EN0-001 Exam Dumps : ARM Accredited Engineer

In an ARMv7-A system, the following C function calculates a simple checksum for an input data packet of variable length. The checksum is defined to be the sum of all of the 16-bit data items in the packet modulo 65536. The parameter data_items contains the number of 2-byte data items in the packet, and it cannot be zero by design.

When using an ARM compiler, which TWO of the following optimizations could improve the performance of this code? (Choose two)

Which one of these statements is TRUE about code running on final hardware without a debugger attached?

An interrupt handler contains the following instruction sequence at the end. The purpose of these instructions is to clear the interrupt request in the interrupt controller and then safely re-enable interrupts.

STR r0, [r1] ; write to interrupt controller register to clear interrupt request

CPSIE i ; re-enable IRQ interrupts

Which of the following instructions should be placed at position in order to ensure that the interrupt controller sees the write before interrupts are re-enabled?