What is the use of writing to the program counter in the arm?

Hi DEEPAKSA R,

Writing to the PC was a common practice on the 32b legacy Arm cores. Before armv4t, there was no BX instruction. Programmers were using a single LDM instruction at the end of their function with the PC in the registers list. This was effectively implementing POP + RETURN in one instruction.

On recent 32b Arm cores it is more frequent to use a BX instruction to explicitly return from a function. Also usually not all the instructions writing to the PC can be predicted.

With the more recent armv8 aarch64, writing directly to the PC is not possible anymore.

Hi DEEPAKSA R,

Writing to the PC was a common practice on the 32b legacy Arm cores. Before armv4t, there was no BX instruction. Programmers were using a single LDM instruction at the end of their function with the PC in the registers list. This was effectively implementing POP + RETURN in one instruction.

On recent 32b Arm cores it is more frequent to use a BX instruction to explicitly return from a function. Also usually not all the instructions writing to the PC can be predicted.

With the more recent armv8 aarch64, writing directly to the PC is not possible anymore.