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LDAEXD

Load-Acquire Exclusive Doubleword loads a doubleword from memory, writes it to two registers and:

• If the address has the Shared Memory attribute, marks the physical address as exclusive access for the executing PE in a global monitor
• Causes the executing PE to indicate an active exclusive access in the local monitor.

The instruction also acts as a barrier instruction with the ordering requirements 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 n : integer = UInt(Rn); if Rt[0] == '1' || t2 == 15 || n == 15 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

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

CONSTRAINED UNPREDICTABLE behavior

If t == t2, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The load instruction executes but the destination register takes an unknown value.

Assembler Symbols