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## FRECPX

Floating-point reciprocal exponent (predicated).

Invert the exponent leaving the fractional part unchanged 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.

The result of this instruction can be used with FMULX to convert arbitrary elements in mathematical vector space to "unit vectors" or "direction vectors" of length 1.

 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 1 1 0 0 1 0 1 size 0 0 1 1 0 0 1 0 1 Pg Zn Zd

#### SVE

FRECPX <Zd>.<T>, <Pg>/M, <Zn>.<T>

```if !HaveSVE() then UNDEFINED;
if size == '00' then UNDEFINED;
integer esize = 8 << UInt(size);
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);```

### Assembler Symbols

 Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T> Is the size specifier, encoded in size:
size <T>
00 RESERVED
01 H
10 S
11 D
 Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.
 Is the name of the source scalable vector register, encoded in the "Zn" field.

### Operation

```CheckSVEEnabled();
integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(VL) operand = Z[n];
bits(VL) result = Z[d];

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

Z[d] = result;```

### Operational information

This instruction might be immediately preceded in program order by a MOVPRFX instruction that conforms to all of the following requirements, otherwise the behavior of either or both instructions is unpredictable:

• The MOVPRFX instruction must specify the same destination register as this instruction.
• The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.
The MOVPRFX instructions that can be used with this instruction are as follows:
• An unpredicated MOVPRFX instruction.
• A predicated MOVPRFX instruction using the same governing predicate register and source element size as this instruction.