fsqrt

SVE Floating-Point Square Root

FSQRT <Zdn>.<T>, <Pg>/M, <Zdn>.<T>

Calculates square root of floats.

Details

SVE floating-point square root: computes the square root of each active element in Zdn and stores the result back in Zdn. Elements where the predicate is false are left unchanged. Floating-point exception flags (IOC, DZC, OFC, UFC, IXC) are updated according to the IEEE 754 standard; no integer condition flags are affected. This is an SVE-only instruction.

Pseudocode Operation

for i = 0 to VL-1
  if Pg[i] == '1' then
    Zdn[i] ← FPSquareRoot(Zdn[i])
  // else Zdn[i] unchanged
// FP exception flags updated per IEEE 754

Example

FSQRT z0.s.T, p0/m/M, z0.s.T

Encoding

Binary Layout
01100101
size
0011
0
1
101
Pg
Zn
Zd
 
Format SVE FP Unary
Opcode 0x650DA000
Extension SVE

Operands

  • Zdn
    Combined destination/source scalable vector register (SVE)
  • Pg
    Mask

Reference (Arm A64 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0x2EF9F800 FSQRT <Vd>.<T>, <Vn>.<T> A64 0 | Q | 1 | 01110 | 1 | 111100 | 11111 | 10 | Rn | Rd
0x2EA1F800 FSQRT <Vd>.<T>, <Vn>.<T> A64 0 | Q | 1 | 011101 | sz | 10000 | 11111 | 10 | Rn | Rd
0x1EE1C000 FSQRT <Hd>, <Hn> A64 0 | 0 | 0 | 11110 | 11 | 10000 | 11 | 10000 | Rn | Rd
0x1E21C000 FSQRT <Sd>, <Sn> A64 0 | 0 | 0 | 11110 | 00 | 10000 | 11 | 10000 | Rn | Rd
0x1E61C000 FSQRT <Dd>, <Dn> A64 0 | 0 | 0 | 11110 | 01 | 10000 | 11 | 10000 | Rn | Rd
0x650DA000 FSQRT <Zd>.<T>, <Pg>/M, <Zn>.<T> A64 01100101 | size | 0011 | 0 | 1 | 101 | Pg | Zn | Zd

Description

Calculate the square root of each active floating-point element of the source vector, and place the results in the corresponding elements of the destination vector. Inactive elements in the destination vector register remain unmodified.

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
bits(PL) mask = P[g, PL];
bits(VL) operand = if AnyActiveElement(mask, esize) then Z[n, VL] else Zeros(VL);
bits(VL) result = Z[d, VL];

for e = 0 to elements-1
    if ActivePredicateElement(mask, e, esize) then
        bits(esize) element = Elem[operand, e, esize];
        Elem[result, e, esize] = FPSqrt(element, FPCR);

Z[d, VL] = result;