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

UABA

Unsigned absolute difference and accumulate.

Compute the absolute difference between unsigned integer values in elements of the second source vector and corresponding elements of the first source vector, and add the difference to the corresponding elements of the destination vector. This instruction is unpredicated.

if !HaveSVE2() then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);
boolean unsigned = TRUE;

Assembler Symbols

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(VL) operand1 = Z[n];
bits(VL) operand2 = Z[m];
bits(VL) result = Z[da];

for e = 0 to elements-1
    integer element1 = Int(Elem[operand1, e, esize], unsigned);
    integer element2 = Int(Elem[operand2, e, esize], unsigned);
    bits(esize) absdiff = Abs(element1 - element2)<esize-1:0>;
    Elem[result, e, esize] = Elem[result, e, esize] + absdiff;

Z[da] = 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.

This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX instruction must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is unpredictable:

• The MOVPRFX instruction must be unpredicated.
• The MOVPRFX instruction must specify the same destination register as this instruction.
• The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.