LDR (register, SIMD&FP) -- A64

Load SIMD&FP Register (register offset). This instruction loads a SIMD&FP register from memory. The address that is used for the load is calculated from a base register value and an offset register value. The offset can be optionally shifted and extended.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

boolean wback = FALSE; boolean postindex = FALSE; integer scale = UInt(opc<1>:size); if scale > 4 then UNDEFINED; if option<1> == '0' then UNDEFINED; // sub-word index ExtendType extend_type = DecodeRegExtend(option); integer shift = if S == '1' then scale else 0;

Assembler Symbols

<Bt>	Is the 8-bit name of the SIMD&FP register to be transferred, encoded in the "Rt" field.

<Dt>	Is the 64-bit name of the SIMD&FP register to be transferred, encoded in the "Rt" field.

<Ht>	Is the 16-bit name of the SIMD&FP register to be transferred, encoded in the "Rt" field.

<Qt>	Is the 128-bit name of the SIMD&FP register to be transferred, encoded in the "Rt" field.

<St>	Is the 32-bit name of the SIMD&FP 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.

<Wm>	When option<0> is set to 0, is the 32-bit name of the general-purpose index register, encoded in the "Rm" field.

<Xm>	When option<0> is set to 1, is the 64-bit name of the general-purpose index register, encoded in the "Rm" field.

For the 8-bit variant: is the index extend specifier, encoded in option:

option	<extend>
010	UXTW
110	SXTW
111	SXTX

For the 128-bit, 16-bit, 32-bit and 64-bit variant: is the index extend/shift specifier, defaulting to LSL, and which must be omitted for the LSL option when <amount> is omitted. encoded in option:

option	<extend>
010	UXTW
011	LSL
110	SXTW
111	SXTX

For the 8-bit variant: is the index shift amount, it must be #0, encoded in "S" as 0 if omitted, or as 1 if present.

For the 16-bit variant: is the index shift amount, optional only when <extend> is not LSL. Where it is permitted to be optional, it defaults to #0. It is encoded in S:

S	<amount>
0	#0
1	#1

For the 32-bit variant: is the index shift amount, optional only when <extend> is not LSL. Where it is permitted to be optional, it defaults to #0. It is encoded in S:

S	<amount>
0	#0
1	#2

For the 64-bit variant: is the index shift amount, optional only when <extend> is not LSL. Where it is permitted to be optional, it defaults to #0. It is encoded in S:

S	<amount>
0	#0
1	#3

For the 128-bit variant: is the index shift amount, optional only when <extend> is not LSL. Where it is permitted to be optional, it defaults to #0. It is encoded in S:

S	<amount>
0	#0
1	#4

Shared Decode

integer n = UInt(Rn); integer t = UInt(Rt); integer m = UInt(Rm); AccType acctype = AccType_VEC; MemOp memop = if opc<0> == '1' then MemOp_LOAD else MemOp_STORE; integer datasize = 8 << scale; boolean tag_checked = memop != MemOp_PREFETCH;

Operation

bits(64) offset = ExtendReg(m, extend_type, shift); CheckFPEnabled64(); bits(64) address; bits(datasize) data; if HaveMTE2Ext() then SetTagCheckedInstruction(tag_checked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n]; if ! postindex then address = address + offset; case memop of when MemOp_STORE data = V[t]; Mem[address, datasize DIV 8, acctype] = data; when MemOp_LOAD data = Mem[address, datasize DIV 8, acctype]; V[t] = data; if wback then if postindex then address = address + offset; if n == 31 then SP[] = address; else X[n] = address;

Operational information

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 v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41