Some questions

Fri Apr 27 11:24:39 UTC 2007

>> > Why do you need to build an indirect jump table? What are
>> you trying
>> > to do?
>> >
>> I am implementing a smalltalk. It compiles directly to
>> machine code, with exupery. The last time I asked something
>> to the list I was starting to use exupery. Now I am almost
>> done with that (without many optimizations). I am doing unit
>> testing right now.
>> My first mail to the list asked what would be the best to
>> implement a new st, so, in my implementation I use:
>> 0 tagged ints.
>> A simple (and a little fat) object memory.
>> A very straightforward send mechanism (with C calling
>> convention for calling methods).
>> No contexts, but using BlockClosures (frames are the same as
>> in C, the C compiler does not differentiate C code from ST code).
>
> Hi Guille, I don't get something here. If you are using Exupery to
> generate
> asm code why are you talking about a C compiler?
>
Hi Guille, I don't get something here. If you are using Exupery to generate
asm code why are you talking about a C compiler?

Ok, short answer:

The ST VM is responsible for a lot of things, one of them is to interpret
bytecodes. In my ST every method is stored in x86 machine code, so, I
don’t need any interpreter to interpret methods (the CPU does all that).,
but VM’s have to deal with a lot of other things, like primitives and
method lookups. That part is done in C.

Long answer:
Right now building my VM is a little messy, this is more or less what I do:

•	File out the classes I need from Squeak.

Right now I use only ~50 basic classes, and ~40 test classes. The file out
mechanism generates one file per class, called “ClassName.st”

•	Compile methods in squeak

I load every *.st file from squeak (I said load, not file in!). While I
read the classes I compile the methods with SmaCC – Refactory Browser  -
Exupery. This generates assembler as an intermediate step, but the final
step produces x86 machine code. This is stored in every method.

•	Generate assembler files from squeak

Once everything is compiled I generate an assembler file for every class,
for example “ClassName.s”. This could be a little confusing. I already
compiled everything, why would I need to generate assembler files? Because
assembler files are very handy to represent the image, take a look into a
real method:

/* Test>>test Method bytecodes */
.global Test_Class_test_bytecodes
Test_Class_test_bytecodes:
	.int ByteArray + 1
	.int 154 /* Number: 77 */
	.int 17888 /* Number: 8944 */
.global _Test_Class_test_bytecodes
_Test_Class_test_bytecodes:
	.byte 85, 137, 229, 139, 69, 8, 80, 184
	.int Test_Class_test_literals + 1
	.byte 139, 64, 11, 232
	.int getMethodIP - 4 - .
	.byte 255, 208, 129, 196, 4, 0, 0, 0, 139, 69, 8, 80, 184
	.int Test_Class_test_literals + 1
	.byte 139, 64, 15, 232
	.int getMethodIP - 4 - .
	.byte 255, 208, 129, 196, 4, 0, 0, 0, 80, 184
	.int Test_Class_test_literals + 1
	.byte 139, 64, 19, 232
	.int getMethodIP - 4 - .
	.byte 255, 208, 129, 196, 4, 0, 0, 0, 201, 195
	.align 2

As you can see, that is not assembler, but those bytes, are generated with
Exupery. Notice the references to other Objects. It is very easy to
represent the image with this method. For example, look how an array would
be represented in this way:

/* Array */
.global Test_Class_test_literals
Test_Class_test_literals:
	.int Array + 1
	.int 24 /* Number: 12 */
	.int 9784 /* Number: 4892 */
.global _Test_Class_test_literals
_Test_Class_test_literals:
	.int symbol_initialize + 1
	.int symbol_selfTest + 1
	.int symbol_printString + 1

Those + 1 , are there because of the 0 tagged integers.

•	Generate a library with the code

With all the .s files I generate a library

•	Compile everything into a static executable

I compile the library and the other C files into a static executable. I do
that because right now, I haven’t implemented the st compiler. And that’s
why I still need squeak. When I implement the compiler (SmaCC-RB-Exupery),
I will have to generate some kind of dynamic loading of the st part.

Cheers
Guille

>> I compile the ST code from .st files to .s (assembler) using
>> SmaCC, RefactoryBrowser, and then exupery, I still need
>> squeak in order to run all that.
>> I only use the bottom layer of exupery, (does not use
>> IntermediateXXXXXX
>> classes)
>> I implemented the cmovxx instruction in exupery, because it
>> is very useful.
>> But I need jump tables to implement for example, faster
>> versions of ifTrue:ifFalse:, and a lot of other things. This
>> could lead to faster results.
>> Right Now I am getting (with the same machine), tinyBenchmarks:
>> Squeak: 172043010 bytecodes/sec; 5468700 sends/sec
>> Squeak/Exupery: 775757575 bytecodes/sec; 13569800 sends/sec.
>> myST/Exupery: 1072251308 bytecodes/sec; 36056442 sends/sec
>>
> That are numbers!
>
> Cheers,
>
> Sebastian
>
>
>> > Bryce
>> > _______________________________________________
>> > Exupery mailing list
>> > Exupery at lists.squeakfoundation.org
>> > http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/exupery
>> >
>> Cheers
>> Guille
>>
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