You copied the Doc URL to your clipboard.

UQSHRN, UQSHRN2

Unsigned saturating Shift Right Narrow (immediate). This instruction reads each vector element in the source SIMD&FP register, right shifts each result by an immediate value, saturates each shifted result to a value that is half the original width, puts the final result into a vector, and writes the vector to the lower or upper half of the destination SIMD&FP register. All the values in this instruction are unsigned integer values. The results are truncated. For rounded results, see UQRSHRN.

The UQSHRN instruction writes the vector to the lower half of the destination register and clears the upper half, while the UQSHRN2 instruction writes the vector to the upper half of the destination register without affecting the other bits of the register.

If overflow occurs with any of the results, those results 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

313029282726252423222120191817161514131211109876543210
011111110!= 0000immb100101RnRd
Uimmhop

Scalar

UQSHRN <Vb><d>, <Va><n>, #<shift>

integer d = UInt(Rd);
integer n = UInt(Rn);

if immh == '0000' then UNDEFINED;
if immh<3> == '1' then UNDEFINED;
integer esize = 8 << HighestSetBit(immh);
integer datasize = esize;
integer elements = 1;
integer part = 0;

integer shift = (2 * esize) - UInt(immh:immb);
boolean round = (op == '1');
boolean unsigned = (U == '1');

Vector

313029282726252423222120191817161514131211109876543210
0Q1011110!= 0000immb100101RnRd
Uimmhop

Vector

UQSHRN{2} <Vd>.<Tb>, <Vn>.<Ta>, #<shift>

integer d = UInt(Rd);
integer n = UInt(Rn);

if immh == '0000' then SEE(asimdimm);
if immh<3> == '1' then UNDEFINED;
integer esize = 8 << HighestSetBit(immh);
integer datasize = 64;
integer part = UInt(Q);
integer elements = datasize DIV esize;

integer shift = (2 * esize) - UInt(immh:immb);
boolean round = (op == '1');
boolean unsigned = (U == '1');

Assembler Symbols

2 Is the second and upper half specifier. If present it causes the operation to be performed on the upper 64 bits of the registers holding the narrower elements, and is encoded in Q:
Q 2
0 [absent]
1 [present]
<Vd>

Is the name of the SIMD&FP destination register, encoded in the "Rd" field.

<Tb> Is an arrangement specifier, encoded in immh:Q:
immh Q <Tb>
0000 x SEE Advanced SIMD modified immediate
0001 0 8B
0001 1 16B
001x 0 4H
001x 1 8H
01xx 0 2S
01xx 1 4S
1xxx x RESERVED
<Vn>

Is the name of the SIMD&FP source register, encoded in the "Rn" field.

<Ta> Is an arrangement specifier, encoded in immh:
immh <Ta>
0000 SEE Advanced SIMD modified immediate
0001 8H
001x 4S
01xx 2D
1xxx RESERVED
<Vb> Is the destination width specifier, encoded in immh:
immh <Vb>
0000 RESERVED
0001 B
001x H
01xx S
1xxx RESERVED
<d>

Is the number of the SIMD&FP destination register, in the "Rd" field.

<Va> Is the source width specifier, encoded in immh:
immh <Va>
0000 RESERVED
0001 H
001x S
01xx D
1xxx RESERVED
<n>

Is the number of the first SIMD&FP source register, encoded in the "Rn" field.

<shift> For the scalar variant: is the right shift amount, in the range 1 to the destination operand width in bits, encoded in immh:immb:
immh <shift>
0000 RESERVED
0001 (16-UInt(immh:immb))
001x (32-UInt(immh:immb))
01xx (64-UInt(immh:immb))
1xxx RESERVED
For the vector variant: is the right shift amount, in the range 1 to the destination element width in bits, encoded in immh:immb:
immh <shift>
0000 SEE Advanced SIMD modified immediate
0001 (16-UInt(immh:immb))
001x (32-UInt(immh:immb))
01xx (64-UInt(immh:immb))
1xxx RESERVED

Operation

CheckFPAdvSIMDEnabled64();
bits(datasize*2) operand = V[n];
bits(datasize) result;
integer round_const = if round then (1 << (shift - 1)) else 0;
integer element;
boolean sat;

for e = 0 to elements-1
    element = (Int(Elem[operand, e, 2*esize], unsigned) + round_const) >> shift;
    (Elem[result, e, esize], sat) = SatQ(element, esize, unsigned);
    if sat then FPSR.QC = '1';

Vpart[d, part] = result;