LDAPURSW

Load-acquire RCpc register signed word (unscaled)

This instruction calculates an address from a base register and an immediate offset, loads a signed word from memory, sign-extends it, and writes it to a register.

LDAPURSW loads from memory with AcquirePC semantics.

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

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

Unscaled offset class

(FEAT_LRCPC2)

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	0	0	1	1	0	0	1	1	0	0	imm9									0	0	Rn					Rt
size								opc

Encoding

LDAPURSW <Xt>, [<Xn|SP>{, #<simm>}]

Decode

if !IsFeatureImplemented(FEAT_LRCPC2) then EndOfDecode(Decode_UNDEF); end; let offset : bits(64) = SignExtend{}(imm9);

Assembler Symbols

<Xt>	Is the 64-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.

<simm>

Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field.

Shared Decode

let t : integer{} = UInt(Rt); let n : integer{} = UInt(Rn); let datasize : integer{} = 32; let acquirepc : boolean = TRUE; let tagchecked : boolean = n != 31;

Operation

var address : bits(64); let accdesc : AccessDescriptor = CreateAccDescLDAcqPC(tagchecked, acquirepc, t); if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; address = AddressAdd(address, offset, accdesc); let data : bits(datasize) = Mem{datasize}(address, accdesc); X{64}(t) = SignExtend{64}(data);

Operational information

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

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