Link against lld for linking compiled object files

comment.txt

@@ -24,7 +24,7 @@ WASI_SDK_PATH=`pwd`/wasi-sdk-24.0-x86_64-linux WASI_SYSROOT=`pwd`/wasi-sdk-24.0-
 If you just want to run it, https://github.com/oligamiq/rust_wasm/tree/main/rustc_llvm
 ```
 $ mkdir tmp
-$ echo 'fn main() { println!("Hello World!"); }' | wasmtime run -Sthreads=y -Spreview2=n --dir tmp::/ --dir dist --env RUST_MIN_STACK=16777216 dist/bin/rustc.wasm - --sysroot dist --target wasm32-wasip1-threads -Csave-temps
+$ echo 'fn main() { println!("Hello World!"); }' | wasmtime run -Sthreads=y -Spreview2=n --dir tmp::/ --dir dist --env RUST_MIN_STACK=16777216 dist/bin/rustc.wasm - --sysroot dist --target x86_64-unknown-linux-gnu -Csave-temps
 $ gcc -fuse-ld=lld tmp/rmeta*/lib.rmeta tmp/rust_out.*.o dist/lib/rustlib/x86_64-unknown-linux-gnu/lib/lib*.rlib -o rust_out
 $ ./rust_out
 Hello World!
@@ -33,8 +33,7 @@ Hello World!
 to Wasi
 ```
 $ mkdir tmp
-$ echo 'fn main() { println!("Hello World!"); }' | wasmtime run -Sthreads=y -Spreview2=n --dir tmp::/ --dir dist --env RUST_MIN_STACK=16777216 dist/bin/rustc.wasm - --sysroot dist --target wasm32-wasip1-threads -Csave-temps
-$ wasi-sdk-24.0-x86_64-linux/bin/wasm-ld --shared-memory --max-memory=1073741824 --import-memory --export __main_void -z stack-size=1048576 --stack-first --allow-undefined --no-demangle --import-memory --export-memory --shared-memory dist/lib/rustlib/wasm32-wasip1-threads/lib/self-contained/crt1-command.o tmp/rust_out.*.o dist/lib/rustlib/wasm32-wasip1-threads/lib/lib*.rlib -L dist/lib/rustlib/wasm32-wasip1-threads/lib/self-contained -lc -o rust_out.wasm
-$ wasmtime run -Sthreads=y rust_out.wasm
+$ echo 'fn main() { println!("Hello World!"); }' | wasmtime run -Sthreads=y -Spreview2=n --dir tmp::/ --dir dist --env RUST_MIN_STACK=16777216 dist/bin/rustc.wasm - --sysroot dist --target wasm32-wasip1
+$ wasmtime run tmp/rust_out.wasm
 Hello World!
 ```

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -801,6 +801,29 @@ fn link_natively(
 
     // Invoke the system linker
     info!("{cmd:?}");
+
+    #[cfg(target_os = "wasi")]
+    if matches!(flavor, LinkerFlavor::Gnu(Cc::No, Lld::Yes) | LinkerFlavor::WasmLld(Cc::No)) {
+        extern "C" {
+            fn RustRunLld(
+                argc: std::ffi::c_int,
+                argv: *const *const std::ffi::c_char,
+            ) -> std::ffi::c_int;
+        }
+
+        let cmd = cmd.command();
+        println!("Linking using {cmd:?}");
+        let mut args = cmd
+            .get_args()
+            .map(|arg| std::ffi::CString::new(arg.as_encoded_bytes()).unwrap())
+            .collect::<Vec<_>>();
+        args.insert(0, std::ffi::CString::new(cmd.get_program().as_encoded_bytes()).unwrap());
+        let argv = args.iter().map(|arg| arg.as_ptr()).collect::<Vec<_>>();
+
+        let ret = unsafe { RustRunLld(args.len() as std::ffi::c_int, argv.as_ptr()) };
+        std::process::exit(ret);
+    }
+
     let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
     let unknown_arg_regex =
         Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();

compiler/rustc_fs_util/src/lib.rs

@@ -1,4 +1,3 @@
-#[cfg(any(unix, windows, target_os = "wasi"))]
 use std::ffi::CString;
 use std::path::{absolute, Path, PathBuf};
 use std::{fs, io};
@@ -77,14 +76,18 @@ pub fn link_or_copy<P: AsRef<Path>, Q: AsRef<Path>>(p: P, q: Q) -> io::Result<Li
     }
 }
 
-#[cfg(unix)]
+#[cfg(any(unix, all(target_os = "wasi", target_env = "p1")))]
 pub fn path_to_c_string(p: &Path) -> CString {
     use std::ffi::OsStr;
+    #[cfg(unix)]
     use std::os::unix::ffi::OsStrExt;
+    #[cfg(all(target_os = "wasi", target_env = "p1"))]
+    use std::os::wasi::ffi::OsStrExt;
+
     let p: &OsStr = p.as_ref();
     CString::new(p.as_bytes()).unwrap()
 }
-#[cfg(any(windows, target_os = "wasi"))]
+#[cfg(windows)]
 pub fn path_to_c_string(p: &Path) -> CString {
     CString::new(p.to_str().unwrap()).unwrap()
 }

compiler/rustc_llvm/build.rs

@@ -221,6 +221,7 @@ fn main() {
         .file("llvm-wrapper/CoverageMappingWrapper.cpp")
         .file("llvm-wrapper/SymbolWrapper.cpp")
         .file("llvm-wrapper/Linker.cpp")
+        .file("llvm-wrapper/LLD.cpp")
         .cpp(true)
         .cpp_link_stdlib(None) // we handle this below
         .compile("llvm-wrapper");
@@ -328,6 +329,11 @@ fn main() {
         println!("cargo:rustc-link-lib={kind}={name}");
     }
 
+    println!("cargo:rustc-link-lib=static=LLVMOption");
+    println!("cargo:rustc-link-lib=static=lldCommon");
+    println!("cargo:rustc-link-lib=static=lldELF");
+    println!("cargo:rustc-link-lib=static=lldWasm");
+
     // LLVM ldflags
     //
     // If we're a cross-compile of LLVM then unfortunately we can't trust these

compiler/rustc_llvm/llvm-wrapper/LLD.cpp

@@ -0,0 +1,11 @@
+#include "lld/Common/Driver.h"
+
+LLD_HAS_DRIVER(elf)
+LLD_HAS_DRIVER(wasm)
+
+extern "C" int RustRunLld(int argc, char **argv) {
+    llvm::ArrayRef<const char *> args(argv, argv + argc);
+    auto r = lld::lldMain(args, llvm::outs(), llvm::errs(),
+                         {{lld::Gnu, &lld::elf::link}, {lld::Wasm, &lld::wasm::link}});
+    return r.retCode;
+}

compiler/rustc_target/src/spec/targets/wasm32_wasip1.rs

@@ -23,7 +23,7 @@ pub(crate) fn target() -> Target {
     options.post_link_objects_self_contained = crt_objects::post_wasi_self_contained();
 
     // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
-    options.link_self_contained = LinkSelfContainedDefault::False;
+    options.link_self_contained = LinkSelfContainedDefault::True;
 
     // Right now this is a bit of a workaround but we're currently saying that
     // the target by default has a static crt which we're taking as a signal

compiler/rustc_target/src/spec/targets/wasm32_wasip1_threads.rs

@@ -41,7 +41,7 @@ pub(crate) fn target() -> Target {
     options.post_link_objects_self_contained = crt_objects::post_wasi_self_contained();
 
     // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
-    options.link_self_contained = LinkSelfContainedDefault::False;
+    options.link_self_contained = LinkSelfContainedDefault::True;
 
     // Right now this is a bit of a workaround but we're currently saying that
     // the target by default has a static crt which we're taking as a signal

config.llvm.toml

@@ -10,8 +10,6 @@ debug = false
 debuginfo-level = 0
 
 [llvm]
-cflags = "-march=native"
-cxxflags = "-march=native"
 static-libstdcpp = true
 ninja = false
 download-ci-llvm = false
@@ -24,7 +22,7 @@ docs = false
 extended = false
 tools = []
 host = ["wasm32-wasip1-threads"]
-target = ["x86_64-unknown-linux-gnu", "wasm32-wasip1-threads"]
+target = ["x86_64-unknown-linux-gnu", "wasm32-wasip1"]
 cargo-native-static = true
 
 [install]

src/bootstrap/src/core/build_steps/llvm.rs

@@ -515,6 +515,8 @@ impl Step for Llvm {
             return res;
         }
 
+        cfg.define("LLVM_ENABLE_PROJECTS", "lld");
+
         if target.contains("wasi") {
             let wasi_sysroot = env::var("WASI_SYSROOT").expect("WASI_SYSROOT not set");
             let wasi_sdk_path = std::path::Path::new(&wasi_sysroot)
@@ -669,7 +671,6 @@ impl Step for Llvm {
                 .define("LLVM_TOOL_XCODE_TOOLCHAIN_BUILD", "OFF")
                 .define("LLVM_TOOL_YAML2OBJ_BUILD", "OFF")
                 // .define("LLVM_ENABLE_PROJECTS", "clang;lld")
-                .define("LLVM_ENABLE_PROJECTS", "")
                 // .define("CLANG_ENABLE_ARCMT", "OFF")
                 // .define("CLANG_ENABLE_STATIC_ANALYZER", "OFF")
                 // .define("CLANG_INCLUDE_TESTS", "OFF")
@@ -1211,6 +1212,9 @@ impl Step for Lld {
             // `$ORIGIN` would otherwise be expanded when the `LdFlags` are passed verbatim to
             // cmake.
             ldflags.push_all("-Wl,-rpath,'$ORIGIN/../../../'");
+        } else {
+            // CMake defaults to building executables with rpath enabled.
+            cfg.define("CMAKE_SKIP_RPATH", "ON");
         }
 
         configure_cmake(builder, target, &mut cfg, true, ldflags, &[]);

src/bootstrap/src/core/builder.rs

@@ -2601,6 +2601,12 @@ impl Cargo {
             }
         }
 
+        if target.contains("wasi") {
+            // link-self-contained needs lld to be present, but getting it to
+            // link for wasi is a bit difficult.
+            self.rustflags.arg("-Clink-self-contained=no");
+        }
+
         for arg in linker_args(builder, compiler.host, LldThreads::Yes) {
             self.hostflags.arg(&arg);
         }