Nios® V Processor Reference Manual

ID 683632
Date 12/11/2023

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Document Table of Contents Floating Point Classification

The FCLASS.S instruction classifies the floating-point value into ten possible classifications specified in the following table and returns an integer value.

Table 75.  Floating Point Classification
Classification Description Single Precision FP Representation Return Integer Value
Sign (1 bit) Exponent (8 bit) Mantissa (23 bit)
-infinity Negative infinity 1 0xFF 0 0
-normal Negative normalized non-zero value 1 Any value (except values representing other classes) 1
-subnormal Negative denormalized value 1 0 Non-zero 2
-0 Negative zero value 1 0 0 3
+0 Positive zero value 0 0 0 4
+subnormal Positive denormalized value 0 0 Non-zero 5
+normal Positive normalized non-zero value 0 Any value (except values representing other classes) 6
+infinity Positive infinity 0 0xFF 0 7
Signaling NaN Signaling NaN Don’t Care 0xFF 0x1 to 0x3FFFFF 8
Quiet NaN Quiet NaN Don’t Care 0xFF 0x400000 to 0x7FFFFF 9