fnmsub.s

No synopsis available.

This instruction is defined by:

F, version >= 0

This instruction is included in the following profiles:

RVA20U64 (Mandatory)
RVA22U64 (Mandatory)
RVI20U32 (Optional)
RVI20U64 (Optional)

Encoding

Assembly format

fnmsub.s rd, rs1, rs2, rs3, rm

Synopsis

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

No description available.

Access

M	HS	U	VS	VU
Always	Always	Always	Always	Always

Always

Decode Variables

Bits<5> fs3 = $encoding[31:27];
Bits<5> fs2 = $encoding[24:20];
Bits<5> fs1 = $encoding[19:15];
Bits<3> rm = $encoding[14:12];
Bits<5> fd = $encoding[11:7];

Execution

IDL
Sail

{
  let rs1_val_32b = F_or_X_S(rs1);
  let rs2_val_32b = F_or_X_S(rs2);
  let rs3_val_32b = F_or_X_S(rs3);
  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_32b) : (bits(5), bits(32)) =
        match op {
          FMADD_S  => riscv_f32MulAdd (rm_3b, rs1_val_32b, rs2_val_32b, rs3_val_32b),
          FMSUB_S  => riscv_f32MulAdd (rm_3b, rs1_val_32b, rs2_val_32b, negate_S (rs3_val_32b)),
          FNMSUB_S => riscv_f32MulAdd (rm_3b, negate_S (rs1_val_32b), rs2_val_32b, rs3_val_32b),
          FNMADD_S => riscv_f32MulAdd (rm_3b, negate_S (rs1_val_32b), rs2_val_32b, negate_S (rs3_val_32b))
        };
      accrue_fflags(fflags);
      F_or_X_S(rd) = rd_val_32b;
      RETIRE_SUCCESS
    }
  }
}