Implement asm comments

lib/mjit/insn_compiler.rb

@@ -19,14 +19,14 @@ def putnil(jit, ctx, asm)
     def leave(jit, ctx, asm)
       assert_eq!(ctx.stack_size, 1)
 
-      # Check interrupts
+      asm.comment("RUBY_VM_CHECK_INTS(ec)")
       asm.mov(:eax, [EC, C.rb_execution_context_t.offsetof(:interrupt_flag)])
       asm.test(:eax, :eax)
       asm.jz(not_interrupted = asm.new_label(:not_interrupted))
       Compiler.compile_exit(jit, ctx, asm) # TODO: use ocb
       asm.write_label(not_interrupted)
 
-      # Pop the current frame (ec->cfp++)
+      asm.comment("pop stack frame")
       asm.add(CFP, C.rb_control_frame_t.size) # cfp = cfp + 1
       asm.mov([EC, C.rb_execution_context_t.offsetof(:cfp)], CFP) # ec->cfp = cfp
 

lib/mjit/x86_assembler.rb

@@ -10,10 +10,13 @@ class Label < Data.define(:id, :name); end
     # REX =   0100WR0B
     REX_W = 0b01001000
 
+    attr_reader :comments
+
     def initialize
       @bytes = []
-      @label_id = 0
       @labels = {}
+      @label_id = 0
+      @comments = Hash.new { |h, k| h[k] = [] }
     end
 
     def compile(addr)
@@ -173,6 +176,10 @@ def test(left, right)
       end
     end
 
+    def comment(message)
+      @comments[@bytes.size] << message
+    end
+
     def new_label(name)
       Label.new(id: @label_id += 1, name:)
     end

lib/ruby_vm/mjit/compiler.rb

@@ -26,11 +26,13 @@ class Compiler
     # @param ctx [RubyVM::MJIT::Context]
     # @param asm [RubyVM::MJIT::X86Assembler]
     def self.compile_exit(jit, ctx, asm)
-      # update pc
+      asm.comment("exit to interpreter")
+
+      # Update pc
       asm.mov(:rax, jit.pc) # rax = jit.pc
       asm.mov([CFP, C.rb_control_frame_t.offsetof(:pc)], :rax) # cfp->pc = rax
 
-      # update sp
+      # Update sp
       if ctx.stack_size > 0
         asm.add(SP, C.VALUE.size * ctx.stack_size) # rbx += stack_size
         asm.mov([CFP, C.rb_control_frame_t.offsetof(:sp)], SP) # cfp->sp = rbx
@@ -45,6 +47,7 @@ def self.compile_exit(jit, ctx, asm)
 
     # @param mem_block [Integer] JIT buffer address
     def initialize(mem_block)
+      @comments = Hash.new { |h, k| h[k] = [] }
       @mem_block = mem_block
       @write_pos = 0
       @insn_compiler = InsnCompiler.new
@@ -56,6 +59,7 @@ def call(iseq)
       return if iseq.body.param.flags.has_opt
 
       asm = X86Assembler.new
+      asm.comment("Block: #{iseq.body.location.label}@#{iseq.body.location.pathobj}:#{iseq.body.location.first_lineno}")
       compile_prologue(asm)
       compile_block(asm, iseq)
       iseq.body.jit_func = compile(asm)
@@ -73,11 +77,20 @@ def write_addr
     def compile(asm)
       start_addr = write_addr
 
+      # Write machine code
       C.mjit_mark_writable
       @write_pos += asm.compile(start_addr)
       C.mjit_mark_executable
 
       end_addr = write_addr
+
+      # Convert comment indexes to addresses
+      asm.comments.each do |index, comments|
+        @comments[start_addr + index] += comments
+      end
+      asm.comments.clear
+
+      # Dump disasm if --mjit-dump-disasm
       if C.mjit_opts.dump_disasm && start_addr < end_addr
         dump_disasm(start_addr, end_addr)
       end
@@ -92,6 +105,8 @@ def compile(asm)
     #
     # @param asm [RubyVM::MJIT::X86Assembler]
     def compile_prologue(asm)
+      asm.comment("MJIT entry")
+
       # Save callee-saved registers used by JITed code
       asm.push(SP)
 
@@ -124,6 +139,7 @@ def compile_block(asm, iseq)
     # @param ctx [RubyVM::MJIT::Context]
     # @param asm [RubyVM::MJIT::X86Assembler]
     def compile_insn(jit, ctx, asm, insn)
+      asm.comment("Insn: #{insn.name}")
       case insn.name
       when :putnil then @insn_compiler.putnil(jit, ctx, asm)
       when :leave  then @insn_compiler.leave(jit, ctx, asm)
@@ -137,9 +153,16 @@ def decode_insn(encoded)
 
     def dump_disasm(from, to)
       C.dump_disasm(from, to).each do |address, mnemonic, op_str|
+        @comments.fetch(address, []).each do |comment|
+          puts bold("  # #{comment}")
+        end
         puts "  0x#{"%x" % address}: #{mnemonic} #{op_str}"
       end
       puts
     end
+
+    def bold(text)
+      "\e[1m#{text}\e[0m"
+    end
   end
 end

mjit_c.rb

@@ -578,7 +578,7 @@ def C.rb_iseq_location_t
       pathobj: [self.VALUE, Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), pathobj)"), true],
       base_label: [self.VALUE, Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), base_label)"), true],
       label: [self.VALUE, Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), label)"), true],
-      first_lineno: [CType::Immediate.parse("int"), Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), first_lineno)"), true],
+      first_lineno: [CType::Immediate.parse("int"), Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), first_lineno)")],
       node_id: [CType::Immediate.parse("int"), Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), node_id)")],
       code_location: [self.rb_code_location_t, Primitive.cexpr!("OFFSETOF((*((struct rb_iseq_location_struct *)NULL)), code_location)")],
     )

tool/mjit/bindgen.rb

@@ -423,7 +423,6 @@ def push_target(target)
   ruby_fields: {
     rb_iseq_location_struct: %w[
       base_label
-      first_lineno
       label
       pathobj
     ]