Load Register Signed Word (immediate) loads a word from memory, sign-extends it to 64 bits, and writes the result to a register. The address that is used for the load is calculated from a base register and an immediate offset. For information about addressing modes, see Load/Store addressing modes.
It has encodings from 3 classes: Post-index , Pre-index and Unsigned offset
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 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | imm9 | 0 | 1 | Rn | Rt | ||||||||||||||||
size | VR | opc |
boolean wback = TRUE; boolean postindex = TRUE; bits(64) offset = SignExtend(imm9, 64);
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 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | imm9 | 1 | 1 | Rn | Rt | ||||||||||||||||
size | VR | opc |
boolean wback = TRUE; boolean postindex = FALSE; bits(64) offset = SignExtend(imm9, 64);
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 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | imm12 | Rn | Rt | |||||||||||||||||||
size | VR | opc |
boolean wback = FALSE; boolean postindex = FALSE; bits(64) offset = LSL(ZeroExtend(imm12, 64), 2);
For information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly LDRSW (immediate).
<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 signed immediate byte offset, in the range -256 to 255, encoded in the "imm9" field. |
<pimm> |
Is the optional positive immediate byte offset, a multiple of 4 in the range 0 to 16380, defaulting to 0 and encoded in the "imm12" field as <pimm>/4. |
integer t = UInt(Rt); integer n = UInt(Rn); boolean nontemporal = FALSE; boolean tagchecked = wback || n != 31; Constraint c; boolean wb_unknown = FALSE; if wback && n == t && n != 31 then c = ConstrainUnpredictable(Unpredictable_WBOVERLAPLD); assert c IN {Constraint_WBSUPPRESS, Constraint_UNKNOWN, Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_WBSUPPRESS wback = FALSE; // Writeback is suppressed when Constraint_UNKNOWN wb_unknown = TRUE; // Writeback is UNKNOWN when Constraint_UNDEF UNDEFINED; when Constraint_NOP EndOfInstruction();
bits(64) address; boolean privileged = PSTATE.EL != EL0; AccessDescriptor accdesc = CreateAccDescGPR(MemOp_LOAD, nontemporal, privileged, tagchecked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n, 64]; if !postindex then address = AddressAdd(address, offset, accdesc); bits(32) data = Mem[address, 4, accdesc]; X[t, 64] = SignExtend(data, 64); if wback then if wb_unknown then address = bits(64) UNKNOWN; elsif postindex then address = AddressAdd(address, offset, accdesc); if n == 31 then SP[] = address; else X[n, 64] = address;
If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.
Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45
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