Resurrect asm comment support

Merged: https://github.com/ruby/ruby/pull/13131

zjit.c

@@ -156,6 +156,18 @@ rb_zjit_reserve_addr_space(uint32_t mem_size)
 #endif
 }
 
+unsigned long
+rb_RSTRING_LEN(VALUE str)
+{
+    return RSTRING_LEN(str);
+}
+
+char *
+rb_RSTRING_PTR(VALUE str)
+{
+    return RSTRING_PTR(str);
+}
+
 void
 rb_zjit_compile_iseq(const rb_iseq_t *iseq, rb_execution_context_t *ec, bool jit_exception)
 {

zjit/src/asm/mod.rs

@@ -1,3 +1,4 @@
+use std::collections::BTreeMap;
 //use std::fmt;
 use std::rc::Rc;
 use std::cell::RefCell;
@@ -34,6 +35,12 @@ pub struct CodeBlock {
     // Current writing position
     write_pos: usize,
 
+    // A switch for keeping comments. They take up memory.
+    keep_comments: bool,
+
+    // Comments for assembly instructions, if that feature is enabled
+    asm_comments: BTreeMap<usize, Vec<String>>,
+
     // Set if the CodeBlock is unable to output some instructions,
     // for example, when there is not enough space or when a jump
     // target is too far away.
@@ -42,14 +49,37 @@ pub struct CodeBlock {
 
 impl CodeBlock {
     /// Make a new CodeBlock
-    pub fn new(mem_block: Rc<RefCell<VirtualMem>>) -> Self {
+    pub fn new(mem_block: Rc<RefCell<VirtualMem>>, keep_comments: bool) -> Self {
         Self {
             mem_block,
             write_pos: 0,
+            keep_comments,
+            asm_comments: BTreeMap::new(),
             dropped_bytes: false,
         }
     }
 
+    /// Add an assembly comment if the feature is on.
+    pub fn add_comment(&mut self, comment: &str) {
+        if !self.keep_comments {
+            return;
+        }
+
+        let cur_ptr = self.get_write_ptr().raw_addr(self);
+
+        // If there's no current list of comments for this line number, add one.
+        let this_line_comments = self.asm_comments.entry(cur_ptr).or_default();
+
+        // Unless this comment is the same as the last one at this same line, add it.
+        if this_line_comments.last().map(String::as_str) != Some(comment) {
+            this_line_comments.push(comment.to_string());
+        }
+    }
+
+    pub fn comments_at(&self, pos: usize) -> Option<&Vec<String>> {
+        self.asm_comments.get(&pos)
+    }
+
     pub fn get_write_pos(&self) -> usize {
         self.write_pos
     }

zjit/src/backend/arm64/mod.rs

@@ -935,9 +935,8 @@ impl Assembler
             let mut insn_gc_offsets: Vec<u32> = Vec::new();
 
             match insn {
-                Insn::Comment(_text) => {
+                Insn::Comment(text) => {
-                    //cb.add_comment(text);
+                    cb.add_comment(text);
-                    unimplemented!("comments are not supported yet");
                 },
                 Insn::Label(_target) => {
                     //cb.write_label(target.unwrap_label_idx());

zjit/src/backend/mod.rs

@@ -1657,7 +1657,7 @@ impl Assembler
         #[cfg(feature = "disasm")]
         if get_option!(dump_disasm) {
             let end_addr = cb.get_write_ptr();
-            let disasm = crate::disasm::disasm_addr_range(start_addr.raw_ptr(cb) as usize, end_addr.raw_ptr(cb) as usize);
+            let disasm = crate::disasm::disasm_addr_range(cb, start_addr.raw_ptr(cb) as usize, end_addr.raw_ptr(cb) as usize);
             println!("{}", disasm);
         }
         ret
@@ -2153,16 +2153,14 @@ impl Assembler {
 
 /// Macro to use format! for Insn::Comment, which skips a format! call
 /// when not dumping disassembly.
-/*
 macro_rules! asm_comment {
     ($asm:expr, $($fmt:tt)*) => {
-        if $crate::options::get_option_ref!(dump_disasm).is_some() {
+        if $crate::options::get_option!(dump_disasm) {
             $asm.push_insn(Insn::Comment(format!($($fmt)*)));
         }
     };
 }
 pub(crate) use asm_comment;
-*/
 
 #[cfg(test)]
 mod tests {

zjit/src/backend/x86_64/mod.rs

@@ -477,9 +477,8 @@ impl Assembler
             let mut insn_gc_offsets: Vec<u32> = Vec::new();
 
             match insn {
-                Insn::Comment(_text) => {
+                Insn::Comment(text) => {
-                    unimplemented!("comments are not supported yet");
+                    cb.add_comment(text);
-                    //cb.add_comment(text);
                 },
 
                 // Write the label at the current position

zjit/src/codegen.rs

@@ -10,10 +10,10 @@ use crate::{
 use crate::get_option;
 
 /// Compile SSA IR into machine code
-pub fn gen_function(cb: &mut CodeBlock, function: &Function) -> Option<CodePtr> {
+pub fn gen_function(cb: &mut CodeBlock, function: &Function, iseq: IseqPtr) -> Option<CodePtr> {
     // Set up special registers
     let mut asm = Assembler::new();
-    gen_entry_prologue(&mut asm);
+    gen_entry_prologue(&mut asm, iseq);
 
     // Compile each instruction in the IR
     for insn in function.insns.iter() {
@@ -28,22 +28,15 @@ pub fn gen_function(cb: &mut CodeBlock, function: &Function) -> Option<CodePtr>
     }
 
     // Generate code if everything can be compiled
-    let start_ptr = cb.get_write_ptr();
+    let start_ptr = asm.compile(cb).map(|(start_ptr, _)| start_ptr);
-    asm.compile_with_regs(cb, Assembler::get_alloc_regs()); // TODO: resurrect cache busting for arm64
     cb.mark_all_executable();
 
-    #[cfg(feature = "disasm")]
+    start_ptr
-    if get_option!(dump_disasm) {
-        let end_ptr = cb.get_write_ptr();
-        let disasm = crate::disasm::disasm_addr_range(start_ptr.raw_ptr(cb) as usize, end_ptr.raw_ptr(cb) as usize);
-        println!("{}", disasm);
-    }
-
-    Some(start_ptr)
 }
 
 /// Compile an interpreter entry block to be inserted into an ISEQ
-fn gen_entry_prologue(asm: &mut Assembler) {
+fn gen_entry_prologue(asm: &mut Assembler, iseq: IseqPtr) {
+    asm_comment!(asm, "YJIT entry point: {}", iseq_get_location(iseq, 0));
     asm.frame_setup();
 
     // Save the registers we'll use for CFP, EP, SP

zjit/src/cruby.rs

@@ -630,6 +630,44 @@ pub fn cstr_to_rust_string(c_char_ptr: *const c_char) -> Option<String> {
     }
 }
 
+// Location is the file defining the method, colon, method name.
+// Filenames are sometimes internal strings supplied to eval,
+// so be careful with them.
+pub fn iseq_get_location(iseq: IseqPtr, pos: u16) -> String {
+    let iseq_label = unsafe { rb_iseq_label(iseq) };
+    let iseq_path = unsafe { rb_iseq_path(iseq) };
+    let iseq_lineno = unsafe { rb_iseq_line_no(iseq, pos as usize) };
+
+    let mut s = if iseq_label == Qnil {
+        "None".to_string()
+    } else {
+        ruby_str_to_rust(iseq_label)
+    };
+    s.push_str("@");
+    if iseq_path == Qnil {
+        s.push_str("None");
+    } else {
+        s.push_str(&ruby_str_to_rust(iseq_path));
+    }
+    s.push_str(":");
+    s.push_str(&iseq_lineno.to_string());
+    s
+}
+
+
+// Convert a CRuby UTF-8-encoded RSTRING into a Rust string.
+// This should work fine on ASCII strings and anything else
+// that is considered legal UTF-8, including embedded nulls.
+fn ruby_str_to_rust(v: VALUE) -> String {
+    let str_ptr = unsafe { rb_RSTRING_PTR(v) } as *mut u8;
+    let str_len: usize = unsafe { rb_RSTRING_LEN(v) }.try_into().unwrap();
+    let str_slice: &[u8] = unsafe { std::slice::from_raw_parts(str_ptr, str_len) };
+    match String::from_utf8(str_slice.to_vec()) {
+        Ok(utf8) => utf8,
+        Err(_) => String::new(),
+    }
+}
+
 /// A location in Rust code for integrating with debugging facilities defined in C.
 /// Use the [src_loc!] macro to crate an instance.
 pub struct SourceLocation {

zjit/src/cruby_bindings.inc.rs

@@ -908,6 +908,8 @@ extern "C" {
     pub fn rb_jit_cont_each_iseq(callback: rb_iseq_callback, data: *mut ::std::os::raw::c_void);
     pub fn rb_zjit_get_page_size() -> u32;
     pub fn rb_zjit_reserve_addr_space(mem_size: u32) -> *mut u8;
+    pub fn rb_RSTRING_LEN(str_: VALUE) -> ::std::os::raw::c_ulong;
+    pub fn rb_RSTRING_PTR(str_: VALUE) -> *mut ::std::os::raw::c_char;
     pub fn rb_iseq_encoded_size(iseq: *const rb_iseq_t) -> ::std::os::raw::c_uint;
     pub fn rb_iseq_opcode_at_pc(iseq: *const rb_iseq_t, pc: *const VALUE) -> ::std::os::raw::c_int;
     pub fn rb_iseq_pc_at_idx(iseq: *const rb_iseq_t, insn_idx: u32) -> *mut VALUE;

zjit/src/disasm.rs

@@ -1,5 +1,9 @@
-#[cfg(feature = "disasm")]
+use crate::asm::CodeBlock;
-pub fn disasm_addr_range(start_addr: usize, end_addr: usize) -> String {
+
+pub const BOLD_BEGIN: &str = "\x1b[1m";
+pub const BOLD_END: &str = "\x1b[22m";
+
+pub fn disasm_addr_range(cb: &CodeBlock, start_addr: usize, end_addr: usize) -> String {
     use std::fmt::Write;
 
     let mut out = String::from("");
@@ -34,7 +38,12 @@ pub fn disasm_addr_range(start_addr: usize, end_addr: usize) -> String {
 
     // For each instruction in this block
     for insn in insns.as_ref() {
-        // TODO: support comments
+        // Comments for this block
+        if let Some(comment_list) = cb.comments_at(insn.address() as usize) {
+            for comment in comment_list {
+                writeln!(&mut out, "  {BOLD_BEGIN}# {comment}{BOLD_END}").unwrap();
+            }
+        }
         writeln!(&mut out, "  {insn}").unwrap();
     }
 

zjit/src/lib.rs

@@ -10,6 +10,7 @@ mod cast;
 mod virtualmem;
 mod asm;
 mod backend;
+#[cfg(feature = "disasm")]
 mod disasm;
 mod options;
 
@@ -93,7 +94,7 @@ pub extern "C" fn rb_zjit_iseq_gen_entry_point(iseq: IseqPtr, _ec: EcPtr) -> *co
 
     // Compile SSA IR into machine code
     let cb = ZJITState::get_code_block();
-    match gen_function(cb, &ssa) {
+    match gen_function(cb, &ssa, iseq) {
         Some(start_ptr) => start_ptr.raw_ptr(cb),
 
         // Compilation failed, continue executing in the interpreter only

zjit/src/state.rs

@@ -50,7 +50,7 @@ impl ZJITState {
             );
             let mem_block = Rc::new(RefCell::new(mem_block));
 
-            CodeBlock::new(mem_block.clone())
+            CodeBlock::new(mem_block.clone(), options.dump_disasm)
         };
         #[cfg(test)]
         let cb = CodeBlock::new_dummy();