fcvt.s.wu

Convert unsigned 32-bit integer to single-precision float

This instruction is defined by:

  • F, version >= F@2.2.0

This instruction is included in the following profiles:

  • RVA20S64 (Optional)

  • RVA20U64 (Mandatory)

  • RVA22S64 (Optional)

  • RVA22U64 (Mandatory)

  • RVA23S64 (Optional)

  • RVA23U64 (Mandatory)

  • RVB23S64 (Optional)

  • RVB23U64 (Mandatory)

  • RVI20U32 (Optional)

  • RVI20U64 (Optional)

Encoding

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Assembly format

fcvt.s.wu fd, rs1, rm

Synopsis

This instruction must have data-independent timing when extension Zkt is enabled.

Converts a 32-bit unsigned integer in integer register rs1 into a floating-point number in floating-point register fd.

All floating-point to integer and integer to floating-point conversion instructions round according to the rm field. A floating-point register can be initialized to floating-point positive zero using fcvt.s.w rd, x0, which will never set any exception flags.

All floating-point conversion instructions set the Inexact exception flag if the rounded result differs from the operand value and the Invalid exception flag is not set.

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

Bits<5> rs1 = $encoding[19:15];
Bits<3> rm = $encoding[14:12];
Bits<5> fd = $encoding[11:7];

Execution

  • IDL

  • Sail

check_f_ok($encoding);
RoundingMode rounding_mode = rm_to_mode(rm, $encoding);
X[fd] = ui32_to_f32(X[rs1], rounding_mode);
mark_f_state_dirty();
{
  assert(sizeof(xlen) >= 64);
  let rs1_val_LU = X(rs1)[63..0];
  match (select_instr_or_fcsr_rm (rm)) {
    None() => { handle_illegal(); RETIRE_FAIL },
    Some(rm') => {
      let rm_3b = encdec_rounding_mode(rm');
      let (fflags, rd_val_S) = riscv_ui64ToF32 (rm_3b, rs1_val_LU);

      accrue_fflags(fflags);
      F_or_X_S(rd) = rd_val_S;
      RETIRE_SUCCESS
    }
  }
}

Exceptions

This instruction may result in the following synchronous exceptions:

  • IllegalInstruction