[cc] improve assembly header comments

Author: jgarzik

cc/arch/aarch64/codegen.rs

@@ -1102,10 +1102,10 @@ impl Aarch64CodeGen {
     }
 
     fn emit_header(&mut self) {
-        // Header comment and initial text section
-        self.push_lir(Aarch64Inst::Directive(Directive::Comment(
-            "Generated by pcc (AArch64)".into(),
-        )));
+        // Header comments with compiler and target info (GCC-style)
+        for comment in crate::arch::codegen::generate_header_comments(&self.target) {
+            self.push_lir(Aarch64Inst::Directive(Directive::Comment(comment)));
+        }
         self.push_lir(Aarch64Inst::Directive(Directive::Text));
     }
 

cc/arch/codegen.rs

@@ -12,6 +12,40 @@
 use crate::ir::Module;
 use crate::target::Target;
 
+/// pcc version string for assembly header
+pub const PCC_VERSION: &str = env!("CARGO_PKG_VERSION");
+
+/// Generate header comment lines for assembly output (GCC-style)
+/// Returns a vector of comment strings to be emitted
+pub fn generate_header_comments(target: &Target) -> Vec<String> {
+    let mut comments = Vec::new();
+
+    // Compiler identification
+    comments.push(format!("Generated by pcc {}", PCC_VERSION));
+
+    // Target triple (normalized format)
+    let os_triple = match target.os {
+        crate::target::Os::Linux => "unknown-linux-gnu",
+        crate::target::Os::MacOS => "apple-darwin",
+        crate::target::Os::FreeBSD => "unknown-freebsd",
+    };
+    comments.push(format!("Target: {}-{}", target.arch, os_triple));
+
+    // ABI info
+    comments.push(format!(
+        "ABI: LP64, pointer={}bit, long={}bit, char={}",
+        target.pointer_width,
+        target.long_width,
+        if target.char_signed {
+            "signed"
+        } else {
+            "unsigned"
+        }
+    ));
+
+    comments
+}
+
 /// Trait for architecture-specific code generators
 pub trait CodeGenerator {
     /// Generate assembly code for the given IR module

cc/arch/x86_64/codegen.rs

@@ -949,10 +949,10 @@ impl X86_64CodeGen {
     }
 
     fn emit_header(&mut self) {
-        // Header comment and initial text section
-        self.push_lir(X86Inst::Directive(Directive::Comment(
-            "Generated by pcc (x86-64)".into(),
-        )));
+        // Header comments with compiler and target info (GCC-style)
+        for comment in crate::arch::codegen::generate_header_comments(&self.target) {
+            self.push_lir(X86Inst::Directive(Directive::Comment(comment)));
+        }
         self.push_lir(X86Inst::Directive(Directive::Text));
     }