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Assembler User Guide

Preface Overview of the Assembler Overview of the ARM Architecture Structure of Assembly Language Modules Writing ARM Assembly Language Condition Codes Using the Assembler Symbols, Literals, Expressions, and Operators VFP Programming Assembler Command-line Options ARM and Thumb Instructions ARM and Thumb instruction summary Instruction width specifiers Flexible second operand (Operand2) Syntax of Operand2 as a constant Syntax of Operand2 as a register with optional shi Shift operations Saturating instructions Condition code suffixes ADC ADD ADR (PC-relative) ADR (register-relative) ADRL pseudo-instruction AND ASR B BFC BFI BIC BKPT BL BLX BX BXJ CBZ and CBNZ CDP and CDP2 CLREX CLZ CMP and CMN CPS CPY pseudo-instruction DBG DMB DSB EOR ERET HVC ISB IT LDC and LDC2 LDM LDR (immediate offset) LDR (PC-relative) LDR (register offset) LDR (register-relative) LDR pseudo-instruction LDR, unprivileged LDREX LSL LSR MCR and MCR2 MCRR and MCRR2 MLA MLS MOV MOV32 pseudo-instruction MOVT MRC and MRC2 MRRC and MRRC2 MRS (PSR to general-purpose register) MRS (system coprocessor register to ARM register) MSR (ARM register to system coprocessor register) MSR (general-purpose register to PSR) MUL MVN NEG pseudo-instruction NOP ORN (Thumb only) ORR PKHBT and PKHTB PLD and PLI POP PUSH QADD QADD8 QADD16 QASX QDADD QDSUB QSAX QSUB QSUB8 QSUB16 RBIT REV REV16 REVSH RFE ROR RRX RSB RSC SADD8 SADD16 SASX SBC SBFX SDIV SEL SETEND SEV SHADD8 SHADD16 SHASX SHSAX SHSUB8 SHSUB16 SMC SMLAxy SMLAD SMLAL SMLALD SMLALxy SMLAWy SMLSD SMLSLD SMMLA SMMLS SMMUL SMUAD SMULxy SMULL SMULWy SMUSD SRS SSAT SSAT16 SSAX SSUB8 SSUB16 STC and STC2 STM STR (immediate offset) STR (register offset) STR, unprivileged STREX SUB SUBS pc, lr SVC SWP and SWPB SXTAB SXTAB16 SXTAH SXTB SXTB16 SXTH SYS TBB and TBH TEQ TST UADD8 UADD16 UASX UBFX UDIV UHADD8 UHADD16 UHASX UHSAX UHSUB8 UHSUB16 UMAAL UMLAL UMULL UND pseudo-instruction UQADD8 UQADD16 UQASX UQSAX UQSUB8 UQSUB16 USAD8 USADA8 USAT USAT16 USAX USUB8 USUB16 UXTAB UXTAB16 UXTAH UXTB UXTB16 UXTH WFE WFI YIELD VFP Instructions Directives Reference Via File Syntax

TST

10.150 TST

Test bits.

Syntax

TST{cond} Rn, Operand2
where:
cond
is an optional condition code.
Rn
is the ARM register holding the first operand.
Operand2
is a flexible second operand.

Operation

This instruction tests the value in a register against Operand2. It updates the condition flags on the result, but does not place the result in any register.
The TST instruction performs a bitwise AND operation on the value in Rn and the value of Operand2. This is the same as an ANDS instruction, except that the result is discarded.

Register restrictions

In this Thumb instruction, you cannot use SP or PC for Rn or Operand2.
In this ARM instruction, use of SP or PC is deprecated in ARMv6T2 and above.
For ARM instructions:
  • If you use PC (R15) as Rn, the value used is the address of the instruction plus 8.
  • You cannot use PC for any operand in any data processing instruction that has a register-controlled shift.

Condition flags

This instruction:
  • Updates the N and Z flags according to the result.
  • Can update the C flag during the calculation of Operand2.
  • Does not affect the V flag.

16-bit instructions

The following form of the TST instruction is available in Thumb code, and is a 16-bit instruction:
TST Rn, Rm
Rn and Rm must both be Lo registers.

Architectures

This ARM instruction is available in all architectures that support the ARM instruction set.
The TST Thumb instruction is available in all architectures that support the Thumb instruction set.

Examples

    TST     r0, #0x3F8
    TSTNE   r1, r5, ASR r1
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