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Swap halfword in memory atomically loads a 16-bit halfword 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.
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | A | R | 1 | Rs | 1 | 0 | 0 | 0 | 0 | 0 | Rn | Rt | ||||||||||||
size |
if !HaveAtomicExt() then UNDEFINED;
integer t =() then UnallocatedEncoding();
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_ORDEREDATOMICRWAccType_ORDEREDRW else AccType_ATOMICRW;
AccType stacctype = if R == '1' then AccType_ORDEREDATOMICRWAccType_ORDEREDRW else AccType_ATOMICRW;
<Ws> | Is the 32-bit name of the general-purpose register to be stored, encoded in the "Rs" field. |
<Wt> | Is the 32-bit name of the general-purpose register to be loaded, encoded in the "Rt" field. |
<Xn|SP> | 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;
ifif n == 31 then HaveMTEExt() then
SetNotTagCheckedInstruction(n == 31);
if n == 31 then
CheckSPAlignment();
address = SP[];
else
address = X[n];
// All observers in the shareability domain observe the
// following load and store atomically.
data = Mem[address, datasize DIV 8, ldacctype];
Mem[address, datasize DIV 8, stacctype] = X[s];
X[t] = ZeroExtend(data, regsize);
Internal version only: isa v30.25v29.05, AdvSIMD v27.01v26.0, pseudocode v85-xml-00bet8_rc3v35.3
; Build timestamp: 2018-09-13T132018-06-16T09:0445
Copyright © 2010-2018 ARM Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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