| blob | cf1a690f73eda715b2629d0be594939645fa1fc0 |
1 require 'voodoo/generators/common_code_generator'
2 require 'set'
4 module Voodoo
5 # = MIPS GNU Assembler Code Generator
6 #
7 # The MIPS code generator generates assembly code for use with
8 # the GNU assembler.
9 #
10 # == Calling Convention
11 #
12 # The first four arguments are passed in the registers $4 through $7.
13 # Any additional arguments are passed on the stack, starting at
14 # $sp + 16. Words $sp through $sp + 12 will be available for the called
15 # function to use. $sp will always be a multiple of 8.
16 #
17 # The return address for the called function is passed in $31.
18 #
19 # When performing a position-independent call, the address of the called
20 # function is passed in $25.
21 #
22 # The called function will store its return value in $2.
23 #
24 # The called function is required to preserve the values of registers
25 # $16 through $23 and register $30.
26 #
27 # This calling convention is compatible with the System V ELF ABI.
28 #
29 # == Call Frames
30 #
31 # Call frames have the following layout:
32 #
33 # When a function is called, it receives a stack frame that looks like
34 # the following:
35 #
36 # :
37 # old frame
38 # argn
39 # :
40 # arg4
41 # empty3
42 # empty2
43 # empty1
44 # empty0 <-- $sp points here
45 #
46 # The function prologue of functions generated by this code generator
47 # creates activation frames that look as follows:
48 #
49 # :
50 # old frame
51 # argn
52 # :
53 # arg4
54 # arg3
55 # arg2
56 # arg1
57 # arg0 <-- $fp points here
58 # return address
59 # pointer to Global Offset Table
60 # saved $fp
61 # local0
62 # :
63 # local7
64 # local8
65 # :
66 # localn
67 # padding <-- $sp points here
68 #
69 # In words:
70 #
71 # The four empty slots provided by the caller are used to store
72 # arguments 0 through 3 (originally passed in $4 through $7),
73 # if necessary.
74 #
75 # The stack frame created below the four slots provided by the caller
76 # contains the following data, in order:
77 #
78 # - Saved return address (originally passed in $31), if necessary.
79 #
80 # - Saved pointer to global offset table (computed from $25), if necessary.
81 #
82 # - Saved value of $fp, if necessary.
83 #
84 # - Saved values of caller's locals 0 through 7
85 # (originally in $16 through $23), if necessary.
86 #
87 # - Values of our locals > 8, if necessary.
88 #
89 # - Padding to align $sp on a multiple of 8, if necessary.
90 #
91 #
92 # In accordance with the System V ELF ABI for MIPS, the pointer to
93 # the global offset table is calculated as follows:
94 #
95 # $gp = _gp_disp + $25
96 #
97 # where $gp is the register to store the pointer, $25 is the register
98 # holding the address of the called function, and _gp_disp is the
99 # offset between the beginning of the function and the global offset table.
100 #
101 # Callee-Save Registers
102 #
103 # Registers $16 through $23 and $28 through $30 are callee-save.
104 #
105 # All other registers are caller-save.
106 #
107 class MIPSGasGenerator < CommonCodeGenerator
108 def initialize params
109 @WORDSIZE_BITS = 2
110 @WORDSIZE = 1 << @WORDSIZE_BITS
111 @CODE_ALIGNMENT = 0
112 @DATA_ALIGNMENT = @WORDSIZE
113 @STACK_ALIGNMENT_BITS = 3
114 @STACK_ALIGNMENT = 1 << @STACK_ALIGNMENT_BITS
115 @FP_OFFSET = -3 * @WORDSIZE
116 @FUNCTION_ALIGNMENT = @WORDSIZE
117 @GP_OFFSET = -2 * @WORDSIZE
118 @INITIAL_FRAME_SIZE = 4 * @WORDSIZE
119 @REGISTER_ARG_BASE = 4
120 @NREGISTER_ARGS = 4
121 @LOCAL_REGISTERS = [:'$16', :'$17', :'$18', :'$19',
122 :'$20', :'$21', :'$22', :'$23']
123 @LOCAL_REGISTERS_SET = Set.new @LOCAL_REGISTERS
124 @REGISTER_LOCAL_BASE = 16
125 @NREGISTER_LOCALS = @LOCAL_REGISTERS.length
126 @RA_OFFSET = -@WORDSIZE
127 @RETURN = :'$2'
128 @TEMPORARY = :'$1'
129 @FUNCTION = :'$25'
130 @GOT = :'$28'
131 @SAVE_FRAME_REGISTERS = [:'$16', :'$17', :'$18', :'$19', :'$20',
132 :'$21', :'$22', :'$23', :'$28', :'$29',
133 :'$30']
134 @SAVED_FRAME_LAYOUT = {}
135 @SAVE_FRAME_REGISTERS.each_with_index { |r,i| @SAVED_FRAME_LAYOUT[r] = i }
136 @TEMPORARIES = [:'$8', :'$9', :'$10', :'$11',
137 :'$12', :'$13', :'$14', :'$15']
138 @function_end_label = nil
139 @imports = {}
140 @if_labels = []
141 super params
142 @output_file_suffix = '.s'
143 @saved_registers = []
144 @features.merge! \
145 :'bits-per-word' => '32',
146 :'bytes-per-word' => '4'
147 case @architecture
148 when :mips
149 @features[:'byte-order'] = 'big-endian'
150 when :mipsel
151 @features[:'byte-order'] = 'little-endian'
152 else
153 raise ArgumentError.new("#{self.class} does not support " +
154 "architecture #{@architecture}")
155 end
156 end
158 # Adds immediate to source and stores the result in target.
159 def addiu target, source, immediate, temporary = @TEMPORARY
160 if immediate >= -32768 && immediate < 32767
161 emit "addiu #{target}, #{source}, #{immediate}\n"
162 elsif source == "$0"
163 emit "lui #{target}, #{(immediate >> 16) & 0xffff}\n"
164 emit "ori #{target}, #{target}, #{immediate & 0xffff}\n"
165 else
166 addiu temporary, "$0", immediate
167 emit "addu #{target}, #{source}, #{temporary}\n"
168 end
169 end
171 # Return the offset from the frame base at which the nth argument is
172 # stored.
173 def arg_offset n
174 n * @WORDSIZE
175 end
177 # Returns an $fp-relative reference for the nth (0-based) argument.
178 def arg_reference n
179 offset_reference(arg_offset(n))
180 end
182 # Returns the register in which the nth (0-based) argument is stored, or
183 # nil if not stored in a register.
184 def arg_register n
185 if register_arg? n
186 "$#{@REGISTER_ARG_BASE + n}"
187 else
188 nil
189 end
190 end
192 def auto_bytes n, register
193 if n.kind_of? Integer
194 # Maintain stack alignment
195 n = (n + @STACK_ALIGNMENT - 1) / @STACK_ALIGNMENT * @STACK_ALIGNMENT
196 grow_stack n
197 else
198 temporary = @TEMPORARIES.pop
199 begin
200 load_value_into_register n, register
201 emit "addi #{register}, #{@STACK_ALIGNMENT - 1}\n"
202 emit "li #{temporary}, -#{@STACK_ALIGNMENT}\n"
203 emit "and #{register}, #{register}, #{temporary}\n"
204 emit "sub $sp, #{register}\n"
205 ensure
206 @TEMPORARIES.push temporary
207 end
208 end
209 emit "move #{register}, $sp\n" unless register == "$sp"
210 end
212 def auto_words n, register
213 if n.kind_of? Integer
214 auto_bytes n * @WORDSIZE, register
215 else
216 load_value_into_register n, register
217 if @STACK_ALIGNMENT_BITS > @WORDSIZE_BITS
218 bits = @STACK_ALIGNMENT_BITS - @WORDSIZE_BITS
219 emit "addi #{register}, #{(1 << bits) - 1}\n"
220 emit "srl #{register}, #{register}, #{bits}\n"
221 emit "sll #{register}, #{register}, #{@STACK_ALIGNMENT_BITS}\n"
222 else
223 emit "sll #{register}, #{register}, #{@WORDSIZE_BITS}\n"
224 end
225 emit "sub $sp, $sp, #{register}\n"
226 emit "move #{register}, $sp\n" unless register == "$sp"
227 end
228 end
230 # Begins a new block.
231 def begin_block *code
232 # If we are at top-level, create a frame
233 if @environment == @top_level
234 create_frame count_locals(code)
235 end
236 environment = Environment.new @environment
237 @environment = environment
238 end
240 # Emits function prologue and declare _formals_ as function arguments.
241 def begin_function formals, nlocals
242 if @environment != @top_level
243 raise "Cannot begin function when already in a function"
244 end
246 environment = Environment.new @environment
247 @frame_size = 0
248 formals.each {|x| environment.add_arg x, arg_offset(environment.args)}
249 @environment = environment
250 @function_end_label = gensym
251 emit_function_prologue formals, nlocals
252 end
254 # Defines a byte with the given value.
255 def byte value
256 emit ".byte #{value}\n"
257 end
259 # Calls a function.
260 def call func, *args
261 # Grow the stack frame, subject to 3 conditions:
262 # 1. There must be enough space to hold all arguments
263 # 2. $sp must remain a multiple of 8
264 # 3. We must provide space for at least 4 words
265 increment = ([args.length, 4].max * @WORDSIZE + 7) / 8 * 8
266 grow_stack increment
268 # Put arguments in the right places
269 n = 0
270 while n < args.length
271 if n < @NREGISTER_ARGS
272 # Put arguments up to @NREGISTER_ARGS in registers
273 load_value_into_register args[n], arg_register(n)
274 else
275 # Put other arguments on the stack
276 load_value_into_register args[n], @TEMPORARY
277 emit "sw #{@TEMPORARY}, #{n * @WORDSIZE}($sp)\n"
278 end
279 n = n + 1
280 end
282 # Load function address
283 if global? func
284 if @imports.has_key? func
285 # Load address from global offset table
286 emit "lw #{@FUNCTION}, %call16(#{func})(#{@GOT})\n"
287 else
288 # Assume label defined in this module
289 emit "lui #{@FUNCTION}, %hi(#{func})\n"
290 emit "addiu #{@FUNCTION}, %lo(#{func})\n"
291 end
292 else
293 # Load address
294 load_value_into_register func, "#{@FUNCTION}"
295 end
297 # Perform call
298 emit "jalr #{@FUNCTION}\n"
299 # brach delay slot
300 emit "nop\n"
302 # Restore original stack frame
303 grow_stack -increment
305 # restore gp
306 emit "lw #{@GOT}, #{@GP_OFFSET}($fp)\n"
307 end
309 # Emits a comment.
310 def comment text
311 emit "# #{text}\n"
312 end
314 # Starts a conditional using the specified branch instruction
315 # after the comparison.
316 def common_if comp, x, y = nil
317 temporaries = @TEMPORARIES.dup
318 xreg = load_value x, temporaries[0]
319 temporaries.delete xreg
320 yreg = load_value y, temporaries[0]
321 temporaries.delete yreg
323 falselabel = @environment.gensym
324 @if_labels.push falselabel
326 case comp
327 when :ifeq
328 emit "bne #{xreg}, #{yreg}, #{falselabel}\n"
329 when :ifge
330 emit "slt #{@TEMPORARY}, #{xreg}, #{yreg}\n"
331 emit "bne #{@TEMPORARY}, $0, #{falselabel}\n"
332 when :ifgt
333 emit "slt #{@TEMPORARY}, #{yreg}, #{xreg}\n"
334 emit "beq #{@TEMPORARY}, $0, #{falselabel}\n"
335 when :ifle
336 emit "slt #{@TEMPORARY}, #{yreg}, #{xreg}\n"
337 emit "bne #{@TEMPORARY}, $0, #{falselabel}\n"
338 when :iflt
339 emit "slt #{@TEMPORARY}, #{xreg}, #{yreg}\n"
340 emit "beq #{@TEMPORARY}, $0, #{falselabel}\n"
341 when :ifne
342 emit "beq #{xreg}, #{yreg}, #{falselabel}\n"
343 else
344 raise "Unknown conditional: #{comp}"
345 end
346 emit "nop\n"
347 end
349 # Creates an activation frame which can store nlocals local variables.
350 def create_frame nlocals
351 @frame_size = @INITIAL_FRAME_SIZE
352 if nlocals > 0
353 @frame_size = @frame_size + (nlocals * @WORDSIZE + 7) / 8 * 8
354 end
355 grow_stack @frame_size
356 @saved_registers = []
357 end
359 def emit_align alignment
360 emit ".align #{alignment}\n"
361 end
363 # Emits function prologue.
364 def emit_function_prologue formals = [], nlocals = 0
365 # Calculate new value for $gp
366 emit "lui #{@GOT}, %hi(_gp_disp)\n"
367 emit "addiu #{@GOT}, %lo(_gp_disp)\n"
368 emit "addu #{@GOT}, #{@GOT}, #{@FUNCTION}\n"
370 create_frame nlocals
372 # Save return address
373 emit "sw $31, #{@frame_size - @WORDSIZE}($sp)\n"
375 # Save gp
376 emit "sw #{@GOT}, #{@frame_size - 2 * @WORDSIZE}($sp)\n"
378 # Save fp
379 emit "sw $fp, #{@frame_size - 3 * @WORDSIZE}($sp)\n"
381 # Point fp at where sp was before we created the frame
382 addiu "$fp", "$sp", @frame_size
384 # Save parameters 0 .. 3 in the stack space that the caller
385 # should have allocated for them.
386 [@NREGISTER_ARGS, formals.length].min.times do |n|
387 ref = offset_reference(@environment[formals[n]])
388 emit "sw $#{n + @REGISTER_ARG_BASE}, #{ref}\n"
389 end
390 end
392 # Loads a word into a register.
393 def emit_load_word register, base, offset
394 emit "lw #{register}, #{offset * @WORDSIZE}(#{base})\n"
395 end
397 # Stores the value of a register in memory.
398 def emit_store_word register, base, offset
399 emit "sw #{register}, #{offset * @WORDSIZE}(#{base})\n"
400 end
402 # Ends a function body.
403 def end_function
404 if @environment == @top_level
405 raise "Cannot end function when not in a function"
406 end
408 label @function_end_label
409 # Restore saved locals
410 [@NREGISTER_LOCALS, @environment.locals].min.times do |n|
411 emit "lw #{local_register n}, #{local_reference n}\n"
412 end
413 @saved_registers = []
414 # Load return address
415 emit "lw $31, #{@RA_OFFSET}($fp)\n"
416 # Restore stack pointer
417 emit "move $sp, $fp\n"
418 # Restore frame pointer
419 emit "lw $fp, #{@FP_OFFSET}($fp)\n"
420 # Return
421 emit "jr $31\n"
422 emit "nop\n"
424 @function_end_label = nil
425 @environment = @top_level
426 end
428 # Ends the current block.
429 def end_block
430 # If we are returning to top level, restore stack pointer
431 if @environment.parent == @top_level
432 grow_stack -@frame_size
433 @saved_registers = []
434 end
436 # Restore old value of @environment
437 @environment = @environment.parent
438 end
440 # Ends a conditional.
441 def end_if
442 label = @if_labels.pop
443 emit "#{label}:\n"
444 end
446 # Evaluates the binary operation expr and store the result in register.
447 def eval_binop expr, register
448 temporaries = @TEMPORARIES.dup
449 x = load_value expr[1], temporaries[0]
450 temporaries.delete x
451 y = load_value expr[2], temporaries[0]
452 temporaries.delete y
454 case expr[0]
455 when :asr
456 emit "srav #{register}, #{x}, #{y}\n"
457 when :bsr
458 emit "srlv #{register}, #{x}, #{y}\n"
459 when :div
460 emit "div $0, #{x}, #{y}\n"
461 emit "mflo #{register}\n"
462 when :mod
463 emit "div $0, #{x}, #{y}\n"
464 emit "mfhi #{register}\n"
465 when :mul
466 emit "mult #{x}, #{y}\n"
467 emit "mflo #{register}\n"
468 when :rol
469 emit "subu #{@TEMPORARY}, $0, #{y}\n"
470 emit "srlv #{@TEMPORARY}, #{x}, #{@TEMPORARY}\n"
471 emit "sllv #{register}, #{x}, #{y}\n"
472 emit "or #{register}, #{register}, #{@TEMPORARY}\n"
473 when :ror
474 emit "subu #{@TEMPORARY}, $0, #{y}\n"
475 emit "sllv #{@TEMPORARY}, #{x}, #{@TEMPORARY}\n"
476 emit "srlv #{register}, #{x}, #{y}\n"
477 emit "or #{register}, #{register}, #{@TEMPORARY}\n"
478 when :shl
479 emit "sllv #{register}, #{x}, #{y}\n"
480 when :shr
481 emit "srlv #{register}, #{x}, #{y}\n"
482 else
483 emit "#{expr[0]} #{register}, #{x}, #{y}\n"
484 end
485 end
487 # Evaluates the expression expr and store the result in register.
488 def eval_expr expr, register
489 if expr.length == 1
490 # Load value
491 load_value_into_register expr[0], register
492 else
493 # Evaluate expression
494 op = expr[0]
495 case op
496 when :'auto-bytes'
497 auto_bytes expr[1], register
498 when :'auto-words'
499 auto_words expr[1], register
500 when :call
501 call *expr[1..-1]
502 emit "move #{register}, #{@RETURN}\n" if register != @RETURN
503 when :'get-byte'
504 get_byte expr[1], expr[2], register
505 when :'get-word'
506 get_word expr[1], expr[2], register
507 when :not
508 eval_binop [:nor, 0, expr[1]], register
509 else
510 if binop? op
511 eval_binop expr, register
512 else
513 raise "Not a magic word: #{op}"
514 end
515 end
516 end
517 end
519 # Exports symbols from the current section.
520 def export *symbols
521 symbols.each { |sym| emit ".globl #{sym}\n" }
522 end
524 # Loads byte from _base_ + _offset_ into _register_.
525 def get_byte base, offset, register
526 # If base is an integer, but offset isn't, swap them
527 if !integer?(offset) && integer?(base)
528 base, offset = [offset, base]
529 end
531 if integer? offset
532 base_reg = load_value base
533 emit "lb #{register}, #{offset}(#{base_reg})\n"
534 else
535 eval_binop [:add, base, offset], @TEMPORARY
536 emit "lb #{register}, 0(#{@TEMPORARY})\n"
537 end
538 end
540 # Loads word from _base_ + _offset_ * _@WORDSIZE_ into _register_.
541 def get_word base, offset, register
542 if integer? offset
543 base_reg = load_value base
544 emit "lw #{register}, #{offset * @WORDSIZE}(#{base_reg})\n"
545 else
546 offset_reg = @TEMPORARIES.pop
547 begin
548 load_value_into_register offset, offset_reg
549 base_reg = load_value base
550 emit "sll #{offset_reg}, #{offset_reg}, 2\n" # multiply by @WORDSIZE
551 emit "add #{@TEMPORARY}, #{base_reg}, #{offset_reg}\n"
552 emit "lw #{register}, 0(#{@TEMPORARY})\n"
553 ensure
554 @TEMPORARIES.push offset_reg
555 end
556 end
557 end
559 # Jumps to an address.
560 def goto address
561 if global? address
562 emit "j #{address}\n"
563 else
564 register = load_value address, @TEMPORARY
565 emit "jr #{register}\n"
566 end
567 emit "nop\n"
568 end
570 # Grows the stack by n bytes.
571 def grow_stack n
572 addiu "$sp", "$sp", -n
573 end
575 # Starts the false path of a conditional.
576 def ifelse
577 newlabel = @environment.gensym
578 emit "j #{newlabel}\n"
579 emit "nop\n"
580 label = @if_labels.pop
581 emit "#{label}:\n"
582 @if_labels.push newlabel
583 end
585 # Tests if x is equal to y
586 def ifeq x, y
587 common_if :ifeq, x, y
588 end
590 # Tests if x is greater than or equal to y
591 def ifge x, y
592 common_if :ifge, x, y
593 end
595 # Tests if x is strictly greater than y
596 def ifgt x, y
597 common_if :ifgt, x, y
598 end
600 # Tests if x is less than or equal to y
601 def ifle x, y
602 common_if :ifle, x, y
603 end
605 # Tests if x is strictly less than y
606 def iflt x, y
607 common_if :iflt, x, y
608 end
610 # Tests if x different from y
611 def ifne x, y
612 common_if :ifne, x, y
613 end
615 # Imports labels into the current section.
616 def import *symbols
617 # Record imported labels in @imports
618 symbols.each { |sym| @imports[sym] = sym }
619 end
621 # Emits a label.
622 def label name
623 emit "#{name}:\n"
624 end
626 # Introduces a new local variable.
627 def let symbol, *expr
628 n = @environment.locals
629 register = local_register n
630 ref = local_reference n
631 if register
632 # We will use a register to store the value
633 @environment.add_local symbol, register
634 # Save current value of register
635 emit "sw #{register}, #{ref}\n"
636 @saved_registers << register
637 # Set new value
638 eval_expr expr, register
639 else
640 # We will use the stack to store the value
641 @environment.add_local symbol, local_offset(n)
642 eval_expr expr, @TEMPORARY
643 emit "sw #{@TEMPORARY}, #{ref}\n"
644 end
645 end
647 # Loads the value at the given address.
648 def load_at address, register = @TEMPORARY
649 load_value_into_register address, register
650 emit "lw #{register}, 0(#{register})\n"
651 register
652 end
654 # Loads a value into a register.
655 # Returns the name of the register.
656 # If the value was already in a register, the name of that
657 # register is returned.
658 # Else, the value is loaded into a register and the name of
659 # that register is returned. The register to use in that case
660 # may be specified using the optional second argument.
661 def load_value x, register = @TEMPORARY
662 if substitution? x
663 x = substitute_number x[1]
664 end
666 if x == 0
667 return "$0"
668 elsif integer? x
669 addiu register, "$0", x
670 return register
671 elsif symbol? x
672 binding = @environment[x]
673 if register? binding
674 # Value is already in a register. Return register name.
675 return binding
676 elsif binding.kind_of? Integer
677 # Load value from memory.
678 emit "lw #{register}, #{offset_reference binding}\n"
679 return register
680 else
681 # Assume global
682 emit "lui #{register}, %hi(#{x})\n"
683 emit "addiu #{register}, %lo(#{x})\n"
684 return register
685 end
686 elsif at_expr? x
687 load_at x[1], register
688 else
689 raise "Don't know how to load #{x.inspect}"
690 end
691 end
693 # Loads a value into a specific register.
694 def load_value_into_register x, register
695 reg = load_value x, register
696 if reg != register
697 emit "move #{register}, #{reg}\n"
698 end
699 end
701 # Returns the offset from the frame base at which the nth local is stored.
702 # For register locals this is the offset at which the saved
703 # value (from the calling function) is stored.
704 def local_offset n
705 -(n + 4) * @WORDSIZE
706 end
708 # Returns an $sp-relative reference for the nth (0-based) local.
709 def local_reference n
710 offset_reference(local_offset(n))
711 end
713 # Returns the register in which the nth local (0-based) is stored, or
714 # nil if not stored in a register.
715 def local_register n
716 @LOCAL_REGISTERS[n]
717 end
719 # Computes the maximum number of locals that would fit in the current
720 # frame size.
721 def max_locals
722 # + 1, because the initial frame size has room for 1 local
723 (@frame_size - @INITIAL_FRAME_SIZE) / @WORDSIZE + 1
724 end
726 # Given an offset relative to the base of the frame, returns
727 # an reference to that memory location.
728 def offset_reference offset
729 "#{offset}($fp)"
730 end
732 # Returns true if the nth (0-based) local is stored in a register.
733 def register_local? n
734 n < @NREGISTER_LOCALS
735 end
737 # Returns from a function.
738 #
739 # _words_ may contain an expression to be evaluated. The result
740 # of the evaluation is returned from the function.
741 def ret *words
742 # Compute return value and store it in @RETURN
743 eval_expr(words, @RETURN) unless words.empty?
744 # Go to epilogue
745 goto @function_end_label
746 end
748 # Saves the current frame at the given location.
749 def save_frame location
750 load_value_into_register location, @TEMPORARY
751 @SAVE_FRAME_REGISTERS.each_with_index do |register,i|
752 emit "sw #{register}, #{i * @WORDSIZE}(#{@TEMPORARY})\n"
753 end
754 end
756 # Sets a variable to the result of evaluating an expression.
757 def set symbol, *expr
758 if at_expr? symbol
759 eval_expr expr, @RETURN
760 load_value_into_register symbol.to_s[1..-1].to_sym, @TEMPORARY
761 emit "sw #{@RETURN}, 0(#{@TEMPORARY})\n"
762 else
763 x = @environment[symbol]
764 if x == nil
765 raise "Cannot change value of constant #{symbol}"
766 elsif register? x
767 eval_expr expr, x
768 else
769 # Should be an integer.
770 eval_expr expr, @TEMPORARY
771 emit "sw #{@TEMPORARY}, #{offset_reference x}\n"
772 end
773 end
774 end
776 # Sets the byte at _base_ + _offset_ to _value_.
777 def set_byte base, offset, value
778 # If base is an integer, but offset isn't, swap them
779 if !integer?(offset) && integer?(base)
780 base, offset = [offset, base]
781 end
783 value_reg = @TEMPORARIES.pop
784 load_value_into_register value, value_reg
785 begin
786 if integer? offset
787 base_reg = load_value base
788 emit "sb #{value_reg}, #{offset}(#{base_reg})\n"
789 else
790 eval_binop [:add, base, offset], @TEMPORARY
791 emit "sb #{value_reg}, 0(#{@TEMPORARY})\n"
792 end
793 ensure
794 @TEMPORARIES.push value_reg
795 end
796 end
798 # Sets the word at _base_ + _offset_ * +@WORDSIZE+ to _value_.
799 def set_word base, offset, value
800 value_reg = @TEMPORARIES.pop
801 load_value_into_register value, value_reg
802 begin
803 if integer? offset
804 base_reg = load_value base
805 emit "sw #{value_reg}, #{offset * @WORDSIZE}(#{base_reg})\n"
806 else
807 offset_reg = @TEMPORARIES.pop
808 begin
809 load_value_into_register offset, offset_reg
810 base_reg = load_value base
811 emit "sll #{offset_reg}, #{offset_reg}, 2\n"
812 emit "add #{@TEMPORARY}, #{base_reg}, #{offset_reg}\n"
813 emit "sw #{value_reg}, 0(#{@TEMPORARY})\n"
814 ensure
815 @TEMPORARIES.push offset_reg
816 end
817 end
818 ensure
819 @TEMPORARIES.push value_reg
820 end
821 end
823 # Defines a string with the given value.
824 def string value
825 code = ''
826 value.each_byte do |b|
827 if b == 92
828 code << "\\\\"
829 elsif b >= 32 && b < 127 && b != 34
830 code << b.chr
831 else
832 code << sprintf("\\%03o", b)
833 end
834 end
835 emit ".ascii \"#{code}\"\n"
836 end
838 # Calls a function, re-using the current call frame if possible.
839 def tail_call func, *args
840 # Compute number of stack arguments
841 nstackargs = number_of_stack_arguments args.length
842 # If we need more stack arguments than we have now,
843 # perform a normal call and return
844 if nstackargs > number_of_stack_arguments(@environment.args)
845 emit "# Not enough space for proper tail call; using regular call\n"
846 ret :call, func, *args
847 end
849 # Back up any stack arguments we will need after we overwrite them
850 temporaries = @TEMPORARIES.dup
851 nlocals = @environment.locals
852 (@NREGISTER_ARGS...args.length).each do |i|
853 x = @environment[args[i]]
854 if integer?(x) && x < arg_offset(i)
855 # args[i] is in a location that will have been overwritten by the
856 # time we get around to passing argument i to the called function.
857 # Make a backup of the value before we overwrite it.
858 if temporaries.empty?
859 # Oh dear, we're out of temporaries.
860 # Store the value in the current stack frame, extending it
861 # as necessary.
862 if nlocals >= max_locals
863 grow_stack 8
864 end
865 reg = load_value args[i]
866 emit "sw #{reg}, #{local_reference nlocals}\n"
867 args[i] = [:local, nlocals]
868 nlocals = nlocals + 1
869 else
870 # Load the argument into a temporary
871 reg = temporaries.shift
872 load_value_into_register args[i], reg
873 # Update args[i] so we know how to get to it later
874 args[i] = [:reg, reg]
875 end
876 end
877 end
879 # Set stack arguments
880 (@NREGISTER_ARGS...args.length).each do |i|
881 arg = args[i]
882 reg = @TEMPORARY
884 # Load value
885 if arg.kind_of? Array
886 # Special cases, created above
887 case arg[0]
888 when :reg
889 reg = arg[1]
890 when :local
891 emit "lw #{reg}, #{local_reference arg[1]}\n"
892 end
893 else
894 load_value_into_register arg, reg
895 end
897 # Store value in designated place
898 emit "sw #{reg}, #{arg_reference i}\n"
899 end
901 # Set register arguments
902 [@NREGISTER_ARGS,args.length].min.times do |i|
903 reg = arg_register i
904 load_value_into_register args[i], reg
905 end
907 # Load function address
908 if global? func
909 if @imports.has_key? func
910 # Load address from global offset table
911 emit "lw #{@FUNCTION}, %call16(#{func})(#{@GOT})\n"
912 else
913 # Assume label defined in this module
914 emit "lui #{@FUNCTION}, %hi(#{func})\n"
915 emit "addiu #{@FUNCTION}, %lo(#{func})\n"
916 end
917 else
918 # Load address
919 load_value_into_register func, "#{@FUNCTION}"
920 end
922 # Restore saved registers
923 [@NREGISTER_LOCALS, @environment.locals].min.times do |n|
924 emit "lw #{local_register n}, #{local_reference n}\n"
925 end
927 # Restore return address
928 emit "lw $31, #{@RA_OFFSET}($fp)\n"
930 # Restore stack pointer
931 emit "move $sp, $fp\n"
933 # Restore frame pointer
934 emit "lw $fp, #{@FP_OFFSET}($fp)\n"
936 # Perform call
937 emit "jr #{@FUNCTION}\n"
938 # brach delay slot
939 emit "nop\n"
940 end
942 # Defines a word with the given value
943 def word value
944 emit ".int #{value}\n"
945 end
947 # Write generated code to the given IO object.
948 def write io
949 io.puts ".set noat"
950 @sections.each do |section,code|
951 unless code.empty?
952 io.puts ".section #{section.to_s}"
953 io.puts code
954 io.puts
955 end
956 end
957 end
959 end
961 # Register class for big endian MIPS
962 Voodoo::CodeGenerator.register_generator MIPSGasGenerator,
963 :architecture => :mips,
964 :format => :gas
967 # Register class for little endian MIPS
968 Voodoo::CodeGenerator.register_generator MIPSGasGenerator,
969 :architecture => :mipsel,
970 :format => :gas
972 end