UQDECW (vector)
Unsigned saturating decrement vector by multiple of 32-bit predicate constraint element count
Determines the number of active 32-bit elements implied by the named predicate constraint, multiplies that by an immediate in the range 1 to 16 inclusive, and then uses the result to decrement all destination vector elements. The results are saturated to the 32-bit unsigned integer range.
The named predicate constraint limits the number of active elements in a single predicate to:
A fixed number (VL1 to VL256)
The largest power of two (POW2)
The largest multiple of three or four (MUL3 or MUL4)
All available, implicitly a multiple of two (ALL).
Unspecified or out of range constraint encodings generate an empty predicate or zero element count rather than Undefined Instruction exception.
Green
False
True
0
0
0
0
0
1
0
0
1
0
1
0
1
1
0
0
1
1
UQDECW <Zdn>.S{, <pattern>{, MUL #<imm>}}
if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED;
constant integer esize = 32;
constant integer dn = UInt(Zdn);
constant bits(5) pat = pattern;
constant integer imm = UInt(imm4) + 1;
constant boolean unsigned = TRUE;
<Zdn>
Is the name of the source and destination scalable vector register, encoded in the "Zdn" field.
<pattern>
Is the optional pattern specifier, defaulting to ALL,
pattern
<pattern>
00000
POW2
00001
VL1
00010
VL2
00011
VL3
00100
VL4
00101
VL5
00110
VL6
00111
VL7
01000
VL8
01001
VL16
01010
VL32
01011
VL64
01100
VL128
01101
VL256
0111x
#uimm5
101x1
#uimm5
10110
#uimm5
1x0x1
#uimm5
1x010
#uimm5
1xx00
#uimm5
11101
MUL4
11110
MUL3
11111
ALL
<imm>
Is the immediate multiplier, in the range 1 to 16, defaulting to 1, encoded in the "imm4" field.
CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer elements = VL DIV esize;
constant integer count = DecodePredCount(pat, esize);
constant bits(VL) operand1 = Z[dn, VL];
bits(VL) result;
for e = 0 to elements-1
constant integer element1 = Int(Elem[operand1, e, esize], unsigned);
(Elem[result, e, esize], -) = SatQ(element1 - (count * imm), esize, unsigned);
Z[dn, VL] = result;