jump to a location

plz help me .. how can i do that ..
when i used the move function it returned error
i am using GNU compiler

asm("MOV PC,=ADDR"); returns error as shifting register expected
no error when asm("MOV PC,0x8000");

how can i jump to code block whose address is in global variable

i have also tried LDR R0 and BX r0 as in startup.s

To jump to a function whose address is in a global var, you don't need to go low-level. Declare your var as a function pointer:

    // declare pmain var as a function pointer to a int(void) function
    int (*pmain)(void);


    // do whatever you do, and load the target address in pmain
    pmain = (int (*)(void)) 0x40000000; // cast it to the func ptr type

    // ...

    // now call the code pointed by pmain.
    pmain();

    // pmain will never return ...

This produces code like:

0x00000250  E3A00101  MOV       R0,#0x40000000
0x00000254  E1A0E00F  MOV       R14,PC
0x00000258  E12FFF10  BX        R0

That is only one extra instruction from doing MOV PC, R0, generally irrelevant in a ARM processor.

Another point in your post is to optimize for a function that never returns. The RVCT has the function qualifier __declspec(noreturn) to tell the compiler that it is OK to remove the function return code from the target function.