lh

Load halfword

This instruction is defined by:

  • I, version >= I@2.1.0

This instruction is included in the following profiles:

  • MockProfile 64-bit S-mode (Mandatory)

  • MockProfile 64-bit Unpriv (Mandatory)

  • RVA20S64 (Mandatory)

  • RVA20U64 (Mandatory)

  • RVA22S64 (Mandatory)

  • RVA22U64 (Mandatory)

  • RVA23M64 (Mandatory)

  • RVA23S64 (Mandatory)

  • RVA23U64 (Mandatory)

  • RVB23M64 (Mandatory)

  • RVB23S64 (Mandatory)

  • RVB23U64 (Mandatory)

  • RVI20U32 (Mandatory)

  • RVI20U64 (Mandatory)

Encoding

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Assembly format

lh rd, imm(rs1)

Synopsis

Load 16 bits of data into register xd from an address formed by adding xs1 to a signed offset. Sign extend the result.

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

Bits<12> imm = $encoding[31:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];

Execution

  • IDL

  • Sail

XReg virtual_address = X[xs1] + $signed(imm);
X[xd] = %%LINK%func;sext;sext%%(%%LINK%func;read_memory;read_memory%%<16>(virtual_address, $encoding), 16);
{
  let offset : xlenbits = sign_extend(imm);
  /* Get the address, X(xs1) + offset.
     Some extensions perform additional checks on address validity. */
  match ext_data_get_addr(xs1, offset, Read(Data), width) {
    Ext_DataAddr_Error(e)  => { ext_handle_data_check_error(e); RETIRE_FAIL },
    Ext_DataAddr_OK(vaddr) =>
      if   check_misaligned(vaddr, width)
      then { handle_mem_exception(vaddr, E_Load_Addr_Align()); RETIRE_FAIL }
      else match translateAddr(vaddr, Read(Data)) {
        TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
        TR_Address(paddr, _) =>
          match (width) {
            BYTE =>
              process_load(xd, vaddr, mem_read(Read(Data), paddr, 1, aq, rl, false), is_unsigned),
            HALF =>
              process_load(xd, vaddr, mem_read(Read(Data), paddr, 2, aq, rl, false), is_unsigned),
            WORD =>
              process_load(xd, vaddr, mem_read(Read(Data), paddr, 4, aq, rl, false), is_unsigned),
            DOUBLE if sizeof(xlen) >= 64 =>
              process_load(xd, vaddr, mem_read(Read(Data), paddr, 8, aq, rl, false), is_unsigned),
            _ => report_invalid_width(__FILE__, __LINE__, width, "load")
          }
      }
  }
}

Exceptions

This instruction may result in the following synchronous exceptions:

  • LoadAccessFault

  • LoadAddressMisaligned

  • LoadPageFault