SQDMLSL, SQDMLSL2 (by element)

Signed saturating doubling multiply-subtract long (by element)

This instruction multiplies each vector element in the lower or upper half of the first source SIMD&FP register by the specified vector element of the second source SIMD&FP register, doubles the results, and subtracts the final results from the vector elements of the destination SIMD&FP register. The destination vector elements are twice as long as the elements that are multiplied. All the values in this instruction are signed integer values.

If overflow occurs with any of the results, those results are saturated. If saturation occurs, the cumulative saturation bit FPSR.QC is set.

The SQDMLSL instruction extracts vector elements from the lower half of the first source register. The SQDMLSL2 instruction extracts vector elements from the upper half of the first source register.

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

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	1									0	1	1	1		0
		U						size		L	M	Rm					o2			H		Rn					Rd

SQDMLSL <Va><d>, <Vb><n>, <Vm>.<Ts>[<index>]

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
constant integer idxdsize = 64 << UInt(H);
integer index;
bit Rmhi;
case size of
    when '01' index = UInt(H:L:M); Rmhi = '0';
    when '10' index = UInt(H:L); Rmhi = M;
    otherwise EndOfDecode(Decode_UNDEF);

constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer m = UInt(Rmhi:Rm);

constant integer esize = 8 << UInt(size);
constant integer datasize = esize;
constant integer elements = 1;
constant integer part = 0;

Encoding: Vector

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	1									0	1	1	1		0
	Q	U						size		L	M	Rm					o2			H		Rn					Rd

SQDMLSL{2} <Vd>.<Ta>, <Vn>.<Tb>, <Vm>.<Ts>[<index>]

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
constant integer idxdsize = 64 << UInt(H);
integer index;
bit Rmhi;
case size of
    when '01' index = UInt(H:L:M); Rmhi = '0';
    when '10' index = UInt(H:L); Rmhi = M;
    otherwise EndOfDecode(Decode_UNDEF);

constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer m = UInt(Rmhi:Rm);

constant integer esize = 8 << UInt(size);
constant integer datasize = 64;
constant integer part = UInt(Q);
constant integer elements = datasize DIV esize;

Operation

CheckFPAdvSIMDEnabled64();
constant bits(datasize)   operand1 = Vpart[n, part, datasize];
constant bits(idxdsize)   operand2 = V[m, idxdsize];
constant bits(2*datasize) operand3 = V[d, 2*datasize];
bits(2*datasize) result;
integer element1;
integer element2;
bits(2*esize) product;
integer accum;
boolean sat1;
boolean sat2;

element2 = SInt(Elem[operand2, index, esize]);
for e = 0 to elements-1
    element1 = SInt(Elem[operand1, e, esize]);
    (product, sat1) = SignedSatQ(2 * element1 * element2, 2 * esize);
    accum = SInt(Elem[operand3, e, 2*esize]) - SInt(product);
    (Elem[result, e, 2*esize], sat2) = SignedSatQ(accum, 2 * esize);
    if sat1 || sat2 then FPSR.QC = '1';

V[d, 2*datasize] = result;

Explanations

<Va>: <d>: Is the number of the SIMD&FP destination register, encoded in the "Rd" field.
<Vb>: <n>: Is the number of the first SIMD&FP source register, encoded in the "Rn" field.
<Vm>: <Ts>: <index>: 2: <Vd>: Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<Ta>: <Vn>: Is the name of the first SIMD&FP source register, encoded in the "Rn" field.
<Tb>: