Load-Acquire RCpc Register Halfword (unscaled) calculates an address from a base register and an immediate offset, loads a halfword from memory, zero-extends it, and writes it to a register.
The instruction has memory ordering semantics as described in Load-Acquire, Load-AcquirePC, and Store-Release, except that:
- There is no ordering requirement, separate from the requirements of a Load-AcquirePC or a Store-Release, created by having a Store-Release followed by a Load-AcquirePC instruction.
- The reading of a value written by a Store-Release by a Load-AcquirePC instruction by the same observer does not make the write of the Store-Release globally observed.
This difference in memory ordering is not described in the pseudocode.
For information about memory accesses, see Load/Store addressing modes.
bits(64) offset = SignExtend(imm9, 64);
Is the 32-bit name of the general-purpose register to be transferred, encoded in the "Rt" field.
Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.
Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field.
if HaveMTEExt() then SetNotTagCheckedInstruction(!tag_checked); bits(64) address; bits(16) data; if n == 31 then CheckSPAlignment(); address = SP; else address = X[n]; address = address + offset; data = Mem[address, 2, AccType_ORDERED]; X[t] = ZeroExtend(data, 32);
If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.