Emerge Yul recompiler (#1)

Provide a modified (and incomplete) version of ZKSync zksolc that can compile the most basic contracts

crates/linker/src/lib.rs

@@ -0,0 +1,77 @@
+use std::{env, ffi::CString, fs};
+
+use lld_sys::LLDELFLink;
+use revive_builtins::COMPILER_RT;
+
+const LINKER_SCRIPT: &str = r#"
+SECTIONS {
+    .text : { KEEP(*(.text.polkavm_export)) *(.text .text.*) }
+}"#;
+
+fn invoke_lld(cmd_args: &[&str]) -> bool {
+    let c_strings = cmd_args
+        .iter()
+        .map(|arg| CString::new(*arg).expect("ld.lld args should not contain null bytes"))
+        .collect::<Vec<_>>();
+
+    let args: Vec<*const libc::c_char> = c_strings.iter().map(|arg| arg.as_ptr()).collect();
+
+    unsafe { LLDELFLink(args.as_ptr(), args.len()) == 0 }
+}
+
+fn polkavm_linker<T: AsRef<[u8]>>(code: T) -> anyhow::Result<Vec<u8>> {
+    let mut config = polkavm_linker::Config::default();
+    config.set_strip(true);
+
+    polkavm_linker::program_from_elf(config, code.as_ref())
+        .map(|blob| blob.as_bytes().to_vec())
+        .map_err(|reason| anyhow::anyhow!("polkavm linker failed: {}", reason))
+}
+
+pub fn link<T: AsRef<[u8]>>(input: T) -> anyhow::Result<Vec<u8>> {
+    let dir = tempfile::tempdir().expect("failed to create temp directory for linking");
+    let output_path = dir.path().join("out.so");
+    let object_path = dir.path().join("out.o");
+    let linker_script_path = dir.path().join("linker.ld");
+    let compiler_rt_path = dir.path().join("libclang_rt.builtins-riscv32.a");
+
+    fs::write(&object_path, input).map_err(|msg| anyhow::anyhow!("{msg} {object_path:?}"))?;
+
+    if env::var("PVM_LINKER_DUMP_OBJ").is_ok() {
+        fs::copy(&object_path, "/tmp/out.o")?;
+    }
+
+    fs::write(&linker_script_path, LINKER_SCRIPT)
+        .map_err(|msg| anyhow::anyhow!("{msg} {linker_script_path:?}"))?;
+
+    fs::write(&compiler_rt_path, COMPILER_RT)
+        .map_err(|msg| anyhow::anyhow!("{msg} {compiler_rt_path:?}"))?;
+
+    let ld_args = [
+        "ld.lld",
+        "--error-limit=0",
+        "--relocatable",
+        "--emit-relocs",
+        "--no-relax",
+        "--gc-sections",
+        "--library-path",
+        dir.path().to_str().expect("should be utf8"),
+        "--library",
+        "clang_rt.builtins-riscv32",
+        linker_script_path.to_str().expect("should be utf8"),
+        object_path.to_str().expect("should be utf8"),
+        "-o",
+        output_path.to_str().expect("should be utf8"),
+    ];
+
+    if invoke_lld(&ld_args) {
+        return Err(anyhow::anyhow!("ld.lld failed"));
+    }
+
+    if env::var("PVM_LINKER_DUMP_SO").is_ok() {
+        fs::copy(&output_path, "/tmp/out.so")?;
+    };
+
+    let blob = fs::read(&output_path)?;
+    polkavm_linker(blob)
+}