Auto merge of #57514 - michaelwoerister:xlto-tests, r=<try>

compiletest: Support opt-in Clang-based run-make tests and use them for testing xLTO.

Some cross-language run-make tests need a Clang compiler that matches the LLVM version of `rustc`. Since such a compiler usually isn't available these tests (marked with the `needs-matching-clang`
directive) are ignored by default.

For some CI jobs we do need these tests to run unconditionally though. In order to support this a `--force-clang-based-tests` flag is added to compiletest. If this flag is specified, `compiletest` will fail if it can't detect an appropriate version of Clang.

@rust-lang/infra The PR doesn't yet enable the tests yet. Do you have any recommendation for which jobs to enable them?

cc #57438

r? @alexcrichton

.travis.yml

@@ -19,7 +19,7 @@ matrix:
     - env: IMAGE=x86_64-gnu-llvm-6.0 RUST_BACKTRACE=1
       if: type = pull_request OR branch = auto
 
-    - env: IMAGE=dist-x86_64-linux DEPLOY=1
+    - env: IMAGE=x86_64-gnu-debug
       if: branch = try OR branch = auto
 
     # "alternate" deployments, these are "nightlies" but have LLVM assertions

src/bootstrap/test.rs

@@ -1108,9 +1108,7 @@ impl Step for Compiletest {
         };
         let lldb_exe = if builder.config.lldb_enabled && !target.contains("emscripten") {
             // Test against the lldb that was just built.
-            builder.llvm_out(target)
-                .join("bin")
-                .join("lldb")
+            builder.llvm_out(target).join("bin").join("lldb")
         } else {
             PathBuf::from("lldb")
         };
@@ -1127,6 +1125,26 @@ impl Step for Compiletest {
             }
         }
 
+        if let Some(var) = env::var_os("RUSTBUILD_FORCE_CLANG_BASED_TESTS") {
+            match &var.to_string_lossy().to_lowercase()[..] {
+                "1" | "yes" | "on" => {
+                    assert!(builder.config.lldb_enabled,
+                        "RUSTBUILD_FORCE_CLANG_BASED_TESTS needs Clang/LLDB to \
+                         be built.");
+                    let clang_exe = builder.llvm_out(target).join("bin").join("clang");
+                    cmd.arg("--run-clang-based-tests-with").arg(clang_exe);
+                }
+                "0" | "no" | "off" => {
+                    // Nothing to do.
+                }
+                other => {
+                    // Let's make sure typos don't get unnoticed
+                    panic!("Unrecognized option '{}' set in \
+                            RUSTBUILD_FORCE_CLANG_BASED_TESTS", other);
+                }
+            }
+        }
+
         // Get paths from cmd args
         let paths = match &builder.config.cmd {
             Subcommand::Test { ref paths, .. } => &paths[..],

src/ci/docker/x86_64-gnu-debug/Dockerfile

@@ -7,6 +7,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   curl \
   ca-certificates \
   python2.7 \
+  python2.7-dev \
   git \
   cmake \
   sudo \
@@ -16,9 +17,15 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+ENV RUSTBUILD_FORCE_CLANG_BASED_TESTS 1
 ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
+
 ENV RUST_CONFIGURE_ARGS \
       --build=x86_64-unknown-linux-gnu \
       --enable-debug \
+      --enable-lld \
+      --enable-lldb \
       --enable-optimize
-ENV SCRIPT python2.7 ../x.py build
+ENV SCRIPT \
+  python2.7 ../x.py build && \
+  python2.7 ../x.py test src/test/run-make-fulldeps --test-args clang

src/test/run-make-fulldeps/cross-lang-lto-clang/Makefile

@@ -0,0 +1,25 @@
+# needs-matching-clang
+
+# This test makes sure that cross-language inlining actually works by checking
+# the generated machine code.
+
+-include ../tools.mk
+
+all: cpp-executable rust-executable
+
+cpp-executable:
+	$(RUSTC) -Zcross-lang-lto=on -o $(TMPDIR)/librustlib-xlto.a -Copt-level=2 -Ccodegen-units=1 ./rustlib.rs
+	$(CLANG) -flto=thin -fuse-ld=lld -L $(TMPDIR) -lrustlib-xlto -o $(TMPDIR)/cmain ./cmain.c -O3
+	# Make sure we don't find a call instruction to the function we expect to
+	# always be inlined.
+	llvm-objdump -d $(TMPDIR)/cmain | $(CGREP) -v -e "call.*rust_always_inlined"
+	# As a sanity check, make sure we do find a call instruction to a
+	# non-inlined function
+	llvm-objdump -d $(TMPDIR)/cmain | $(CGREP) -e "call.*rust_never_inlined"
+
+rust-executable:
+	$(CLANG) ./clib.c -flto=thin -c -o $(TMPDIR)/clib.o -O2
+	(cd $(TMPDIR); $(AR) crus ./libxyz.a ./clib.o)
+	$(RUSTC) -Zcross-lang-lto=on -L$(TMPDIR) -Copt-level=2 -Clinker=$(CLANG) -Clink-arg=-fuse-ld=lld ./main.rs -o $(TMPDIR)/rsmain
+	llvm-objdump -d $(TMPDIR)/rsmain | $(CGREP) -e "call.*c_never_inlined"
+	llvm-objdump -d $(TMPDIR)/rsmain | $(CGREP) -v -e "call.*c_always_inlined"

src/test/run-make-fulldeps/cross-lang-lto-clang/clib.c

@@ -0,0 +1,9 @@
+#include <stdint.h>
+
+uint32_t c_always_inlined() {
+    return 1234;
+}
+
+__attribute__((noinline)) uint32_t c_never_inlined() {
+    return 12345;
+}

src/test/run-make-fulldeps/cross-lang-lto-clang/cmain.c

@@ -0,0 +1,12 @@
+#include <stdint.h>
+
+// A trivial function defined in Rust, returning a constant value. This should
+// always be inlined.
+uint32_t rust_always_inlined();
+
+
+uint32_t rust_never_inlined();
+
+int main(int argc, char** argv) {
+    return rust_never_inlined() + rust_always_inlined();
+}

src/test/run-make-fulldeps/cross-lang-lto-clang/main.rs

@@ -0,0 +1,11 @@
+#[link(name = "xyz")]
+extern "C" {
+    fn c_always_inlined() -> u32;
+    fn c_never_inlined() -> u32;
+}
+
+fn main() {
+    unsafe {
+        println!("blub: {}", c_always_inlined() + c_never_inlined());
+    }
+}

src/test/run-make-fulldeps/cross-lang-lto-clang/rustlib.rs

@@ -0,0 +1,12 @@
+#![crate_type="staticlib"]
+
+#[no_mangle]
+pub extern "C" fn rust_always_inlined() -> u32 {
+    42
+}
+
+#[no_mangle]
+#[inline(never)]
+pub extern "C" fn rust_never_inlined() -> u32 {
+    421
+}

src/tools/compiletest/src/common.rs

@@ -144,6 +144,10 @@ pub struct Config {
     /// (or, alternatively, to silently run them like regular run-pass tests).
     pub force_valgrind: bool,
 
+    /// The path to the Clang executable to run Clang-based tests with. If
+    /// `None` then these tests will be ignored.
+    pub run_clang_based_tests_with: Option<String>,
+
     /// The directory containing the tests to run
     pub src_base: PathBuf,
 

src/tools/compiletest/src/header.rs

@@ -111,6 +111,11 @@ impl EarlyProps {
                 if ignore_llvm(config, ln) {
                     props.ignore = Ignore::Ignore;
                 }
+
+                if config.run_clang_based_tests_with.is_none() &&
+                   config.parse_needs_matching_clang(ln) {
+                    props.ignore = Ignore::Ignore;
+                }
             }
 
             if (config.mode == common::DebugInfoGdb || config.mode == common::DebugInfoBoth) &&
@@ -705,6 +710,10 @@ impl Config {
         }
     }
 
+    fn parse_needs_matching_clang(&self, line: &str) -> bool {
+        self.parse_name_directive(line, "needs-matching-clang")
+    }
+
     /// Parses a name-value directive which contains config-specific information, e.g., `ignore-x86`
     /// or `normalize-stderr-32bit`.
     fn parse_cfg_name_directive(&self, line: &str, prefix: &str) -> ParsedNameDirective {

src/tools/compiletest/src/main.rs

@@ -108,6 +108,12 @@ pub fn parse_config(args: Vec<String>) -> Config {
             "force-valgrind",
             "fail if Valgrind tests cannot be run under Valgrind",
         )
+        .optopt(
+            "",
+            "run-clang-based-tests-with",
+            "path to Clang executable",
+            "PATH",
+        )
         .optopt(
             "",
             "llvm-filecheck",
@@ -298,6 +304,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         docck_python: matches.opt_str("docck-python").unwrap(),
         valgrind_path: matches.opt_str("valgrind-path"),
         force_valgrind: matches.opt_present("force-valgrind"),
+        run_clang_based_tests_with: matches.opt_str("run-clang-based-tests-with"),
         llvm_filecheck: matches.opt_str("llvm-filecheck").map(|s| PathBuf::from(&s)),
         src_base,
         build_base: opt_path(matches, "build-base"),

src/tools/compiletest/src/runtest.rs

@@ -2587,6 +2587,10 @@ impl<'test> TestCx<'test> {
             cmd.env("RUSTC_LINKER", linker);
         }
 
+        if let Some(ref clang) = self.config.run_clang_based_tests_with {
+            cmd.env("CLANG", clang);
+        }
+
         // We don't want RUSTFLAGS set from the outside to interfere with
         // compiler flags set in the test cases:
         cmd.env_remove("RUSTFLAGS");