| blob | dd6afdc08635c1abbe0dad1cdfe43b1d087833e5 |
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 # Exports symbols from the current section.
364 def emit_export *symbols
365 symbols.each { |sym| emit ".globl #{sym}\n" }
366 end
368 # Emits function prologue.
369 def emit_function_prologue formals = [], nlocals = 0
370 # Calculate new value for $gp
371 emit "lui #{@GOT}, %hi(_gp_disp)\n"
372 emit "addiu #{@GOT}, %lo(_gp_disp)\n"
373 emit "addu #{@GOT}, #{@GOT}, #{@FUNCTION}\n"
375 create_frame nlocals
377 # Save return address
378 emit "sw $31, #{@frame_size - @WORDSIZE}($sp)\n"
380 # Save gp
381 emit "sw #{@GOT}, #{@frame_size - 2 * @WORDSIZE}($sp)\n"
383 # Save fp
384 emit "sw $fp, #{@frame_size - 3 * @WORDSIZE}($sp)\n"
386 # Point fp at where sp was before we created the frame
387 addiu "$fp", "$sp", @frame_size
389 # Save parameters 0 .. 3 in the stack space that the caller
390 # should have allocated for them.
391 [@NREGISTER_ARGS, formals.length].min.times do |n|
392 ref = offset_reference(@environment[formals[n]])
393 emit "sw $#{n + @REGISTER_ARG_BASE}, #{ref}\n"
394 end
395 end
397 # Imports labels into the current section.
398 def emit_import *symbols
399 # Record imported labels in @imports
400 symbols.each { |sym| @imports[sym] = sym }
401 end
403 # Emits a label type annotation.
404 def emit_label_type name, type
405 type_map = {
406 :code => "@function",
407 :data => "@object",
408 }
409 emit ".type #{name}, #{type_map[type]}\n"
410 end
412 # Emits a label size annotation.
413 def emit_label_size name
414 emit ".size #{name}, .-#{name}\n"
415 end
417 # Loads a word into a register.
418 def emit_load_word register, base, offset
419 emit "lw #{register}, #{offset * @WORDSIZE}(#{base})\n"
420 end
422 # Stores the value of a register in memory.
423 def emit_store_word register, base, offset
424 emit "sw #{register}, #{offset * @WORDSIZE}(#{base})\n"
425 end
427 # Ends a function body.
428 def end_function
429 if @environment == @top_level
430 raise "Cannot end function when not in a function"
431 end
433 label @function_end_label
434 # Restore saved locals
435 [@NREGISTER_LOCALS, @environment.locals].min.times do |n|
436 emit "lw #{local_register n}, #{local_reference n}\n"
437 end
438 @saved_registers = []
439 # Load return address
440 emit "lw $31, #{@RA_OFFSET}($fp)\n"
441 # Restore stack pointer
442 emit "move $sp, $fp\n"
443 # Restore frame pointer
444 emit "lw $fp, #{@FP_OFFSET}($fp)\n"
445 # Return
446 emit "jr $31\n"
447 emit "nop\n"
449 @function_end_label = nil
450 @environment = @top_level
451 end
453 # Ends the current block.
454 def end_block
455 # If we are returning to top level, restore stack pointer
456 if @environment.parent == @top_level
457 grow_stack -@frame_size
458 @saved_registers = []
459 end
461 # Restore old value of @environment
462 @environment = @environment.parent
463 end
465 # Ends a conditional.
466 def end_if
467 label = @if_labels.pop
468 emit "#{label}:\n"
469 end
471 # Evaluates the binary operation expr and store the result in register.
472 def eval_binop expr, register
473 temporaries = @TEMPORARIES.dup
474 x = load_value expr[1], temporaries[0]
475 temporaries.delete x
476 y = load_value expr[2], temporaries[0]
477 temporaries.delete y
479 case expr[0]
480 when :asr
481 emit "srav #{register}, #{x}, #{y}\n"
482 when :bsr
483 emit "srlv #{register}, #{x}, #{y}\n"
484 when :div
485 emit "div $0, #{x}, #{y}\n"
486 emit "mflo #{register}\n"
487 when :mod
488 emit "div $0, #{x}, #{y}\n"
489 emit "mfhi #{register}\n"
490 when :mul
491 emit "mult #{x}, #{y}\n"
492 emit "mflo #{register}\n"
493 when :rol
494 emit "subu #{@TEMPORARY}, $0, #{y}\n"
495 emit "srlv #{@TEMPORARY}, #{x}, #{@TEMPORARY}\n"
496 emit "sllv #{register}, #{x}, #{y}\n"
497 emit "or #{register}, #{register}, #{@TEMPORARY}\n"
498 when :ror
499 emit "subu #{@TEMPORARY}, $0, #{y}\n"
500 emit "sllv #{@TEMPORARY}, #{x}, #{@TEMPORARY}\n"
501 emit "srlv #{register}, #{x}, #{y}\n"
502 emit "or #{register}, #{register}, #{@TEMPORARY}\n"
503 when :shl
504 emit "sllv #{register}, #{x}, #{y}\n"
505 when :shr
506 emit "srlv #{register}, #{x}, #{y}\n"
507 else
508 emit "#{expr[0]} #{register}, #{x}, #{y}\n"
509 end
510 end
512 # Evaluates the expression expr and store the result in register.
513 def eval_expr expr, register
514 if expr.length == 1
515 # Load value
516 load_value_into_register expr[0], register
517 else
518 # Evaluate expression
519 op = expr[0]
520 case op
521 when :'auto-bytes'
522 auto_bytes expr[1], register
523 when :'auto-words'
524 auto_words expr[1], register
525 when :call
526 call *expr[1..-1]
527 emit "move #{register}, #{@RETURN}\n" if register != @RETURN
528 when :'get-byte'
529 get_byte expr[1], expr[2], register
530 when :'get-word'
531 get_word expr[1], expr[2], register
532 when :not
533 eval_binop [:nor, 0, expr[1]], register
534 else
535 if binop? op
536 eval_binop expr, register
537 else
538 raise "Not a magic word: #{op}"
539 end
540 end
541 end
542 end
544 # Loads byte from _base_ + _offset_ into _register_.
545 def get_byte base, offset, register
546 # If base is an integer, but offset isn't, swap them
547 if !integer?(offset) && integer?(base)
548 base, offset = [offset, base]
549 end
551 if integer? offset
552 base_reg = load_value base
553 emit "lb #{register}, #{offset}(#{base_reg})\n"
554 else
555 eval_binop [:add, base, offset], @TEMPORARY
556 emit "lb #{register}, 0(#{@TEMPORARY})\n"
557 end
558 end
560 # Loads word from _base_ + _offset_ * _@WORDSIZE_ into _register_.
561 def get_word base, offset, register
562 if integer? offset
563 base_reg = load_value base
564 emit "lw #{register}, #{offset * @WORDSIZE}(#{base_reg})\n"
565 else
566 offset_reg = @TEMPORARIES.pop
567 begin
568 load_value_into_register offset, offset_reg
569 base_reg = load_value base
570 emit "sll #{offset_reg}, #{offset_reg}, 2\n" # multiply by @WORDSIZE
571 emit "add #{@TEMPORARY}, #{base_reg}, #{offset_reg}\n"
572 emit "lw #{register}, 0(#{@TEMPORARY})\n"
573 ensure
574 @TEMPORARIES.push offset_reg
575 end
576 end
577 end
579 # Jumps to an address.
580 def goto address
581 if global? address
582 emit "j #{address}\n"
583 else
584 register = load_value address, @TEMPORARY
585 emit "jr #{register}\n"
586 end
587 emit "nop\n"
588 end
590 # Grows the stack by n bytes.
591 def grow_stack n
592 addiu "$sp", "$sp", -n
593 end
595 # Starts the false path of a conditional.
596 def ifelse
597 newlabel = @environment.gensym
598 emit "j #{newlabel}\n"
599 emit "nop\n"
600 label = @if_labels.pop
601 emit "#{label}:\n"
602 @if_labels.push newlabel
603 end
605 # Tests if x is equal to y
606 def ifeq x, y
607 common_if :ifeq, x, y
608 end
610 # Tests if x is greater than or equal to y
611 def ifge x, y
612 common_if :ifge, x, y
613 end
615 # Tests if x is strictly greater than y
616 def ifgt x, y
617 common_if :ifgt, x, y
618 end
620 # Tests if x is less than or equal to y
621 def ifle x, y
622 common_if :ifle, x, y
623 end
625 # Tests if x is strictly less than y
626 def iflt x, y
627 common_if :iflt, x, y
628 end
630 # Tests if x different from y
631 def ifne x, y
632 common_if :ifne, x, y
633 end
635 # Introduces a new local variable.
636 def let symbol, *expr
637 n = @environment.locals
638 register = local_register n
639 ref = local_reference n
640 if register
641 # We will use a register to store the value
642 @environment.add_local symbol, register
643 # Save current value of register
644 emit "sw #{register}, #{ref}\n"
645 @saved_registers << register
646 # Set new value
647 eval_expr expr, register
648 else
649 # We will use the stack to store the value
650 @environment.add_local symbol, local_offset(n)
651 eval_expr expr, @TEMPORARY
652 emit "sw #{@TEMPORARY}, #{ref}\n"
653 end
654 end
656 # Loads the value at the given address.
657 def load_at address, register = @TEMPORARY
658 load_value_into_register address, register
659 emit "lw #{register}, 0(#{register})\n"
660 register
661 end
663 # Loads a value into a register.
664 # Returns the name of the register.
665 # If the value was already in a register, the name of that
666 # register is returned.
667 # Else, the value is loaded into a register and the name of
668 # that register is returned. The register to use in that case
669 # may be specified using the optional second argument.
670 def load_value x, register = @TEMPORARY
671 if substitution? x
672 x = substitute_number x[1]
673 end
675 if x == 0
676 return "$0"
677 elsif integer? x
678 addiu register, "$0", x
679 return register
680 elsif symbol? x
681 binding = @environment[x]
682 if register? binding
683 # Value is already in a register. Return register name.
684 return binding
685 elsif binding.kind_of? Integer
686 # Load value from memory.
687 emit "lw #{register}, #{offset_reference binding}\n"
688 return register
689 else
690 # Assume global
691 if @relocated_symbols.include? x
692 emit "lw #{register}, %got(#{x})(#{@GOT})\n"
693 else
694 emit "lui #{register}, %hi(#{x})\n"
695 emit "addiu #{register}, %lo(#{x})\n"
696 end
697 return register
698 end
699 elsif at_expr? x
700 load_at x[1], register
701 else
702 raise "Don't know how to load #{x.inspect}"
703 end
704 end
706 # Loads a value into a specific register.
707 def load_value_into_register x, register
708 reg = load_value x, register
709 if reg != register
710 emit "move #{register}, #{reg}\n"
711 end
712 end
714 # Returns the offset from the frame base at which the nth local is stored.
715 # For register locals this is the offset at which the saved
716 # value (from the calling function) is stored.
717 def local_offset n
718 -(n + 4) * @WORDSIZE
719 end
721 # Returns an $sp-relative reference for the nth (0-based) local.
722 def local_reference n
723 offset_reference(local_offset(n))
724 end
726 # Returns the register in which the nth local (0-based) is stored, or
727 # nil if not stored in a register.
728 def local_register n
729 @LOCAL_REGISTERS[n]
730 end
732 # Computes the maximum number of locals that would fit in the current
733 # frame size.
734 def max_locals
735 # + 1, because the initial frame size has room for 1 local
736 (@frame_size - @INITIAL_FRAME_SIZE) / @WORDSIZE + 1
737 end
739 # Given an offset relative to the base of the frame, returns
740 # an reference to that memory location.
741 def offset_reference offset
742 "#{offset}($fp)"
743 end
745 # Returns true if the nth (0-based) local is stored in a register.
746 def register_local? n
747 n < @NREGISTER_LOCALS
748 end
750 # Returns from a function.
751 #
752 # _words_ may contain an expression to be evaluated. The result
753 # of the evaluation is returned from the function.
754 def ret *words
755 # Compute return value and store it in @RETURN
756 eval_expr(words, @RETURN) unless words.empty?
757 # Go to epilogue
758 goto @function_end_label
759 end
761 # Saves the current frame at the given location.
762 def save_frame location
763 load_value_into_register location, @TEMPORARY
764 @SAVE_FRAME_REGISTERS.each_with_index do |register,i|
765 emit "sw #{register}, #{i * @WORDSIZE}(#{@TEMPORARY})\n"
766 end
767 end
769 # Sets a variable to the result of evaluating an expression.
770 def set symbol, *expr
771 if at_expr? symbol
772 eval_expr expr, @RETURN
773 load_value_into_register symbol.to_s[1..-1].to_sym, @TEMPORARY
774 emit "sw #{@RETURN}, 0(#{@TEMPORARY})\n"
775 else
776 x = @environment[symbol]
777 if x == nil
778 raise "Cannot change value of constant #{symbol}"
779 elsif register? x
780 eval_expr expr, x
781 else
782 # Should be an integer.
783 eval_expr expr, @TEMPORARY
784 emit "sw #{@TEMPORARY}, #{offset_reference x}\n"
785 end
786 end
787 end
789 # Sets the byte at _base_ + _offset_ to _value_.
790 def set_byte base, offset, value
791 # If base is an integer, but offset isn't, swap them
792 if !integer?(offset) && integer?(base)
793 base, offset = [offset, base]
794 end
796 value_reg = @TEMPORARIES.pop
797 load_value_into_register value, value_reg
798 begin
799 if integer? offset
800 base_reg = load_value base
801 emit "sb #{value_reg}, #{offset}(#{base_reg})\n"
802 else
803 eval_binop [:add, base, offset], @TEMPORARY
804 emit "sb #{value_reg}, 0(#{@TEMPORARY})\n"
805 end
806 ensure
807 @TEMPORARIES.push value_reg
808 end
809 end
811 # Sets the word at _base_ + _offset_ * +@WORDSIZE+ to _value_.
812 def set_word base, offset, value
813 value_reg = @TEMPORARIES.pop
814 load_value_into_register value, value_reg
815 begin
816 if integer? offset
817 base_reg = load_value base
818 emit "sw #{value_reg}, #{offset * @WORDSIZE}(#{base_reg})\n"
819 else
820 offset_reg = @TEMPORARIES.pop
821 begin
822 load_value_into_register offset, offset_reg
823 base_reg = load_value base
824 emit "sll #{offset_reg}, #{offset_reg}, 2\n"
825 emit "add #{@TEMPORARY}, #{base_reg}, #{offset_reg}\n"
826 emit "sw #{value_reg}, 0(#{@TEMPORARY})\n"
827 ensure
828 @TEMPORARIES.push offset_reg
829 end
830 end
831 ensure
832 @TEMPORARIES.push value_reg
833 end
834 end
836 # Defines a string with the given value.
837 def string value
838 code = ''
839 value.each_byte do |b|
840 if b == 92
841 code << "\\\\"
842 elsif b >= 32 && b < 127 && b != 34
843 code << b.chr
844 else
845 code << sprintf("\\%03o", b)
846 end
847 end
848 emit ".ascii \"#{code}\"\n"
849 end
851 # Calls a function, re-using the current call frame if possible.
852 def tail_call func, *args
853 # Compute number of stack arguments
854 nstackargs = number_of_stack_arguments args.length
855 # If we need more stack arguments than we have now,
856 # perform a normal call and return
857 if nstackargs > number_of_stack_arguments(@environment.args)
858 emit "# Not enough space for proper tail call; using regular call\n"
859 ret :call, func, *args
860 end
862 # Back up any stack arguments we will need after we overwrite them
863 temporaries = @TEMPORARIES.dup
864 nlocals = @environment.locals
865 (@NREGISTER_ARGS...args.length).each do |i|
866 x = @environment[args[i]]
867 if integer?(x) && x < arg_offset(i)
868 # args[i] is in a location that will have been overwritten by the
869 # time we get around to passing argument i to the called function.
870 # Make a backup of the value before we overwrite it.
871 if temporaries.empty?
872 # Oh dear, we're out of temporaries.
873 # Store the value in the current stack frame, extending it
874 # as necessary.
875 if nlocals >= max_locals
876 grow_stack 8
877 end
878 reg = load_value args[i]
879 emit "sw #{reg}, #{local_reference nlocals}\n"
880 args[i] = [:local, nlocals]
881 nlocals = nlocals + 1
882 else
883 # Load the argument into a temporary
884 reg = temporaries.shift
885 load_value_into_register args[i], reg
886 # Update args[i] so we know how to get to it later
887 args[i] = [:reg, reg]
888 end
889 end
890 end
892 # Set stack arguments
893 (@NREGISTER_ARGS...args.length).each do |i|
894 arg = args[i]
895 reg = @TEMPORARY
897 # Load value
898 if arg.kind_of? Array
899 # Special cases, created above
900 case arg[0]
901 when :reg
902 reg = arg[1]
903 when :local
904 emit "lw #{reg}, #{local_reference arg[1]}\n"
905 end
906 else
907 load_value_into_register arg, reg
908 end
910 # Store value in designated place
911 emit "sw #{reg}, #{arg_reference i}\n"
912 end
914 # Set register arguments
915 [@NREGISTER_ARGS,args.length].min.times do |i|
916 reg = arg_register i
917 load_value_into_register args[i], reg
918 end
920 # Load function address
921 if global? func
922 if @imports.has_key? func
923 # Load address from global offset table
924 emit "lw #{@FUNCTION}, %call16(#{func})(#{@GOT})\n"
925 else
926 # Assume label defined in this module
927 emit "lui #{@FUNCTION}, %hi(#{func})\n"
928 emit "addiu #{@FUNCTION}, %lo(#{func})\n"
929 end
930 else
931 # Load address
932 load_value_into_register func, "#{@FUNCTION}"
933 end
935 # Restore saved registers
936 [@NREGISTER_LOCALS, @environment.locals].min.times do |n|
937 emit "lw #{local_register n}, #{local_reference n}\n"
938 end
940 # Restore return address
941 emit "lw $31, #{@RA_OFFSET}($fp)\n"
943 # Restore stack pointer
944 emit "move $sp, $fp\n"
946 # Restore frame pointer
947 emit "lw $fp, #{@FP_OFFSET}($fp)\n"
949 # Perform call
950 emit "jr #{@FUNCTION}\n"
951 # brach delay slot
952 emit "nop\n"
953 end
955 # Defines a word with the given value
956 def word value
957 emit ".int #{value}\n"
958 end
960 # Write generated code to the given IO object.
961 def write io
962 io.puts ".set noat"
963 @sections.each do |section,code|
964 unless code.empty?
965 io.puts ".section #{section.to_s}"
966 io.puts code
967 io.puts
968 end
969 end
970 end
972 end
974 # Register class for big endian MIPS
975 Voodoo::CodeGenerator.register_generator MIPSGasGenerator,
976 :architecture => :mips,
977 :format => :gas
980 # Register class for little endian MIPS
981 Voodoo::CodeGenerator.register_generator MIPSGasGenerator,
982 :architecture => :mipsel,
983 :format => :gas
985 end