ldand the Motorola 68HC11 and 68HC12 families
For the Motorola 68HC11,
ld can perform these global optimizations when you specify the ‘--relax’ command-line option.
ld finds all
jmp instructions whose targets are within eight bits, and turns them into eight-bit program-counter relative
bra instructions, respectively.
ld also looks at all 16-bit extended addressing modes and transforms them in a direct addressing mode when the address is in page 0 (between 0 and 0x0ff).
gcc is called with -mrelax, it can emit group of instructions that the linker can optimize to use a 68HC11 direct addressing mode. These instructions consists of
For 68HC11 and 68HC12,
ld can generate trampoline code to call a far function using a normal
jsr instruction. The linker will also change the relocation to some far function to use the trampoline address instead of the function address. This is typically the case when a pointer to a function is taken. The pointer will in fact point to the function trampoline.