sqxtn
Signed Saturating Extract Narrow
Reads wide elements, saturates, and narrows.
Pseudocode Operation
for i = 0 to elements-1 do
temp ← Vn[i]
if temp > max_value_dest or temp < min_value_dest then
Vd[i] ← Saturate(temp)
FPSR.QC ← 1
else
Vd[i] ← temp
endif
endforExample
Encoding
Operands
-
Vd
Destination SIMD/FP vector register -
Vn
First source SIMD/FP vector register
Related
More in NEON (SIMD)
Reference
Instruction Forms
| Encoding | Instruction | ISA | Bit pattern | ||
|---|---|---|---|---|---|
| 0x5E214800 | SQXTN <Vb><d>, <Va><n> | A64 | 01 | 0 | 11110 | size | 10000 | 10100 | 10 | Rn | Rd | ||
| 0x0E214800 | SQXTN{2} <Vd>.<Tb>, <Vn>.<Ta> | A64 | 0 | Q | 0 | 01110 | size | 10000 | 10100 | 10 | Rn | Rd |
Description
Signed saturating extract Narrow. This instruction reads each vector element from the source SIMD&FP register, saturates the value to half the original width, places the result into a vector, and writes the vector to the lower or upper half of the destination SIMD&FP register. The destination vector elements are half as long as the source vector elements. 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 SQXTN instruction writes the vector to the lower half of the destination register and clears the upper half, while the SQXTN2 instruction writes the vector to the upper half of the destination register without affecting the other bits of the 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.
Operation
CheckFPAdvSIMDEnabled64();
bits(2*datasize) operand = V[n, 2*datasize];
bits(datasize) result;
bits(2*esize) element;
boolean sat;
for e = 0 to elements-1
element = Elem[operand, e, 2*esize];
(Elem[result, e, esize], sat) = SatQ(Int(element, unsigned), esize, unsigned);
if sat then FPSR.QC = '1';
Vpart[d, part, datasize] = result;