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Writing ARM and Thumb Assembly Language
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All rights reserved. 2-31
Note
The label used with
ADR
or
ADRL
must be within the same code section. The assembler
faults references to labels that are out of range in the same section. The linker faults
references to labels that are out of range in other code sections.
In Thumb state,
ADR
can generate word-aligned addresses only.
ADRL
is not available in Thumb code. Use it only in ARM code.
Example 2-6 shows the type of code generated by the assembler when assembling
ADR
and
ADRL
pseudo-instructions. It is supplied as
adrlabel.s
in the
examples\asm
subdirectory of the ADS. Refer to Code examples on page 2-2 for instructions on how
to assemble, link, and execute the example.
The instructions listed in the comments are the ARM instructions generated by the
assembler.
Example 2-6
AREA adrlabel, CODE,READONLY
ENTRY ; Mark first instruction to execute
Start
BL func ; Branch to subroutine
stop MOV r0, #0x18 ; angel_SWIreason_ReportException
LDR r1, =0x20026 ; ADP_Stopped_ApplicationExit
SWI 0x123456 ; ARM semihosting SWI
LTORG ; Create a literal pool
func ADR r0, Start ; => SUB r0, PC, #offset to Start
ADR r1, DataArea ; => ADD r1, PC, #offset to DataArea
; ADR r2, DataArea+4300 ; This would fail because the offset
; cannot be expressed by operand2
; of an ADD
ADRL r2, DataArea+4300 ; => ADD r2, PC, #offset1
; ADD r2, r2, #offset2
MOV pc, lr ; Return
DataArea SPACE 8000 ; Starting at the current location,
; clears a 8000 byte area of memory
; to zero
END