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RealView Assembler User's Guide
Preface Introduction Writing ARM Assembly Language
Introduction Overview of the ARM architecture Architecture versions ARM, Thumb, Thumb‑2, and Thumb‑2EE instruction ARM, Thumb, and ThumbEE state Processor mode Registers Instruction set overview Instruction capabilities Structure of assembly language modules Layout of assembly language source files An example ARM assembly language module Calling subroutines Conditional execution The ALU status flags Conditional execution Using conditional execution Example of the use of conditional execution The Q flag Loading constants into registers Direct loading with MOV and MVN Loading with MOV32 Loading with LDR Rd, =const Loading addresses into registers Direct loading with ADR and ADRL Loading addresses with LDR Rd, =label Load and store multiple register instructions Load and store multiple instructions available in Implementing stacks with LDM and STM Block copy with LDM and STM Using macros Test‑and‑branch macro example Unsigned integer division macro example Using frame directives Assembly language changes Assembler Reference ARM and Thumb Instructions Directives ReferenceConditional execution
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| Home > Writing ARM Assembly Language > Conditional execution > Conditional execution | |||
The instructions that can be conditional have an optional condition code, shown in syntax descriptions as {. This condition is encoded in ARM instructions, and encoded in a preceding cond}IT instruction for Thumb-2 instructions. An instruction with a condition code is only executed if the condition code flags in the APSR meet the specified condition. Table 2.2 shows the condition codes that you can use.
On Thumb processors without Thumb-2, the { field is only permitted on certain branch instructions.cond}
Table 2.2 also shows the relationship between condition code suffixes and the N, Z, C and V flags.
Table 2.2. Condition code suffixes
| Suffix | Flags | Meaning |
|---|---|---|
EQ | Z set | Equal |
NE | Z clear | Not equal |
CS/HS | C set | Higher or same (unsigned >= ) |
CC/LO | C clear | Lower (unsigned < ) |
MI | N set | Negative |
PL | N clear | Positive or zero |
VS | V set | Overflow |
VC | V clear | No overflow |
HI | C set and Z clear | Higher (unsigned > ) |
LS | C clear or Z set | Lower or same (unsigned <= ) |
GE | N and V the same | Signed >= |
LT | N and V differ | Signed < |
GT | Z clear, N and V the same | Signed > |
LE | Z set, N and V differ | Signed <= |
AL | Any | Always. This suffix is normally omitted. |
Example 2.3 shows an example of conditional execution.
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