Add test for cross-language LTO

.github/workflows/release.yml

@@ -82,7 +82,7 @@ jobs:
         printf '[profile.release]\nlto = "fat"\n' >> build/build_sysroot/sysroot_src/library/Cargo.toml
         EMBED_LTO_BITCODE=1 ./y.sh test --release --clean --release-sysroot --build-sysroot --keep-lto-tests ${{ matrix.commands }}
 
-    - name: Run y.sh cargo build
+    - name: LTO test
       run: |
         EMBED_LTO_BITCODE=1 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" ) ||:
@@ -92,6 +92,21 @@ jobs:
           exit 1
         fi
 
+    - name: Cross-language LTO test
+      run: |
+        pushd tests/cross_lang_lto
+        gcc -c -flto add.c -masm=intel -fPIC -O3
+        ar rcs libadd.a add.o
+        popd
+
+        EMBED_LTO_BITCODE=1 CHANNEL="release" CG_RUSTFLAGS="-L native=. -Clinker-plugin-lto -Clinker=gcc" ./y.sh cargo build --release --manifest-path tests/cross_lang_lto/Cargo.toml
+        call_found=$(objdump -dj .text tests/cross_lang_lto/target/release/cross_lang_lto | grep -c "call .*my_add" ) ||:
+        if [ $call_found -gt 0 ]; then
+          echo "ERROR: call my_add found in asm"
+          echo "Test is done with cross-language LTO enabled, hence inlining should occur across object files"
+          exit 1
+        fi
+
   # Summary job for the merge queue.
   # ALL THE PREVIOUS JOBS NEED TO BE ADDED TO THE `needs` SECTION OF THIS JOB!
   success_release:

tests/cross_lang_lto/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "cross_lang_lto"
+version = "0.1.0"

tests/cross_lang_lto/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "cross_lang_lto"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

tests/cross_lang_lto/add.c

@@ -0,0 +1,5 @@
+#include <stdint.h>
+
+uint32_t my_add(uint32_t a, uint32_t b) {
+    return a + b;
+}

tests/cross_lang_lto/src/main.rs

@@ -0,0 +1,18 @@
+/*
+ * Compile the C code with:
+ * gcc -c -flto add.c -ffat-lto-objects
+ * ar rcs libadd.a add.o
+ *
+ * Compile the Rust code with:
+ * EMBED_LTO_BITCODE=1 CG_RUSTFLAGS="-L native=. -Clinker-plugin-lto -Clinker=gcc" y cargo run --release
+ */
+
+#[link(name="add")]
+unsafe extern "C" {
+    fn my_add(a: u32, b: u32) -> u32;
+}
+
+fn main() {
+    let res = unsafe { my_add(30, 12) };
+    println!("{}", res);
+}