Swap byte in memory atomically loads an 8-bit byte from a memory location, and stores the value held in a register back to the same memory location. The value initially loaded from memory is returned in the destination register.

For more information about memory ordering semantics see Load-Acquire, Store-Release.

For information about memory accesses see Load/Store addressing modes.



SWPAB (A == 1 && R == 0)

SWPAB <Ws>, <Wt>, [<Xn|SP>]

SWPALB (A == 1 && R == 1)

SWPALB <Ws>, <Wt>, [<Xn|SP>]

SWPB (A == 0 && R == 0)

SWPB <Ws>, <Wt>, [<Xn|SP>]

SWPLB (A == 0 && R == 1)

SWPLB <Ws>, <Wt>, [<Xn|SP>]

if !HaveAtomicExt() then UNDEFINED; integer t = UInt(Rt); integer n = UInt(Rn); integer s = UInt(Rs); integer datasize = 8 << UInt(size); integer regsize = if datasize == 64 then 64 else 32; AccType ldacctype = if A == '1' && Rt != '11111' then AccType_ORDEREDATOMICRW else AccType_ATOMICRW; AccType stacctype = if R == '1' then AccType_ORDEREDATOMICRW else AccType_ATOMICRW; boolean tag_checked = n != 31;

Assembler Symbols


Is the 32-bit name of the general-purpose register to be stored, encoded in the "Rs" field.


Is the 32-bit name of the general-purpose register to be loaded, encoded in the "Rt" field.


Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.


bits(64) address; bits(datasize) data; bits(datasize) store_value; if HaveMTE2Ext() then SetTagCheckedInstruction(tag_checked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n]; store_value = X[s]; data = MemAtomic(address, MemAtomicOp_SWP, store_value, ldacctype, stacctype); X[t] = ZeroExtend(data, regsize);

Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41

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