Chapter 13. ARM Dependent Features

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This pseudo op will always evaluate to a legal ARM instruction that does nothing. Currently it

will evaluate to MOV r0, r0.

LDR

ldr

register

, =

expression

If expression evaluates to a numeric constant then a MOV or MVN instruction will be used in

place of the LDR instruction, if the constant can be generated by either of these instructions.

Otherwise the constant will be placed into the nearest literal pool (if it not already there) and a

PC relative LDR instruction will be generated.

ADR

adr

register

label

This instruction will load the address of

label

into the indicated register. The instruction will

evaluate to a PC relative ADD or SUB instruction depending upon where the label is located. If

the label is out of range, or if it is not defined in the same file (and section) as the ADR instruction,

then an error will be generated. This instruction will not make use of the literal pool.

ADRL

adrl

register

label

This instruction will load the address of

label

into the indicated register. The instruction will

evaluate to one or two PC relative ADD or SUB instructions depending upon where the label is

located. If a second instruction is not needed a NOP instruction will be generated in its place, so

that this instruction is always 8 bytes long.

If the label is out of range, or if it is not defined in the same file (and section) as the ADRL

instruction, then an error will be generated. This instruction will not make use of the literal pool.

For information on the ARM or Thumb instruction sets, see [ARM Software Development Toolkit

Reference Manual], Advanced RISC Machines Ltd.

13.6. Mapping Symbols

The ARM ELF specification requires that special symbols be inserted into object files to mark certain

features:

$a

At the start of a region of code containing ARM instructions.

$t

At the start of a region of code containing THUMB instructions.

$d

At the start of a region of data.

The assembler will automatically insert these symbols for you   there is no need to code them yourself.

Support for tagging symbols ($b, $f, $p and $m) which is also mentioned in the current ARM ELF