UQDECP (vector)

Unsigned saturating decrement vector by count of true predicate elements

Counts the number of true elements in the source predicate and then uses the result to decrement all destination vector elements. The results are saturated to the element unsigned integer range.

The predicate size specifier may be omitted in assembler source code, but this is deprecated and will be prohibited in a future release of the architecture.

313029282726252423222120191817161514131211109876543210
00100101size1010111000000PmZdn
DU

UQDECP <Zdn>.<T>, <Pm>.<T>

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; if size == '00' then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer m = UInt(Pm); constant integer dn = UInt(Zdn); constant boolean unsigned = TRUE;

Assembler Symbols

<Zdn>

Is the name of the source and destination scalable vector register, encoded in the "Zdn" field.

<T>

Is the size specifier, encoded in size:

size <T>
00 RESERVED
01 H
10 S
11 D
<Pm>

Is the name of the source scalable predicate register, encoded in the "Pm" field.

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; constant bits(VL) operand1 = Z[dn, VL]; constant bits(PL) operand2 = P[m, PL]; bits(VL) result; integer count = 0; for e = 0 to elements-1 if ActivePredicateElement(operand2, e, esize) then count = count + 1; for e = 0 to elements-1 constant integer element = Int(Elem[operand1, e, esize], unsigned); (Elem[result, e, esize], -) = SatQ(element - count, esize, unsigned); Z[dn, VL] = result;

Operational information

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


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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