FCLASS

Operation

Classifies an S- or D-format source into a one-hot integer bitmap without changing FFLAGS.

Assembler Syntax

FCLASS.{S|D}(z) Fn(s), Rn(d)

Privilege

Unprivileged

Required CPUID flags

FP

Repeat eligibility

REP eligible

Examines the selected floating-point encoding without generating a floating-point exception condition and writes a one-hot class bitmap to the destination Rn register.

The destination is a one-hot bitmap selected directly from the sign, exponent, fraction, and NaN quiet bit of the S or D source encoding.

FCLASS Result Bitmap

Bit	Class
0	negative infinity
1	negative normal
2	negative subnormal
3	negative zero
4	positive zero
5	positive subnormal
6	positive normal
7	positive infinity
8	signaling NaN
9	quiet NaN

Bits 63..10 of the destination Rn register are zero. No floating-point exception flag is changed.

2.75in

Encodings

FCLASS.{S|D}(z) Fn(s), Rn(d)

Format: Instruction format for FCLASS.{S|D}(z) Fn(s), Rn(d)