FCVTZS (vector, integer)

Floating-point convert to signed integer, rounding toward zero (vector)

This instruction converts a scalar or each element in a vector from a floating-point value to a signed integer value using the Round towards Zero rounding mode, and writes the result to the SIMD&FP destination register.

This instruction can generate a floating-point exception. Depending on the settings in FPCR, the exception results in either a flag being set in FPSR or a synchronous exception being generated. For more information, see Floating-point exceptions and exception traps.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Encoding: Scalar half-precision

Variants: FEAT_AdvSIMD && FEAT_FP16 (FEAT_AdvSIMD && FEAT_FP16)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	1	0	1	1	1	1	0	1	1	1	1	1	0	0	1	1	0	1	1	1	0
		U						o2											o1			Rn					Rd

FCVTZS <Hd>, <Hn>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) || !IsFeatureImplemented(FEAT_FP16) then
    EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 16;
constant integer datasize = esize;
constant integer elements = 1;
constant FPRounding rounding = FPDecodeRounding(o1:o2);
constant boolean unsigned = FALSE;

Encoding: Scalar single-precision and double-precision

Variants: FEAT_AdvSIMD (ARMv8.0)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	1	0	1	1	1	1	0	1		1	0	0	0	0	1	1	0	1	1	1	0
		U						o2	sz										o1			Rn					Rd

FCVTZS <V><d>, <V><n>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 32 << UInt(sz);
constant integer datasize = esize;
constant integer elements = 1;
constant FPRounding rounding = FPDecodeRounding(o1:o2);
constant boolean unsigned = FALSE;

Encoding: Vector half-precision

Variants: FEAT_AdvSIMD && FEAT_FP16 (FEAT_AdvSIMD && FEAT_FP16)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0		0	0	1	1	1	0	1	1	1	1	1	0	0	1	1	0	1	1	1	0
	Q	U						o2											o1			Rn					Rd

FCVTZS <Vd>.<T>, <Vn>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) || !IsFeatureImplemented(FEAT_FP16) then
    EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);

constant integer esize = 16;
constant integer datasize = 64 << UInt(Q);
constant integer elements = datasize DIV esize;
constant FPRounding rounding = FPDecodeRounding(o1:o2);
constant boolean unsigned = FALSE;

Encoding: Vector single-precision and double-precision

Variants: FEAT_AdvSIMD (ARMv8.0)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0		0	0	1	1	1	0	1		1	0	0	0	0	1	1	0	1	1	1	0
	Q	U						o2	sz										o1			Rn					Rd

FCVTZS <Vd>.<T>, <Vn>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
if sz:Q == '10' then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 32 << UInt(sz);
constant integer datasize = 64 << UInt(Q);
constant integer elements = datasize DIV esize;
constant FPRounding rounding = FPDecodeRounding(o1:o2);
constant boolean unsigned = FALSE;

Operation

if elements == 1 && IsFeatureImplemented(FEAT_FPRCVT) then
    CheckFPEnabled64();
else
    CheckFPAdvSIMDEnabled64();

constant bits(datasize) operand = V[n, datasize];

constant boolean merge = elements == 1 && IsMerging(FPCR);
bits(128) result = if merge then V[d, 128] else Zeros(128);
constant integer fracbits = 0;
bits(esize) element;

for e = 0 to elements-1
    element = Elem[operand, e, esize];
    Elem[result, e, esize] = FPToFixed(element, fracbits, unsigned, FPCR, rounding, esize);

V[d, 128] = result;

Explanations

<Hd>: Is the 16-bit name of the SIMD&FP destination register, encoded in the "Rd" field.
<Hn>: Is the 16-bit name of the SIMD&FP source register, encoded in the "Rn" field.
<V>: <d>: Is the number of the SIMD&FP destination register, encoded in the "Rd" field.
<n>: Is the number of the SIMD&FP source register, encoded in the "Rn" field.
<Vd>: Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<T>: <T>: <Vn>: Is the name of the SIMD&FP source register, encoded in the "Rn" field.