LDLAR

Load LOAcquire register

This instruction loads a 32-bit word or 64-bit doubleword from memory, and writes it to a register.

If the destination register is not one of WZR or XZR, LDLAR loads from memory with Acquire semantics.

For more information about memory ordering semantics, see Load LOAcquire, Store LORelease and Load-Acquire, Load-AcquirePC, and Store-Release.

For information about addressing modes, see Load/Store addressing modes.

No offset class

(FEAT_LOR)

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
1	x	0	0	1	0	0	0	1	1	0	(1)	(1)	(1)	(1)	(1)	0	(1)	(1)	(1)	(1)	(1)	Rn					Rt
size									L		Rs					o0	Rt2

32-bit encoding

(size == 10)

LDLAR <Wt>, [<Xn|SP>{, #0}]

64-bit encoding

(size == 11)

LDLAR <Xt>, [<Xn|SP>{, #0}]

Decode (all encodings)

if !IsFeatureImplemented(FEAT_LOR) then EndOfDecode(Decode_UNDEF); constant integer t = UInt(Rt); constant integer n = UInt(Rn); constant integer elsize = 8 << UInt(size); constant integer regsize = if elsize == 64 then 64 else 32; constant boolean acquire = t != 31; constant boolean tagchecked = n != 31;

Assembler Symbols

<Wt>	Is the 32-bit name of the general-purpose register to be transferred, 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.

<Xt>	Is the 64-bit name of the general-purpose register to be transferred, encoded in the "Rt" field.

Operation

bits(64) address; constant integer dbytes = elsize DIV 8; constant AccessDescriptor accdesc = CreateAccDescLOR(MemOp_LOAD, tagchecked, acquire, t); if n == 31 then CheckSPAlignment(); address = SP[64]; else address = X[n, 64]; constant bits(elsize) data = Mem[address, dbytes, accdesc]; X[t, regsize] = ZeroExtend(data, regsize);

Operational information

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

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