c.lbu

Load unsigned byte, 16-bit encoding

Loads a 8-bit value from memory into register xd. It computes an effective address by adding the zero-extended offset, to the base address in register xs1. It expands to lbu xd, offset(xs1).

Assembly format

c.lbu xd, imm(xs1)

Decode Variables

Bits<2> imm = {$encoding[5], $encoding[6]};
Bits<3> xd = $encoding[4:2];
Bits<3> xs1 = $encoding[9:7];

Execution

if (implemented?(ExtensionName::C) && (CSR[misa].C == 1'b0)) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg virtual_address = X[creg2reg(xs1)] + imm;
X[creg2reg(xd)] = read_memory(8, virtual_address, $encoding);

Exceptions

This instruction may result in the following synchronous exceptions:

  • IllegalInstruction

  • LoadAccessFault

  • LoadAddressMisaligned

  • LoadPageFault

Encoding

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Defining extension

Zcb

Access

M

Always

Containing profiles

  • Mandatory: RVA23S64, RVA23U64, RVB23S64, RVB23U64

  • Optional: RVA20S64, RVA20U64, RVA22S64, RVA22U64, RVA23S64, RVA23U64, RVB23S64, RVB23U64, RVI20U32, RVI20U64