gcc - arm-linux-gnueabi compiler options -

i using, arm-linux-gnueabi-gcc compile c programs arm processor in linux. however, not sure default arm mode compiles.

for example, c code:

test.c

unsigned int main() {     return 0x1ffff; }  arm-linux-gnueabi-gcc -o test test.c 

now, when @ disassembly of main() function objdump, can see:

arm-linux-gnueabi-objdump -d test  <main>:      push    {r7}     add r7, sp, #0     movw    r3, #65535  ; 0xffff     movt    r3, #1     mov r0, r3     mov sp, r7     pop {r7}     bx  lr 

it appears disassembly thumb mode of arm (because of push instruction).

how can display disassembly follows:

      .sect ".text"       .global _fn _fn:  movw a1,#65535       movt a1,#1        bx lr 

or this

      .sect ".text"       .global _fn _fn:  ldr a1, con1       bx lr        .sect ".text"       .align 4 con1: .word 0x1ffff 

i saw example here:

http://e2e.ti.com/support/development_tools/compiler/f/343/t/40580.aspx

however, unable view disassembly way displayed there.

thanks.

push doesn't tell in thumb mode, in fact arm's new assembly syntax called unified assembly language means in of cases can compile same code arm or thumb-2 instruction sets.

other problem that, compiling in -o0 mode adds instructions easy of debugability. try -o2 , should instruction flow want.

gcc -v switch in arm-linux-gnueabi-gcc -v should show how built, tells overall default options uses when compiling source code.

one last thing, targeted assembly sequence mentioned uses atpcs register naming scheme (check objdump doc information), uses a1 instead of r0 example. can setting disassembler-options in objdump -m switch. below;

$ arm-linux-gnueabihf-gcc -c -o2 -o test test.c $ arm-linux-gnueabihf-objdump -m reg-names-special-atpcs -d test  test:     file format elf32-littlearm   disassembly of section .text.startup:  00000000 <main>:    0:   f64f 70ff   movw    a1, #65535  ; 0xffff    4:   f2c0 0001   movt    a1, #1    8:   4770        bx  lr    a:   bf00        nop 

another option assembly output gcc using -s switch. below;

$ arm-linux-gnueabihf-gcc -s test.c 

then should new file called test.s in same folder. don't know if there option set register naming.