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FLOGB

Floating-point base 2 logarithm as integer.

This instruction returns the signed integer base 2 logarithm of each floating-point input element |x| after normalization.

This is the unbiased exponent of x used in the representation of the floating-point value, such that, for positive x, x = significand × 2exponent.

The integer results are placed in elements of the destination vector which have the same width (esize) as the floating-point input elements:

* If x is normal, the result is the base 2 logarithm of x.

* If x is subnormal, the result corresponds to the normalized representation.

* If x is infinite, the result is 2(esize-1)-1.

* If x is ±0.0 or NaN, the result is -2(esize-1).

Inactive elements in the destination vector register remain unmodified.

313029282726252423222120191817161514131211109876543210
0110010100011size0101PgZnZd

SVE2

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

if !HaveSVE2() 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

<Zd>

Is the name of the destination scalable vector register, encoded in the "Zd" field.

<T> Is the size specifier, encoded in size:
size<T>
00RESERVED
01H
10S
11D
<Pg>

Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Zn>

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] = FPLogB(element, FPCR); Z[d] = result;

Operational information

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

The MOVPRFX and this instruction is unpredictableinstructions that can be used with this instruction are as follows:


Internal version only: isa v31.05bv31.04, AdvSIMD v29.02, pseudocode v2019-12_rc3_1v2019-09_rc2_1, sve v2019-12_rc3v2019-09_rc3 ; Build timestamp: 2019-12-13T112019-09-27T17:0228

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