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5-16 Copyright © 2000, 2001 ARM Limited. All rights reserved. ARM DUI 0068B
5.2.1 ADD and SUB, low registers
Add and subtract. There are three forms of these instructions that operate on low
registers. You can:
• add or subtract the contents of two registers, and place the result in a third register
• add a small integer to, or subtract it from, the value in a register, and place the
result in a different register
• add a larger integer to, or subtract it from, the value in a register, and return the
result to the same register.
Syntax
op Rd, Rn, Rm
op Rd, Rn, #expr3
op Rd, #expr8
where:
op
is either
ADD
or
SUB
.
Rd
is the destination register. It is also used for the first operand in
op
Rd,#expr8
instructions.
Rn
is a register containing the first operand.
Rm
is a register containing the second operand.
expr3
is an expression evaluating (at assembly time) to an integer in the range
–7 to +7.
expr8
is an expression evaluating (at assembly time) to an integer in the range
–255 to +255.
Usage
op Rd,Rn,Rm
performs an
Rn
+
Rm
or an
Rn
–
Rm
operation, and places the result in
Rd
.
op Rd,Rn,#expr3
performs an
Rn
+
expr3
or an
Rn
–
expr3
operation, and places the result
in
Rd
.
op Rd,#expr8
performs an
Rd
+
expr8
or an
Rd
–
expr8
operation, and places the result in
Rd
.