What does bx lr do in ARM assembly language?
arm, assembly
Solution
It's almost always returning from a function, like `ret` in some other ISAs like AArch64.
`bx` stands for branch and exchange instruction set Which means that according to the lsb (least significant bit) of the address to branch to, the processor will treat the next instruction as ARM or as thumb.
As `lr` usually holds the return address, it means that this is a return from a function, and if the lsb of `lr` is 1, it will treat the code at that address as thumb, otherwise, it will treat it as ARM.
Problem
I can't seem to get my head around what `bx lr` does and how it differs from `bl (label)`. I know that `bl (label)` stores the return address of that function in the link register but I don't know what `bx lr` does.