lha

Load Halfword Algebraic

lha RT, D(RA)

Loads a halfword (16 bits) from memory and sign-extends it to 64 bits.

Encoding

Binary Layout

0:5

6:10

11:15

16:31

Format D-form

Opcode 0xA8000000

Extension Base

Operands

RT
Target Register
D
Displacement
RA
Base Register

Example

lha r3, 0(r4)

// Load signed 16-bit value.

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Loads a 16-bit halfword from memory at address (RA + sign_extend(D)) and places it into RT with sign extension to the full 64-bit width. The base register may be R0 if RA is zero in the instruction. No condition or status registers are affected.

Operation

if RA = 0 then
  EA ← sign_extend(D)
else
  EA ← (RA) + sign_extend(D)
RT ← sign_extend([EA+1:EA])
// Load halfword at EA and sign-extend to 64 bits

Programming Note

The lha instruction is commonly used for loading signed halfword values from memory into a register, ensuring proper sign extension. Ensure that the effective address (EA) is properly aligned to avoid alignment faults. This instruction operates at user privilege level and will raise an exception if the EA is invalid or if there are insufficient privileges.

lha