Load Register (immediate) loads a word or doubleword from memory and writes it to a register. The address that is used for the load is calculated from a base register and an immediate offset. For information about memory accesses, see Load/Store addressing modes. The Unsigned offset variant scales the immediate offset value by the size of the value accessed before adding it to the base register value.
It has encodings from 3 classes: Post-index , Pre-index and Unsigned offset
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1 | x | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | imm9 | 0 | 1 | Rn | Rt | ||||||||||||||||
size | opc |
boolean wback = TRUE; boolean postindex = TRUE; integer scale = UInt(size); bits(64) offset = SignExtend(imm9, 64);
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1 | x | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | imm9 | 1 | 1 | Rn | Rt | ||||||||||||||||
size | opc |
boolean wback = TRUE; boolean postindex = FALSE; integer scale = UInt(size); 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 | x | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | imm12 | Rn | Rt | |||||||||||||||||||
size | opc |
boolean wback = FALSE; boolean postindex = FALSE; integer scale = UInt(size); bits(64) offset = LSL(ZeroExtend(imm12, 64), scale);
For information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly LDR (immediate).
<Wt> |
Is the 32-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. |
<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. |
integer n = UInt(Rn); integer t = UInt(Rt); AccType acctype = AccType_NORMAL; MemOp memop; boolean signed; integer regsize; if opc<1> == '0' then // store or zero-extending load memop = if opc<0> == '1' then MemOp_LOAD else MemOp_STORE; regsize = if size == '11' then 64 else 32; signed = FALSE; else if size == '11' then UNDEFINED; else // sign-extending load memop = MemOp_LOAD; if size == '10' && opc<0> == '1' then UNDEFINED; regsize = if opc<0> == '1' then 32 else 64; signed = TRUE; integer datasize = 8 << scale; boolean tag_checked = memop != MemOp_PREFETCH && (wback || n != 31);
if HaveMTEExt() then SetNotTagCheckedInstruction(!tag_checked); bits(64) address; bits(datasize) data; boolean wb_unknown = FALSE; boolean rt_unknown = FALSE; if memop == MemOp_LOAD && 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(); if memop == MemOp_STORE && wback && n == t && n != 31 then c = ConstrainUnpredictable(Unpredictable_WBOVERLAPST); assert c IN {Constraint_NONE, Constraint_UNKNOWN, Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_NONE rt_unknown = FALSE; // value stored is original value when Constraint_UNKNOWN rt_unknown = TRUE; // value stored is UNKNOWN when Constraint_UNDEF UNDEFINED; when Constraint_NOP EndOfInstruction(); if n == 31 then if memop != MemOp_PREFETCH then CheckSPAlignment(); address = SP[]; else address = X[n]; if ! postindex then address = address + offset; case memop of when MemOp_STORE if rt_unknown then data = bits(datasize) UNKNOWN; else data = X[t]; Mem[address, datasize DIV 8, acctype] = data; when MemOp_LOAD data = Mem[address, datasize DIV 8, acctype]; if signed then X[t] = SignExtend(data, regsize); else X[t] = ZeroExtend(data, regsize); when MemOp_PREFETCH Prefetch(address, t<4:0>); if wback then if wb_unknown then address = bits(64) UNKNOWN; elsif postindex then address = address + offset; if n == 31 then SP[] = address; else X[n] = 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: isa v30.41, AdvSIMD v27.08, pseudocode r8p5_00bet2_rc5, sve v8.5-00bet10_rc5 ; Build timestamp: 2019-03-28T06:34
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