| blob | c2057fad93834dce88fff154c7bf908e9cc5dd5f |
1 require 'voodoo/generators/common_code_generator'
3 module Voodoo
4 # = ARM GNU Assembler Code Generator
5 #
6 # The ARM code generator generates assembly code for use with
7 # the GNU assembler.
8 #
9 # == Calling Convention
10 #
11 # The first four arguments are passed in the registers r0 through r3.
12 # Any additional arguments are passed on the stack, starting at
13 # r13. r13 will always be a multiple of 8.
14 #
15 # The return address for the called function is passed in r14.
16 #
17 # The called function will store its return value in r0.
18 #
19 # The called function is required to preserve the values of registers
20 # r4 through r11 and register r13.
21 #
22 # This calling convention is compatible with the Procedure Call
23 # Standard for the ARM Architecture (AAPCS).
24 #
25 # == Call Frames
26 #
27 # Call frames have the following layout:
28 #
29 # When a function is called, it receives a stack frame that looks like
30 # the following:
31 #
32 # :
33 # old frame
34 # padding
35 # argn
36 # :
37 # arg4 <-- r13 points here
38 #
39 # The function prologue of functions generated by this code generator
40 # creates activation frames that look as follows:
41 #
42 # :
43 # old frame
44 # padding
45 # argn
46 # :
47 # arg4 <-- r11 points here
48 # saved r14
49 # saved r11
50 # :
51 # saved r4 <-- r13 points here
52 #
53 # == Register Usage
54 #
55 # Inside a function, registers r4..r8 and r10 are used for local variables
56 # and function arguments, whereas r11 is used as a frame pointer.
57 #
58 # r12 is used as a temporary, and r3 is used when another temporary
59 # is needed.
60 #
61 class ARMGasGenerator < CommonCodeGenerator
62 def initialize params
63 @WORDSIZE_BITS = 2
64 @WORDSIZE = 1 << @WORDSIZE_BITS
65 @CODE_ALIGNMENT = 4
66 @DATA_ALIGNMENT = @WORDSIZE
67 @FUNCTION_ALIGNMENT = @WORDSIZE
68 @STACK_ALIGNMENT_BITS = 3
69 @STACK_ALIGNMENT = 1 << @STACK_ALIGNMENT_BITS
71 @INITIAL_FRAME_SIZE = 2 * @WORDSIZE
72 @NREGISTER_ARGS = 4
73 @NREGISTER_LOCALS = 6
74 @FP = :r11
75 @RETURN = :r0
76 @TEMPORARY = :r12
77 @constants = []
78 @frame_offset = 0
79 @frame_size = 0
80 @function_end_label = nil
81 @imports = {}
82 @if_labels = []
83 @saved_registers = []
84 super params
85 @output_file_suffix = '.s'
86 @features.merge! \
87 :'bits-per-word' => '32',
88 :'byte-order' => 'little-endian',
89 :'bytes-per-word' => 4
90 end
92 # Create an entry in the constants table,
93 # returning the label that will refer to the constant.
94 # The value may be an integer or a label.
95 def add_constant value
96 label = gensym
97 @constants << [label, value]
98 label
99 end
101 def align alignment = nil
102 unless alignment
103 # Get default alignment
104 case @section
105 when :code
106 alignment = @CODE_ALIGNMENT
107 when :data
108 alignment = @DATA_ALIGNMENT
109 when :function
110 alignment = @FUNCTION_ALIGNMENT
111 else
112 # Use data alignment as default
113 alignment = @DATA_ALIGNMENT
114 end
115 end
116 emit ".align #{alignment}\n" unless alignment == 0
117 end
119 # Returns the fp-relative offset for the nth (0-based) argument.
120 def arg_offset n
121 (n - @NREGISTER_ARGS) * @WORDSIZE
122 end
124 # Returns an fp-relative reference for the nth (0-based) argument.
125 def arg_reference n
126 offset_reference arg_offset(n)
127 end
129 # Return the register in which the nth (0-based) argument is stored, or
130 # nil if not stored in a register
131 def arg_register n
132 # The first @NREGISTER_ARGS arguments are in the v registers,
133 # the rest are on the stack.
134 if register_arg? n
135 "v#{n + 1}"
136 else
137 nil
138 end
139 end
141 def auto_bytes value, register
142 if value.kind_of? Integer
143 grow_frame value
144 else
145 temporary = register == :sp ? @TEMPORARY : register
146 load_value_into_register value, temporary
147 auto_bytes_register temporary
148 end
149 emit "cpy #{register}, sp\n" unless register == :sp
150 end
152 # auto-bytes where the value is supplied in a register and the return
153 # value will be in sp. register must not be sp.
154 def auto_bytes_register register
155 temporary = register == @TEMPORARY ? :r3 : @TEMPORARY
156 emit "add #{register}, #{register}, \##{@STACK_ALIGNMENT - 1}\n"
157 emit "mvn #{temporary}, \##{@STACK_ALIGNMENT - 1}\n"
158 emit "and #{register}, #{register}, #{temporary}\n"
159 emit "sub sp, #{register}\n"
160 end
162 def auto_words value, register
163 if value.kind_of? Integer
164 auto_bytes(value * @WORDSIZE, register)
165 else
166 temporary = register == :sp ? @TEMPORARY : register
167 load_value_into_register value, temporary
168 emit "lsl #{temporary}, #{temporary}, \##{@WORDSIZE_BITS}\n"
169 auto_bytes_register temporary
170 emit "cpy #{register}, sp\n" unless register == :sp
171 end
172 end
174 # Begins a new block.
175 def begin_block *code
176 emit "# begin block\n"
177 # If we are starting a block at top level, create a frame
178 if @environment == @top_level
179 nlocals = count_locals code
180 create_frame nlocals, false
181 end
182 @environment = Environment.new @environment
183 end
185 # Emit function prologue and declare _formals_ as function arguments
186 def begin_function formals, nlocals
187 if @environment != @top_level
188 raise "Can only begin a function at top level"
189 end
191 @function_end_label = gensym
192 emit "# function #{formals.join ' '}\n"
193 environment = Environment.new @environment
194 formals.each_with_index do |formal, i|
195 if i < @NREGISTER_ARGS
196 environment.add_arg formal, arg_register(i)
197 else
198 environment.add_arg formal, arg_offset(i)
199 end
200 end
201 @environment = environment
202 emit_function_prologue formals, nlocals
203 end
205 # Define a byte with the given value
206 def byte value
207 emit ".byte #{value}\n"
208 end
210 # Call a function.
211 def call func, *args
212 emit "# call #{func} #{args.join ' '}\n"
214 # Calculate how many arguments need to be pushed on
215 # the stack, and allocate space for them.
216 nstack_args = number_of_stack_arguments args.length
217 old_frame_offset = @frame_offset
218 old_frame_size = @frame_size
219 grow_frame nstack_args if nstack_args > 0
221 # Put stack arguments on the stack
222 (@NREGISTER_ARGS...args.length).each do |n|
223 load_value_into_register args[n], @TEMPORARY
224 emit "str #{@TEMPORARY}, " +
225 "[sp , \##{(n - @NREGISTER_ARGS) * @WORDSIZE}]\n"
226 end
228 # Put register arguments in the right registers
229 nregister_args = number_of_register_arguments args.length
230 nregister_args.times do |n|
231 load_value_into_register args[n], :"a#{n + 1}"
232 end
234 # Call function
235 if global? func
236 emit "bl #{func}\n"
237 else
238 func_reg = load_value func
239 emit "blx #{func_reg}\n"
240 end
242 # Restore original stack frame
243 if old_frame_size != @frame_size
244 emit "add sp, sp, \##{@frame_size - old_frame_size}\n"
245 @frame_offset = old_frame_offset
246 @frame_size = old_frame_size
247 end
248 end
250 # Creates a stack frame for the given number of arguments
251 # and local variables.
252 def create_frame nvars, save_lr = true
253 # Calculate how many variables we will store in registers,
254 # and how many on the stack.
255 nregister_vars = [nvars, @NREGISTER_LOCALS].min
256 nstack_vars = nvars - nregister_vars
258 # Save the registers we will clobber to the stack.
259 clobbered = []
260 nregister_vars.times do |i|
261 clobbered << :"v#{i < 5 ? i + 1 : i + 2}"
262 end
263 clobbered << @FP
264 clobbered << :lr if save_lr
265 @saved_registers = clobbered
266 emit "stmfd sp!, {#{clobbered.join ', '}}\n"
267 emit "add #{@FP}, sp, \##{clobbered.length * @WORDSIZE}\n"
269 # Calculate frame size so that the stack pointer will
270 # be properly aligned at the end of emit_function_prologue.
271 @frame_size = stack_align((clobbered.length + nstack_vars) * @WORDSIZE)
272 extra_space = @frame_size - clobbered.length * @WORDSIZE
273 if extra_space > 0
274 emit "sub sp, sp, \##{extra_space}\n"
275 end
276 @frame_offset = 0
277 end
279 # Emits a comment.
280 def comment text
281 emit "# #{text}\n"
282 end
284 # Start a conditional using the specified branch instruction
285 # after the comparison.
286 def common_if comp, x, y = nil
287 emit "# #{comp} #{x} #{y}\n"
289 xreg = load_value x, @TEMPORARY
290 yreg = load_value y, :a4
292 falselabel = @environment.gensym
293 @if_labels.push falselabel
295 emit "cmp #{xreg}, #{yreg}\n"
297 lut = { :ifeq => "bne", :ifge => "blt", :ifgt => "ble",
298 :ifle => "bgt", :iflt => "bge", :ifne => "beq" }
299 emit "#{lut[comp]} #{falselabel}\n"
300 end
302 # Destroys the current stack frame.
303 # If ret is true, loads the saved value of lr into pc.
304 def destroy_frame ret = false
305 # Set sp back to where saved registers were stored
306 saved = @saved_registers
307 emit "sub sp, #{@FP}, \##{saved.length * @WORDSIZE}\n"
309 if ret
310 index = saved.index :lr
311 if index
312 saved[index] = :pc
313 else
314 raise "Request to load saved lr into pc, but lr has not been saved"
315 end
316 end
317 emit "ldmfd sp!, {#{saved.join ', '}}\n"
319 emit_constants if ret
320 end
322 # Writes any constants that need to be written to the instruction
323 # stream, and clears the list of constants that need to be written.
324 def emit_constants
325 @constants.each do |x|
326 label x[0]
327 word x[1]
328 end
329 @constants = []
330 end
332 # Emit function prologue.
333 def emit_function_prologue formals = [], nlocals = 0
334 # Calculate the number of arguments we were passed in
335 # registers, the total number of values we need to save
336 # on the stack, then create a stack frame and save
337 # the v registers we will be using.
338 nregister_args = [formals.length, @NREGISTER_ARGS].min
339 nvars = nregister_args + nlocals
340 create_frame nvars, true
342 # Move arguments that were passed in registers into
343 # callee-save registers.
344 nregister_args.times do |i|
345 emit "cpy v#{i + 1}, a#{i + 1}\n"
346 end
347 end
349 # Ends the current block.
350 def end_block
351 emit "# end block\n"
353 # If we are returning to top level, restore stack pointer
354 # and saved registers.
355 if @environment.parent == @top_level
356 offset = @frame_size - @saved_registers.length * @WORDSIZE
357 if offset > 0
358 emit "add sp, sp, \##{offset}\n"
359 end
360 emit "ldmfd sp!, {#{@saved_registers.join ', '}}\n"
361 @frame_size = 0
362 @frame_offset = 0
363 @saved_registers = []
365 # If we need to emit constants, do so now
366 unless @constants.empty?
367 lbl = gensym
368 goto lbl
369 label lbl
370 end
371 end
373 # Restore old value of @environment
374 @environment = @environment.parent
375 end
377 # Ends a function body.
378 def end_function
379 if @environment == @top_level
380 raise "Cannot end function when not in a function"
381 end
383 emit "# function epilogue\n"
384 label @function_end_label
386 destroy_frame true
387 @frame_size = 0
388 @frame_offset = 0
389 @saved_registers = []
390 emit "# end function\n\n"
391 @environment = @top_level
392 end
394 # Ends a conditional.
395 def end_if
396 label @if_labels.pop
397 end
399 # Evaluate the binary operation expr and store the result in register
400 def eval_binop expr, register
401 op = expr[0]
403 # Emulation for div and mod, which ARM does not have instructions for
404 case op
405 when :div
406 func = :"__aeabi_idiv"
407 import func unless @imports.has_key? func
408 call func, expr[1], expr[2]
409 emit "cpy #{register}, r0\n" if register != :r0
410 return
411 when :mod
412 func = :"__aeabi_idivmod"
413 import func unless @imports.has_key? func
414 call func, expr[1], expr[2]
415 emit "cpy #{register}, r1\n" if register != :r1
416 return
417 end
419 x = load_value expr[1], :a4
420 y = load_value expr[2], @TEMPORARY
422 case op
423 when :bsr
424 emit "lsr #{register}, #{x}, #{y}\n"
425 when :or
426 emit "orr #{register}, #{x}, #{y}\n"
427 when :rol
428 emit "rsb #{y}, #{y}, #32\n"
429 emit "ror #{register}, #{x}, #{y}\n"
430 when :shl
431 emit "lsl #{register}, #{x}, #{y}\n"
432 when :shr
433 emit "lsr #{register}, #{x}, #{y}\n"
434 when :xor
435 emit "eor #{register}, #{x}, #{y}\n"
436 else
437 emit "#{expr[0]} #{register}, #{x}, #{y}\n"
438 end
439 end
441 # Evaluates the expression +expr+ and stores the result in +register+.
442 def eval_expr expr, register
443 if expr.length == 1
444 # Load value
445 load_value_into_register expr[0], register
446 else
447 # Evaluate expression
448 op = expr[0]
449 case op
450 when :'auto-bytes'
451 auto_bytes expr[1], register
452 when :'auto-words'
453 auto_words expr[1], register
454 when :call
455 call *expr[1..-1]
456 emit "cpy #{register}, #{@RETURN}\n" if register != @RETURN
457 when :'get-byte'
458 get_byte expr[1], expr[2], register
459 when :'get-word'
460 get_word expr[1], expr[2], register
461 when :not
462 load_value_into_register expr[1], register
463 emit "mvn #{@TEMPORARY}, #0\n"
464 emit "eor #{register}, #{register}, #{@TEMPORARY}\n"
465 else
466 if binop? op
467 eval_binop expr, register
468 else
469 raise "Not a magic word: #{op}"
470 end
471 end
472 end
473 end
475 # Export symbols from the current section
476 def export *symbols
477 symbols.each { |sym| emit ".globl #{sym}\n" }
478 end
480 # Load byte from _base_ + _offset_ into _register_
481 def get_byte base, offset, register
482 # If base is an integer, but offset isn't, swap them
483 if !integer?(offset) && integer?(base)
484 base, offset = [offset, base]
485 end
487 if integer? offset
488 base_reg = load_value base
489 if offset == 0
490 emit "ldrb #{register}, [#{base_reg}]\n"
491 else
492 emit "ldrb #{register}, [#{base_reg}, \##{offset}]\n"
493 end
494 else
495 base_reg = load_value base
496 offset_reg = load_value offset, :a4
497 emit "ldrb #{register}, [#{base_reg}, #{offset_reg}]\n"
498 end
499 end
501 # Load word from _base_ + _offset_ * _@WORDSIZE_ into _register_
502 def get_word base, offset, register
503 if integer? offset
504 base_reg = load_value base
505 if offset == 0
506 emit "ldr #{register}, [#{base_reg}]\n"
507 else
508 emit "ldr #{register}, [#{base_reg}, \##{offset * @WORDSIZE}]\n"
509 end
510 else
511 base_reg = load_value base
512 offset_reg = load_value offset, :a4
513 emit "ldr #{register}, [#{base_reg}, #{offset_reg}, LSL #2]\n"
514 end
515 end
517 # Jump to a label.
518 def goto label
519 emit "b #{label}\n"
521 # If we have constants that need to be emitted, do so now
522 emit_constants
523 end
525 # Grows the current frame by n words, plus padding to
526 # respect alignment rules.
527 def grow_frame nwords
528 increment = stack_align(nwords * @WORDSIZE)
529 emit "sub sp, sp, \##{increment}\n"
530 @frame_size = @frame_size + increment
531 @frame_offset = @frame_offset + increment
532 end
534 # Start the false path of a conditional.
535 def ifelse
536 emit "# else\n"
537 newlabel = @environment.gensym
538 goto newlabel
539 lbl = @if_labels.pop
540 label lbl
541 @if_labels.push newlabel
542 end
544 # Test if x is equal to y
545 def ifeq x, y
546 common_if :ifeq, x, y
547 end
549 # Test if x is greater than or equal to y
550 def ifge x, y
551 common_if :ifge, x, y
552 end
554 # Test if x is strictly greater than y
555 def ifgt x, y
556 common_if :ifgt, x, y
557 end
559 # Test if x is less than or equal to y
560 def ifle x, y
561 common_if :ifle, x, y
562 end
564 # Test if x is strictly less than y
565 def iflt x, y
566 common_if :iflt, x, y
567 end
569 # Test if x different from y
570 def ifne x, y
571 common_if :ifne, x, y
572 end
574 # Import labels into the current section
575 def import *symbols
576 # Record imported labels in @imports
577 symbols.each { |sym| @imports[sym] = sym }
578 end
580 # Emit a label
581 def label name
582 emit "#{name}:\n"
583 end
585 # Introduce a new local variable
586 def let symbol, *expr
587 n = @environment.locals
588 register = local_register n
590 if register
591 # We will use a register to store the value
592 @environment.add_local symbol, register
593 eval_expr expr, register
594 else
595 # We will use the stack to store the value
596 offset = local_offset n
597 @environment.add_local symbol, offset
598 eval_expr expr, @TEMPORARY
599 emit "str #{@TEMPORARY}, #{offset_reference offset}\n"
600 end
601 end
603 # Load the value at the given address.
604 def load_at address, register = @TEMPORARY
605 load_value_into_register address, register
606 emit "ldr #{register}, [#{register}]\n"
607 register
608 end
610 # Load a value into a register.
611 # Returns the name of the register.
612 # If the value was already in a register, the name of that
613 # register is returned.
614 # Else, the value is loaded into a register and the name of
615 # that register is returned. The register to use in that case
616 # may be specified using the optional second argument.
617 def load_value x, register = @TEMPORARY
618 if substitution? x
619 x = substitute_number x[1]
620 end
622 if integer? x
623 if x >= 0 && x <= 255
624 emit "mov #{register}, \##{x}\n"
625 return register
626 elsif x >= -255 && x < 0
627 emit "mvn #{register}, \##{-(x + 1)}\n"
628 return register
629 else
630 lbl = add_constant x
631 emit "ldr #{register}, #{lbl}\n"
632 return register
633 end
634 elsif symbol? x
635 binding = @environment[x]
636 if binding.kind_of? String
637 # Value is already in a register. Return register name.
638 return binding
639 elsif binding.kind_of? Integer
640 # Value is on the stack. Load from the stack.
641 emit "ldr #{register}, #{offset_reference binding}\n"
642 return register
643 else
644 # Assume global
645 lbl = add_constant x
646 emit "ldr #{register}, #{lbl}\n"
647 return register
648 end
649 elsif at_expr? x
650 load_at x[1], register
651 else
652 raise "Don't know how to load #{x.inspect}"
653 end
654 end
656 # Load a value into a specific register
657 def load_value_into_register x, register
658 reg = load_value x, register
659 if reg != register
660 emit "cpy #{register}, #{reg}\n"
661 end
662 end
664 # Returns the fp-relative reference for the nth (0-based) local.
665 def local_offset n
666 -@INITIAL_FRAME_SIZE - (n * @WORDSIZE)
667 end
669 # Return the register in which the nth local (0-based) is stored, or
670 # nil if not stored in a register
671 def local_register n
672 if register_local? n
673 n = n + number_of_register_arguments
674 if n < 5
675 "v#{n + 1}"
676 else
677 "v#{n + 2}"
678 end
679 else
680 nil
681 end
682 end
684 # Calculate the number of register arguments,
685 # given the total number of arguments.
686 def number_of_register_arguments n = @environment.args
687 [n, @NREGISTER_ARGS].min
688 end
690 # Calculate the number of stack arguments,
691 # given the total number of arguments.
692 def number_of_stack_arguments n = @environment.args
693 [0, n - @NREGISTER_ARGS].max
694 end
696 # Given an offset, returns an fp-relative reference.
697 def offset_reference offset
698 "[#{@FP}, \##{offset}]"
699 end
701 # Returns true if the nth (0-based) argument is stored in a register
702 def register_arg? n
703 n < @NREGISTER_ARGS
704 end
706 # Returns true if the nth (0-based) local is stored in a register
707 def register_local? n
708 (n + number_of_register_arguments) < @NREGISTER_LOCALS
709 end
711 # Returns from a function.
712 #
713 # _words_ may contain an expression to be evaluated. The result
714 # of the evaluation is returned from the function.
715 def ret *words
716 emit "# return #{words.join ' '}\n"
717 # Compute return value and store it in @RETURN
718 eval_expr(words, @RETURN) unless words.empty?
719 # Go to epilogue
720 goto @function_end_label
721 end
723 # Set a variable to the result of evaluating an expression
724 def set symbol, *expr
725 if at_expr? symbol
726 eval_expr expr, :r3
727 register = load_value symbol[1]
728 emit "str r3, [#{register}]\n"
729 else
730 x = @environment[symbol]
731 if x == nil
732 raise "Cannot change value of constant #{symbol}"
733 elsif x.kind_of? String
734 eval_expr expr, x
735 else
736 eval_expr expr, @TEMPORARY
737 emit "str #{@TEMPORARY}, #{offset_reference x}\n"
738 end
739 end
740 end
742 # Set the byte at _base_ + _offset_ to _value_
743 def set_byte base, offset, value
744 emit "# set-byte #{base} #{offset} #{value}\n"
745 # If base is an integer, but offset isn't, swap them
746 if !integer?(offset) && integer?(base)
747 base, offset = [offset, base]
748 end
750 if integer? offset
751 base_reg = load_value base, :a4
752 load_value_into_register value, @TEMPORARY
753 if offset == 0
754 emit "strb #{@TEMPORARY}, [#{base_reg}]\n"
755 else
756 emit "strb #{@TEMPORARY}, [#{base_reg}, \##{offset}]\n"
757 end
758 else
759 eval_binop [:add, base, offset], :a4
760 load_value_into_register value, @TEMPORARY
761 emit "strb #{@TEMPORARY}, [a4]\n"
762 end
763 end
765 # Set the word at _base_ + _offset_ * +@WORDSIZE+ to _value_
766 def set_word base, offset, value
767 emit "# set-word #{base} #{offset} #{value}\n"
768 # If base is an integer, but offset isn't, swap them
769 if !integer?(offset) && integer?(base)
770 base, offset = [offset, base]
771 end
773 if integer? offset
774 base_reg = load_value base, :a4
775 load_value_into_register value, @TEMPORARY
776 if offset == 0
777 emit "str #{@TEMPORARY}, [#{base_reg}]\n"
778 else
779 emit "str #{@TEMPORARY}, [#{base_reg}, \##{offset * @WORDSIZE}]\n"
780 end
781 else
782 load_value_into_register base, :a4
783 load_value_into_register offset, @TEMPORARY
784 emit "add a4, a4, #{@TEMPORARY}, LSL #2\n"
785 load_value_into_register value, @TEMPORARY
786 emit "str #{@TEMPORARY}, [a4]\n"
787 end
788 end
790 # Given n, returns the nearest multiple of @STACK_ALIGNMENT
791 # that is >= n.
792 def stack_align n
793 (n + @STACK_ALIGNMENT - 1) / @STACK_ALIGNMENT * @STACK_ALIGNMENT
794 end
796 # Define a string with the given value
797 def string value
798 code = ''
799 value.each_byte do |b|
800 if b == 92
801 code << "\\\\"
802 elsif b >= 32 && b < 127 && b != 34
803 code << b.chr
804 else
805 code << sprintf("\\%03o", b)
806 end
807 end
808 emit ".ascii \"#{code}\"\n"
809 end
811 # Call a function, re-using the current call frame if possible.
812 def tail_call func, *args
813 emit "# tail-call #{func} #{args.join ' '}\n"
815 # Compute number of stack arguments
816 nstackargs = number_of_stack_arguments args.length
817 # If we need more stack arguments than we have now,
818 # perform a normal call and return
819 if nstackargs > number_of_stack_arguments(@environment.args)
820 emit "# Not enough space for proper tail call; using regular call\n"
821 ret :call, func, *args
822 end
824 # We will assign arguments from left to right.
825 # Find places that we will overwrite before we read them,
826 # and store their values in some newly allocated stack space.
827 old_frame_offset = @frame_offset
828 old_frame_size = @frame_size
829 overwritten = {}
830 (@NREGISTER_ARGS...args.length).each do |i|
831 arg = args[i]
832 arg = arg[1] if at_expr? arg
833 if symbol?(arg)
834 binding = @environment[arg]
835 if binding[0] == :arg && binding[1] >= @NREGISTER_ARGS &&
836 binding[1] < i
837 # Argument i is a stack argument, but the value we will assign
838 # it is a stack argument that comes before it, so we will
839 # have overwritten it by the time we get to it.
840 overwritten[arg] = nil
841 end
842 end
843 end
845 unless overwritten.empty?
846 # Allocate space for arguments to be saved
847 grow_frame overwritten.length
848 # Save values
849 offset = 0
850 overwritten.each_key do |key|
851 reg = load_value key
852 emit "str #{reg}, [sp, \##{offset}]\n"
853 overwritten[key] = offset
854 offset = offset + @WORDSIZE
855 end
856 end
858 # Assign arguments
859 args.each_index do |i|
860 arg = args[i]
861 if register_arg? i
862 load_value_into_register arg, "a#{i + 1}"
863 else
864 # Test if this is a value we saved
865 sym = at_expr?(arg) ? arg[1] : arg
866 saved = overwritten[sym]
867 if saved
868 # Saved value, load from stack
869 reg = @TEMPORARY
870 emit "ldr #{reg}, [sp, \##{saved}]\n"
871 else
872 # Regular value, use load_value
873 reg = load_value arg
874 end
875 emit "str #{reg}, #{arg_reference i}\n"
876 end
877 end
879 # Load address of function to be called into @TEMPORARY
880 load_value_into_register func, @TEMPORARY
882 # Destroy current activation frame and enter func
883 destroy_frame false
884 emit "bx #{@TEMPORARY}\n"
885 emit_constants
886 end
888 # Define a word with the given value
889 def word value
890 emit ".int #{value}\n"
891 end
893 end
895 # Register class for little endian ARM
896 Voodoo::CodeGenerator.register_generator ARMGasGenerator,
897 :architecture => :arm,
898 :format => :gas
899 end