Fix requires_lto targets needing lto set in cargo

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -410,7 +410,7 @@ struct CompiledModules {
 
 fn need_bitcode_in_object(tcx: TyCtxt<'_>) -> bool {
     let sess = tcx.sess;
-    sess.opts.cg.embed_bitcode
+    (sess.lto() != config::Lto::No || sess.opts.cg.embed_bitcode)
         && tcx.crate_types().contains(&CrateType::Rlib)
         && sess.opts.output_types.contains_key(&OutputType::Exe)
 }

src/doc/rustc/src/platform-support/amdgcn-amd-amdhsa.md

@@ -56,11 +56,6 @@ Build the library as `cdylib`:
 # Cargo.toml
 [lib]
 crate-type = ["cdylib"]
-
-[profile.dev]
-lto = true # LTO must be explicitly enabled for now
-[profile.release]
-lto = true
 ```
 
 The target-cpu must be from the list [supported by LLVM] (or printed with `rustc --target amdgcn-amd-amdhsa --print target-cpus`).

src/tools/tidy/src/target_specific_tests.rs

@@ -53,7 +53,12 @@ pub fn check(tests_path: &Path, tidy_ctx: TidyCtx) {
         });
 
         // Skip run-make tests as revisions are not supported.
-        if entry.path().strip_prefix(tests_path).is_ok_and(|rest| rest.starts_with("run-make")) {
+        // Skip run-make-cargo tests as they can specify the target in ways we do not detect here.
+        if entry
+            .path()
+            .strip_prefix(tests_path)
+            .is_ok_and(|rest| rest.starts_with("run-make") || rest.starts_with("run-make-cargo"))
+        {
             return;
         }
 

tests/run-make-cargo/amdgpu-lto/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "amdgpu_lto"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+path = "lib.rs"
+crate-type = ["cdylib"]

tests/run-make-cargo/amdgpu-lto/lib.rs

@@ -0,0 +1,9 @@
+#![no_std]
+
+#[panic_handler]
+fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[unsafe(no_mangle)]
+fn foo() {}

tests/run-make-cargo/amdgpu-lto/rmake.rs

@@ -0,0 +1,28 @@
+// Check that compiling for the amdgpu target which has requires_lto=true works with a default
+// cargo configuration.
+
+//@ needs-llvm-components: amdgpu
+//@ needs-rust-lld
+
+#![deny(warnings)]
+
+use run_make_support::{cargo, path};
+
+fn main() {
+    let target_dir = path("target");
+
+    cargo()
+        .args(&[
+            "build",
+            "--release",
+            "--lib",
+            "--manifest-path",
+            "Cargo.toml",
+            "-Zbuild-std=core",
+            "--target",
+            "amdgcn-amd-amdhsa",
+        ])
+        .env("RUSTFLAGS", "-Ctarget-cpu=gfx900")
+        .env("CARGO_TARGET_DIR", &target_dir)
+        .run();
+}