CFLAGS += -ffunction-sections -fdata-sections    # to remove dead code, if any, at link time
LDFLAGS += -Wl,--gc-sections    #remove dead code ("garbage collection")

CFLAGS += -ffunction-sections -fdata-sections    # to remove dead code, if any, at link time  
LDFLAGS += -Wl,--gc-sections    #remove dead code ("garbage collection")

CFLAGS += -ffunction-sections -fdata-sections -Wl,--gc-sections

.text :        /* collect all sections that should go into FLASH after startup  */
    {
/*        *(.text)                    /* all .text sections (code)  */
        *(.text.main)
        *(.text.USART0_setup)
        *(.text.uart0_putc)
        *(.text.Usart_c_irq_handler)
        *(.text.LowLevelInit)
        *(.text.blinker)
                         ...

  .text :
  {
    .......
    *(.text)            /* code */
    *(.text.*)          /* code */

    .............
  } > ROM

0010047c <EnableFIQ>:
  10047c:    e10f0000     mrs    r0, CPSR
  100480:    e3c03040     bic    r3, r0, #64; 0x40
  100484:    e129f003     msr    CPSR_fc, r3
  100488:    e12fff1e     bx    lr
Disassembly of section .text.EnableIRQ:

0010048c <EnableIRQ>:
  10048c:    e10f0000     mrs    r0, CPSR
  100490:    e3c03080     bic    r3, r0, #128; 0x80
  100494:    e129f003     msr    CPSR_fc, r3
  100498:    e12fff1e     bx    lr
Disassembly of section .text.RestoreIRQ:

0010049c <RestoreIRQ>:
  10049c:    e10f2000     mrs    r2, CPSR
  1004a0:    e2000080     and    r0, r0, #128; 0x80
  1004a4:    e3c23080     bic    r3, r2, #128; 0x80
  1004a8:    e1833000     orr    r3, r3, r0
  1004ac:    e129f003     msr    CPSR_fc, r3
  1004b0:    e1a00002     mov    r0, r2
  1004b4:    e12fff1e     bx    lr

main.out: $(OBJECTS) test.cmd
    @ echo "..linking"
    $(LD) $(LFLAGS) -o main.out $(OBJECTS) libc.a libm.a libgcc.a

TOTAL SIZE:
arm-elf-size -t main.out
   text       data        bss        dec        hex    filename
      0          0          0          0          0    main.out
      0          0          0          0          0    (TOTALS)

/* GNU assembler controls  */
.vectors                                    /* all assembler code that follows will go into .vectors section     */
.arm                                    /* compile for 32-bit ARM instruction set                         */
.align                                    /* align section on 32-bit boundary                                 */

/* ============================================================ */
/*                         VECTOR TABLE                              */
/*                                                                */
/*    Must be located in FLASH at address 0x00000000                */
/*                                                                */
/*    Easy to do if this file crt.s is first in the list             */
/*    for the linker step in the makefile, e.g.                    */
/*                                                                */
/*        $(LD) $(LFLAGS) -o main.out  crt.o main.o                */
/*                                                                */
/* ============================================================ */

_vec_reset:        b           _init_reset                /* RESET vector - must be at 0x00000000    */
_vec_undef:        b           AT91F_Undef_Handler        /* Undefined Instruction vector            */
_vec_swi:        b           _vec_swi                /* Software Interrupt vector            */
_vec_pabt:        b           AT91F_Pabt_Handler        /* Prefetch abort vector                */
_vec_dabt:        b           AT91F_Dabt_Handler        /* Data abort vector                    */
_vec_rsv:        nop                                 /* Reserved vector                        */
_vec_irq:        b           AT91F_Irq_Handler        /* Interrupt Request (IRQ) vector        */
_vec_fiq:        b            AT91F_Default_FIQ_handler    /*Fast interrupt request (FIQ) vector    */

.text     /* place remaining code to .text section */

SECTIONS
{
    . = 0;                                /* set location counter to address zero  */
    
    .text :                                /* collect all sections that should go into FLASH after startup  */
    {
        KEEP(*(.vectors))
        *(.text)                        /* all .text sections (code)  */

. = 0x0000000;
         .text : { KEEP(*crt.o (.text)) }>CODE =0
         .text :
         ...