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https://github.com/deplinenoise/deluxe68

A simple register allocator frontend for 68k assembly
https://github.com/deplinenoise/deluxe68

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A simple register allocator frontend for 68k assembly

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# Deluxe68



Deluxe68 is a simple (stupid) register allocator frontend for 68k assembly. It

is a source to source translator, so you'll need your regular assembler to

assemble its output. All it does is automate some tedious register allocation

for you.



## Usage



Usage is simple:



    deluxe68 input.s output.s



## Marking up source code



The following extensions are provided:



### Allocating registers



To pull from the data register pool, use `@dreg`:



                @dreg   a, b, [...]

                moveq   #0,@a

                moveq   #1,@b



Similarly, `@areg` allocates address registers. The stack pointer is

automatically reserved and will never be allocated:



                @areg   ptr

                lea     foo(pc),@ptr



### Killing registers



Use `@kill` to return a register to the pool:



                @dreg   a

                [.. code using @a ..]

                @kill   a

                moveq   #0,@a           ; now generates an error!



### Renaming an allocated register



Often in assembly programming, the purpose of a register changes. You can

express that by renaming the register:



                ; @xcoordptr = x coordinate buffer



                @dreg	x0,x1

                move.w	(@xcoordptr)+,@x0

                move.w	(@xcoordptr)+,@x1

                sub.w	@x0,@x1

                @rename @x1,@deltax         ; @x1 is now no longer a coordinate 



                ; ...



                @kill x0,deltax             ; x1 is now gone, and using it will result in an error



### Using allocated registers



You can subsitute `@name` for a register in any instruction or macro

invokation. The only caveat is if the register has been spilled, in which case

you'll instead get a reference to the stack which can generate a

memory-to-memory instruction that doesn't assemble. In that case, rework the

code.



### Spilling and restoring registers



To explicitly spill a named register to the stack (returning it to the pool) you can use `@spill`:



                @dreg   a

                moveq   #0,@a

                @spill  a               ; a is now on stack

                ...

                ...                     ; more code involving more data register allocation

                ...

                @restore a              ; a is now back in the same register it lived in before



`@spill` and `@restore` can also work with real registers. Spilling a real register ensures that

there is nothing named in that real register. This is useful when calling external code.



### Reserving and unreserving registers



To reserve a real register you can use `@reserve`:



                @reserve d0             ; d0 is no longer available to the allocator

                moveq   #0,d0

                ...

                @unreserve d0           ; return d0 to the register allocator



### Calling subroutines



When you want to call a subroutine then you typically need to place arguments in specific registers.

Use `@spill`/`@reserve` pairs to prepare the registers for use, and `@unreserve`/`@restore` pairs

when you are done:



                @spill  a0,d1

                @reserve a0,d1

                move.l  @foo,a0

                move.l  @bar,d1

                bsr     SomeExternalCode

                @unreserve a0,d1

                @restore a0,d1



If `a0` or `d1` are not allocated, the `@spill`/`@restore` operations will do nothing.

The `@reserve`/`@unreserve` operations are for bookkeeping, and will generate no code.



### Procedures



Mark a procedure entry point with `@proc ProcedureName(: name, [: name ...])`. You can

also use `@proc ProcedureName` (that is, omitting the register-name part

entirely) if your procedure has no arguments.



Doing so accomplishes two things:



- It generates an automatic `movem.l` that stores all touched registers to the stack

- All live registers are killed automatically



Similarly, instead of `rts`, use `@endproc`. This puts the inverse `movem.l` in

place, and also emits the `rts` instruction.



Any registers declared in the procedure header are automatically live and not

available for allocation in the procedure. You can however `@kill` them to

return them to the pool.



### Example



This input:



                        @proc   Foo(a0:ptr, d0:count)



                        @dreg   sum



                        moveq   #0,@sum

                        subq    #1,@count

        .loop           add.w   (@ptr)+,@sum

                        dbf     @count,.loop



                        move.w  @sum,d0

                        @endproc



Generates output similar to:



                        ; @proc   Foo(a0:ptr, d0:count)

                        ; live reg a0 => ptr

                        ; live reg d0 => count



        Foo:

                        movem.l d1,-(sp)



                        ; @dreg   sum

                        ; live reg d1 => sum



                        moveq   #0,d1

                        subq    #1,d0

        .loop           add.w   (a0)+,d1

                        dbf     d0,.loop



                        move.w  d1,d0

                        ; @endproc

                        movem.l (sp)+,d1

                        rts



### License



This software is available under the BSD 2-clause license:



Copyright (c) 2016, Andreas Fredriksson

All rights reserved.



Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions are met:



1. Redistributions of source code must retain the above copyright notice, this

   list of conditions and the following disclaimer.



2. Redistributions in binary form must reproduce the above copyright notice,

   this list of conditions and the following disclaimer in the documentation

   and/or other materials provided with the distribution.



THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE

FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.