rsubhnb

SVE Rounding Subtract Narrow (Bottom)

RSUBHNB <Zd>.<T>, <Zn>.<Tb>, <Zm>.<Tb>

Subtracts, rounds, and narrows (Bottom half).

Pseudocode Operation

No pseudocode available.

Encoding

Binary Layout
01000101
31:24
size
23:22
1
21
Zm
20:16
011
15:13
1
12
1
11
0
10
Zn
9:5
Zd
4:0
 
Format SVE2 Narrowing
Opcode 0x45207800
Extension SVE2

Operands

  • Zd
    Dest
  • Zn
    Src1
  • Zm
    Src2

Related

More in SVE2

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding Instruction ISA Bit pattern
0x45207800 RSUBHNB <Zd>.<T>, <Zn>.<Tb>, <Zm>.<Tb> A64 01000101 | size | 1 | Zm | 011 | 1 | 1 | 0 | Zn | Zd

Description

Subtract each vector element of the second source vector from the corresponding vector element in the first source vector, and place the most significant rounded half of the result in the even-numbered half-width destination elements, while setting the odd-numbered half-width destination elements to zero. This instruction is unpredicated.

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer elements = VL DIV esize;
bits(VL) operand1 = Z[n, VL];
bits(VL) operand2 = Z[m, VL];
bits(VL) result;
constant integer halfesize = esize DIV 2;

for e = 0 to elements-1
    integer element1 = UInt(Elem[operand1, e, esize]);
    integer element2 = UInt(Elem[operand2, e, esize]);
    integer res = ((element1 - element2) + (1 << (halfesize - 1))) >> halfesize;
    Elem[result, 2*e + 0, halfesize] = res<halfesize-1:0>;
    Elem[result, 2*e + 1, halfesize] = Zeros(halfesize);

Z[d, VL] = result;