x86doc › XTEST - Test if in Transactional Execution

XTEST—Test if in Transactional Execution

Opcode/Instruction	Op/En	64/32bit Mode Support	CPUID Feature Flag	Description
NP 0F 01 D6 XTEST	ZO	V/V	HLE or RTM	Test if executing in a transactional region.

Instruction Operand Encoding

Op/En	Operand 1	Operand2	Operand3	Operand4
ZO	N/A	N/A	N/A	N/A

Description

The XTEST instruction queries the transactional execution status. If the instruction executes inside a transaction-ally executing RTM region or a transactionally executing HLE region, then the ZF flag is cleared, else it is set.

Operation

XTEST

IF (RTM_ACTIVE = 1 OR HLE_ACTIVE = 1)
    THEN
         ZF := 0
    ELSE
         ZF := 1
FI;

Flags Affected

The ZF flag is cleared if the instruction is executed transactionally; otherwise it is set to 1. The CF, OF, SF, PF, and AF, flags are cleared.

Intel C/C++ Compiler Intrinsic Equivalent

XTEST int _xtest( void );

SIMD Floating-Point Exceptions

None.

Other Exceptions

#UD	CPUID.(EAX=7, ECX=0):EBX.HLE[bit 4] = 0 and CPUID.(EAX=7, ECX=0):EBX.RTM[bit 11] = 0. If LOCK prefix is used.