elpam

notices for using llvm bitcode

2011-02-04T09:39:00.000-08:00

If someone use ANTLR3 and LLVM 2.7 to construct a compiler, I believe some of my notices/hints written here will be very very useful.

1. function's parameter is read only. you should use "alloca" to create a "local variable" to make function parameter writable.
each "basic block" should have a "terminate" instruction. -> br and ret
each "function module" should have only one "ret" instruction. only one!!!!!!!!!!

here's my solution： create a "entry block" and "return block". puts every "alloca" to "entry block" and create a "alloca" for return variable. Puts "ret" instruction in "return block". If other statement need to return different return value, I just store "return variable" and "br" to "return block".

ANTLR3's tree walker is great to write "multiple pass" symbol table constructor. But it's a little inconvenient for LLVM IR generator.

EX) conditional block, if() ：I need to use IR Builder to create a conditional jump before it's successor not created. When antlr3 walk to this point, my program still don't know how many elsif and else success behind me.

LLVM is ssa system.

But it's impossible to let all of your expression be ssa form (just my experience).
I just using alloca to present cross-statement variable, store these variable to "stack" instead SSA is much good choice for me.
If you want to fully utilize SSA's benefit, you should write your own IR to present an expression. Using ANTLR3's grammar tree, you don't need to worry about your IR's operator priority. Just be careful for assignment's LHF and RHS.

symbol mangling (compiler)

2011-02-03T07:43:00.000-08:00

in the past year (2010), I'm working for a "action script" like language compiler.
Integrate with LLVM and ANTLR3, It's really easy to come out a "worked and lots of buggies" compiler. My target code is not just execute on a hardware, and it's not designed for general purpose. According to above situation, design a GOOD enough environment to verify my works.

1. there's no entry point for these program. (main function). I need to design another way to invoke my function. Either integrate with "C/C++" or just using cheat mangling to create a main function.
2. Because our platform target is very specially, the function signatures are different between language level and "llvm bitcode" level. (for other purpose, will append function parameter and change parameter types). If I want to using C/C++ to call my llvm bitcode, I need to get correct script name mangling and invoke function with correct parameters.

........mmmmm just mumbling. After read NameMangling: http://en.wikipedia.org/wiki/Name_mangling#Complex_example .

I think i need to change my old/stupid mangling design.

Hint for gitorious

2011-01-22T01:30:00.000-08:00

2011, Jan.

If you want to install/construct your own gitorious server on your ubuntu 10.10LTS.
Please remember do not use ruby 1.9.1

There's too many compatiable issue need to be fixed.
If you just a newbie with RoR. just use 1.8, don't challenge it.

GObject - First Vala Programming

2009-12-12T07:28:00.000-08:00


svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

為達到最佳效果，請使用以上指令下載範例碼並與以下投影片一起服用。

Coppy from wiki:Vala "Vala is a programming language that was created with the goal of bringing modern language features to C, without additional runtime requirements and with little overhead, by targeting the GObject object system. It was developed by Jürg Billeter and Raffaele Sandrini. The syntax borrows heavily from C#. Rather than being compiled directly to assembler or to an intermediate language, Vala is compiled to C which is then compiled with the platform's standard C compiler."

According above description, any program written by Vala could translate to standard C code. So I add this topic between GObject tutorial. Because it really save our time for development.

I rewrote the sample previous GObject example by using Vala. You will find those boring redundant code are no longer need to self-written.


/* 6-1 - maman-bar.vala */
public class MamanBar : Object {
public int a;
public int b;

public MamanBar(){
      a = 1; b = 2;
}
public void dumpall() {
      stdout.printf ("a = %d b = %d\n",a,b);
}

}


#> valac -o maman-bar-vala maman-bar.vala main.vala
#> ./maman-bar-vala
a = 1 b = 2

I would like to demo how to connect vala and c together. We use the same C code from previous sample.


int main (int argc, char *argv[])
{
 /* this function should be executed first. Before everything  */
 g_type_init();

 /* Create our object */
 MamanBar *bar = maman_bar_new();
 maman_bar_dumpall( bar );

 return 0;
}

The only difference are compile commands.


#> valac -C -H maman-bar.h  maman-bar.vala
#> cc `pkg-config --cflags glib-2.0 gtk+-2.0`   -c -o main.o main.c
#> cc `pkg-config --cflags glib-2.0 gtk+-2.0`   -c -o maman-bar.o maman-bar.c
#> cc -o maman-bar-c main.o maman-bar.o `pkg-config --libs glib-2.0 gtk+-2.0`
#> ./maman-bar-c
a = 1 b = 2

GObject - Virtual Function

2009-12-11T07:38:00.000-08:00


svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

為達到最佳效果，請使用以上指令下載範例碼並與以下投影片一起服用。

= Member Function =
: the functions which have a self parameter

If you ever write python code to implement about CLASS. The class member function may look like bellow:


def f(self):
    return 'hello world'

You can find out the first parameter always be class itself. And the function will use 'self' to access the member value. The same principle we use in GObject programming.
We always use thiz (instead this, because C++ syntax) for first parameter in each member functions. Whether public function or private function.

= Public Member Function =
: What's different between "Just Function" and "Public Member Function"?

Same as C++, in GObject programming, all the functions define in the class structure header with first self parameter are public member functions.
In example 5-1 we use a public member function to replace what we done in main.c, dump all member value.


void maman_bar_dump_all_value( MamanBar* thiz )
{
    printf(" bar->a = (%d) bar->b = (%d)\n", thiz->a, thiz->b );
}

= Private Member Function =
: just simple rule, static functions (with first self parameter) are private

It's too simple. I believe we don't need to explain this idea.

= Member Function with Virtual Feature =



/* 5-2 */
/* maman-bar.h */
struct _MamanBarClass {
    GObjectClass parent;
    /* class members */

    void (* incAll) ( MamanBar* );
};

/* maman-bar.c */
static void maman_bar_class_init ( MamanBarClass* class)
{
    class->incAll = maman_bar_inc_all;
}

In this step, we need to explain what's different between MamanBar and MamanBarClass. We use g_object_new to allocate a memory size from heap, and g_object_new invoke function maman_bar_init to initialize this memory region. But different from MamanBar, MamanBarClass should only exists one copy during one time period.


    maman_bar_dump_all_value( bar );
    MAMAN_BAR_GET_CLASS( bar ) -> incAll(bar);
    maman_bar_dump_all_value( bar );

In above sample code, you can see we use MAMAN_BAR_GET_CLASS to access CLASS structure, and use it to invoke the class member functions.
The whole idea in virtual function is child class will use it's member function replace the parent class's member function pointer.

= Virtual Function =

Base on example 4-2. We implement sub-bar class and replace the parent's class function pointer.


/* 5-3 */
/* sub-bar.c */
static void sub_bar_class_init ( SubBarClass* class)
{
    MamanBarClass* parent_class = class;
    parent_class->incAll = sub_bar_inc_all;
}

After constructor invoke (base_init and class_init ...), we can invoke child function by using parent's fp. It's simple and easy to use.


/* main.c */
    SubBar *subbar = g_object_new (SUB_BAR_TYPE, NULL);
    sub_bar_dump_all_value( subbar );
    MAMAN_BAR_GET_CLASS( subbar ) -> incAll( subbar );
    sub_bar_dump_all_value( subbar );

Gobject - Inherit (Chinese)

2009-11-30T21:30:00.000-08:00

svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

Of course, you can download the source by using above command.
I found there's some different between GLIB v2.0 and v2.2.
So I rewrote the example code. and separated the "STEPS" more detail.

I believe it will be helpfull for someone(?) who wanna study GObject in dummy.

Gobject - Inherit (Chinese)

View more documents from Kai-Feng Chou.

* BTW. i give up Google Doc in this time. because it can't not upload odf file. and i don't want to twit the slide every time :( .

OpenEmbedded Build Process

2009-11-25T18:07:00.000-08:00

I Just draw a diagram to explain the OpenEmbedded build process for internal project. If it's useful for someone else, just take it.

Open Embedded Build Process (One Page)

View more documents from Kai-Feng Chou.

OOP in C - Before GObject

2009-11-23T20:01:00.000-08:00

svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

為達到最佳效果，請使用以上指令下載範例碼並與以下投影片一起服用。

we need to try write something before GObject programming. It let us understand more for "WHY USING GOBJECT". I write some example file, you can try to rewrite them after you read the slide and sample code.

Enjoy It.

OOP in C - Before GObject

View more presentations from Kai-Feng Chou.

OOP in C - Virtual Function

2009-11-22T05:38:00.000-08:00

svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

為達到最佳效果，請使用以上指令下載範例碼並與以下投影片一起服用。

OO的Member Function 其實是可以使用Function Pointer及Structure來描述 (廢話)

struct A 
{
int a;
FP  method_a;
};

再加上一點技巧, 就可以完成Virtual Function的實作 :)
Enjoy It.

OOP in C - Virtual Function

View more documents from elpam.

OOP in C - Inherit

2009-11-21T08:08:00.000-08:00


svn checkout http://gobject-learing.googlecode.com/svn/trunk/ gobject-learing-read-only

為達到最佳效果，請使用以上指令下載範例碼並與以下投影片一起服用。

其實說穿了，整個概念就是以下的程式碼。


/* 1-4.h */

struct A{

int a;

int b;

};

struct B{

struct A parent;

int c;

};

OOP in C - Inherit

View more documents from elpam.

another half

2009-11-20T11:17:00.000-08:00

well, let's start to sort out what i done before.

GObject learning for first. After that i plan to post out the real-mode programming tutorial.