 20, 2025 · May 20, 2025 · May 21, 2025 · Jun 15, 2025
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
@@ -62,7 +62,7 @@ jobs:
     - name: Build
       run: |
         ./y.sh prepare --only-libcore
-        EMBED_LTO_BITCODE=1 ./y.sh build --sysroot --release --release-sysroot
+        ./y.sh build --sysroot --release --release-sysroot
         ./y.sh test --cargo-tests
         ./y.sh clean all
 
@@ -79,11 +79,11 @@ jobs:
       run: |
         # FIXME(antoyo): we cannot enable LTO for stdarch tests currently because of some failing LTO tests using proc-macros.
         echo -n 'lto = "fat"' >> build_system/build_sysroot/Cargo.toml
-        EMBED_LTO_BITCODE=1 ./y.sh test --release --clean --release-sysroot --build-sysroot --keep-lto-tests ${{ matrix.commands }}
+        ./y.sh test --release --clean --release-sysroot --build-sysroot --keep-lto-tests ${{ matrix.commands }}
 
     - name: Run y.sh cargo build
       run: |
-        EMBED_LTO_BITCODE=1 CHANNEL="release" ./y.sh cargo build --release --manifest-path tests/hello-world/Cargo.toml
+        CHANNEL="release" ./y.sh cargo build --release --manifest-path tests/hello-world/Cargo.toml
         call_found=$(objdump -dj .text tests/hello-world/target/release/hello_world | grep -c "call .*mylib.*my_func" ) ||:
         if [ $call_found -gt 0 ]; then
           echo "ERROR: call my_func found in asm"

diff --git a/Cargo.lock b/Cargo.lock
@@ -81,6 +81,18 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26145e563e54f2cadc477553f1ec5ee650b00862f0a58bcd12cbdc5f0ea2d2f4"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasi",
+]
+
 [[package]]
 name = "hermit-abi"
 version = "0.3.1"
@@ -111,9 +123,9 @@ checksum = "5aaeb2981e0606ca11d79718f8bb01164f1d6ed75080182d3abf017e6d244b6d"
 
 [[package]]
 name = "linux-raw-sys"
-version = "0.4.14"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "78b3ae25bc7c8c38cec158d1f2757ee79e9b3740fbc7ccf0e59e4b08d793fa89"
+checksum = "cd945864f07fe9f5371a27ad7b52a172b4b499999f1d97574c9fa68373937e12"
 
 [[package]]
 name = "memchr"
@@ -137,6 +149,12 @@ version = "1.20.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1261fe7e33c73b354eab43b1273a57c8f967d0391e80353e51f764ac02cf6775"
 
+[[package]]
+name = "r-efi"
+version = "5.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "74765f6d916ee2faa39bc8e68e4f3ed8949b48cccdac59983d287a7cb71ce9c5"
+
 [[package]]
 name = "regex"
 version = "1.8.4"
@@ -166,9 +184,9 @@ dependencies = [
 
 [[package]]
 name = "rustix"
-version = "0.38.42"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f93dc38ecbab2eb790ff964bb77fa94faf256fd3e73285fd7ba0903b76bedb85"
+checksum = "c71e83d6afe7ff64890ec6b71d6a69bb8a610ab78ce364b3352876bb4c801266"
 dependencies = [
  "bitflags",
  "errno",
@@ -188,12 +206,12 @@ dependencies = [
 
 [[package]]
 name = "tempfile"
-version = "3.14.0"
+version = "3.20.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28cce251fcbc87fac86a866eeb0d6c2d536fc16d06f184bb61aeae11aa4cee0c"
+checksum = "e8a64e3985349f2441a1a9ef0b853f869006c3855f2cda6862a94d26ebb9d6a1"
 dependencies = [
- "cfg-if",
  "fastrand",
+ "getrandom",
  "once_cell",
  "rustix",
  "windows-sys",
@@ -242,6 +260,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.14.2+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9683f9a5a998d873c0d21fcbe3c083009670149a8fab228644b8bd36b2c48cb3"
+dependencies = [
+ "wit-bindgen-rt",
+]
+
 [[package]]
 name = "winapi"
 version = "0.3.9"
@@ -345,3 +372,12 @@ name = "windows_x86_64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
+
+[[package]]
+name = "wit-bindgen-rt"
+version = "0.39.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f42320e61fe2cfd34354ecb597f86f413484a798ba44a8ca1165c58d42da6c1"
+dependencies = [
+ "bitflags",
+]
diff --git a/Cargo.toml b/Cargo.toml
@@ -31,7 +31,7 @@ gccjit = "2.7"
 [dev-dependencies]
 boml = "0.3.1"
 lang_tester = "0.8.0"
-tempfile = "3.7.1"
+tempfile = "3.20.0"
 
 [profile.dev]
 # By compiling dependencies with optimizations, performing tests gets much faster.

diff --git a/Readme.md b/Readme.md
@@ -135,16 +135,6 @@ $ CHANNEL="release" $CG_GCCJIT_DIR/y.sh cargo run
 
 If you compiled cg_gccjit in debug mode (aka you didn't pass `--release` to `./y.sh test`) you should use `CHANNEL="debug"` instead or omit `CHANNEL="release"` completely.
 
-### LTO
-
-To use LTO, you need to set the variable `EMBED_LTO_BITCODE=1` in addition to setting `lto = "fat"` in the `Cargo.toml`.
-
-Failing to set `EMBED_LTO_BITCODE` will give you the following error:
-
-```
-error: failed to copy bitcode to object file: No such file or directory (os error 2)
-```
-
 ### Rustc
 
 If you want to run `rustc` directly, you can do so with:

diff --git a/libgccjit.version b/libgccjit.version
@@ -1 +1 @@
-04ce66d8c918de9273bd7101638ad8724edf5e21
+9244ae6e2e96e7d255c73fbd4a9f345e0cd96f35
diff --git a/src/back/lto.rs b/src/back/lto.rs
@@ -21,6 +21,7 @@ use std::ffi::{CStr, CString};
 use std::fs::{self, File};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
+use std::sync::atomic::Ordering;
 
 use gccjit::{Context, OutputKind};
 use object::read::archive::ArchiveFile;
@@ -41,7 +42,7 @@ use tempfile::{TempDir, tempdir};
 
 use crate::back::write::save_temp_bitcode;
 use crate::errors::{DynamicLinkingWithLTO, LtoBitcodeFromRlib, LtoDisallowed, LtoDylib};
-use crate::{GccCodegenBackend, GccContext, SyncContext, to_gcc_opt_level};
+use crate::{GccCodegenBackend, GccContext, LTO_SUPPORTED, LtoMode, SyncContext, to_gcc_opt_level};
 
 pub fn crate_type_allows_lto(crate_type: CrateType) -> bool {
     match crate_type {
@@ -303,7 +304,7 @@ fn fat_lto(
             info!("linking {:?}", name);
             match bc_decoded {
                 SerializedModule::Local(ref module_buffer) => {
-                    module.module_llvm.should_combine_object_files = true;
+                    module.module_llvm.lto_mode = LtoMode::Fat;
                     module
                         .module_llvm
                         .context
@@ -611,7 +612,7 @@ pub fn optimize_thin_module(
     // that LLVM Context and Module.
     //let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
     //let llmod_raw = parse_module(llcx, module_name, thin_module.data(), &dcx)? as *const _;
-    let mut should_combine_object_files = false;
+    let mut lto_mode = LtoMode::None;
     let context = match thin_module.shared.thin_buffers.get(thin_module.idx) {
         Some(thin_buffer) => Arc::clone(&thin_buffer.context),
         None => {
@@ -622,7 +623,7 @@ pub fn optimize_thin_module(
                 SerializedModule::Local(ref module_buffer) => {
                     let path = module_buffer.0.to_str().expect("path");
                     context.add_driver_option(path);
-                    should_combine_object_files = true;
+                    lto_mode = LtoMode::Thin;
                     /*module.module_llvm.should_combine_object_files = true;
                     module
                         .module_llvm
@@ -637,11 +638,13 @@ pub fn optimize_thin_module(
             Arc::new(SyncContext::new(context))
         }
     };
+    let lto_supported = LTO_SUPPORTED.load(Ordering::SeqCst);
     let module = ModuleCodegen::new_regular(
         thin_module.name().to_string(),
         GccContext {
             context,
-            should_combine_object_files,
+            lto_mode,
+            lto_supported,
             // TODO(antoyo): use the correct relocation model here.
             relocation_model: RelocModel::Pic,
             temp_dir: None,

diff --git a/src/back/write.rs b/src/back/write.rs
@@ -12,7 +12,7 @@ use rustc_target::spec::SplitDebuginfo;
 
 use crate::base::add_pic_option;
 use crate::errors::CopyBitcode;
-use crate::{GccCodegenBackend, GccContext};
+use crate::{GccCodegenBackend, GccContext, LtoMode};
 
 pub(crate) fn codegen(
     cgcx: &CodegenContext<GccCodegenBackend>,
@@ -24,12 +24,8 @@ pub(crate) fn codegen(
     {
         let context = &module.module_llvm.context;
 
-        let should_combine_object_files = module.module_llvm.should_combine_object_files;
-
-        // NOTE: Only generate object files with GIMPLE when this environment variable is set for
-        // now because this requires a particular setup (same gcc/lto1/lto-wrapper commit as libgccjit).
-        // TODO(antoyo): remove this environment variable.
-        let fat_lto = env::var("EMBED_LTO_BITCODE").as_deref() == Ok("1");
+        let lto_mode = module.module_llvm.lto_mode;
+        let lto_supported = module.module_llvm.lto_supported;
 
         let bc_out = cgcx.output_filenames.temp_path_for_cgu(
             OutputType::Bitcode,
@@ -43,80 +39,48 @@ pub(crate) fn codegen(
         );
 
         if config.bitcode_needed() {
-            if fat_lto {
+            let _timer = cgcx
+                .prof
+                .generic_activity_with_arg("GCC_module_codegen_make_bitcode", &*module.name);
+
+            // TODO(antoyo)
+            /*if let Some(bitcode_filename) = bc_out.file_name() {
+                cgcx.prof.artifact_size(
+                    "llvm_bitcode",
+                    bitcode_filename.to_string_lossy(),
+                    data.len() as u64,
+                );
+            }*/
+
+            if config.emit_bc || config.emit_obj == EmitObj::Bitcode {
                 let _timer = cgcx
                     .prof
-                    .generic_activity_with_arg("GCC_module_codegen_make_bitcode", &*module.name);
-
-                // TODO(antoyo)
-                /*if let Some(bitcode_filename) = bc_out.file_name() {
-                    cgcx.prof.artifact_size(
-                        "llvm_bitcode",
-                        bitcode_filename.to_string_lossy(),
-                        data.len() as u64,
-                    );
-                }*/
-
-                if config.emit_bc || config.emit_obj == EmitObj::Bitcode {
-                    let _timer = cgcx.prof.generic_activity_with_arg(
-                        "GCC_module_codegen_emit_bitcode",
-                        &*module.name,
-                    );
+                    .generic_activity_with_arg("GCC_module_codegen_emit_bitcode", &*module.name);
+                if lto_supported {
                     context.add_command_line_option("-flto=auto");
                     context.add_command_line_option("-flto-partition=one");
                     // TODO(antoyo): remove since we don't want fat objects when it is for Bitcode only.
                     context.add_command_line_option("-ffat-lto-objects");
-                    context.compile_to_file(
-                        OutputKind::ObjectFile,
-                        bc_out.to_str().expect("path to str"),
-                    );
                 }
+                context
+                    .compile_to_file(OutputKind::ObjectFile, bc_out.to_str().expect("path to str"));
+            }
 
-                if config.emit_obj == EmitObj::ObjectCode(BitcodeSection::Full) {
-                    let _timer = cgcx.prof.generic_activity_with_arg(
-                        "GCC_module_codegen_embed_bitcode",
-                        &*module.name,
-                    );
+            if config.emit_obj == EmitObj::ObjectCode(BitcodeSection::Full) {
+                let _timer = cgcx
+                    .prof
+                    .generic_activity_with_arg("GCC_module_codegen_embed_bitcode", &*module.name);
+                if lto_supported {
                     // TODO(antoyo): maybe we should call embed_bitcode to have the proper iOS fixes?
                     //embed_bitcode(cgcx, llcx, llmod, &config.bc_cmdline, data);
 
                     context.add_command_line_option("-flto=auto");
                     context.add_command_line_option("-flto-partition=one");
                     context.add_command_line_option("-ffat-lto-objects");
-                    // TODO(antoyo): Send -plugin/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/liblto_plugin.so to linker (this should be done when specifying the appropriate rustc cli argument).
-                    context.compile_to_file(
-                        OutputKind::ObjectFile,
-                        bc_out.to_str().expect("path to str"),
-                    );
-                }
-            } else {
-                if config.emit_bc || config.emit_obj == EmitObj::Bitcode {
-                    let _timer = cgcx.prof.generic_activity_with_arg(
-                        "GCC_module_codegen_emit_bitcode",
-                        &*module.name,
-                    );
-                    context.compile_to_file(
-                        OutputKind::ObjectFile,
-                        bc_out.to_str().expect("path to str"),
-                    );
-                }
-
-                if config.emit_obj == EmitObj::ObjectCode(BitcodeSection::Full) {
-                    // TODO(antoyo): we might want to emit to emit an error here, saying to set the
-                    // environment variable EMBED_LTO_BITCODE.
-                    let _timer = cgcx.prof.generic_activity_with_arg(
-                        "GCC_module_codegen_embed_bitcode",
-                        &*module.name,
-                    );
-                    // TODO(antoyo): maybe we should call embed_bitcode to have the proper iOS fixes?
-                    //embed_bitcode(cgcx, llcx, llmod, &config.bc_cmdline, data);
-
-                    // TODO(antoyo): Send -plugin/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/liblto_plugin.so to linker (this should be done when specifying the appropriate rustc cli argument).
-                    context.compile_to_file(
-                        OutputKind::ObjectFile,
-                        bc_out.to_str().expect("path to str"),
-                    );
                 }
+                // TODO(antoyo): Send -plugin/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/liblto_plugin.so to linker (this should be done when specifying the appropriate rustc cli argument).
+                context
+                    .compile_to_file(OutputKind::ObjectFile, bc_out.to_str().expect("path to str"));
             }
         }
 
@@ -165,7 +129,10 @@ pub(crate) fn codegen(
                     context.set_debug_info(true);
                     context.dump_to_file(path, true);
                 }
-                if should_combine_object_files {
+                if lto_mode != LtoMode::None {
+                    let fat_lto = lto_mode == LtoMode::Fat;
+                    // We need to check if we're doing LTO since this code is also used for the
+                    // dummy ThinLTO implementation to combine the object files.
                     if fat_lto {
                         context.add_command_line_option("-flto=auto");
                         context.add_command_line_option("-flto-partition=one");
Original file line number	Diff line number	Diff line change
		@@ -1 +1 @@
		04ce66d8c918de9273bd7101638ad8724edf5e21
		9244ae6e2e96e7d255c73fbd4a9f345e0cd96f35