WHILEHS (predicate)
While decrementing unsigned scalar higher or same as scalar
Generate a predicate that starting from the highest numbered element is true while the decrementing value of the first, unsigned scalar operand is higher or same as the second scalar operand and false thereafter down to the lowest numbered element.
If the second scalar operand is equal to the minimum unsigned integer value then a condition which includes an equality test can never fail and the result will be an all-true predicate.
The full width of the scalar operands is significant for the purposes of comparison, and the full width first operand is decremented by one for each destination predicate element, irrespective of the predicate result element size. The first general-purpose source register is not itself updated.
The predicate result is placed in the predicate destination register. Sets the First (N), None (Z), !Last (C) condition flags based on the predicate result, and the V flag to zero.
Green
False
0
0
1
0
0
1
0
1
1
0
0
0
1
0
0
WHILEHS <Pd>.<T>, <R><n>, <R><m>
if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED;
constant integer esize = 8 << UInt(size);
constant integer rsize = 32 << UInt(sf);
constant integer n = UInt(Rn);
constant integer m = UInt(Rm);
constant integer d = UInt(Pd);
constant boolean unsigned = TRUE;
constant SVECmp op = Cmp_GE;
<Pd>
Is the name of the destination scalable predicate register, encoded in the "Pd" field.
<T>
Is the size specifier,
size
<T>
00
B
01
H
10
S
11
D
<R>
Is a width specifier,
<n>
Is the number [0-30] of the source general-purpose register or the name ZR (31), encoded in the "Rn" field.
<m>
Is the number [0-30] of the source general-purpose register or the name ZR (31), encoded in the "Rm" field.
CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(PL) mask = Ones(PL);
bits(rsize) operand1 = X[n, rsize];
constant bits(rsize) operand2 = X[m, rsize];
bits(PL) result;
boolean last = TRUE;
constant integer psize = esize DIV 8;
for e = elements-1 downto 0
boolean cond;
case op of
when Cmp_GT cond = (Int(operand1, unsigned) > Int(operand2, unsigned));
when Cmp_GE cond = (Int(operand1, unsigned) >= Int(operand2, unsigned));
last = last && cond;
constant bit pbit = if last then '1' else '0';
Elem[result, e, psize] = ZeroExtend(pbit, psize);
operand1 = operand1 - 1;
PSTATE.<N,Z,C,V> = PredTest(mask, result, esize);
P[d, PL] = result;