SQRSHRN, SQRSHRN2

Signed saturating Rounded 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 signed integer values. The destination vector elements are half as long as the source vector elements. The results are rounded. For truncated results, see SQSHRN.

The SQRSHRN instruction writes the vector to the lower half of the destination register and clears the upper half, while the SQRSHRN2 instruction writes the vector to the upper half of the destination register without affecting the other bits of the register.

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

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

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');