Load-Acquire RCpc ordered pair of registers
This instruction calculates an address from a base register value and an optional offset, loads two 32-bit words or two 64-bit doublewords from memory, and writes them to two registers. For information on single-copy atomicity and alignment requirements, see Requirements for single-copy atomicity and Alignment of data accesses. The instruction also has memory ordering semantics, as described in Load-Acquire, Load-AcquirePC, and Store-Release, except that:
For information about addressing modes, see Load/Store addressing modes.
| 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 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | Rt2 | 0 | 0 | 0 | x | 1 | 0 | Rn | Rt | ||||||||||||
| size | L | opc2 | |||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_LRCPC3) then EndOfDecode(Decode_UNDEF); constant boolean ispair = TRUE; constant boolean postindex = opc2<0> == '0'; boolean wback = opc2<0> == '0';
LDIAPP has the same CONSTRAINED UNPREDICTABLE behavior as LDP. For information about this CONSTRAINED UNPREDICTABLE behavior, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly LDP and LDIAPP.
| <Wt1> |
Is the 32-bit name of the first general-purpose register to be transferred, encoded in the "Rt" field. |
| <Wt2> |
Is the 32-bit name of the second general-purpose register to be transferred, encoded in the "Rt2" field. |
| <Xn|SP> |
Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. |
| <Xt1> |
Is the 64-bit name of the first general-purpose register to be transferred, encoded in the "Rt" field. |
| <Xt2> |
Is the 64-bit name of the second general-purpose register to be transferred, encoded in the "Rt2" field. |
constant integer t = UInt(Rt); constant integer t2 = UInt(Rt2); constant integer n = UInt(Rn); constant integer scale = 2 + UInt(size<0>); constant integer datasize = 8 << scale; constant integer offset = if opc2<0> == '0' then (2 << scale) else 0; constant boolean tagchecked = wback || n != 31; boolean rt_unknown = FALSE; boolean wb_unknown = FALSE; if wback && (t == n || t2 == n) && n != 31 then constant Constraint 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 EndOfDecode(Decode_UNDEF); when Constraint_NOP EndOfDecode(Decode_NOP); if t == t2 then constant Constraint c = ConstrainUnpredictable(Unpredictable_LDPOVERLAP); assert c IN {Constraint_UNKNOWN, Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_UNKNOWN rt_unknown = TRUE; // result is UNKNOWN when Constraint_UNDEF EndOfDecode(Decode_UNDEF); when Constraint_NOP EndOfDecode(Decode_NOP);
bits(64) address; bits(datasize) data1; bits(datasize) data2; constant integer dbytes = datasize DIV 8; constant AccessDescriptor accdesc = CreateAccDescLDAcqPC(tagchecked, ispair); if n == 31 then CheckSPAlignment(); address = SP[64]; else address = X[n, 64]; if !postindex then address = AddressAdd(address, offset, accdesc); bits(2*datasize) full_data; full_data = Mem[address, 2*dbytes, accdesc]; if BigEndian(accdesc.acctype) then data2 = full_data<(datasize-1):0>; data1 = full_data<(2*datasize-1):datasize>; else data1 = full_data<(datasize-1):0>; data2 = full_data<(2*datasize-1):datasize>; if rt_unknown then data1 = bits(datasize) UNKNOWN; data2 = bits(datasize) UNKNOWN; X[t, datasize] = data1; X[t2, datasize] = data2; if wback then if wb_unknown then address = bits(64) UNKNOWN; elsif postindex then address = AddressAdd(address, offset, accdesc); if n == 31 then SP[64] = 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 v2024-12_rel, pseudocode v2024-12_rel ; Build timestamp: 2024-12-15T22:18
Copyright © 2010-2024 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.