XTEST — Test If In Transactional Execution

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

Instruction Operand Encoding

Op/En	Operand 1	Operand2	Operand3	Operand4
A	NA	NA	NA	NA

Description

The XTEST instruction queries the transactional execution status. If the instruction executes inside a transactionally 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):HLE[bit 4] = 0 and CPUID.(EAX=7, ECX=0):RTM[bit 11] = 0. If LOCK or 66H or F2H or F3H prefix is used.