ttest

Transaction Test

TTEST <Xd>

Tests the transaction nesting depth.

Details

Reads the current transaction nesting depth and state into a 64-bit register. The lower bits contain the nesting depth (0 if not in a transaction), and bits 31:0 contain transaction state information including the failure reason if a prior transaction aborted. No condition flags are affected. AArch64-only; requires TME extension.

Pseudocode Operation

Xd ← TME_NESTING_DEPTH
Xd[31:0] ← TME_STATE_AND_FAILURE_INFO
Xd[63:32] ← 0

Example

TTEST x0

Encoding

Binary Layout

1101010100100

011

0011

0001

011

Format System

Opcode 0xD5233160

Extension TME (Transactional)

Operands

Xd
Destination 64-bit integer register

Reference (Arm A64 ISA)

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xD5233160	TTEST <Xt>		A64		1101010100100 \| 011 \| 0011 \| 0001 \| 011 \| Rt

Description

This instruction writes the depth of the transaction to the destination register, or the value 0 otherwise.

Operation

if !IsTMEEnabled() then UNDEFINED;

X[t, 64] = (TSTATE.depth)<63:0>;