Procedure

1. Create a C source file, litpool.c, containing the following code:

   int f1() {
       return 0xdeadbeef;
   }
   int f2() {
       return 0xdeadbeef;
   }

2. Compile the source with -S to create an assembly file:
   armclang -c -S -target arm-arm-none-eabi -mcpu=cortex-m0 -ffunction-sections litpool.c -o litpool.s

   Note

   -ffunction-sections is the default.

   Because 0xdeadbeef is a difficult constant to create using instructions, a literal pool is created, for example:

   ...
   f1:
   	.fnstart
   @ BB#0:
   	ldr	r0, __arm_cp.0_0
   	bx	lr
   	.p2align	2
   @ BB#1:
   __arm_cp.0_0:
   	.long	3735928559              @ 0xdeadbeef
   ...
   	.fnend
   
   ...
   	.code	16                      @ @f2
   	.thumb_func
   f2:
   	.fnstart
   @ BB#0:
   	ldr	r0, __arm_cp.1_0
   	bx	lr
   	.p2align	2
   @ BB#1:
   __arm_cp.1_0:
   	.long	3735928559              @ 0xdeadbeef
   ...
   	.fnend
   ...

   Note

   There is one copy of the constant for each function, because armclang cannot share these constants between both functions.
3. Compile the source to create an object:
   armclang -c -target arm-arm-none-eabi -mcpu=cortex-m0 litpool.c -o litpool.o
4. Link the object file using the --merge_litpools option:
   armlink --cpu=Cortex-M0 --merge_litpools litpool.o -o litpool.axf

   Note

   --merge_litpools is the default.
5. Run fromelf to view the image structure:
   fromelf -c -d -s -t -v -z litpool.axf
   The following example shows the result of the merge:

   ...
       f1
           0x00008000:    4801        .H      LDR      r0,[pc,#4] ; [0x8008] = 0xdeadbeef
           0x00008002:    4770        pG      BX       lr
       f2
           0x00008004:    4800        .H      LDR      r0,[pc,#0] ; [0x8008] = 0xdeadbeef
           0x00008006:    4770        pG      BX       lr
       $d.4
       __arm_cp.1_0
           0x00008008:    deadbeef    ....    DCD    3735928559
   ...