ARM Software Development Toolkit User Guide 5.7. Load and store multiple register instructions

5.7. Load and store multiple register instructions

The ARM and Thumb instruction sets include instructions that load and store multiple registers to and from memory.

Multiple register transfer instructions provide an efficient way of moving the contents of several registers to and from memory. They are most often used for block copy and for stack operations for context changing at subroutine entry and exit. The advantages of using a multiple register transfer instruction instead of a series of single data transfer instructions include:

Smaller code size.
There is only a single instruction fetch overhead, rather than many instruction fetches.
Only one register writeback cycle is required for a multiple register load or store, as opposed to one for each register.
On uncached ARM processors, the first word of data transferred by a load or store multiple is always a nonsequential memory cycle, but all subsequent words transferred can be sequential memory cycles. Sequential memory cycles are faster in most systems.

Note

The lowest numbered register is transferred to or from the lowest memory address accessed, and the highest numbered register to or from the highest address accessed. The order the of registers in the register list in the instructions makes no difference.

Use the -checkreglist assembler option to check that registers in register lists are specified in increasing order. See Command syntax in the ARM Software Development Toolkit Reference Guide.

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