t27c --backend ml: thin glue for host file I/O (Closes #10085)

bootstrap/src/compiler.rs

@@ -7405,6 +7405,19 @@ the parser used to read it as `{}` followed by a negation",
 // Code Generator
 // ============================================================================
 
+/// The whole host syscall layer (Linux): open/read/write/close on a real fd, return the count or -errno.
+const HOST_IO_ZIG: &str = r#"
+const __t27_posix = @import("std").posix;
+fn __t27_host_ret(r: usize) i32 { return @truncate(@as(isize, @bitCast(r))); }
+fn __t27_host_open(path: [*:0]const u8, mode: i32) i32 {
+    const f: __t27_posix.O = if (mode != 0) .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true } else .{};
+    return __t27_host_ret(__t27_posix.system.open(path, f, 0o644));
+}
+fn __t27_host_read(fd: i32, b: []u8) i32 { return __t27_host_ret(__t27_posix.system.read(fd, b.ptr, b.len)); }
+fn __t27_host_write(fd: i32, b: []const u8) i32 { return __t27_host_ret(__t27_posix.system.write(fd, b.ptr, b.len)); }
+fn __t27_host_close(fd: i32) i32 { return __t27_host_ret(__t27_posix.system.close(fd)); }
+"#;
+
 pub struct Codegen {
     output: String,
     indent: u32,
@@ -8290,6 +8303,12 @@ impl Codegen {
                 self.gen_decl(decl);
             }
         }
+        // `--backend ml`: the host's file syscalls, only for a spec that calls them.
+        let mut host = false;
+        Self::visit_calls(&ast.children, &mut |c| host |= matches!(c.name.as_str(), "host_open" | "host_read" | "host_write" | "host_close"));
+        if host {
+            self.write(HOST_IO_ZIG);
+        }
     }
 
     /// Generate Zig code with project-aware import resolution.
@@ -10448,6 +10467,10 @@ impl Codegen {
                         "sin" => Some("@sin"),
                         "cos" => Some("@cos"),
                         "tanh" => Some("std.math.tanh"),
+                        "host_open" => Some("__t27_host_open"),
+                        "host_read" => Some("__t27_host_read"),
+                        "host_write" => Some("__t27_host_write"),
+                        "host_close" => Some("__t27_host_close"),
                         _ => None,
                     };
                     if let Some(b) = builtin {

bootstrap/src/main.rs

@@ -1336,7 +1336,7 @@ enum Commands {
     Compile {
         /// Input file path
         input: String,
-        /// Backend: zig, verilog, or c
+        /// Backend: zig, verilog, c, or ml
         #[arg(long, default_value = "zig")]
         backend: String,
         /// Output file path (default: input with backend extension)
@@ -6220,7 +6220,10 @@ fn compile_source(source: &str, backend: &str) -> Result<String, String> {
 
 fn run_compile(input_path: &str, backend: &str, output: Option<&str>) -> anyhow::Result<()> {
     let path = Path::new(input_path);
-    let source = fs::read_to_string(path)?;
+    let mut source = fs::read_to_string(path)?;
+    if backend == "ml" {
+        source = use_resolve::resolve(path, &source);
+    }
 
     let ast = compiler::Compiler::parse_ast(&source)
         .map_err(|e| anyhow::anyhow!("Parse error: {}", e))?;
@@ -6269,6 +6272,13 @@ fn run_compile(input_path: &str, backend: &str, output: Option<&str>) -> anyhow:
     }
     fs::write(&out_path, &code)?;
     println!("wrote {}", out_path.display());
+    if backend == "ml" {
+        let exe = out_path.with_extension("");
+        let mut zig = std::process::Command::new("zig");
+        zig.arg("build-exe").arg(&out_path).arg(format!("-femit-bin={}", exe.display()));
+        anyhow::ensure!(zig.status()?.success(), "zig build-exe failed");
+        println!("built {}", exe.display());
+    }
     Ok(())
 }