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VQDMLSL

Vector Saturating Doubling Multiply Subtract Long multiplies corresponding elements in two doubleword vectors, subtracts double the products from corresponding elements of a quadword vector, and places the results in the same quadword vector.

The second operand can be a scalar instead of a vector. For more information about scalars see Advanced SIMD scalars.

If any of the results overflow, they are saturated. The cumulative saturation bit, FPSCR.QC, is set if saturation occurs. For details see Pseudocode details of saturation.

Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.

It has encodings from the following instruction sets: A32 ( A1 and A2 ) and T32 ( T1 and T2 ) .

A1

313029282726252423222120191817161514131211109876543210
111100101D!= 11VnVd1011N0M0Vm
sizeop

A1

VQDMLSL{<c>}{<q>}.<dt> <Qd>, <Dn>, <Dm>

if size == '11' then SEE "Related encodings";
if size == '00' || Vd<0> == '1' then UNDEFINED;
add = (op == '0');
scalar_form = FALSE;  d = UInt(D:Vd);  n = UInt(N:Vn);  m = UInt(M:Vm);
esize = 8 << UInt(size);  elements = 64 DIV esize;

A2

313029282726252423222120191817161514131211109876543210
111100101D!= 11VnVd0111N1M0Vm
sizeop

A2

VQDMLSL{<c>}{<q>}.<dt> <Qd>, <Dn>, <Dm>[<index>]

if size == '11' then SEE "Related encodings";
if size == '00' || Vd<0> == '1' then UNDEFINED;
add = (op == '0');
scalar_form = TRUE;  d = UInt(D:Vd);  n = UInt(N:Vn);
if size == '01' then esize = 16;  elements = 4;  m = UInt(Vm<2:0>);  index = UInt(M:Vm<3>);
if size == '10' then esize = 32;  elements = 2;  m = UInt(Vm);  index = UInt(M);

T1

15141312111098765432101514131211109876543210
111011111D!= 11VnVd1011N0M0Vm
sizeop

T1

VQDMLSL{<c>}{<q>}.<dt> <Qd>, <Dn>, <Dm>

if size == '11' then SEE "Related encodings";
if size == '00' || Vd<0> == '1' then UNDEFINED;
add = (op == '0');
scalar_form = FALSE;  d = UInt(D:Vd);  n = UInt(N:Vn);  m = UInt(M:Vm);
esize = 8 << UInt(size);  elements = 64 DIV esize;

T2

15141312111098765432101514131211109876543210
111011111D!= 11VnVd0111N1M0Vm
sizeop

T2

VQDMLSL{<c>}{<q>}.<dt> <Qd>, <Dn>, <Dm>[<index>]

if size == '11' then SEE "Related encodings";
if size == '00' || Vd<0> == '1' then UNDEFINED;
add = (op == '0');
scalar_form = TRUE;  d = UInt(D:Vd);  n = UInt(N:Vn);
if size == '01' then esize = 16;  elements = 4;  m = UInt(Vm<2:0>);  index = UInt(M:Vm<3>);
if size == '10' then esize = 32;  elements = 2;  m = UInt(Vm);  index = UInt(M);

Related encodings: See Advanced SIMD data-processing for the T32 instruction set, or Advanced SIMD data-processing for the A32 instruction set.

Assembler Symbols

<c>

For encoding A1 and A2: see Standard assembler syntax fields. This encoding must be unconditional.

For encoding T1 and T2: see Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<dt> Is the data type for the elements of the operands, encoded in size:
size <dt>
01 S16
10 S32
<Qd>

Is the 128-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field as <Qd>*2.

<Dn>

Is the 64-bit name of the first SIMD&FP source register, encoded in the "N:Vn" field.

<Dm>

For encoding A1 and T1: is the 64-bit name of the second SIMD&FP source register, encoded in the "M:Vm" field.

For encoding A2 and T2: is the 64-bit name of the second SIMD&FP source register, encoded in the "Vm<2:0>" field when <dt> is S16, otherwise the "Vm" field.

<index>

Is the element index in the range 0 to 3, encoded in the "M:Vm<3>" field when <dt> is S16, otherwise in range 0 to 1, encoded in the "M" field.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();  CheckAdvSIMDEnabled();
    if scalar_form then op2 = SInt(Elem[Din[m],index,esize]);
    for e = 0 to elements-1
        if !scalar_form then op2 = SInt(Elem[Din[m],e,esize]);
        op1 = SInt(Elem[Din[n],e,esize]);
        // The following only saturates if both op1 and op2 equal -(2^(esize-1))
        (product, sat1) = SignedSatQ(2*op1*op2, 2*esize);
        if add then
            result = SInt(Elem[Qin[d>>1],e,2*esize]) + SInt(product);
        else
            result = SInt(Elem[Qin[d>>1],e,2*esize]) - SInt(product);
        (Elem[Q[d>>1],e,2*esize], sat2) = SignedSatQ(result, 2*esize);
        if sat1 || sat2 then FPSCR.QC = '1';
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