1 require 'voodoo/generators/common_code_generator'
4 # = NASM Code Generator
6 # The NASM code generator is a common base class for generators that output
7 # assembly code for use with the {Netwide Assembler}[http://www.nasm.us/].
9 # This class is used by both the I386NasmGenerator and the
10 # AMD64NasmGenerator, and contains the functionality that is common to
13 # To use the functionality from this class, a subclass must define the
14 # following methods and constants:
18 # - @FUNCTION_ALIGNMENT
20 # - @STACK_ALIGNMENT_BITS
25 # - @AX, @BX, @CX, @DX, @BP, and @SP
26 class NasmGenerator < CommonCodeGenerator
27 def initialize params = {}
30 @output_file_suffix = '.asm'
37 # Export symbols from the current section
39 case real_section_name(section)
41 symbols.each { |sym| emit "global #{sym}:function\n" }
43 @relocated_symbols.merge symbols
44 symbols.each { |sym| emit "global #{sym}:data #{sym}.end-#{sym}\n" }
48 # Continue execution at the given address
50 with_temporary do |temporary|
51 value_ref = load_value value, temporary
52 emit "jmp #{value_ref}\n"
56 # Import labels into the current section
58 if real_section_name(section) != ".text"
59 @relocated_symbols.merge symbols
61 emit "extern #{symbols.join ', '}\n"
69 def emit_label_size name
73 def emit_label_type name, type
81 # Define a byte with the given value
86 # Define a dword with the given value
91 # Define a qword with the given value
96 # Define a string with the given value
100 value.each_byte do |b|
101 if b >= 32 && b < 127 && b != 39
105 code << ',' unless code.empty?
114 code << ',' unless code.empty?
119 code << "'" if in_quote
127 def emit_align alignment
128 emit "align #{alignment}\n"
135 # Emits function epilogue.
136 def emit_function_epilogue formals = []
140 # Ends a function body
142 if @environment == @top_level
143 raise "Cannot end function when not in a function"
145 @environment = @top_level
149 # Returns from a function.
151 # _words_ may contain an expression to be evaluated. The result
152 # of the evaluation is returned from the function.
154 eval_expr(words) unless words.empty?
155 emit_function_epilogue
163 # Begins a new block.
164 def begin_block *code
165 # If entering a block at top level,
166 # Save @BP, then set @BP to @SP
167 if @environment == @top_level
169 emit "mov #{@BP}, #{@SP}\n"
171 environment = Environment.new @environment
172 @environment = environment
175 # Ends the current block.
177 # Restore old value of @environment
178 @environment = @environment.parent
180 # If returning to top level, restore old @BP
181 emit "leave\n" if @environment == @top_level
185 # == Memory Allocation
188 # Allocates n bytes on the stack and stores a pointer to the allocated
189 # memory in the specified register. The number of bytes is rounded up
190 # to the nearest multiple of @STACK_ALIGNMENT.
191 def auto_bytes n, register = @RETURN_REG
192 if n.kind_of? Integer
193 auto_bytes_immediate n, register
195 load_value_into_register n, register
196 auto_bytes_register register, register
200 # Implements auto_bytes where the number of bytes to allocate is given
201 # as an immediate value.
202 def auto_bytes_immediate nbytes, register
203 nbytes = ((nbytes + @STACK_ALIGNMENT - 1) >> @STACK_ALIGNMENT_BITS) <<
204 @STACK_ALIGNMENT_BITS
205 emit "sub #{@SP}, #{nbytes}\n"
206 emit "mov #{register}, #{@SP}\n" if register != @SP
209 # Implements auto_bytes where the number of bytes is supplied in a
211 def auto_bytes_register nbytes, register = @RETURN_REG
212 emit "add #{nbytes}, #{@STACK_ALIGNMENT - 1}\n"
213 emit "shr #{nbytes}, #{@STACK_ALIGNMENT_BITS}\n"
214 emit "shl #{nbytes}, #{@STACK_ALIGNMENT_BITS}\n"
215 emit "sub #{@SP}, #{nbytes}\n"
216 emit "mov #{register}, #{@SP}\n" if register != @SP
219 # Allocates n words on the stack and stores a pointer to the allocated
220 # memory in the specified register.
221 def auto_words n, register = @RETURN_REG
222 if n.kind_of? Integer
223 auto_bytes_immediate n * @WORDSIZE, register
225 load_value_into_register n, register
226 if @STACK_ALIGNMENT_BITS > @WORDSIZE_BITS
227 emit "add #{register}, " +
228 "#{(1 << @STACK_ALIGNMENT_BITS >> @WORDSIZE_BITS) - 1}\n"
229 emit "shr #{register}, #{@STACK_ALIGNMENT_BITS - @WORDSIZE_BITS}\n"
230 emit "shl #{register}, #{STACK_ALIGNMENT_BITS}\n"
232 emit "shl #{register}, #{@WORDSIZE_BITS}\n"
234 emit "sub #{@SP}, #{register}\n"
235 emit "mov #{register}, #{@SP}\n" if register != @SP
243 # Introduces a new local variable.
244 def let symbol, *words
245 loc = local_offset_or_register @environment.locals
246 @environment.add_local symbol, loc
254 # End a conditional body
256 label = @if_labels.pop
261 # == Value Classification
264 # Tests if an operand is an immediate operand
265 def immediate_operand? operand
269 # Tests if an operand is a memory operand
270 def memory_operand? operand
271 operand.kind_of?(String) && operand[0] == ?[
278 # Loads a word into a register.
279 def emit_load_word register, base, offset = 0
281 emit "mov #{register}, [#{base}]\n"
283 emit "mov #{register}, [#{base} + #{offset} * #{@WORDSIZE}]\n"
287 # Create a value reference to an address.
288 # Invoking this code may clobber @BX and/or @CX
289 def load_address base, offset, scale
290 base_ref = load_value base, @BX
291 offset_ref = load_value offset, @CX
295 # Only an integer base
298 # Some complex base; load in @BX
299 emit "mov #{@BX}, #{base_ref}\n"
303 if integer? offset_ref
304 # Only a scaled offset
305 "[#{offset_ref.to_i * scale}]"
307 # Some complex offset; load in @CX
308 emit "mov #{@CX}, #{offset_ref}\n"
309 "[#{@CX} * #{scale}]"
311 elsif integer? base_ref
312 if integer? offset_ref
313 # All integers, combine them together
314 "[#{base_ref.to_i + (offset_ref.to_i * scale)}]"
316 # Complex offset; use @CX
317 emit "mov #{@CX}, #{offset_ref}\n"
318 "[#{base_ref} + #{@CX} * #{scale}]"
320 elsif integer? offset_ref
321 # Complex base, integer offset; use @BX
322 emit "mov #{@BX}, #{base_ref}\n"
323 "[#{@BX} + #{offset_ref.to_i * scale}]"
325 # Both base and offset are complex
326 # Use both @BX and @CX
327 emit "mov #{@BX}, #{base_ref}\n"
328 emit "mov #{@CX}, #{offset_ref}\n"
329 "[#{@BX} + #{@CX} * #{scale}]"
333 # Load the value at the given address.
334 # Invoking this code may clobber @BX.
335 def load_at address, reg
336 if integer?(address) || (global?(address) &&
337 !@relocated_symbols.include?(address))
340 load_value_into_register address, @BX
345 # Loads the value associated with the given symbol.
346 def load_symbol symbol, reg
347 x = @environment[symbol]
350 elsif x.kind_of? Integer
354 if @relocated_symbols.include? symbol
355 "[rel #{symbol} wrt ..gotpc]"
363 # Returns a string that can be used to refer to the loaded value.
364 def load_value value, reg
365 if substitution? value
366 value = substitute_number value[1]
370 if @WORDSIZE > 4 && (value < -2147483648 || value > 2147483647)
371 # AMD64 can load immediate values that are outside the range
372 # that can be represented as a 32-bit signed integer, but
373 # only with a mov instruction that loads the value into a
375 emit "mov #{@WORD_NAME} #{reg}, #{value}\n"
381 load_symbol value, reg
383 load_at value[1], reg
385 raise "Don't know how to load #{value.inspect}"
389 # Loads a value into a register.
390 def load_value_into_register value, register
391 value_ref = load_value value, register
392 set_register register, value_ref
399 # Stores the value of a register in memory.
400 def emit_store_word register, base, offset = 0
402 emit "mov [#{base}], #{register}\n"
404 emit "mov [#{base} + #{offset} * #{@WORDSIZE}], #{register}\n"
408 # Evaluate the expr in words and store the result in target
409 def set target, *words
411 raise "Cannot change value of integer #{target}"
412 elsif global?(target)
413 raise "Cannot change value of global #{target}"
416 if words.length != 1 || words[0] != target
417 if symbol?(target) && symbol?(@environment[target])
418 eval_expr words, @environment[target]
420 eval_expr words, @RETURN_REG
421 target_ref = load_value target, @BX
422 emit "mov #{target_ref}, #{@RETURN_REG}\n"
427 # Set the byte at _base_ + _offset_ to _value_
428 def set_byte base, offset, value
429 if immediate_operand?(value)
432 load_value_into_register value, @RETURN_REG
435 addr_ref = load_address base, offset, 1
436 emit "mov byte #{addr_ref}, #{value_ref}\n"
439 # Set the word at _base_ + _offset_ * +@WORDSIZE+ to _value_
440 def set_word base, offset, value
441 if immediate_operand?(value)
442 value_ref = load_value value, @RETURN_REG
444 load_value_into_register value, @RETURN_REG
445 value_ref = @RETURN_REG
447 addr_ref = load_address base, offset, @WORDSIZE
448 emit "mov #{@WORD_NAME} #{addr_ref}, #{value_ref}\n"
451 # Divide x by y and store the quotient in target
454 target_ref = load_value target, @BX
455 emit "mov #{target_ref}, #{@AX}\n"
458 # Divide target by x and store the quotient in target
460 div target, target, x
463 # Divide x by y and store the remainder in target
466 target_ref = load_value target, @BX
467 emit "mov #{target_ref}, #{@DX}\n"
470 # Divide target by x and store the remainder in target
472 mod target, target, x
475 # Multiply x by y and store the result in target
478 target_ref = load_value target, @BX
479 emit "mov #{target_ref}, #{@RETURN_REG}\n"
482 # Multiply target by x and store the result in target
484 mul target, target, x
492 # The quotient is stored in @AX, the remainder in @DX.
494 with_temporary do |temporary|
495 x_ref = load_value_into_register x, @AX
496 y_ref = load_value y, temporary
497 emit "mov #{@DX}, #{@AX}\n"
498 emit "sar #{@DX}, #{@WORDSIZE * 8 - 1}\n"
499 if immediate_operand?(y_ref)
500 set_register @BX, y_ref
503 emit "idiv #{@WORD_NAME} #{y_ref}\n"
508 # Evaluate an expression.
509 # The result is stored in _register_ (@RETURN_REG by default).
510 # The following registers may be clobbered: @AX, @BX, @CX, @DX
511 def eval_expr words, register = @RETURN_REG
514 emit "xor #{register}, #{register}\n"
516 load_value_into_register words[0], register
521 when :asr, :bsr, :rol, :ror, :shl, :shr
525 load_value_into_register words[2], @CX
528 load_value_into_register words[1], register
529 emit "#{action_to_mnemonic op} #{register}, #{y_ref}\n"
531 auto_bytes words[1], register
533 auto_words words[1], register
536 emit "mov #{register}, #{@RETURN_REG}\n" if register != @RETURN_REG
538 eval_div words[1], words[2]
539 set_register register, @AX
541 # Get address reference
542 address_ref = load_address words[1], words[2], 1
543 # Load byte from address
546 set_register register, 0
547 set_register :al, address_ref
549 set_register register, 0
550 set_register :bl, address_ref
552 set_register register, 0
553 set_register :cl, address_ref
555 set_register register, 0
556 set_register :dl, address_ref
559 set_register :al, address_ref
560 set_register register, @AX
563 address_ref = load_address words[1], words[2], @WORDSIZE
564 set_register register, address_ref
566 eval_div words[1], words[2]
567 set_register register, @DX
569 eval_mul words[1], words[2], register
571 load_value_into_register words[1], register
572 emit "not #{register}\n"
575 x_ref = load_value words[1], @DX
576 y_ref = load_value words[2], @BX
577 emit "mov #{register}, #{x_ref}\n" unless register == x_ref
578 emit "#{op} #{register}, #{y_ref}\n"
580 raise "Not a magic word: #{words[0]}"
587 # The result is stored in @AX by default, but
588 # a different register can be specified by passing
590 def eval_mul x, y, register = @AX
591 x_ref = load_value x, @DX
592 y_ref = load_value y, @BX
594 if immediate_operand? x_ref
595 if immediate_operand? y_ref
596 set_register register, x_ref * y_ref
598 emit "imul #{register}, #{y_ref}, #{x_ref}\n"
600 elsif immediate_operand? y_ref
601 emit "imul #{register}, #{x_ref}, #{y_ref}\n"
602 elsif y_ref != register
603 emit "mov #{register}, #{x_ref}\n" unless x_ref == register
604 emit "imul #{register}, #{y_ref}\n"
606 emit "imul #{register}, #{x_ref}\n"
614 # Start a conditional using the specified branch instruction
615 # after the comparison.
616 def common_if branch, x, y = nil
617 # Inverses of branches. E.g.
632 y_ref = load_value y, @DX
633 x_ref = load_value x, @AX
634 if immediate_operand?(x_ref)
635 # Can't have an immediate value as the first operand.
636 if immediate_operand?(y_ref)
637 # Both are immediates. Put the first in a register.
638 emit "mov #{@AX}, #{x_ref}\n"
641 # y isn't immediate; swap x and y.
642 x_ref, y_ref = [y_ref, x_ref]
643 branch = inverse_branch[branch]
645 elsif memory_operand?(x_ref) && memory_operand?(y_ref)
646 # Can't have two memory operands. Move the first into a register.
647 emit "mov #{@AX}, #{x_ref}\n"
650 truelabel = @environment.gensym
651 falselabel = @environment.gensym
652 @if_labels.push falselabel
654 emit "cmp #{@WORD_NAME} #{x_ref}, #{y_ref}\n"
655 emit "#{branch} #{truelabel}\n"
656 emit "jmp #{falselabel}\n"
657 emit "#{truelabel}:\n"
662 label = @if_labels.pop
666 # Start the false path of a conditional.
668 newlabel = @environment.gensym
669 emit "jmp #{newlabel}\n"
670 label = @if_labels.pop
672 @if_labels.push newlabel
675 # Test if x is equal to y
680 # Test if x is greater than or equal to y
685 # Test if x is strictly greater than y
690 # Test if x is less than or equal to y
695 # Test if x is strictly less than y
700 # Test if x different from y
709 # Translates a Voodoo action name to an x86 mnemonic
710 def action_to_mnemonic action
726 # Returns a memory reference for the address at the given offset
727 # from the frame pointer.
728 def offset_reference offset
730 "[#{@BP} + #{offset}]"
732 "[#{@BP} - #{-offset}]"
738 # Set a register to a value.
739 # The value must be a valid operand to the mov instruction.
740 def set_register register, value_ref
745 emit "xor #{register}, #{register}\n"
747 emit "mov #{register}, #{value_ref}\n"
755 # Write generated code to the given IO object.
757 io.puts "bits #{@WORDSIZE * 8}\n\n"
758 @sections.each do |section,code|
760 io.puts "section #{section.to_s}"