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RealView Assembler User's Guide

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RealView Assembler User's Guide

Preface Introduction Writing ARM Assembly Language Assembler Reference ARM and Thumb Instructions Instruction summary Memory access instructions Address alignment LDR and STR (immediate offset) LDR and STR (register offset) LDR and STR (User mode) LDR (pc-relative) ADR PLD, PLDW, and PLI LDM and STM PUSH and POP RFE SRS LDREX and STREX CLREX SWP and SWPB General data processing instructions Flexible second operand ADD, SUB, RSB, ADC, SBC, and RSC SUBS pc, lr AND, ORR, EOR, BIC, and ORN CLZ CMP and CMN MOV and MVN MOVT TST and TEQ SEL REV, REV16, REVSH, and RBIT ASR, LSL, LSR, ROR, and RRX SDIV and UDIV Multiply instructions MUL, MLA, and MLS UMULL, UMLAL, SMULL, and SMLAL SMULxy and SMLAxy SMULWy and SMLAWy SMLALxy SMUAD{X} and SMUSD{X} SMMUL, SMMLA, and SMMLS SMLAD and SMLSD SMLALD and SMLSLD UMAAL Saturating instructions Saturating arithmetic QADD, QSUB, QDADD, and QDSUB SSAT and USAT Parallel instructions Parallel add and subtract USAD8 and USADA8 SSAT16 and USAT16 Packing and unpacking instructions BFC and BFI SBFX and UBFX SXT, SXTA, UXT, and UXTA PKHBT and PKHTB Branch and control instructions B, BL, BX, BLX, and BXJ IT CBZ and CBNZ TBB and TBH Coprocessor instructions CDP and CDP2 MCR, MCR2, MCRR, and MCRR2 MRC, MRC2, MRRC and MRRC2 LDC, LDC2, STC, and STC2 Miscellaneous instructions BKPT SVC MRS MSR CPS SMC SETEND NOP, SEV, WFE, WFI, and YIELD DBG, DMB, DSB, and ISB Instruction width selection in Thumb Instruction width specifiers, .W and .N Different behavior for some instructions Diagnostic warning ThumbEE instructions ENTERX and LEAVEX CHKA HB, HBL, HBLP, and HBP Pseudo-instructions ADRL pseudo-instruction MOV32 pseudo-instruction LDR pseudo-instruction UND pseudo-instruction Directives Reference

CBZ and CBNZ

4.8.3. CBZ and CBNZ

Compare and Branch on Zero, Compare and Branch on Non-Zero.

Syntax

CBZ Rn, label
CBNZ Rn, label

where:

Rn

is the register holding the operand.

label

is the branch destination.

Usage

You can use the CBZ or CBNZ instructions to avoid changing the condition code flags and to reduce the number of instructions.

Except that it does not change the condition code flags, CBZ Rn, label is equivalent to:

    CMP     Rn, #0
    BEQ     label

Except that it does not change the condition code flags, CBNZ Rn, label is equivalent to:

    CMP     Rn, #0
    BNE     label

Restrictions

The branch destination must be within 4 to 130 bytes after the instruction.

These instructions must not be used inside an IT block.

Condition flags

These instructions do not change the flags.

Architectures

These 16-bit Thumb instructions are available in ARMv6T2 and above.

There are no ARM or 32-bit Thumb versions of these instructions.

Copyright © 2007, 2008 ARM Limited. All rights reserved.ARM DUI 0379B
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