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How to call function from ARM Assembler-processors blog?
In do_something we push the link register to the stack, so that we can pop it back off again to return, even though the call to abs will have overwritten the original contents of the link register.
Is the ARMv7-M architecture reference manual provided as is?
Your access to the information in this ARM Architecture Re ference Manual is conditiona l upon your acceptance that you will not use or permit others to use the information fo r the purposes of determining whether implementations of the ARM architecture infringe any third party patents. This ARM Architecture Reference Manual is provided “as is”.
Why does the program store R4 in arm?
The program stores r4, because the Arm procedure call standard specifies that r4-r11 must be preserved between function calls and that the called function is responsible for that preservation.
How does the link register work in arm?
One important thing to remember when working with the link register is that the latest Arm processors provide Return Stack Prediction in addition to normal branch prediction. If the processor comes across an instruction like pop {…,pc} or bx lr it will try to ‘branch predict’ the return.
Can a BL be used as a branch instruction?
On the other hand, if you have large sections of code there or if your code uses the status flags, you can implement all sorts of branching using conditional execution: Thus the single simple branch instruction can replace all of those branch and jump instructions present in other processors. BL is another branch instruction.
When to use a macro in ARM Assembler?
Once you move beyond short sequences of optimised Arm assembler, the next likely step will be to managing more complex, optimised routines using macros and functions. Macros are good for short repeated sequences, but often quickly increase the size of your code.