fcvt.s.h
Convert single-precision float to a half-precision float
This instruction is defined by:
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anyOf:
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Zfh, version >= 0
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Zfhmin, version >= 0
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This instruction is included in the following profiles:
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RVA22U64 (Mandatory)
Synopsis
Converts a single-precision number in floating-point register fs1 into a half-precision floating-point number in floating-point register fd.
fcvt.s.h will never round, and so the 'rm' field is effectively ignored.
Decode Variables
Bits<5> fs1 = $encoding[19:15];
Bits<3> rm = $encoding[14:12];
Bits<5> fd = $encoding[11:7];Execution
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IDL
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Sail
check_f_ok($encoding);
Bits<32> sp_value = f[fs1][31:0];
Bits<1> sign = sp_value[31];
Bits<8> exp = sp_value[30:23];
Bits<23> frac = sp_value[22:0];
if (exp == 0xFF) {
if (frac != 0) {
if ((sp_value & 0x00400000) != 0) {
set_fp_flag(FpFlag::NV);
}
f[fd] = nan_box<16, FLEN>(HP_CANONICAL_NAN);
} else {
f[fd] = nan_box<16, FLEN>(packToF16UI(sign, 0x1F, 0));
}
} else {
Bits<16> frac16 = (frac >> 9) | frac & 0x1ff) != 0 ? 1 : 0); if ((exp | frac16) == 0) { f[fd] = nan_box<16, FLEN>(packToF16UI(sign, 0, 0;
} else {
assert(false, "TODO: implement roundPackToF16");
}
}
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_H) = riscv_ui64ToF16 (rm_3b, rs1_val_LU);
accrue_fflags(fflags);
F_or_X_H(rd) = rd_val_H;
RETIRE_SUCCESS
}
}
}