fsw

Single-precision floating-point store

This instruction is defined by:

  • F, version >= 0

This instruction is included in the following profiles:

  • RVA20S64 (Mandatory)

  • RVA20U64 (Mandatory)

  • RVA22S64 (Mandatory)

  • RVA22U64 (Mandatory)

Encoding

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Assembly format

fsw fs2, rs1, imm

Synopsis

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

The fsw instruction stores a single-precision floating-point value in fs2 to memory at address rs1 + imm.

fsw does not modify the bits being transferred; in particular, the payloads of non-canonical NaNs are preserved.

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

Bits<12> imm = {$encoding[31:25], $encoding[11:7]};
Bits<5> fs2 = $encoding[24:20];
Bits<5> rs1 = $encoding[19:15];

Execution

  • IDL

  • Sail

check_f_ok($encoding);
XReg virtual_address = X[rs1] + $signed(imm);
write_memory<32>(virtual_address, f[fs2][31:0], $encoding);
{
  let offset : xlenbits = sign_extend(imm);
  let (aq, rl, con) = (false, false, false);
  /* Get the address, X(rs1) + offset.
     Some extensions perform additional checks on address validity. */
  match ext_data_get_addr(rs1, offset, Write(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_SAMO_Addr_Align()); RETIRE_FAIL }
      else match translateAddr(vaddr, Write(Data)) {
        TR_Failure(e, _)    => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
        TR_Address(addr, _) => {
          let eares : MemoryOpResult(unit) = match width {
            BYTE   => MemValue () /* bogus placeholder for illegal size */,
            HALF   => mem_write_ea(addr, 2, aq, rl, false),
            WORD   => mem_write_ea(addr, 4, aq, rl, false),
            DOUBLE => mem_write_ea(addr, 8, aq, rl, false)
          };
          match (eares) {
            MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
            MemValue(_) => {
              let rs2_val = F(rs2);
              match (width) {
                BYTE => { handle_illegal(); RETIRE_FAIL },
                HALF => process_fstore (vaddr, mem_write_value(addr, 2, rs2_val[15..0], aq, rl, con)),
                WORD => process_fstore (vaddr, mem_write_value(addr, 4, rs2_val[31..0], aq, rl, con)),
                DOUBLE if sizeof(flen) >= 64 =>
                  process_fstore (vaddr, mem_write_value(addr, 8, rs2_val, aq, rl, con)),
                _ => report_invalid_width(__FILE__, __LINE__, width, "floating point store"),
              };
            }
          }
        }
      }
  }
}

Exceptions

This instruction may result in the following synchronous exceptions:

  • IllegalInstruction

  • LoadAccessFault

  • StoreAmoAccessFault

  • StoreAmoAddressMisaligned

  • StoreAmoPageFault