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SQRDMULH (by element)

Signed saturating Rounding Doubling Multiply returning High half (by element). This instruction multiplies each vector element in the first source SIMD&FP register by the specified vector element of the second source SIMD&FP register, doubles the results, places the most significant half of the final results into a vector, and writes the vector to the destination SIMD&FP register.

The results are rounded. For truncated results, see SQDMULH.

If any of the results overflows, they are saturated. If saturation occurs, the cumulative saturation bit FPSR.QC is set.

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.

It has encodings from 2 classes: Scalar and Vector

Scalar

 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 size L M Rm 1 1 0 1 H 0 Rn Rd op

Scalar

SQRDMULH <V><d>, <V><n>, <Vm>.<Ts>[<index>]

```integer idxdsize = if H == '1' then 128 else 64;
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 UNDEFINED;

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

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

boolean round = (op == '1');```

Vector

 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 Q 0 0 1 1 1 1 size L M Rm 1 1 0 1 H 0 Rn Rd op

Vector

SQRDMULH <Vd>.<T>, <Vn>.<T>, <Vm>.<Ts>[<index>]

```integer idxdsize = if H == '1' then 128 else 64;
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 UNDEFINED;

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

integer esize = 8 << UInt(size);
integer datasize = if Q == '1' then 128 else 64;
integer elements = datasize DIV esize;

boolean round = (op == '1');```

Assembler Symbols

<V> Is a width specifier, encoded in size:
size <V>
00 RESERVED
01 H
10 S
11 RESERVED
 Is the number of the SIMD&FP destination register, encoded in the "Rd" field.
 Is the number of the first SIMD&FP source register, encoded in the "Rn" field.
 Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<T> Is an arrangement specifier, encoded in size:Q:
size Q <T>
00 x RESERVED
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 x RESERVED
 Is the name of the first SIMD&FP source register, encoded in the "Rn" field.
<Vm> Is the name of the second SIMD&FP source register, encoded in size:M:Rm:
size <Vm>
00 RESERVED
01 0:Rm
10 M:Rm
11 RESERVED
Restricted to V0-V15 when element size <Ts> is H.
<Ts> Is an element size specifier, encoded in size:
size <Ts>
00 RESERVED
01 H
10 S
11 RESERVED
<index> Is the element index, encoded in size:L:H:M:
size <index>
00 RESERVED
01 H:L:M
10 H:L
11 RESERVED

Operation

```CheckFPAdvSIMDEnabled64();
bits(datasize) operand1 = V[n];
bits(idxdsize) operand2 = V[m];
bits(datasize) result;
integer round_const = if round then 1 << (esize - 1) else 0;
integer element1;
integer element2;
integer product;
boolean sat;

element2 = SInt(Elem[operand2, index, esize]);
for e = 0 to elements-1
element1 = SInt(Elem[operand1, e, esize]);
product = (2 * element1 * element2) + round_const;
// The following only saturates if element1 and element2 equal -(2^(esize-1))
(Elem[result, e, esize], sat) = SignedSatQ(product >> esize, esize);
if sat then FPSR.QC = '1';

V[d] = result;```