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STLEXD

Store-Release Exclusive Doubleword stores a doubleword from two registers to memory if the executing PE has exclusive access to the memory at that address, and returns a status value of 0 if the store was successful, or of 1 if no store was performed.

The instruction also has memory ordering semantics as described in Load-Acquire, Store-Release.

For more information about support for shared memory see Synchronization and semaphores. For information about memory accesses see Memory accesses.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

Decode for this encoding

let t : integer = UInt(Rt); let t2 : integer = t + 1; let d : integer = UInt(Rd); let n : integer = UInt(Rn); if d == 15 || Rt[0] == '1' || t2 == 15 || n == 15 then UnpredictableProcedure(); end; if d == n || d == t || d == t2 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If d == t, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The store instruction executes but the value stored is unknown.

If d == n, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction performs the store to an UNKNOWN address.

If Rt<0> == '1', then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction executes with the additional decode: Rt<0> = '0'.
• The instruction executes with the additional decode: t2 = t.
• The instruction executes as described, with no change to its behavior and no additional side effects.

If Rt == '1110', then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction is handled as described in Using R15.

T1

Decode for this encoding

let d : integer = UInt(Rd); let t : integer = UInt(Rt); let t2 : integer = UInt(Rt2); let n : integer = UInt(Rn); if d == 15 || t == 15 || t2 == 15 || n == 15 then UnpredictableProcedure(); end; if d == n || d == t || d == t2 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If d == t, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The store instruction executes but the value stored is unknown.

If d == n, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction performs the store to an UNKNOWN address.

Assembler Symbols

Operational information

This instruction is a data-independent-time instruction as described in About the DIT bit.

2026-03_rel 2026-03-26 20:48:11

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