Couple of changes to make it easier to compile rustc for wasm

compiler/rustc_driver_impl/src/lib.rs

@@ -29,13 +29,12 @@ use std::path::PathBuf;
 use std::process::{self, Command, Stdio};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, OnceLock};
-use std::time::{Duration, Instant, SystemTime};
+use std::time::{Instant, SystemTime};
 use std::{env, str};
 
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_codegen_ssa::{CodegenErrors, CodegenResults};
-use rustc_const_eval::CTRL_C_RECEIVED;
 use rustc_data_structures::profiling::{
     TimePassesFormat, get_resident_set_size, print_time_passes_entry,
 };
@@ -1577,8 +1576,8 @@ pub fn install_ctrlc_handler() {
         // time to check CTRL_C_RECEIVED and run its own shutdown logic, but after a short amount
         // of time exit the process. This sleep+exit ensures that even if nobody is checking
         // CTRL_C_RECEIVED, the compiler exits reasonably promptly.
-        CTRL_C_RECEIVED.store(true, Ordering::Relaxed);
-        std::thread::sleep(Duration::from_millis(100));
+        rustc_const_eval::CTRL_C_RECEIVED.store(true, Ordering::Relaxed);
+        std::thread::sleep(std::time::Duration::from_millis(100));
         std::process::exit(1);
     })
     .expect("Unable to install ctrlc handler");

compiler/rustc_fs_util/src/lib.rs

@@ -76,10 +76,14 @@ 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()
 }

src/bootstrap/src/core/builder.rs

@@ -1683,10 +1683,24 @@ impl<'a> Builder<'a> {
         match mode {
             Mode::Std | Mode::ToolBootstrap | Mode::ToolStd => {}
             Mode::Rustc | Mode::Codegen | Mode::ToolRustc => {
-                // Build proc macros both for the host and the target
+                // Build proc macros both for the host and the target unless proc-macros are not
+                // supported by the target.
                 if target != compiler.host && cmd_kind != Kind::Check {
-                    cargo.arg("-Zdual-proc-macros");
-                    rustflags.arg("-Zdual-proc-macros");
+                    let error = command(self.rustc(compiler))
+                        .arg("--target")
+                        .arg(target.rustc_target_arg())
+                        .arg("--print=file-names")
+                        .arg("--crate-type=proc-macro")
+                        .arg("-")
+                        .run_capture(self)
+                        .stderr();
+                    let not_supported = error
+                        .lines()
+                        .any(|line| line.contains("unsupported crate type `proc-macro`"));
+                    if !not_supported {
+                        cargo.arg("-Zdual-proc-macros");
+                        rustflags.arg("-Zdual-proc-macros");
+                    }
                 }
             }
         }

src/bootstrap/src/utils/shared_helpers.rs

@@ -49,6 +49,8 @@ pub fn exe(name: &str, target: &str) -> String {
         format!("{name}.exe")
     } else if target.contains("uefi") {
         format!("{name}.efi")
+    } else if target.contains("wasm") {
+        format!("{name}.wasm")
     } else {
         name.to_string()
     }