Arm® A64 Instruction Set Architecture: Future Architecture Technologies in the A architecture profile

SUNPKHI, SUNPKLO

Signed unpack and extend half of vector.

Unpack elements from the lowest or highest half of the source vector and then sign-extend them to place in elements of twice their size within the destination vector. This instruction is unpredicated.

It has encodings from 2 classes: High half and Low half

High half

if !HaveSVE() then UNDEFINED;
if size == '00' then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Zn);
integer d = UInt(Zd);
boolean unsigned = FALSE;
boolean hi = TRUE;

Low half

if !HaveSVE() then UNDEFINED;
if size == '00' then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Zn);
integer d = UInt(Zd);
boolean unsigned = FALSE;
boolean hi = FALSE;

Assembler Symbols

CheckSVEEnabled();
integer elements = VL DIV esize;
integer hsize = esize DIV 2;
bits(VL) operand = Z[n];
bits(VL) result;

for e = 0 to elements-1
    bits(hsize) element = if hi then Elem[operand, e + elements, hsize] else Elem[operand, e, hsize];
    Elem[result, e, esize] = Extend(element, esize, unsigned);

Z[d] = result;

Operational information

If PSTATE.DIT is 1:

• The execution time of this instruction is independent of:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.