This is a collection of Intel®’ IA32® Software Developer's Manuals (URL of the day) and AMD' AMD64 Architecture Programmer's Manual together with the related specifications, application notes, white papers, and change logs. The collection aims to keep all available revisions. It was originally created by Michal Necasek, see OS/2 Museum.

If you have a public document, related to the IA32® specifications and missing from the collection, please mail it to me. The content of this URL and all sub-ULRs is available for convenient bulk download by rsync x86docs password "" (empty).

LDAPRH -- A64

LDAPRH

Load-acquire RCpc register halfword

This instruction derives an address from a base register value, loads a halfword from the derived address in memory, zero-extends it and writes it to a register.

If the destination register is not one of WZR or XZR, LDAPRH 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.

Integer
(FEAT_LRCPC)

313029282726252423222120191817161514131211109876543210
01111000101(1)(1)(1)(1)(1)110000RnRt
sizeVRARRso3opc

Encoding

LDAPRH <Wt>, [<Xn|SP> {, #0}]

Decode for this encoding

if !IsFeatureImplemented(FEAT_LRCPC) then EndOfDecode(Decode_UNDEF); end; let t : integer{} = UInt(Rt); let n : integer{} = UInt(Rn); let acquirepc : boolean = TRUE; let tagchecked : boolean = n != 31;

Assembler Symbols

<Wt>

Is the 32-bit name of the general-purpose register to be loaded, 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.

Operation

var address : bits(64); var data : bits(16); let accdesc : AccessDescriptor = CreateAccDescLDAcqPC(tagchecked, acquirepc, t); if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; data = Mem{16}(address, accdesc); X{32}(t) = ZeroExtend{32}(data);

Operational information

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


2026-03_rel 2026-03-26 20:48:11

Copyright © 2010-2026 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.