XEND — Transactional End

Instruction Operand Encoding

Description

The instruction marks the end of an RTM code region. If this corresponds to the outermost scope (that is, including this XEND instruction, the number of XBEGIN instructions is the same as number of XEND instructions), the logical processor will attempt to commit the logical processor state atomically. If the commit fails, the logical processor will rollback all architectural register and memory updates performed during the RTM execution. The logical processor will resume execution at the fallback address computed from the outermost XBEGIN instruction. The EAX register is updated to reflect RTM abort information.

XEND executed outside a transactional region will cause a #GP (General Protection Fault).

Operation

IF (RTM_ACTIVE = 0) THEN
    SIGNAL #GP
    ELSE
    RTM_NEST_COUNT--
    IF (RTM_NEST_COUNT = 0) THEN
        Try to commit transaction
        IF fail to commit transactional execution
            THEN
            GOTO RTM_ABORT_PROCESSING;
            ELSE (* commit success *)
            RTM_ACTIVE ← 0
        FI;
    FI;
FI;
(* For any RTM abort condition encountered during RTM execution *)
RTM_ABORT_PROCESSING:
Restore architectural register state
Discard memory updates performed in transaction
Update EAX with status
RTM_NEST_COUNT ← 0
RTM_ACTIVE ← 0
IF 64-bit Mode
    THEN
    RIP ← fallbackRIP
    ELSE
    EIP ← fallbackEIP
FI;
END

Flags Affected

None

Intel C/C++ Compiler Intrinsic Equivalent

XEND:
void _xend( void );

SIMD Floating-Point Exceptions

None

Other Exceptions