Test thin+fat lto in cross-lang-lto-clang

Also add `.lto()` helper to `run-make-support` and use it in the added
tests.

Author: Flakebi

src/tools/run-make-support/src/external_deps/rustc.rs

@@ -171,6 +171,12 @@ impl Rustc {
         self
     }
 
+    /// This flag enables LTO in the specified form.
+    pub fn lto(&mut self, option: &str) -> &mut Self {
+        self.cmd.arg(format!("-Clto={option}"));
+        self
+    }
+
     /// This flag defers LTO optimizations to the linker.
     pub fn linker_plugin_lto(&mut self, option: &str) -> &mut Self {
         self.cmd.arg(format!("-Clinker-plugin-lto={option}"));

tests/run-make/cross-lang-lto-clang/rmake.rs

@@ -28,15 +28,23 @@ static C_NEVER_INLINED_PATTERN: &'static str = "bl.*<c_never_inlined>";
 static C_NEVER_INLINED_PATTERN: &'static str = "call.*c_never_inlined";
 
 fn main() {
+    test_lto("thin");
+    test_lto("fat");
+}
+
+fn test_lto(lto: &str) {
+    let clang_lto = if lto == "fat" { "full" } else { lto };
+
     rustc()
+        .lto(lto)
         .linker_plugin_lto("on")
         .output(static_lib_name("rustlib-xlto"))
         .opt_level("2")
         .codegen_units(1)
         .input("rustlib.rs")
         .run();
     clang()
-        .lto("thin")
+        .lto(clang_lto)
         .use_ld("lld")
         .arg("-lrustlib-xlto")
         .out_exe("cmain")
@@ -57,9 +65,10 @@ fn main() {
         .input("cmain")
         .run()
         .assert_stdout_contains_regex(RUST_NEVER_INLINED_PATTERN);
-    clang().input("clib.c").lto("thin").arg("-c").out_exe("clib.o").arg("-O2").run();
+    clang().input("clib.c").lto(clang_lto).arg("-c").out_exe("clib.o").arg("-O2").run();
     llvm_ar().obj_to_ar().output_input(static_lib_name("xyz"), "clib.o").run();
     rustc()
+        .lto(lto)
         .linker_plugin_lto("on")
         .opt_level("2")
         .linker(&env_var("CLANG"))
@@ -72,9 +81,12 @@ fn main() {
         .input("rsmain")
         .run()
         .assert_stdout_not_contains_regex(C_ALWAYS_INLINED_PATTERN);
-    llvm_objdump()
-        .disassemble()
-        .input("rsmain")
-        .run()
-        .assert_stdout_contains_regex(C_NEVER_INLINED_PATTERN);
+
+    let dump = llvm_objdump().disassemble().input("rsmain").run();
+    if lto == "thin" {
+        dump.assert_stdout_contains_regex(C_NEVER_INLINED_PATTERN);
+    } else {
+        // fat lto inlines this anyway
+        dump.assert_stdout_not_contains_regex(C_NEVER_INLINED_PATTERN);
+    }
 }

tests/run-make/fat-then-thin-lto/rmake.rs

@@ -8,8 +8,8 @@
 use run_make_support::{dynamic_lib_name, llvm_objdump, rustc};
 
 fn main() {
-    rustc().input("lib.rs").opt_level("3").arg("-Clto=fat").run();
-    rustc().input("main.rs").panic("abort").opt_level("3").arg("-Clto=thin").run();
+    rustc().input("lib.rs").opt_level("3").lto("fat").run();
+    rustc().input("main.rs").panic("abort").opt_level("3").lto("thin").run();
 
     llvm_objdump()
         .input(dynamic_lib_name("main"))

tests/run-make/linker-plugin-lto-fat/rmake.rs

@@ -13,7 +13,10 @@ fn main() {
     rustc()
         .input("main.rs")
         .opt_level("3")
-        .args(&["-Clto=fat", "-Clinker-plugin-lto", "-Zlinker-features=+lld", "-Clink-arg=ir.bc"])
+        .lto("fat")
+        .linker_plugin_lto("on")
+        .link_arg("ir.bc")
+        .arg("-Zlinker-features=+lld")
         .run();
 
     llvm_objdump()