Add My Idea to the C++ Compiler

From: Bryan Parkoff (bryan.nospam.parkoff_at_nospam.com)
Date: 12/28/03 

Date: Sun, 28 Dec 2003 04:14:37 GMT

    You may notice that switch (...) is much faster than function that can
gain a big improved performance because it only use JMP instruction however
function is required to use CALL, PUSH, and POP instruction that can be
slower.
    I created three functions in an array. Array is called
pArray_Func[xx](). pArray_Func[xx]() contains three functions. "xx" can be
used to point each function.
    Let say, I have over 1,000 functions. I would put "inline" to each
functions. It does not matter that each function may contain more than 50
lines. It is really BIG that C/C++ compiler tells "inline" is used for
short like 3-5 lines ONLY. I have decided to tell C/C++ compiler by forcing
"inline" there because I don't care if my code is getting bigger and bigger.
I allow 50 lines to be copied to each functions. CALL, PUSH, and POP
instructions can always be removed automatically by the C/C++ compiler
before JMP instruction can always be placed each function.
    It is very neat according to my design that I wanted. If I care to keep
small code rather than big code, "inline" should not be used.
    Right now, there is a big problem. I can't place "inline" into
pArray_Func[xx](). I can see why. JMP can show "JMP [EAX+EDX*4] that will
work fine. C/C++ compiler can only place "CALL [EAX+EDX*4] into
pArrayFunc[xx](). It is not designed to replace from "CALL [EAX+EDX*4]" to
"JMP [EAX+EDX*4] if "inline" is there. C/C++ compiler will always ignore
"inline".
    Another option is to place 1,000 functions inside switch (...). Look
like below.

switch (xx)
{
    case 1:
        Func1();
    case 2:
        Func2();
    case 3:
        Func3();
}

    C/C++ compiler can see this code above before it can place "inline" to
each functions inside switch (...). It is very annoying me because I have
to read switch (...) from line to line by scrolling up/down. It is very
long for me to read. It is not HARD to FIND BUG (off my point).
    I would want to see only 3 or 4 lines there instead of over 20,000 lines
that contains switch (...). pArrayFunc() may be very useful. We should
tell the C/C++ authors to add keyword like __USE_JMP_INLINE instead of
__inline, _inline, or inline.
    Newest version of C/C++ compiler like Intel Compiler can accept
__USE_JMP_INLINE. "__USE_JMP_INLINE" will be added to pArrayFunc[xx](), but
"inline" will always be same for 1,000 functions. After you compile your
C++ source code, it will recognize "__USE_JMP_INLINE", it will rename from
"CALL [EAX+EDX*4]" to "JMP [EAX+EDX*4]" so each functions' PUSH and POP
instructions will be removed. It will look like real JMP Table inside
pArrayFunc[xx](). It would be perfect for easy reading.
    Please state your opinion what you think about my idea to modify C/C++
compiler's source code. ***Do not tell that there is no __USE_JMP_INLINE to
all C/C++ compiler. Please ask the authors to add __USE_JMP_INLINE keyword.
It would be perfect and neat C++ coding.***

    I have put pArrayFunc[xx]() inside C++ class example below. It gives
you an idea however "__USE_JMP_INLINE" does not EXIST, but should be added
near the future.

#include <stdio.h>

class Test

{

public:

            inline void Get_a() { printf("A: %d\n", _a); }

            inline void Get_b() { printf("B: %d\n", _b); }

            inline void Get_c() { printf("C: %d\n", _c); }

            inline void Set_a(unsigned int a) { _a = a; }

            inline void Set_b(unsigned int b) { _b = b; }

            inline void Set_c(unsigned int c) { _c = c; }

            typedef void (Test::*Action)();

            static const Action Menu[3];

            inline void Call();

private:

            unsigned int _a;

            unsigned int _b;

            unsigned int _c;

};

const Test::Action Test::Menu[3] =

{

            &Test::Get_a,

            &Test::Get_b,

            &Test::Get_c

};

inline void Test::Call()

{

            for (int a = 0; a <= 2; a++)

                        (this->*Menu[a])();

}

void main(void)

{

            Test test;

            test.Set_a(1);

            test.Set_b(2);

            test.Set_c(3);

            test.Call();

            return;

} 

-- 
Bryan Parkoff

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