From 3fce7045cb9b4cbd892f8a5189e3849478791eea Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Thu, 26 Sep 2024 18:24:29 +0200
Subject: [PATCH] Link against lld for linking compiled object files

---
 compiler/rustc_codegen_ssa/src/back/link.rs | 23 +++++++++++++++++++++
 compiler/rustc_llvm/build.rs                |  6 ++++++
 compiler/rustc_llvm/llvm-wrapper/LLD.cpp    | 11 ++++++++++
 config.llvm.toml                            |  2 +-
 src/bootstrap/src/core/build_steps/llvm.rs  |  3 ++-
 5 files changed, 43 insertions(+), 2 deletions(-)
 create mode 100644 compiler/rustc_llvm/llvm-wrapper/LLD.cpp

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index af7f9d0f34af1..0b3c202ec48a2 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/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();
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index abc8f8bf974cc..a2829032fd554 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/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
diff --git a/compiler/rustc_llvm/llvm-wrapper/LLD.cpp b/compiler/rustc_llvm/llvm-wrapper/LLD.cpp
new file mode 100644
index 0000000000000..182ea9534b31d
--- /dev/null
+++ b/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;
+}
diff --git a/config.llvm.toml b/config.llvm.toml
index 1a64513e1ed48..ababcbb76a0dc 100644
--- a/config.llvm.toml
+++ b/config.llvm.toml
@@ -24,7 +24,7 @@ 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]
diff --git a/src/bootstrap/src/core/build_steps/llvm.rs b/src/bootstrap/src/core/build_steps/llvm.rs
index 3c1acb2cf1f00..24f6cf965bf43 100644
--- a/src/bootstrap/src/core/build_steps/llvm.rs
+++ b/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")